LIQUIDMETAL® DESIGN GUIDE 3.0 LIQUIDMETAL® TECHNOLOGIES DESIGN GUIDE REV. 3.0 TABLE OF CONTENTS

7 Chapter 1: WHAT ARE AMORPHOUS METALS? 13 Chapter 2: METAL MOLDING PROCESS OVERVIEW 19 Chapter 3: MATERIAL PROPERTIES (DATA SHEET) • Mechanical properties & fatigue strength • Thermal properties • Environmental & operating temperatures • Corrosion resistance • Surface finish • Electrical properties 21 Chapter 4: APPLICATION CHARACTERISTICS OF THE LIQUIDMETAL PROCESS • Application characteristics • Design characteristics • Shot size & cavitation • Dimensional accuracy & repeatability • Technology comparisons • As-molded surface finish • Reflectivity properties • Biocompatibility

® • Corrosion resistance Disclaimer: This Liquidmetal Design Guide is subject to change and update at • Magnetism any time without notice and any errors are subject to correction without liability. 35 Chapter 5: DRAFT REQUIREMENTS Copyright: Liquidmetal Technologies, Inc. June 1, 2015

3 39 Chapter 6: WALL THICKNESS • Minimum & maximum wall thicknesses 41 Chapter 7: RADII & FILLETS 43 Chapter 8: HOLES & SLOTS 45 Chapter 9: THREADS 47 Chapter 10: SURFACE FEATURES & TEXTURING 49 Chapter 11: MOLDING BEHAVIOR & PART AESTHETICS • Material flow • Gating & part geometry best practices • Heat checking • Shrinkage & sink marks • Parting line & witness marks 53 Chapter 12: EJECTION 55 Chapter 13: UNDERCUTS 57 Chapter 14: OVERMOLDING • Plastic overmolding • Metal overmolding 61 Chapter 15: POST PROCESSING ALTERNATIVES • Bead & media blasting • Machining • Welding • Painting & PVD

5 WHAT ARE AMORPHOUS METALS?

1 WHAT ARE AMORPHOUS METALS? Interest in amorphous metals is appearing in a diverse range of sources, including news articles, trade magazines, scientific journals, and investment publications. Many of the exotic metal alloys being described are actually the same material being referred to by different names. For example, Liquidmetal® alloys, Vitreloy, amorphous metal, and metallic glass are basically synonyms for the same new class of metals, which exhibit an amorphous (random or disordered) microstructure. To understand what these INTRODUCTION metals are, and more importantly, to better understand how they are utilized, Welcome to the new Liquidmetal® Technologies Design Guide. Our we will step back and review some history and include a few basic principles of “metallurgy.” ultimate goal is to help you get the most benefit from the technology by enabling you to design the best parts possible for your product Metallurgy is an ancient practice which focuses on the development and application. In the following chapters you will discover Liquidmetal’s processing of metal alloys for specific applications. Ancient metallurgists technology background, process overview, as well as significant devised bronze and carbon steel alloys for improving weapons while modern metallurgists have developed aircraft-grade aluminum and titanium alloys material properties and how they pertain to various applications. for the latest demanding aerospace applications. Despite centuries of You’ll also have the opportunity to explore practical design rules technological advancement, metal alloys have almost always shared the and manufacturing best practices that will help you take advantage common thread of having a crystalline microstructure; that is, their atoms are of the unique Liquidmetal properties and process in a number of arranged in naturally occurring patterns that represent the most stable form example applications. of the material (try shaking a glass jar full of marbles and then watch as the

7 WHAT ARE AMORPHOUS METALS?

spheres settle into a closely packed arrangement). The crystalline structure of < the liquid state (where no conventional metals is both an advantage and a disadvantage when it comes crystal structure exists) to to processing and mechanical properties. room temperature without 9 10 ← Pure Metals forming a crystalline These materials exhibit broad trends that limit what can be done with them. structure (since the For example, a metal’s melting temperature is usually proportional to its 6 ← Early Metallic Glasses formation of crystals takes hardness and a material’s strength is usually inversely proportional to its ) 10 s time, as with the shaking ductility. This means that alloys with low melting points (which can be cast 3 jar analogy). By rapidly readily) are often soft and have low-strength while alloys with high melting 10 cooling, one could trap the points (which cannot be cast easily) are often hard, brittle, and have high- (K/ ® “liquid-like” microstructure c Liquidmetal Alloys strength. 0 ← R 10 into the non-crystalline These empirical rules have governed the development of metal alloys for (or “amorphous”) solid, Silicate Glasses creating a new class of centuries and it explains the traditional competition between materials for -3 ← specific applications. For example, if one were to design a metal case there 10 metal alloys, which can be might be a competition between aluminum alloys, titanium, and steel. called amorphous. Aluminum alloys can be die-cast into near net-shapes, which would lower the Early amorphous production costs, but are soft and scratch easily. Steel sheets can be stamped metals could only be and are very scratch resistant, but steel is much denser than aluminum and Figure 1. Cooling rates required to achieve an manufactured in very amorphous microstructure in various materials. cannot form smaller, complex features. Low-density titanium alloys have high- thin ribbons, using a strength; however, their high melting points are not easily cast or subsequently sputtering method to machined. This is a simplified illustration of the complex tradeoff decisions achieve the massive cooling rates required to defeat the normal crystallization that designers and engineers must balance when using metal alloys in a vast that occurs when metal changes from a liquid to a solid. Nevertheless, low- universe of applications. cost commercial sheet fabrication of these thin ribbon materials led to a very The fundamental innovations leading up to Liquidmetal® technology date successful industry. Amorphous metal ribbons have been wound and used as back to the early 1960s with the development of gold-silicon alloys that could transformer coils and anti-theft I.D. tags due to their magnetic properties. be formed into a non-crystalline (also known as “amorphous”) microstructure In the early 1990s with support from NASA, Caltech formulated Vitreloy, at extremely high cooling rates. By designing alloy compositions around the first bulk metallic glass (BMG) alloy with a thickness much greater than deep melting points (also called “eutectics”), the alloy could be cooled from

9 WHAT ARE AMORPHOUS METALS?

Alloy in Molten State

1mm. Adding to this significant discovery, it alloys are generally stronger than conventional alloys because they do not was the first amorphous alloy that required have grain boundaries or crystal defects such as vacancies, interstitials, modest cooling rates of only tens of degrees dislocations, or stacking faults—Figure 2. per second (providing orders of magnitude In addition to high strength, Liquidmetal® parts exhibit very high elastic strain

improvement over earlier alloys—Figure 1). < limits compared to conventional alloys. We occasionally hear concerns of < Liquidmetal® amorphous metals have amorphous alloys being “brittle” or easy to break, but usually the criticism Amorphous Atomic Ordinary Alloys remarkable physical properties compared Structure Naturally Crystallize comes in the absence of recognizing the highly elastic characteristic of the to conventional alloys. In the molten state, material. Combining these levels of strength and elasticity produces a very robust material. When amorphous alloys do fail, the failure mode is quite conventional alloys also possess an amorphous Equiaxed Grains structure or liquid-like atomic arrangement. abrupt. However, part-design freedom is tremendous due to the overall However, during the cooling process while < < Columnar Grains unique properties of the alloys, which we discuss in more detail in the transitioning to its solid phase, conventional following chapters. alloys naturally tend to crystallize into regular < Chill Crystals geometric microstructures beginning with the chill crystals that start forming on the outer < surface. Columnar grains begin to form after < AMORPHOUS ATOMIC CRYSTALLINE ATOMIC the chill crystals and lastly the equiaxed grains STRUCTURE STRUCTURE are last to form in the center furthest from the outer cooling surfaces. These structures often result in weak regions along the boundaries of these crystalline geometric structures, which are commonly referred to as grain boundaries. In contrast, (Right) A 3-point bend test

Liquidmetal alloys retain an amorphous, demonstrates the high elastic limit of liquid-like microstructure in their solid state. < Liquidmetal alloys. The 0.85mm thick Liquidmetal alloys solidify as a frozen liquid plate is under approximately 1.5% without a phase transformation. Liquidmetal strain and returns to its exact original as-molded size and shape when the load is released. Since the entire elastic region is within the proportional limit, Figure 2. WEAK REGION all stress-strain responses are linear and the original geometry is fully recoverable up to 1.8% strain. 11 METAL MOLDING PROCESS OVERVIEW

2 METAL MOLDING PROCESS OVERVIEW The Liquidmetal® molding process begins with crystalline ingots, which are automatically loaded for melting. Liquidmetal alloy ingots in the shape of cylindrical rods weighing up to 100 grams are heated under vacuum. When the alloy is fully molten the metal is injected under pressure into permanent steel molds similar to conventional plastic injection molds. Mold temperatures are controlled to cool and solidify the Liquidmetal alloy into final part geometries until the part is ready for ejection. By the time the part is ejected from the mold it has achieved full material properties in this single-step molding process. Parts can be designed to include the same level of three- dimensional complexity as plastic injection molded parts. Let’s take a closer look at the molding technology and the process for producing Liquidmetal amorphous alloy parts. The injection molding machines used for the Liquidmetal process replace a conventional plastic injection molding screw and barrel assembly with a special injection unit tailored for the Liquidmetal process. The injection of amorphous metals is completely different from traditional die-casting and plastics processing, requiring precise control over melt temperatures and viscosities while under vacuum.

13 METAL MOLDING PROCESS OVERVIEW

Liquidmetal® Technologies partnered with ENGEL who developed an The molding process is automated to provide hands-free continuous e-motion machine for processing amorphous alloys. The injection molding production. Ingots are loaded into the melt chamber using a servo-driven machine has a very efficient, compact material melting and injection system robot. After ingot insertion, the robot then removes the finished parts from the with a melt chamber that holds the cylindrical rod or ingot. The alloy ingot is previous molding cycle within the same sequence, and places them onto a heated to a molten state by a special induction heating system that heats the conveyor belt with integrated cooling fans. material to temperatures >1000°C. Once parts have been injection molded, they are ready to use except for Once the alloy is molten, the material is injected into the mold using profile removing gates and runners. To remove gates and runners, there are a few parameters that are similar to conventional plastic injection molding. The suitable approaches depending on the requirements of the finished part. If entire system is kept under an extreme vacuum level to prevent the formation slight gate vestige is acceptable, waterjet cutting can be used. In cases where of crystals and oxides, allowing for the best possible amorphous alloy parts. little or no gate witness is desired, CNC machining can be employed to Cycle times for Liquidmetal melt and injection cycles range from two to three remove the gate and runner system. minutes (i.e., mold close to open). A sophisticated and real time control system manages the end-to-end molding process—including data recording, sensors, safety, maintenance, and the challenge of managing the entire injection cycle. The machine carefully controls each parameter for precise part-to-part repeatability.

(Left) Liquidmetal ingot next to a US quarter coin for scale. 15 ENGEL e-motion injection molding machine for processing Liquidmetal® alloys.

(Above) Precise process and flow controls allow small parts with high cavitation molds to fill with high yields.

ENGEL injection molding machine parts (Above Left) Medical conveyor belt suturing component produced by Liquidmetal® Technologies, Inc. (Right) Liquidmetal parts cooling on a conveyor belt. 17 MATERIAL PROPERTIES

3 MATERIAL PROPERTIES As discussed in previous chapters, Liquidmetal® alloys have distinctive combinations of mechanical, thermal, environmental, and other physical properties due to their amorphous atomic microstructures. These properties should underpin the decision by designers and engineers to successfully apply Liquidmetal alloys to particular applications. We encourage the use of finite element analysis and other modeling tools that harness the material properties data (provided on the following page) in order to make informed design decisions that enable novel or superior component performance. Our solutions engineers are equipped to walk customers through this process when necessary. Additional details concerning more advanced material properties can also be provided by our research and development team. At present, our commercial manufacturing process is compatible with two different five-component zirconium-based Liquidmetal alloys, one of which is now free of beryllium.

19 APPLICATION CHARACTERISTICS OF THE LIQUIDMETAL® PROCESS Table 1. LM105 LM105

COMPOSITION HEAT CAPACITY, C P at.% Zr52.5-Ti5-Cu17.9-Ni14.6-Al10 J/kg.K 329 wt.% Zr65.7-Cu15.6-Ni11.7-Al13.7-Ti3.3 BTU/lb.°F 0.08 DENSITY, ρ THERMAL EXPANSION, α 3 g/cm 6.57 mm/m.K 12.0 4 3 (lb/in ) 0.237 min/in.°F 6.7 HARDNESS THERMAL CONDUCTIVITY, k W/m.K - Vickers 563 APPLICATION

THERMAL BTU/ft.hr.°F - Rockwell C 53 GLASS TRANSITION TEMPERATURE, Tg YIELD STRENGTH, CHARACTERISTICS OF THE σy °C 399 MPa 1524 °F 750 (ksi) 231 LIQUIDMETAL PROCESS CRYSTALLIZATION TEMPERATURE, Tx Liquidmetal technology offers part designers several unique capabilities. At SPECIFIC STRENGTH, s/r °C 468 the most basic level, the process is a simple one-step molding operation that MPa.cm 3/g 232 °F 874 produces three-dimensionally complex metal parts with impressive physical (ksi.in 3/lb) 231/0.237` STD. OPERATING TEMPERATURE properties and surface finishes. This unique combination of capabilities is not FLEXURAL STRENGTH, s °C <250 known to exist with any other commercial metalworking process. MPa 2133 °F <482 (ksi) 309 SALT SPRAY (ASTM B117) Liquidmetal technology is well suited for smaller, complex, high-strength, and MECHANICAL YOUNG’S MODULUS, E After 336 hours No Detectable Degradation high-precision metal parts. Generally, parts up to 80 grams are candidates GPa 92.7 RESISTANCE TO ACIDITY Yes for the process. Since the molding process is similar to plastic injection ENVIRONMENTAL (Msi) 13.4 RESISTANCE TO ALKALINITY Yes molding, many of the same design rules and requirements are employed. ELASTICITY, e BIOCOMPATIBILITY Unlike machining, where designers must consider the cost and time to remove Toxicity, Irritation, Sensitization, Systemic material to achieve a final geometry, the Liquidmetal process allows designers (% of Original Shape) 1.80% Pass BIO Toxicity, Hemocompatibility the freedom to design products for efficient assembly and functional FATIGUE STRENGTH, Mutagenicity, Pyrogenicity Pass 7 requirements. This eliminates material scrap and the sensitivity to incremental MPa @ 10 cycles 304 SURFACE FINISH Functional and Cosmetic 7 costs associated with discrete machining steps required to produce final part (ksi @ 10 cycles) 44.1 Type As-cast, Blasted, Polished geometry. IMPACT STRENGTH ROUGHNESS, Ra

J - mm 0.05 SURFACE (ft.lb) - min 2 FRACTURE TOUGHNESS, KIC ELECTRICAL RESISTIVITY, r MPa√m ~40 μΩ.cm 160 ksi√in ~36 POISSON’S RATIO, n 0.38 μΩ.in 63 ELECTRICAL 21 APPLICATION CHARACTERISTICS OF THE LIQUIDMETAL® PROCESS

APPLICATION CHARACTERISTICS SHOT SIZE / PART WEIGHT / NUMBER OF MOLD Liquidmetal® is an excellent solution for applications requiring three or more of the following characteristics: CAVITIES The maximum shot size for the Liquidmetal molding process today is limited • Exceptional dimensional control and repeatability to 100 grams. Approximately 20 to 30 grams of the shot are consumed by • Excellent corrosion resistance cold-wells and runners in the mold, thus leaving 70 to 80 grams available for the parts. Since the Liquidmetal process is able to inject high cavitation molds • Brilliant surface finish in a single step, excellent part-cost economies can be realized. Designers • High strength quickly learn that small parts benefit from the technology by allowing • High hardness, scratch & wear resistance multiple mold cavities to produce many parts in a one-step operation. Larger • High elastic limit parts limited to one or two mold cavities are possible; however, the best applications for larger parts are ones that require substantial amounts of • Non-magnetic conventional machining and labor. The density of Liquidmetal LM105 alloy is 6.57 g/cm3, which results in a DESIGN CHARACTERISTICS maximum part volume of 11 cm3 to 13 cm3. The low specific gravity of Here are a few basic guidelines for identifying candidate Liquidmetal parts: Liquidmetal alloys compared to wrought stainless steels and other steel alloys provides another interesting and unique advantage, by providing weight • Part weight up to 80 grams (100 grams maximum total shot size of which reduction in combination with the high strength and performance properties. 80 grams is usable) • Maximum dimension of 100mm 3 • Outer draft angles of 0.5O to 3O DENSITY (g/cm ) • Inner draft angles of 1O to 5O LIQUIDMETAL MAGNESIUM ALUMINUM TITANIUM STAINLESS STEEL • Wall thickness 0.6mm to 4.0mm • Dimensional tolerances of ±.025 mm for critical dimensions LM105 AZ-91 380 Series 6A1-4V 17-4PH • Production volumes from tens of thousands to millions of parts Table 2. Density comparison between 6.57 1.8 2.8 4.4 7.7 various materials.

23 APPLICATION CHARACTERISTICS OF THE LIQUIDMETAL® PROCESS

DIMENSIONAL ACCURACY AND REPEATABILITY Because the Liquidmetal process has a high level of accuracy and With the application of manufacturing process simulation and analysis tools, repeatability, over-specifying tolerances for non-critical or standard features the Liquidmetal® process can achieve dimensional accuracy and repeatability may unnecessarily increase the cost of the injection mold tooling. Similar results that are usually only common to production CNC (Computer tolerances should be specified for the mold cavities that are desired on the Numerical Control) machining processes. But the Liquidmetal process final part. Over-specifying tolerances for less important features may create accomplishes these results at much lower costs than machining. Today, unnecessary work and associated costs to produce the mold cavities for these designers can expect dimensional accuracy and repeatability of ±0.075% non-critical part features. of a given part dimension. Of course, recognition of mold fabrication tolerance capabilities, especially on high cavitation molds, needs to be considered before committing part specifications. Liquidmetal alloys solidify during the molding process nearly isotropically, so design sensitivities to the 0.4% solidification shrinkage of the material and dimensional tolerances of DIMENSION METRIC IMPERIAL part features are insignificant. The challenge for the Liquidmetal process Table 3. This chart displays typical tolerances for Critical to Function ±0.0203mm for dimensions up to 25.4mm ±0.0008” for dimensions up to 1.0” is working with injection mold fabricators that emphasize dimensional as-molded Liquidmetal Linear Features ±0.0203mm for each additional 25.4mm ±0.0008” for each additional 1.0” accuracy of mold cavities and those who specialize in accomplishing this with parts. Please note the high-cavitation tooling. two categories of Linear Non-Critical/Standard ±0.05mm for dimensions up to 25.4mm ±0.002” for dimensions up to 1.0” Features. Linear Features ±0.025mm for each additional 25.4mm ±0.001” for each additional 1.0” Freezing incompressible molten metal during the injection molding process without changes to the atomic structure of the material plays a significant Flatness 0.05mm 0.002” role in the resulting dimensional accuracy and repeatability of the process. Straightness 0.05mm 0.002” This highly unique aspect of dimensional control is not inherent to any Angularity 0.001mm/mm 0.0004” in/in other metalworking technology. Furthermore, high-performance material Concentricity 0.05mm (// to parting line) 0.002” (// to parting line) properties are achieved without any post-molding heat-treating or annealing requirements that are common with other crystalline metal alloys. This benefit Circularity 0.05mm (// to parting line) 0.002” (// to parting line) avoids further loss of dimensional control from residual stress, part warpage, distortion, or growth with many heat treating processes used by conventional crystalline metal alloys.

25 APPLICATION CHARACTERISTICS OF THE LIQUIDMETAL® PROCESS

TECHNOLOGY COMPARISONS 2000 In summary, the Liquidmetal process is an ideal There is no one perfect technology solution for all applications. As new manufacturing solution for three-dimensionally complex products continually evolve and develop, both proven and leading-edge parts, including those with unsupported features, and technologies should be considered and evaluated for performance, quality, parts that require all or some of the following: ® 1500 and cost objectives. The Liquidmetal process provides a unique set of • Incredible Accuracy application characteristics that differentiate it from other manufacturing • Amazing Repeatability technologies. Table 4 compares the core strengths of the Liquidmetal process against other popular metalworking technologies • Remarkable Properties 1000 • Brilliant Surface Finish Liquidmetal alloys provide a unique combination of high-strength and elastic properties. Many plastics are known for their elastic properties, but their • Scratch Resistance

strength levels are generally low. There are many crystalline metal alloys that YIELD STRENGTH (MPa) • Corrosion Resistance offer a wide range of strength characteristics, but none offer high-strength 500 The uniqueness of the Liquidmetal alloys and combined with high-elastic limits like Liquidmetal alloys—Figure 3. manufacturing process provide results that are impressive for a fully-automated, complex, metal part INVESTMENT manufacturing process. Liquidmetal alloys can be LIQUIDMETAL DIE CASTING MIM CASTING MACHINING 0 successfully applied in a very broad range of markets, Low Cost/High Part Complexity YES Yes Yes No No Table 4. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 such as automotive, aerospace, defense, dental, Comparison of ELASTICITY (%) industrial, medical, and sporting equipment. Fine Surface Finish <2.0 Ra (micro the Liquidmetal YES No No No Yes inches) without secondary operations process and various other High Elastic Limit YES No No No No metalworking Single Process Step YES No No No No technologies.

No Heat Treating Required to YES No No No No Achieve High Hardness Figure 3. (Graph above) No Heat Treating Required to YES No No No No Liquidmetal alloys have a unique Achieve High Strength combination of the high-strength of metals and the elasticity of plastics. Low Process Scrap YES Yes Yes No No Tolerance Control (% of feature size) +/- 0.075 +/- 0.4 +/- 0.3 +/- 0.5 +/- 0.075 (Left) A standard 4-point bend test fixture loading a 1.85mm thick rectangular Liquidmetal bar for material quality assurance purposes. As-molded parts can return to their original geometries after 27 undergoing strains up to 1.8%. APPLICATION CHARACTERISTICS OF THE LIQUIDMETAL® PROCESS

AS-MOLDED SURFACE FINISH REFLECTIVITY PROPERTIES Liquidmetal® alloys mimic the surface condition on the injection Liquidmetal alloys can replicate tool surfaces, whether polished or textured. mold cavities used for producing parts. As a result, very fine surface The alloys have good as-molded reflectivity and Ra values of 0.038µm finishes are achievable. This result cannot be duplicated by any other (1.5µin.), giving a nice specular reflection. known metal molding or metal forming process technology. The only means through which other processes can accomplish surface finishes comparable to as-molded Liquidmetal alloys is to apply costly secondary Figure 5. operations such as those described in the chart below: REFLECTIVITY OF LIQUIDMETAL LM-001B 60

Ra μm 50 25 12.5 6.4 3.2 1.6 .8 .4 .2 .1 .05 .025 .012 55 Figure 4. CASTING Table 5. Liquidmetal Less Frequent 50 MIM Common MEASUREMENT* VALUE Die Casting 45 PV 652.173 A Investment Casting (Above) Two Liquidmetal parts demonstrating the Reflectivity (%) 40 material’s nearly optical as-molded surface finish. Sand Casting RMS 23.938 A ABRASIVE 35 Superfinishing Ra 16.730 A 30 Lapping *values for polished LM sample 360 460 560 660 Polishing Wavelength (nm) METAL CUTTING Grinding

Turning

Milling

2000 1000 500 250 125 64 32 16 8 4 2 1 .5 Ra μIn 29 APPLICATION CHARACTERISTICS OF THE LIQUIDMETAL® PROCESS

BIOCOMPATIBILITY CORROSION RESISTANCE Liquidmetal alloys are highly corrosion resistant. Even when exposed to harsh conditions, they perform very well compared to other traditional DEVICE CATEGORIZED BY BIOLOGICAL EFFECT alloys normally selected for corrosion resistant applications. The chart below Table 6. Completed demonstrates the superior performance of Liquidmetal alloys over 316 Biocompatibility Tests for stainless steel in both hydrochloric acid and sulfuric acid solutions. NATURE OF BODY CONTACT DURATION Liquidmetal® As-Molded CONTACT A - Limited (<24 hrs.) LM105 Alloy. Evalution tests B - Prolonged (>24 hrs. to 30 d.) consideration from ISO TOTAL DISSOLUTION CONCENTRATION (PPM) CATEGORY CONTACT Hemo- compatibility C - Permanent (>30 d.) Cytotoxicity Sensitization Irritation or Intracutaneous Reactivity Systemic Toxicity 10993-1. Figure 6. A X X X Required

B X X X X = Completed & Passed 3600 SS-316 C X X X

A X X X Surface Mucosal Device Membrane B X X X

Breached or A X X X Compromised Surface B X X X

A X X X X X Blood Path, Indirect B External X X X X X Communicating 500 Device Tissue/ A X X X Bone/Dentin 250 Circulating 100 Blood A X X X X X 0 0 0 0

Implant Tissue/Bone A X X X 1N HCl 1N H SO NaOH pH13 Seawater Device 2 4 31 APPLICATION CHARACTERISTICS OF THE LIQUIDMETAL® PROCESS

LIQUIDMETAL ® ALLOYS ARE NON-MAGNETIC Austenitic stainless steel alloys are paramagnetic (meaning that in the When it comes to magnetic properties, Liquidmetal alloys are often compared presence of an external magnetic field they generate a small non-permanent with certain austenitic stainless steel alloys; that is, casually described as field of their own in the same direction as the primary field). They also have being "non-magnetic.” a typical relative magnetic permeability (X = 1 + K, where K is the magnetic susceptibility) between 1.05 and 1.1, which is actually significantly higher than However, this is slightly misleading since all materials have a magnetic most materials which are considered to be “non-magnetic” such as plastics or response of some sort, and there are several differences between Liquidmetal wood with a permeability of ~1.0000004 (a perfectly non-magnetic material alloys and stainless steel that should be taken into account for applications would have a relative permeability of 1). Additionally, even high grade involving electromagnetic properties. austenitic stainless steels can spontaneously regain ferromagnetic properties Figure 7. during processes that change the crystal structure of the stainless steel such as fluctuation in composition, cold working, welding or thermal history. Because of these effects, the measured susceptibility in a “non–magnetic" stainless steel part can be quite high, which is why the magnetic properties of lower grade stainless steels, like 304, can be described as “unstable.” Liquidmetal alloys are very mildly diamagnetic (in the presence of an external magnetic field they generate a very small response field which opposes the primary field). Their relative magnetic permeabilities are therefore slightly less than one. However, because they do not contain any ferrous elements or crystal lattice structures that allow for exchange effects among inner-core electrons, they have very stable magnetic properties that would be similar to materials such as copper (weakly diamagnetic at X = 0.999991) or titanium (weakly paramagnetic at X = 1.0001), which do not have any ferromagnetic tendencies. In short, unlike austenitic stainless steel alloys, Liquidmetal alloys cannot become magnetized over time.

Images: Horton and Parsell, ORNL, 2001

33 DRAFT REQUIREMENTS

5 DRAFT REQUIREMENTS Draft is the amount of taper or slope given to mold cavity features and other mold components such as cores. The purpose of including draft is to permit easy ejection of the molded part. One of the beneficial characteristics of the Liquidmetal® molding process is that full material properties are achieved by the end of the molding cycle. This means Liquidmetal alloy parts achieve high-hardness and high-strength during the molding process. These properties combined with the approximately 0.4% material shrinkage makes draft angles a critical element for successful mold design. If adequate draft is not included, especially on internal part features, a part may become permanently trapped in the mold cavity. Additionally, incorporating proper draft angles can help avoid premature mold wear and extend the mold life, thus reducing overall tooling costs. All molded surfaces, which are normally perpendicular to the parting line of the mold, require draft for proper ejection of the molded part from the mold. This draft requirement, expressed as an angle, is not fixed. The specific draft angle required will vary with the type of feature or surface specified, the depth of the surface, and the Liquidmetal alloy selected. Typical draft angle requirements for internal surfaces will be in the range of three to five degrees while external surfaces of the part can be reduced to the range of one to three degrees. It is possible to achieve zero draft surfaces on some walls by adding slides, lifters, and collapsible cores. The amount

35 DRAFT REQUIREMENTS

of draft required is highly dependent on part geometry, but the following The larger the part in the Z-direction (parallel to the pull), the smaller the guidelines (next page) are useful in establishing baseline requirements. draft angles can become. For die-casting alloys, there is a general rule that Liquidmetal® engineers are also available for a collaborative review of your applies to draft requirements based on material. Below is such a table with part design to ensure proper draft angles are specified. Liquidmetal® alloys included.

ALLOY GROUP INNER SURFACES OUTER SURFACES HOLE (TOTAL) Table 7. Comparison of ZINC AND ZA 50 100 34 draft angle requirements for Liquidmetal compared to other MAGNESIUM 35 70 24 die-cast alloys. The C value is ALUMINUM 30 60 20 a dimensionless number that generates a suggested draft COPPER 25 50 17 angle based on the depth of the LIQUIDMETAL 15 30 10 wall that is being drafted.

DEPTH, L (mm) DRAFT (degrees) Table 8. An example of the draft 0.5 5.4 angle that would be required for an inner surface of a Liquidmetal 1 3.8 part based on wall depth. 2 2.7 57.2738 DRAFT ANGLE = 5 1.7 C √ L

37 WALL THICKNESS

6 WALL THICKNESS Defining optimum wall thicknesses while designing parts for the Liquidmetal® process plays a critical role in achieving desired part quality results. There are two process elements that are tied to wall thickness specifications. The first is related to the flow characteristics of the material during molding and the second is achieving the final desired material properties. Liquidmetal alloys' excellent mechanical properties are dependent upon achieving targeted cooling rates once the material has been injected into the mold cavities. As wall thicknesses increase beyond limits that can be rapidly cooled, crystallization can occur which is undesirable and can diminish the physical properties of the material. Thin walls are most likely to be amorphous in the final part. However, if wall thicknesses become too thin, the material can freeze prematurely and impede complete filling of the mold cavity. In general, wall sectional thicknesses of parts designed for Liquidmetal alloys should be in the range of 0.6mm to 4.0mm. The optimal thickness for molding characteristics and resulting physical properties of the material is 1.0mm to 1.5mm. While thicker and thinner sections beyond these regions are technically possible, the molded part quality and physical properties may be affected. Liquidmetal alloys exhibit high yield strength. This property is achieved in the as-molded part without any post molding heat treatments, as is necessary with conventional crystalline metallic alloys. Also, since there is no phase

39 RADII & FILLETS

transformation that takes place during the cooling of the material, there is no post molding distortion from residual stress. Both of these process attributes often eliminate the need for other geometric features such as ribs and 7 supporting features. Due to the high yield strength of the alloy; it is not necessary to include ribs or other supporting features within the part. Since there is no warping of the RADII & FILLETS material after the part is removed from the mold, holding the part within Liquidmetal® alloy is quite viscous in the molten state during the injection tolerance does not become dependent on additional support throughout the molding process, and because of this material property, it is important to part. include large, generous radii whenever possible. It is possible to achieve a sharp edge or corner, but this must be done along a parting line or other ® Liquidmetal engineers use specialized and sophisticated mold-flow or fluid- mold component intersection such as a slide mechanism. Part designers flow simulation software to assist customers with design reviews for candidate should be aware that in regions where they specify a sharp edge, there parts. Simulation results are used to validate part designs, ensure an optimal would be a corresponding sharp in the tool. Again, due to the viscosity of the cavity layout, and determine the number of cavities that can be incorporated material during molding and rapid cooling during the molding process there into a single shot. may be more irregularity in the appearance of the edge. By including radii, corners will look more consistent across the entire part. The preferred minimum radius for the Liquidmetal molding process is 0.25mm. Whenever possible, you should increase the radii size to further improve the molded and aesthetic part quality. Radii of 0.5mm and larger are ideal and will improve the molding process significantly. Utilizing a larger radius will also help increase tool life, aid in release of the part from the tool, and improve the surface finish of the final part. It is also important to note that larger radii and fillets strengthen a part by eliminating stress risers.

41 HOLES AND SLOTS

8 HOLES & SLOTS Holes, slots, irregular depressions, or cored-out shapes in your part design are readily achievable with the Liquidmetal® molding process. However, some small features may translate into fragile injection mold components, which require higher levels of mold maintenance and expense. Designers should carefully consider the following guidelines when specifying smaller internal part features that would require delicate tooling components. Generally, you should keep the depth-to-diameter or depth-to-width ratio within 2:1. That is, the diameter or width of a hole should be no less than half of its depth. It is also important to apply draft to holes whether they are through-holes or blind holes. Reference the chapter on draft requirements in this design guide for suggested draft angles. When designing intersecting internal geometric features, such as two meeting holes with centerlines at 90 degrees apart for example, it is important to design your part such that the use of mold components with flats on the mating surfaces can be accomplished.

43 THREADS

It is critical to avoid mating complex surfaces that require high-precision finished shut-off surfaces to prevent unwanted flash and tool wear. Mating 9 complex shut-off surfaces cost more to produce and are also very expensive to maintain. Utilizing flat and simple mating features or shut-off surfaces of the mold components improves mold up-time and reduces maintenance in THREADS production. Threads can be produced in Liquidmetal® parts, but there are important design considerations that must be followed to accommodate the molding ® Liquidmetal engineers are always available to provide additional design process. This design guide will discuss both internal and external threads, assistance when you are uncertain about specific part-design conditions and which require different design considerations. their impact on mold fabrication and maintenance costs. External threads can generally be molded directly into the part with no special requirements as long as the mid-plane of the threads is located along the parting line of the mold. Unscrewing mechanisms do not work with the Liquidmetal process as the material shrinkage interferes with their function. To ensure that parting line witness and potential molding flash does not impact the functional quality of the threads, flats are highly recommended 180 degrees apart on both sides of the part along the parting line. These flats should form a three degree drafted surface beginning 0.125mm below the minor diameter of the thread.

45 SURFACE FEATURES & TEXTURING

The approach to producing internal threads varies with the size specification of the thread. Because 0.4% material shrinkage occurs during the molding process, unscrewing threaded cores are not a viable option. For small 10 threads with major diameters <15mm, threaded inserts can be mechanically pressed into blind holes in the part—similar to what is commonly done in plastic parts. Liquidmetal® Technologies has produced many applications successfully with this concept. Minimum pull-out force specifications of SURFACE FEATURES >20Kgf are possible. Alternatively, machined stainless steel inserts can be laser welded in place to provide substantially greater pull-out strength. Keep & TEXTURING ® in mind that threaded bushings of this type are more costly than common A variety of finishes can be applied to Liquidmetal parts. The various threaded brass inserts. surfaces range from as-molded to tumbled, sand-blasted, polished, physical vapor deposition (PVD), and painted alternatives. One of the most Large internal threads with major diameters >15mm can potentially be remarkable features of the Liquidmetal process is its ability to provide an as- produced with collapsible threaded cores, but overall part geometry and molded brilliant finish of 2µin to 4µin (0.05µm to 0.1µm) surface roughness. its effect on mold cavity layout and mold construction must be carefully This is simply accomplished by polishing the mold cavity surfaces to the considered. Liquidmetal engineers can provide design assistance in these desired finish of the final part. cases to ensure a successful outcome. Sandblasting is a low cost alternative for a matte or satin metallic finish. Surface finishes with greater complexity tend to cost more as the primary driver of cost associated with these treatments is the time spent producing them. As is the case with plastic injection molding, there is an endless array of possibilities for surface features. Everything from logos to diamond and straight knurling is possible. There are no other known molding processes that can provide this level of design flexibility in high-strength, as-molded, metal components. In many metalworking technologies, especially machining, these special surface features must be added by additional or secondary operations, which adds cost to the final part.

47 MOLDING BEHAVIOR & PART AESTHETICS

11 MOLDING BEHAVIOR & PART AESTHETICS MATERIAL FLOW Amorphous metal alloys are quite viscous when compared to other molten metals. The closest comparison is plastics in an injection molding process. Of course, Liquidmetal® materials are molded at much higher temperatures than plastics. The viscosity of the Liquidmetal alloy is dependent on both the injection temperature and the strain rate that the material undergoes as it fills the mold cavities. Due to this material property, our alloys can be injected at a rate that allows for a laminar flow. In many cases, this helps improve the cosmetic qualities of the part. Caution should be exercised when designing large parts with very thin sections where final aesthetics are important. In these situations, it will be necessary to inject the material into the mold cavities at a higher rate, which could impact the aesthetics with flow lines becoming evident in the finished part. Flow lines generally do not have any appreciable dimensions and they do not represent any material strength concerns in the final part. Since the material is fairly viscous during the molding process, it tends to follow the path of least resistance, which are the regions of greatest part thickness. For this reason, it is important to minimize changes in cross- sectional thickness throughout the part. Doing so will avoid unwanted flow

49 MOLDING BEHAVIOR & PART AESTHETICS

characteristics and will help eliminate molding defects. While cross-sectional temperature, velocity, and strain rate combine to make this area undergo thickness transitions are not always possible to avoid, Liquidmetal® engineers the greatest amount of heat checking. Depending on the design of the part, can assist your design validation process by conducting flow simulations. different sub-insert materials may be used in the tool to help reduce the This can help ensure a desirable process outcome prior to fabricating an growth of erosion on the cavity steel. One such material that can be used is expensive injection mold. beryllium copper. GATING SHRINKAGE AND SINK MARKS The molten amorphous metal requires channels to travel from the entrance Amorphous metal parts undergo a very small amount of shrinkage during of the mold to the part cavities. As in plastics, these channels are known as the molding process (around 0.4%), which proves to be an advantage when it runners. Where the runner meets the part is known as the gate. Once the comes to holding tight part tolerances and achieving good repeatability from part has cooled in the mold, the gate is removed from the part with one of a part to part. Depending on the geometry of the part, it is possible to see sink variety of possible operations including, water-jet cutting, CNC machining, or marks on the surface. There are certain design steps that can be taken to by breaking the part off at the runner system. Often the best gating locations avoid sink marks: are large flat surfaces of the part. Surfaces selected for gating should not be cosmetic surfaces. It is also important to remember to gate into the thicker 1. Design the part with a nominal wall thickness of 1.0mm to 1.5mm. sections of the part, as filling the mold cavity from thick to thin sections is 2. Design the part so that as the material flows into the part geometry, it critical to achieving optimum part quality. fills from the thicker sections to the thinner sections of the part. It is also best to avoid gating on a complex surface (curved or otherwise). 3. Provide gradual transitions from thick to thin sections, including Failing to heed this advice will make it more difficult to blend the final part generous radii and fillets. Avoid abrupt or stepped transitions. perfectly without noticeable evidence of gating. PARTING LINE AND WITNESS MARKS HEAT CHECKING Where the two halves of the mold meet is known as the parting line. Liquidmetal’s molding process involves injecting material at high temperatures Placement of the parting line relative to the part geometry is crucial for into mold cavities made from hardened die-steel that is at a relatively low ensuring an easily molded part design and successful part function. comparative temperature. This causes significant temperature fluctuations After molding, the parting line will likely leave a small witness mark. in the mold cavity steel that can promote heat checking or micro-cracking Generally, this witness can be on the order of 0.075mm, or 0.003in. The of the cavity surface over time. The most highly effected zones are typically position of the witness line should be selected so that it does not interfere with just inside the part where the gate is located. At this region in the part, the

51 EJECTION

the part’s intended function or aesthetics. Slides or other moving mold parts will also exhibit these same characteristics wherever they shut off on other mold components. 12 Ejector pins will also have witness marks. Ejector pins should be set slightly proud so witness marks are sub-flush on the actual molded part. EJECTION At the conclusion of the Liquidmetal® molding cycle, parts are ejected from the mold by movable components such as ejector pins and lifters. A small circular witness mark is left where the pin contacts the part, known as an ejector pin witness.

53 UNDERCUTS

During the design phase of the mold for your part, Liquidmetal® engineers will advise you on the optimal size and location of ejector pins to ensure that the part is safely removed from the mold. Some simple part geometries can 13 be designed with little to no ejection, but will require much increased draft angles so that they can be released easily from the mold. Smooth ejection is a critical aspect of manufacturing a Liquidmetal part. UNDERCUTS Because of the tremendous strength of the Liquidmetal parts immediately External undercut features such as holes, slots, profiled grooves, and other after molding, straight, clean ejection is important to avoid stress and drag on geometric shapes can be readily produced by using a slide mechanism in mold surfaces. the mold. This is just one of many part design advantages offered by the Liquidmetal® process. Including undercut features in the mold design can eliminate the need for costly post molding operations such as slot grinding or machining. When designing undercuts, proper draft and radii must be included to (Left) Ejector pins are located in various ensure that slide mechanisms can be retracted from the part without causing locations to push the molded part out as straight as possible to avoid stress and damage to the part or mold. When applying draft angles, identify the drag on the mold surfaces. direction that the slide will be pulled away from the part and apply draft from that angle. Internal undercuts that have no direct line of sight from the outside of the part are much more difficult to produce in the mold. In some cases, it is possible to use collapsible cores. However, the use of collapsible cores is dependent on the size of the feature. Internal undercut features requiring collapsible cores will add additional expense to the mold fabrication process.

55 OVERMOLDING

14 OVERMOLDING Overmolding is a technique that is often used to enhance part designs and provide additional function to an otherwise single material component. A few examples of overmolding are in applications that require ergonomics, sealing, insulation, and even safety. Insert overmolding has been performed on Liquidmetal® parts many times over the years. Overmolding Liquidmetal parts usually entails placing the processed Liquidmetal part into a secondary mold that then fills plastic or rubber over, around, and through the Liquidmetal part. When overmolding Liquidmetal parts, special attention must be paid to the shut-off surfaces between the Liquidmetal part and the overmolding mold. This means that additional resources will be necessary to ensure that the tolerances on those surfaces are held to a high standard. Doing so will avoid flashing of the overmold material. With any overmolding application, adhesion to the substrate is the key factor that needs careful consideration during the original part design phase. Ribs, undercuts, and other mechanical interlocks will help improve the bond between the Liquidmetal part and the overmolded material. The design will need to be reviewed on a case-by-case basis to determine the best way to achieve optimal adhesion results.

57 (Left) Close-up view of how plastic flows around and through a precision molded Liquidmetal® component to achieve a strong mechanical connection. METAL OVERMOLDING Another overmolding technique that can be used with our process is to actually overmold a metal part that is inserted into the Liquidmetal® mold. There are a number of reasons to consider this technique such as: 1. Reduce part cost by minimizing the mass of amorphous metal material required for the part and increasing the number of parts that can be cast per shot. 2. Create larger parts by utilizing less of the amorphous metal material. 3. Increase amorphous content by reducing wall thickness and utilizing materials with a higher thermal conductivity than the tool steel used for molds. 4. Simplify post-processing of components by machining features out of more machinable metal such as aluminum, stainless steel, or some other non-amorphous metal material. 5. Improve cosmetics of a final part by optimizing wall thickness transitions throughout the part. 6. Provide superior material properties by possessing properties from both metals. To determine whether this type of technique will fit with your application, (Right) Liquidmetal component before please discuss the concept with a Liquidmetal engineer. and after the overmolding process. Clear resin is often used while optimizing the plastic overmolding.

59 POST PROCESSING ALTERNATIVES

15 POST PROCESSING ALTERNATIVES A wide array of post processing alternatives are available for Liquidmetal® parts should you want to achieve specific results outside of the basic requirement to de-gate parts after molding. Some of the more commonly applied post-processing techniques include bead and media blasting, machining, laser welding and e-beam joining, painting, gluing, and physical vapor deposition (PVD). BEAD & MEDIA BLASTING Bead blasting or media blasting is commonly used on many metal components to achieve varying degrees of satin finishes. This is also possible with Liquidmetal components. The process involves spraying hard media such as silica glass, ceramic, and various metals under high pressure and high velocities at the surface of the targeted metal parts. By altering the media type, size, and velocity, a varying degree of surface finishes can be achieved. While one of the unique benefits of the Liquidmetal process and its alloys is the ability to achieve brilliantly fine surface finishes, some applications require subtle or low reflectivity appearances. In these cases, media blasting is a relatively low-cost approach to achieving those results.

61 POST PROCESSING ALTERNATIVES

MACHINING Machining is one approach used to remove gates and runners from Liquidmetal® parts, but it can also be applied to generate additional features or achieve dimensional tolerances that may not be possible with the Liquidmetal molding process alone. Liquidmetal alloys are hard after molding, but not impossible to machine. In fact, Liquidmetal parts can be (Right) Example CNC readily machined using the appropriate equipment and cutting tools. Our machining center for processing ® engineering team is available for advice and suggestions should you want to Liquidmetal parts. apply machining techniques on your own. (Below) Example of a media blasted satin finish part, next WELDING to a Liquidmetal ingot used for Welding is a joining process commonly used to build larger structures out of molding. smaller components. Welds provide the strength, efficiency, versatility, and economic advantages necessary to build the myriad of structures and objects all around us—bridges, skyscrapers, automobiles, boats, oil rigs, jewelry, sculptures, and more. Because amorphous metal formation requires specific critical cooling rates, the part size and thickness are limited; however, these limitations can be overcome with welding. Liquidmetal alloy can be welded to itself and dissimilar metals (such as titanium, aluminum, and stainless steel), though the methods are still being optimized. Our engineering team will work with you to develop the optimal methods, offering more flexibility in part design and performance, and increased opportunities for high-performance assemblies.

63 (Below) Three main regions of a micrograph are observed: base material, heat affected zone, and fusion zone. The fusion zone looks identical to the base material with mostly amorphous content, POST PROCESSING ALTERNATIVES while the heat affected zone has only minimal crystallization (darker particles).

PAINTING & PVD As with parts made from other metalworking technologies, Liquidmetal® parts can readily be painted with a range of traditional techniques and can also be processed through PVD processes. Painting requires the same cleaning and surface preparation other metal parts require such as removing oils and primering bare metal surfaces. Care should be taken to avoid extended paint baking cycle temperatures above 250°C. PVD processes are used to apply high-purity coatings such as titanium, chromium, and aluminum to metal parts. In the PVD process, these coating materials are either evaporated by (Above) Electron beam welded butt-joint of the 3.6 mm wide necked region of tensile specimen. heat or bombarded with ions (sputtering). While the PVD coating metal is being vaporized, a reactive gas is introduced which forms a compound with (Below) Figure 8. E-beam weld microhardness of Liquidmetal® alloy shows most featureless joint. the metal vapor and is deposited on the metal parts as a thin and highly adherent coating. Various coatings can provide a range of characteristics including, high hardness, wear resistance, corrosion resistance, chemical and temperature resistance, and other properties.

(Below) Electron beam welded butt-joint of 9.6 mm wide plates. The weld beaded up in the 3.6 mm wide specimen while the weld was mostly flush with the two parent plates of 9.6 mm width.

(Right) Examples of painted Liquidmetal components.

(Next Page) Examples of PVD (physical vapor deposition) coatings on Liquidmetal components.

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Liquidmetal® Technologies – Corporate 30452 Esperanza • Rancho Santa Margarita, CA 92688 • 949.635.2100 www.liquidmetal.com