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A Case For Liquidmetal® Alloys

A new material and process is making its introduction into the manufacturing realm. Could Liquidmetal alloys be the answer to many of your manufacturing difficulties? See how the material stacks up against similar materials and processes. And explore new ways of approaching small, complex part design.

When developing a new design, designers of metal components must always consider the manufacturing methods available to them. At the same time, they must consider the geometric possibilities and material characteristic needs for the particular functional and performance requirements of the application they are designing for. This is not always a simple task.

Other manufacturing options

If dimensional precision is needed, CNC machining could be the solution. While precision is certainly available with this process, it generally comes with elevated cost - particularly when high levels of part complexity are also needed. Investment casting, die-casting, and metal injection molding (MIM) all provide good levels of part complexity, but each has a limitation that designers need to consider.

Investment casting, for example, yields higher levels of dimensional variation (in the range of +/- 0.5% of a given feature size). However, it also produces generally rough surface finishes and is limited in the feature details it can provide on small, complex parts. Often, investment cast parts are machined to achieve fine feature details, tolerances, and surface finish needs. These operations all add incremental costs to the final product. Investment cast parts are also subject to internal voids, which can negatively impact process yields. Die-casting provides excellent part complexity, but Why choose the Liquidmetal? is limited to a small range of metals - all of which have inferior physical properties in comparison to A combination of an unusual metal alloy with most stainless and low alloy steels. Excessive flash highly useful properties, and a shape forming is also common among die-cast components. process common to plastic components. This As a result, secondary finishing operations are provides a new set of possibilities for metal parts frequently required. Dimensional control is better fabrication and component designs not previously with die-casting than investment casting, but possible with other metalworking technologies. not nearly as good as production machining processes. For many applications, secondary machining operations are required.

MIM offers significant part complexity in a wide range of metal alloys, but the early promise of it becoming a true net-shape process has not If you need 2 or more been met. Dimensional control with MIM is also better than investment casting, but cannot of the items below, you compete with discrete machining processes. Furthermore, dimensional variation increases likely have a Liquidmetal with part dimension size. This is primarily due to the multiple process steps required to produce application MIM parts. Compounding metal powders with polymer binders for injection molding, de-binding to remove the sacrificial binders, and sintering to consolidate the metal powders into the final Exceptional dimensional control and desired part shape are the primary sources of repeatability variation. The large percentage of shrinkage that occurs from the molded part size to the as- sintered, or final, part size, combined with the Excellent corrosion resistance effects of gravity and surface tension during the large size transition in sintering, contribute unique dimensional control and shape retention Brilliant surface finish challenges. Part-to-part consistency varies enough that a large percentage of MIM parts require secondary operations to achieve required final High Strength dimensions and part shape.

The list of metalworking technologies is long and High Elastic limit goes well beyond the three processes mentioned. Others include Swiss screw machining, stamping, High hardness, scratch & wear fine blanking, cold heading, roll forming, resistance powdered metal, forging, spray forming and many others. Non-magnetic

Complex shapes that can be molded Precision As you can see from the data, the Liquidmetal process provides significantly high levels of With the Liquidmetal process, there is finally precision and repeatability, far better than many a production metal forming technology with other metal forming technologies. Consider the dimensional control and repeatability that rivals challenge to produce the part geometry used in production machining processes, without the this study with other manufacturing technologies associated costs and material scrap. Liquidmetal such as MIM/PIM, investment casting, die casting, alloy LM106c features a molding process with an cold forming, forging, and stamping. Furthermore, incredibly small amount of shrinkage (0.25%). add in the as-molded surface finish capabilities of Liquidmetal technology, and you have additionally In a recent study, a total of 128 parts (32 per complicated matters for competing technologies. cavity), which can be seen on the back cover of this paper, from a four cavity sales sample mold Having excellent dimensional control provides were inspected. The four measurements are many advantages to the metal part designer. plotted below. Those advantages include: greater design flexibility, better fit between assembled Each cavity plot includes the calculated six-sigma components, more precise part performance, capability of that cavity. Additionally, the combined improved overall product performance, ability to six sigma capability across all four cavities insert mold reliably for downstream conjoining of (128 parts) was calculated and plotted. The materials, and reduced stack-up tolerances among colored lines in each of the following four charts parts in an assembly. represents the individual cavities and the solid black line represents the combined six sigma plot for all four cavities.

40 120 σ Cavity 1 = 3.74µm 3σ =11.23µm _ 6σ =22.32μm σ Cavity 2 = 2.75µm _ σ Cavity 1 = 2.06µm 35 χ =41.79mm χ =2.27mm σ Cavity 3 = 4.66µm 100 σ Cavity 2 = 2.06µm σ Cavity 4 = 4.35µm 6σ =80.46µm σ Cavity 3 = 2,93µm 30 σ All Parts = 13.41µm _ σ Cavity 4 = 1.45µm 3σ =11.23µm χ =41.81mm 80 σ All Parts = 3.72µm 25 _ 3σ =4.34μm χ =41.80mm 3σ =13.98µm _ _ (χ) (χ) χ χ =2.27mm 20 _ =41.83mm 60 χ ,σ 3σ =6.17μm =41.80mm ˚

χ,σ 3σ =6.18μm φ

φ 15 3σ =13.05µm 40 3σ =8.80μm _ χ =2.27mm 10 _ χ 20 =2.27mm 5 _ χ =2.27mm 0 0 41.74 41.76 41.78 41.80 41.82 41.84 41.86 2.255 2.260 2.265 2.270 2.275 2.280 2.285 2.290 Dimension (mm) Dimension (mm) Chart Y: Capability data for the 41.81mm dimension. Chart Y: Capability data for the 2.27mm dimension.

60 4.0 σ Cavity 1 = 0.10˚ σ Cavity 1 = 3.00µm 6σ =0.6˚ σ Cavity 2 = 0.06˚ 50 σ Cavity 2 = 2.30µm 3.5 3σ =5.38μm σ Cavity 3 = 0.09˚ σ Cavity 3 = 1.96µm 3σ =5.88μm σ Cavity 4 = 1.79µm 3.0 σ Cavity 4 = 0.05˚ _ 40 σ All Parts = 11.28 µm σ All Parts = 0.10˚ 3σ =6.89μm χ =89.87˚ _ _ _ χ 2.5 χ =20.81mm χ =20.82mm 30 =20.79mm

(χ) 6σ =67.68 μm (χ) 3σ =8.99μm

,σ _ 2.0 ,σ ˚

χ ˚ φ =20.81mm 3σ =0.16˚ 3σ =0..17˚ 20 _ φ χ =20.80mm 1.5 _ _ χ χ 10 =89.80˚ =89.96˚ 1.0 3σ = 0.27˚ 3σ =0.31˚ _ _ χ =89.92˚ 0 .5 χ =89.82˚

0 20.76 20.78 20.80 20.82 20.84 20.86 89.4 89.6 89.8 90.0 90.2 Dimension (mm) Dimension (degrees) Chart Y: Capability data for the 20.81mm dimension. Chart Y: Capability data for the 90º angle. Corrosion Resistance Total dissolution concentration (PPM)

LM106c alloy provides impressive corrosion 1N HCL 1N H SO resistance compared to materials like 316 2 4 Stainless Steel, traditionally thought of as go-to materials for applications in corrosive SS-316 SS-316 environments. When tested against 316 SS in 3600 500 hydrochloric acid and sulfuric acid solutions, LM106c significantly outperformed 316 SS in both Liquidmetal Liquidmetal cases (see the table to the right). 250 100

The superior corrosion resistance of Liquidmetal is advantageous in a variety of markets and NaOH pH13 Seawater industries. Possible applications include: automotive decorative and harsh environment applications, aerospace, defense applications, SS-316 SS-316 dental, industrial equipment, food processing 0 0 equipment components, marine, medical devices, sporting equipment components for outdoor Liquidmetal Liquidmetal applications, and more. 0 0

In addition to corrosion resistance, the chart below summarizes LM106c’s biocompatibility test results.

TEST RESULT

ISO 10993 Cytotoxicity Pass (Non-cytotoxic) Sensitzation Pass (Non-sensitizing) Irritation or Intracutaneous Reactivity Pass (Non-irritating) Systemic Toxicity (acute) Pass (Non-systemic-toxic) • Material Mediated Pyrogenicity Test • Pass • Acute Systemic Toxicity Test, 2 Extracts • Pass

Nickel Release As-molded Pass Blasted and Passivated Pass

Surface Finish like all other metal alloys, so inherent material characteristics, such as grain boundaries, do not The Liquidmetal process produces a surface influence the reflective properties that can be roughness down to 0.05 Ra μm, an equally achieved. impressive property. This value cannot be achieved through any other process without secondary With Liquidmetal, specifying excellent surface operations, such as: superfinishing, lapping or finish does not force any trade-offs. For example, polishing. you don’t need to give up dimensional control or corrosion resistance to achieve the desired surface In some applications, reflective properties finish. Liquidmetal alloy and the injection molding are important. The as-molded surface finish process allow all the properties to be taken of Liquidmetal alloy provides good specular advantage of simultaneously. reflection. w

However, Liquidmetal can also be polished, but sees unique results due to its amorphous structure. The material does not have a crystalline structure

Ra μm 50 25 12.5 6.4 3.2 1.6 .8 .4 .2 .1 .05 .025 .012 ST Liquidmetal Less Frequent MIM Common Die Casting

Investment Casting

Sand Casting

RSE Superfinishing

Lapping

Polishing

ETL UTT Grinding

Turning

Milling

2000 1000 500 250 125 64 32 16 8 4 2 1 .5 Ra μIn Elasticity, strength, and hardness

As shown to the right, the properties of LM106c are comparable or superior to the properties of a variety of other materials from varying process technologies.

With Liquidmetal, now you can combine the strength of heat-treated 420 Stainless Steel, with the corrosion resistance of 316 Stainless Steel, a surface finish of 0.05 Ra μm, and a 20% reduction in mass over stainless or steel alloys – with no trade-offs.

A particularly unique property of LM106c is its high level of elasticity (1.6%, as a percentage of its original shape). This property can provide particular advantages in certain applications that other materials cannot. Examples include:

• A medical device could flex under stress, but not plastically deform. • A pressure transducer housing that requires repeated flexure without plastic deformation or work-hardening. • A precision spring that requires a highly repeatable force when stressed to a given dimension.

These applications are made possible by Liquidmetal alloy - a new material that can provide new solutions or solve problems where a solution did not previously exist.

Not to be forgotten, LM106c’s as-molded hardness (47 Rockwell C) is competitive with post-processed and heat-treated stainless steels. Distinct to Liquidmetal alloy, the hardness value is consistent through the material, not just on the surface. As a result, applications of wear, or components requiring scratch resistance can benefit from Liquidmetal. Magnetism and RF shielding Conclusion

Liquidmetal alloy is classified as “non-magnetic” The broad range of valuable material properties and behaves like paramagnetic materials. As a creates an even greater range of application very mildly diamagnetic alloy, in the presence opportunities from Liquidmetal alloy. Part of an external magnetic field it generates a geometry sophistication is not always needed with very small response field which opposes the the expansive material properties available. With a primary field. Generally speaking, it is very process developed around an advanced injection weakly attracted to a magnetic force, and is often molding technology, part applications are nearly compared with certain austenitic stainless steel limitless. alloys. Part complexity similar to plastic components Liquidmetal alloy cannot be magnetized and with impressive material properties gives design cannot be caused to retain any magnetism they engineers options previously unavailable, may be exposed to. impossible, or economically impractical with metal parts production. The chart below demonstrates that Liquidmetal alloy is not an efficient electromagnetic shielding material and is actually quite transparent to RF radiation when compared to ferrous materials with similar densities and strengths. However, with a large enough wall-thickness and Faraday cage designs, it is possible to create a barrier for weak signals if necessary. Housings for magnetic switch applications, components in MRI equipment, or applications involving high RF power are applications that could benefit from this property.

DIAMAGNETIC SIGNATURE OF LIQUIDMETAL ALLOY

1.E+03 LM106c Skin Depth (mm) 1.E+02 Copper Skin Depth (mm) 1.E+01 Steel Skin Depth (mm)

1.E+00

1.E-01 Skin (mm) Depth

1.E-02

1.E-03

1.E-04

1.0E+00 1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08 1.0E+09 1.0E+10 Electromagnetic Radiation Frequncy (Hz) (949) 635-2100 liquidmetal.com v12-1/6/20