DOCSLIB.ORG

Section 1 Introduction to Alloy Phase Diagrams

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Section 1 Introduction to Alloy Phase Diagrams Copyright © 1992 ASM International® ASM Handbook, Volume 3: Alloy Phase Diagrams All rights reserved. Hugh Baker, editor, p 1.1-1.29 www.asminternational.org Section 1 Introduction to Alloy Phase Diagrams Hugh Baker, Editor ALLOY PHASE DIAGRAMS are useful to exhaust system). Phase diagrams also are con- terms "phase" and "phase field" is seldom made, metallurgists, materials engineers, and materials sulted when attacking service problems such as and all materials having the same phase name are scientists in four major areas: (1) development of pitting and intergranular corrosion, hydrogen referred to as the same phase. new alloys for specific applications, (2) fabrica- damage, and hot corrosion. Equilibrium. There are three types of equili- tion of these alloys into useful configurations, (3) In a majority of the more widely used commer- bria: stable, metastable, and unstable. These three design and control of heat treatment procedures cial alloys, the allowable composition range en- conditions are illustrated in a mechanical sense in for specific alloys that will produce the required compasses only a small portion of the relevant Fig. l. Stable equilibrium exists when the object mechanical, physical, and chemical properties, phase diagram. The nonequilibrium conditions is in its lowest energy condition; metastable equi- and (4) solving problems that arise with specific that are usually encountered inpractice, however, librium exists when additional energy must be alloys in their performance in commercial appli- necessitate the knowledge of a much greater por- introduced before the object can reach true stabil- cations, thus improving product predictability. In tion of the diagram. Therefore, a thorough under- ity; unstable equilibrium exists when no addi- all these areas, the use of phase diagrams allows standing of alloy phase diagrams in general and tional energy is needed before reaching meta- research, development, and production to be done their practical use will prove to be of great help stability or stability. Although true stable equilib- more efficiently and cost effectively. to a metallurgist expected to solve problems in rium conditions seldom exist in metal objects, the In the area of alloy development, phase dia- any of the areas mentioned above. study of equilibrium systems is extremely valu- grams have proved invaluable for tailoring exist- able, because it constitutes a limiting condition ing alloys to avoid overdesign in current applica- from which actual conditions can be estimated. tions, designing improved alloys for existing and Common Terms Polymorphism.The structure of solid elements new applications, designing special alloys for and compounds under stable equilibrium condi- special applications, and developing alternative Before the subject of alloy phase diagrams is tions is crystalline, and the crystal structure of alloys or alloys with substitute alloying elements discussed in detail, several of the commonly used each is unique. Some elements and compounds, to replace those containing scarce, expensive, terms will be discussed. however, are polymorphic (multishaped); that is, hazardous, or "critical" alloying elements. Appli- Phases. All materials exist in gaseous, liquid, or their structure transforms from one crystal struc- cation of alloy phase diagrams in processing in- solid form (usually referred to as a phase), de- ture to another with changes in temperature and cludes their use to select proper parameters for pending on the conditions of state. State variables pressure, each unique structure constituting a dis- working ingots, blooms, and billets, fmding include composition, temperature, pressure, mag- tinctively separate phase. The term allotropy (ex- causes and cures for microporosity and cracks in netic field, electrostatic field, gravitational field, isting in another form) is usually used to describe castings and welds, controlling solution heat and so on. The term "phase" refers to that region polymorphic changes in chemical elements. treating to prevent damage caused by incipient of space occupied by a physically homogeneous Crystal structure of metals and alloys is discussed melting, and developing new processing technol- material. However, there are two uses of the term: in a later section of this Introduction; the allo- ogy. the strict sense normally used by physical scien- tropic transformations of the elements are listed In the area of performance, phase diagrams give tists and the somewhat looser sense normally used in the Appendix to this Volume. an indication of which phases are thermodynami- by materials engineers. Metastable Phases. Under some conditions, cally stable in an alloy and can be expected to be In the strictest sense, homogeneous means that metastable crystal structures can form instead of present over a long time when the part is subjected the physical properties throughout the region of stable structures. Rapid freezing is a common to a particular temperature (e.g., in an automotive space occupied by the phase are absolutely iden- method of producing metastable structures, but tical, and any change in condition of state, no some (such as Fe3C, or"cementite") are produced matter how small, will result in a different phase. at moderately slow cooling rates. With extremely For example, a sample of solid metal with an rapid freezing, even thermodynamically unstable apparently homogeneous appearance is not truly structures (such as amorphous metal "glasses") a single-phase material, because the pressure con- can be produced. dition varies in the sample due to its own weight Systems. A physical system consists of a sub- in the gravitational field. stance (or a group of substances) that is isolated In a phase diagram, however, each single-phase from its surroundings, a concept used to facilitate field (phase fields are discussed in a following study of the effects of conditions of state. "Iso- Ill section) is usually given a single label, and engi- lated" means that there is no interchange of mass neers often find it convenient to use this label to between the substance and its surroundings: The (a) (b) (c) refer to all the materials lying within the field, substances in alloy systems, for example, might regardless of how much the physical properties of be two metals, such as copper and zinc; a metal the materials continuously change from one part and a nonmetal, such as iron and carbon; a metal Fig. I Mechanical equilibria: (a) Stable. (b) Metas- of the field to another. This means that in en- and an intermetallic compound, such as iron and table. (c) Unstable gineering practice, the distinction between the cementite; or several metals, such as aluminum, 1*2/Introduction to Alloy Phase Diagrams magnesium, and manganese. These substances constitute the components comprising the system and should not be confused with the various quid) phases found within the system. A system, how- 4 ever, also can consist of a single component, such Solid 2 as an element or compound. Liquid / Solidus Phase Diagrams. In order to record and visual- ize the results of studying the effects of state variables on a system, diagrams were devised to show the relationships between the various I Ot phases that appear within the system under equi- Gas librium conditions. As such, the diagrams are variously called constitutional diagrams, equilib- f rium diagrams, or phase diagrams. A single- Temperature component phase diagram can be simply a one- or two-dimensional plot showing the phase changes in the substance as temperature and/or Fig. 2 Schematic pressure-temperature phase diagram pressure change. Most diagrams, however, are two- or three-dimensional plots describing the phase relationships in systems made up of two or more components, and these usually contain beled fields. Stable equilibrium between any two phases occurs along their mutual boundary, and fields (areas) consisting of mixed-phase fields, as Composition B well as single-phase fields. The plotting schemes invariant equilibrium among all three phases oc- A in common use are described in greater detail in curs at the so-called triple point, O, where the three boundaries intersect. This point also is Fig. 3 Schematic binary phase diagram showing mis- subsequent sections of this Introduction. cibility in both the liquid and solid states System Components. Phase diagrams and the called an invariant point because, at that location systems they describe are often classified and on the diagram, all externally controllable factors named for the number (in Latin) of components are fixed (no degrees of freedom). At this point, in the system: all three states (phases) are in equilibrium, but any The Gibbs phase rule applies to all states of changes in pressure and/or temperature will cause matter (solid, liquid, and gaseous), but when the Number of Name of one or two of the states (phases) to disappear. effect of pressure is constant, the rule reduces to: components system or diagrum Univariant Equilibrium. The phase rule says One Unary that stable equilibrium between two phases in a f=c-p+ 1 Two Binary unary system allows one degree of freedom (f= Three Temary 1 - 2 + 2). This condition, called univariant The stable equilibria for binary systems are sum- Four Quatemary equilibrium or monovariant equilibrium, is illus- Five Quinary marized as follows: Six Sexinary trated as lines 1, 2, and 3 separating the single- phase fields in Fig. 2. Either pressure or tempera- Seven Septenary Number of Number of Degrees of Eight Octanary ture may be freely selected, but not both. Once a components ph~es freedom Equilibrium Nine Nonary pressure is selected, there is only one temperature Ten Decinary that will satisfy equilibrium conditions, and con- 2 3 0 Invariant 2 1 Univariant versely. The three curves that issue from the triple 2 l 2 Bivariant point are called triple curves: line 1, representing Phase Rule. Thephase rule, first announced by the reaction between the solid and the gas phases, J. Willard Gibbs in 1876, relates the physical state is the sublimation curve; line 2 is the melting of a mixture to the number of constituents in the curve; and line 3 is the vaporization curve.
Load more

Recommended publications
  • Low Temperature Soldering Using Sn-Bi Alloys
    LOW TEMPERATURE SOLDERING USING SN-BI ALLOYS Morgana Ribas, Ph.D., Anil Kumar, Divya Kosuri, Raghu R. Rangaraju, Pritha Choudhury, Ph.D., Suresh Telu, Ph.D., Siuli Sarkar, Ph.D. Alpha Assembly Solutions, Alpha Assembly Solutions India R&D Centre Bangalore, KA, India [email protected] ABSTRACT package substrate and PCB [2-4]. This represents a severe Low temperature solder alloys are preferred for the limitation on using the latest generation of ultra-thin assembly of temperature-sensitive components and microprocessors. Use of low temperature solders can substrates. The alloys in this category are required to reflow significantly reduce such warpage, but available Sn-Bi between 170 and 200oC soldering temperatures. Lower solders do not match Sn-Ag-Cu drop shock performance [5- soldering temperatures result in lower thermal stresses and 6]. Besides these pressing technical requirements, finding a defects, such as warping during assembly, and permit use of low temperature solder alloy that can replace alloys such as lower cost substrates. Sn-Bi alloys have lower melting Sn-3Ag-0.5Cu solder can result in considerable hard dollar temperatures, but some of its performance drawbacks can be savings from reduced energy cost and noteworthy reduction seen as deterrent for its use in electronics devices. Here we in carbon emissions [7]. show that non-eutectic Sn-Bi alloys can be used to improve these properties and further align them with the electronics In previous works [8-11] we have showed how the use of industry specific needs. The physical properties and drop micro-additives in eutectic Sn-Bi alloys results in significant shock performance of various alloys are evaluated, and their improvement of its thermo-mechanical properties.
    [Show full text]
  • Recent Progress on Deep Eutectic Solvents in Biocatalysis Pei Xu1,2, Gao‑Wei Zheng3, Min‑Hua Zong1,2, Ning Li1 and Wen‑Yong Lou1,2*
    Xu et al. Bioresour. Bioprocess. (2017) 4:34 DOI 10.1186/s40643-017-0165-5 REVIEW Open Access Recent progress on deep eutectic solvents in biocatalysis Pei Xu1,2, Gao‑Wei Zheng3, Min‑Hua Zong1,2, Ning Li1 and Wen‑Yong Lou1,2* Abstract Deep eutectic solvents (DESs) are eutectic mixtures of salts and hydrogen bond donors with melting points low enough to be used as solvents. DESs have proved to be a good alternative to traditional organic solvents and ionic liq‑ uids (ILs) in many biocatalytic processes. Apart from the benign characteristics similar to those of ILs (e.g., low volatil‑ ity, low infammability and low melting point), DESs have their unique merits of easy preparation and low cost owing to their renewable and available raw materials. To better apply such solvents in green and sustainable chemistry, this review frstly describes some basic properties, mainly the toxicity and biodegradability of DESs. Secondly, it presents several valuable applications of DES as solvent/co-solvent in biocatalytic reactions, such as lipase-catalyzed transester‑ ifcation and ester hydrolysis reactions. The roles, serving as extractive reagent for an enzymatic product and pretreat‑ ment solvent of enzymatic biomass hydrolysis, are also discussed. Further understanding how DESs afect biocatalytic reaction will facilitate the design of novel solvents and contribute to the discovery of new reactions in these solvents. Keywords: Deep eutectic solvents, Biocatalysis, Catalysts, Biodegradability, Infuence Introduction (1998), one concept is “Safer Solvents and Auxiliaries”. Biocatalysis, defned as reactions catalyzed by bio- Solvents represent a permanent challenge for green and catalysts such as isolated enzymes and whole cells, has sustainable chemistry due to their vast majority of mass experienced signifcant progress in the felds of either used in catalytic processes (Anastas and Eghbali 2010).
    [Show full text]
  • The Basics of Soldering
    TECH SOLUTION: SOLDER The Basics of Soldering SUmmARY BY Chris Nash, INDIUM CORPORATION IN In this article, I will present a basic overview of soldering for those Soldering uses a filler metal and, in who are new to the world of most cases, an appropriate flux. The soldering and for those who could filler metals are typically alloys (al- though there are some pure metal sol- use a refresher. I will discuss the ders) that have liquidus temperatures below 350°C. Elemental metals com- definition of soldering, the basics monly alloyed in the filler metals or of metallurgy, how to choose the solders are tin, lead, antimony, bis- muth, indium, gold, silver, cadmium, proper alloy, the purpose of a zinc, and copper. By far, the most flux, soldering temperatures, and common solders are based on tin. Fluxes often contain rosin, acids (or- typical heating sources for soldering ganic or mineral), and/or halides, de- operations. pending on the desired flux strength. These ingredients reduce the oxides on the solder and mating pieces. hroughout history, as society has evolved, so has the need for bond- Basic Solder Metallurgy ing metals to metals. Whether the As heat is gradually applied to sol- need for bonding metals is mechani- der, the temperature rises until the Tcal, electrical, or thermal, it can be accom- alloy’s solidus point is reached. The plished by using solder. solidus point is the highest temper- ature at which an alloy is completely Metallurgical Bonding Processes solid. At temperatures just above Attachment of one metal to another can solidus, the solder is a mixture of be accomplished in three ways: welding, liquid and solid phases (analogous brazing, and soldering.
    [Show full text]
  • Robust High-Temperature Heat Exchangers (Topic 2A Gen 3 CSP Project; DE-EE0008369)
    Robust High-Temperature Heat Exchangers (Topic 2A Gen 3 CSP Project; DE-EE0008369) Illustrations of: (left) porous WC preform plates, (middle) dense-wall ZrC/W plates with horizontal channels and vertical vias. (Right) Backscattered electron image of the dense microstructure of a ZrC/W cermet. Team: Ken H. Sandhage1 (PI), Kevin P. Trumble1 (Co-PI), Asegun Henry2 (Co-PI), Aaron Wildberger3 (Co-PI) 1School of Materials Engineering, Purdue University, W. Lafayette, IN 2Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 3Vacuum Process Engineering, Inc., Sacramento, CA Concentrated Solar Power Tower “Concentrating Solar Power Gen3 Demonstration Roadmap,” M. Mehos, C. Turchi, J. Vidal, M. Wagner, Z. Ma, C. Ho, W. Kolb, C. Andraka, A. Kruizenga, Technical Report NREL/TP-5500-67464, National Renewable Energy Laboratory, 2017 Concentrated Solar Power Tower Heat Exchanger “Concentrating Solar Power Gen3 Demonstration Roadmap,” M. Mehos, C. Turchi, J. Vidal, M. Wagner, Z. Ma, C. Ho, W. Kolb, C. Andraka, A. Kruizenga, Technical Report NREL/TP-5500-67464, National Renewable Energy Laboratory, 2017 State of the Art: Metal Alloy Printed Circuit HEXs Current Technology: • Printed Circuit HEXs: patterned etching of metallic alloy plates, then diffusion bonding • Metal alloy mechanical properties degrade significantly above 600oC D. Southall, S.J. Dewson, Proc. ICAPP '10, San Diego, CA, 2010; R. Le Pierres, et al., Proc. SCO2 Power Cycle Symposium 2011, Boulder, CO, 2011; D. Southall, et al., Proc. ICAPP '08, Anaheim,
    [Show full text]
  • MICROALLOYED Sn-Cu Pb-FREE SOLDER for HIGH TEMPERATURE APPLICATIONS
    As originally published in the SMTA Proceedings. MICROALLOYED Sn-Cu Pb-FREE SOLDER FOR HIGH TEMPERATURE APPLICATIONS Keith Howell1, Keith Sweatman1, Motonori Miyaoka1, Takatoshi Nishimura1, Xuan Quy Tran2, Stuart McDonald2, and Kazuhiro Nogita2 1 Nihon Superior Co., Ltd., Osaka, Japan 2 The University of Queensland, Brisbane, Australia [email protected] require any of the materials or substances listed in Annex II (of the Directive) ABSTRACT • is scientifically or technical impracticable While the search continues for replacements for the • the reliability of the substitutes is not ensured highmelting-point, high-Pb solders on which the • the total negative environmental, health and electronics industry has depended for joints that maintain consumer safety impacts caused by substitution are their integrity at high operating temperatures, an likely to outweigh the total environmental, health investigation has been made into the feasibility of using a and safety benefits thereof.” hypereutectic Sn-7Cu in this application. While its solidus temperature remains at 227°C the microstructure, which A recast of the Directive issued in June 2011 includes the has been substantially modified by stabilization and grain statement that for such exemptions “the maximum validity refining of the primary Cu6Sn5 by microalloying additions period which may be renewed shall… be 5 years from 21 July of Ni and Al, makes it possible for this alloy to maintain its 2011”. The inference from this statement is that there is an integrity and adequate strength even after long term expectation that alternatives to the use of solders with a lead exposure to temperatures up to 150°C. In this paper the content of 85% or more will be found before 21st July 2016.
    [Show full text]
  • Lecture 15: 11.02.05 Phase Changes and Phase Diagrams of Single- Component Materials
    3.012 Fundamentals of Materials Science Fall 2005 Lecture 15: 11.02.05 Phase changes and phase diagrams of single- component materials Figure removed for copyright reasons. Source: Abstract of Wang, Xiaofei, Sandro Scandolo, and Roberto Car. "Carbon Phase Diagram from Ab Initio Molecular Dynamics." Physical Review Letters 95 (2005): 185701. Today: LAST TIME .........................................................................................................................................................................................2� BEHAVIOR OF THE CHEMICAL POTENTIAL/MOLAR FREE ENERGY IN SINGLE-COMPONENT MATERIALS........................................4� The free energy at phase transitions...........................................................................................................................................4� PHASES AND PHASE DIAGRAMS SINGLE-COMPONENT MATERIALS .................................................................................................6� Phases of single-component materials .......................................................................................................................................6� Phase diagrams of single-component materials ........................................................................................................................6� The Gibbs Phase Rule..................................................................................................................................................................7� Constraints on the shape of
    [Show full text]
  • Phase Diagrams
    Module-07 Phase Diagrams Contents 1) Equilibrium phase diagrams, Particle strengthening by precipitation and precipitation reactions 2) Kinetics of nucleation and growth 3) The iron-carbon system, phase transformations 4) Transformation rate effects and TTT diagrams, Microstructure and property changes in iron- carbon system Mixtures – Solutions – Phases Almost all materials have more than one phase in them. Thus engineering materials attain their special properties. Macroscopic basic unit of a material is called component. It refers to a independent chemical species. The components of a system may be elements, ions or compounds. A phase can be defined as a homogeneous portion of a system that has uniform physical and chemical characteristics i.e. it is a physically distinct from other phases, chemically homogeneous and mechanically separable portion of a system. A component can exist in many phases. E.g.: Water exists as ice, liquid water, and water vapor. Carbon exists as graphite and diamond. Mixtures – Solutions – Phases (contd…) When two phases are present in a system, it is not necessary that there be a difference in both physical and chemical properties; a disparity in one or the other set of properties is sufficient. A solution (liquid or solid) is phase with more than one component; a mixture is a material with more than one phase. Solute (minor component of two in a solution) does not change the structural pattern of the solvent, and the composition of any solution can be varied. In mixtures, there are different phases, each with its own atomic arrangement. It is possible to have a mixture of two different solutions! Gibbs phase rule In a system under a set of conditions, number of phases (P) exist can be related to the number of components (C) and degrees of freedom (F) by Gibbs phase rule.
    [Show full text]
  • Phase Transitions in Multicomponent Systems
    Physics 127b: Statistical Mechanics Phase Transitions in Multicomponent Systems The Gibbs Phase Rule Consider a system with n components (different types of molecules) with r phases in equilibrium. The state of each phase is defined by P,T and then (n − 1) concentration variables in each phase. The phase equilibrium at given P,T is defined by the equality of n chemical potentials between the r phases. Thus there are n(r − 1) constraints on (n − 1)r + 2 variables. This gives the Gibbs phase rule for the number of degrees of freedom f f = 2 + n − r A Simple Model of a Binary Mixture Consider a condensed phase (liquid or solid). As an estimate of the coordination number (number of nearest neighbors) think of a cubic arrangement in d dimensions giving a coordination number 2d. Suppose there are a total of N molecules, with fraction xB of type B and xA = 1 − xB of type A. In the mixture we assume a completely random arrangement of A and B. We just consider “bond” contributions to the internal energy U, given by εAA for A − A nearest neighbors, εBB for B − B nearest neighbors, and εAB for A − B nearest neighbors. We neglect other contributions to the internal energy (or suppose them unchanged between phases, etc.). Simple counting gives the internal energy of the mixture 2 2 U = Nd(xAεAA + 2xAxBεAB + xBεBB) = Nd{εAA(1 − xB) + εBBxB + [εAB − (εAA + εBB)/2]2xB(1 − xB)} The first two terms in the second expression are just the internal energy of the unmixed A and B, and so the second term, depending on εmix = εAB − (εAA + εBB)/2 can be though of as the energy of mixing.
    [Show full text]
  • Copper Alloys
    THE COPPER ADVANTAGE A Guide to Working With Copper and Copper Alloys www.antimicrobialcopper.com CONTENTS I. Introduction ............................. 3 PREFACE Conductivity .....................................4 Strength ..........................................4 The information in this guide includes an overview of the well- Formability ......................................4 known physical, mechanical and chemical properties of copper, Joining ...........................................4 as well as more recent scientific findings that show copper has Corrosion ........................................4 an intrinsic antimicrobial property. Working and finishing Copper is Antimicrobial ....................... 4 techniques, alloy families, coloration and other attributes are addressed, illustrating that copper and its alloys are so Color ..............................................5 adaptable that they can be used in a multitude of applications Copper Alloy Families .......................... 5 in almost every industry, from door handles to electrical circuitry to heat exchangers. II. Physical Properties ..................... 8 Copper’s malleability, machinability and conductivity have Properties ....................................... 8 made it a longtime favorite metal of manufacturers and Electrical & Thermal Conductivity ........... 8 engineers, but it is its antimicrobial property that will extend that popularity into the future. This guide describes that property and illustrates how it can benefit everything from III. Mechanical
    [Show full text]
  • Introduction to Phase Diagrams*
    ASM Handbook, Volume 3, Alloy Phase Diagrams Copyright # 2016 ASM InternationalW H. Okamoto, M.E. Schlesinger and E.M. Mueller, editors All rights reserved asminternational.org Introduction to Phase Diagrams* IN MATERIALS SCIENCE, a phase is a a system with varying composition of two com- Nevertheless, phase diagrams are instrumental physically homogeneous state of matter with a ponents. While other extensive and intensive in predicting phase transformations and their given chemical composition and arrangement properties influence the phase structure, materi- resulting microstructures. True equilibrium is, of atoms. The simplest examples are the three als scientists typically hold these properties con- of course, rarely attained by metals and alloys states of matter (solid, liquid, or gas) of a pure stant for practical ease of use and interpretation. in the course of ordinary manufacture and appli- element. The solid, liquid, and gas states of a Phase diagrams are usually constructed with a cation. Rates of heating and cooling are usually pure element obviously have the same chemical constant pressure of one atmosphere. too fast, times of heat treatment too short, and composition, but each phase is obviously distinct Phase diagrams are useful graphical representa- phase changes too sluggish for the ultimate equi- physically due to differences in the bonding and tions that show the phases in equilibrium present librium state to be reached. However, any change arrangement of atoms. in the system at various specified compositions, that does occur must constitute an adjustment Some pure elements (such as iron and tita- temperatures, and pressures. It should be recog- toward equilibrium. Hence, the direction of nium) are also allotropic, which means that the nized that phase diagrams represent equilibrium change can be ascertained from the phase dia- crystal structure of the solid phase changes with conditions for an alloy, which means that very gram, and a wealth of experience is available to temperature and pressure.
    [Show full text]
  • Alloys: Making an Alloy
    Inspirational chemistry 21 Alloys: making an alloy Index 2.3.1 2 sheets In this experiment, students make an alloy (solder) from tin and lead and compare its properties to those of pure lead. Equipment required Per pair or group of students: ■ About 2 g lead ■ About 2 g tin ■ Crucible ■ Pipe clay triangle ■ Bunsen, tripod and heatproof mat ■ Spatula ■ Carbon powder – 1 spatula per student ■ Tongs ■ 2 sand trays or sturdy metal lids ■ Sand ■ Access to a balance ■ Eye protection. Health and safety The most likely incident in this experiment is a student burning themselves so warn them that the equipment will be hot. Pouring molten metal can be hazardous if you are not sure how to use tongs correctly – it would be worth demonstrating how to use them safely. Some tongs in schools do not grip well. Every pair must be checked before the start of the experiment. Eye protection should be worn. Lead is a toxic metal. If it is heated for too long or too high above its melting point it could start to give off fumes. Ensure that the laboratory is well ventilated, warn students against breathing in the fumes given off by their sample during the experiment and tell them to heat the metals no longer than is necessary to get them to melt. 22 Inspirational chemistry Results Hardness testing should show clearly that the alloy is harder than the pure lead. The alloy can be used to scratch the lead convincingly. The lead does not leave a mark on the alloy. (Students may need to be reminded how to do this simple test – just try to scratch one metal with the other.) The density of the alloy should be less than that of the lead, but this test is fairly subjective.
    [Show full text]
  • Definition of Design Allowables for Aerospace Metallic Materials
    Definition of Design Allowables for Aerospace Metallic Materials AeroMat Presentation 2007 Jana Jackson Design Allowables for Aerospace Industry • Design for aerospace metallic structures must be approved by FAA certifier • FAA accepts "A-Basis" and "B-Basis" values published in MIL-HDBK-5, and now MMPDS (Metallic Materials Properties Development and Standardization) as meeting the regulations of FAR 25.613. OR • The designer must have sufficient data to verify the design allowables used. Design Allowables for Aerospace Industry • The FAA views the MMPDS handbook as a vital tool for aircraft certification and continued airworthiness activities. • Without the handbook, FAA review and approval of applicant submittals becomes more difficult, more costly and less consistent. • There could be multiple data submission for the same material that are conflicting or other instances that would require time consuming analysis and adjudication by the FAA. What is meant by A-Basis, B-Basis ? S = Specification Minimum • B-Basis: At least 90% of population A = T equals or exceeds value with 95% 99 confidence. B = T90 • A-Basis: At least 99% of population equals or exceeds value with 95% confidence or the specification minimum when it is lower. Æ Mechanical Property (i.e., FTY, et al) What is the MMPDS Handbook? • Metallic Materials Properties Development and Standardization • Origination: ANC-5 in 1937 (prepared by Army- Navy-Commerce Committee on Aircraft Requirements) • In 1946 the United States Air Force sanctioned the creation of a database to include physical and mechanical properties of aerospace materials. • This database was created in 1958 and dubbed Military Handbook-5 (or MIL-HDBK-5 for short).
    [Show full text]