Guided Learning 2 - Materials engineering science processing and design 3rd edition Copyright(c)2014 Michael Ashby Hugh Shercliff David Cebon

Guided Learning 2 - Materials engineering science...

This preview shows page 1 - 8 out of 38 pages.

Materials: engineering, science, processing and design, 3rd edition Copyright (c)2014 Michael Ashby, Hugh Shercliff, David Cebon
Materials: engineering, science, processing and design, 3rd edition Copyright (c)2014 Michael Ashby, Hugh Shercliff, David Cebon Metallic alloy Mixture of a metal with other metals or non-metals; ceramics too can be mixed to form a ceramic alloy Components The chemical elements that make up alloys Binary alloy Alloy containing two components, ternary alloys contain three, quaternary four, and so on Concentration Defines the amount of components in weight or atomic %
Materials: engineering, science, processing and design, 3rd edition Copyright (c)2014 Michael Ashby, Hugh Shercliff, David Cebon Phase All parts of an alloy microstructure with the same atomic structure are a single phase In a binary alloy, the solid microstructure takes one of three forms A single solid solution Two separated solutions A chemical compound, with a separated solid solution Solid solution A solid in which one or more elements are dissolved in another so that they are homogenously dispersed at an atomic scale
Materials: engineering, science, processing and design, 3rd edition Copyright (c)2014 Michael Ashby, Hugh Shercliff, David Cebon Constitution of an alloy Phases present Weight fraction of each phase Composition of each phase Thermodynamic equilibrium The constitution is stable and there is no further tendency for it to change Equilibrium constitution State of lowest Gibbs free energy for a given composition, temperature, and pressure U – internal energy p – pressure V – volume T - temperature H (U+pV) – enthalpy S - entropy
Materials: engineering, science, processing and design, 3rd edition Copyright (c)2014 Michael Ashby, Hugh Shercliff, David Cebon Figure GL2.1 Phase diagram Diagram with temperature and composition as axes, showing the equilibrium constitution Liquidus line Phase boundary that limits the bottom of the liquid field Solidus line Phase boundary giving the upper limit of the single-phase solid field
Materials: engineering, science, processing and design, 3rd edition Copyright (c)2014 Michael Ashby, Hugh Shercliff, David Cebon Figure GL2.2 Isomorphous phase diagram Simplest possible example where the solid-state is a solid solution for all compositions This behavior is unusual because there is almost always a limit to how much one element can be dissolved in another
Materials: engineering, science, processing and design, 3rd edition Copyright (c)2014 Michael Ashby, Hugh Shercliff, David Cebon Figure GL2.3 Solubility limit composition at which an element will no longer dissolve in another element at a given temperature The figure shows a phase diagram for sugar and water A point is reached where no more sugar will dissolve A similar point exists where sugar cannot absorb any more water These are saturated solutions and is characteristic of mixtures of two equilibrium phases, both of which are solutions Saturation limits for both phases rise with increased temps

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture