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Introduction of phasediagram

RUPESH MISHRAM-Tech final year

29/04/2013

Introduction of phasediagram

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outline

Introduction

Application of the phase diagram

The method to build a phase diagram experiments

CALPHAD approach

Challenge

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Introduction

A phase diagram is a type of chart used to show conditions at which

thermodynamically distinct phases can occur at equilibrium.

Common components of a phase diagram are lines of equilibrium or phase

boundaries, which refer to lines that mark conditions under which multiplephases can coexist at equilibrium. Phase transitions occur along lines of

equilibrium.

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Application

Phase diagrams are the foundation in performing basic materials research in

such fields as solidification, crystal growth, joining, solid-state reaction,

phase transformation, oxidation, etc.

On the other hand, a phase diagram also serves as a road map for materialsdesign and process optimization since it is the starting point in the

manipulation of processing variables to achieve the desired microstructures.

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examples

The composition and

melting temperature ofthe traditional SnPbsolder can be directlyobtained from the phasediagram

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examples

The upper temperatureof homogenization

treatment can be gained,besides, it can alsoshow the solidificationprocess of a certain alloy.

x1

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Determine the phase diagram Metallurgyneeds a lot of alloying samples

Diffusion couple (two-phase couple, multi-

components couple)often used todetermine the multi-component systems

measuring tools: EPMA, SEM, XRD(occasionally)

equilibrium

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CALculation of PHAse Diagrams

CALPHAD: common software

Thermo-Calc (founder: B. Sundman)

Pandat (founder: Y.A. Chang)

Lukas program (founder: H.L. Lukas)

ChemSage (founder: G. Eriksson)

FACT (founder: W.T. Thompson)

MTDATA (founder: A.T. Dinsdale)

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General progress of CALPHAD approach

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Rule to build the phase diagram

AA

BB

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Some models

For solution phase (LIQUID, FCC, BCC,HCP..)

ideal substitutional solution model

substitutional-regular solution model

associated model

quisi-chemical model

For IMCs stoichiometry compounds (Neumann-Kopp rule) Compounds with the homogeneity range (sublattice model)

Order-phase of the end member (depends)

Refs. H.L. Lukas, S.G. Fries and B. Sundman, Computational

thermodynamics, Cambridge University Press, NY, 2007

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Challenge

The fundamental experimental experiments are indispensable;

The accuracy of the outcomes deeply depend on the initialparameters inputted by users

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