11 - CIVE 2700 Civil Engineering Materials, Winter 2007...

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CIVE 2700 – Civil Engineering Materials, Winter 2007 1 Phase Diagrams Professor George Hadjisophocleous, Ph.D., P.Eng. Carleton University Department of Civil and Environmental Engineering Ottawa, Ontario CIVE 2700 – Civil Engineering materials, Winter 2007, 2.2 Objectives • Learn solidification process and its impact on material properties • Learn how to use phase diagrams
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CIVE 2700 – Civil Engineering Materials, Winter 2007 2 CIVE 2700 – Civil Engineering materials, Winter 2007, 2.3 Outline • Solidification • Phases • Phase diagrams CIVE 2700 – Civil Engineering materials, Winter 2007, 2.4 Introduction • Metals polymers and glass are generally formed by solidification from melts. • Solidification of glasses does not involve crystallization because molecules and atoms cannot rearrange to an ordered structure before solidification is complete. • With fast cooling rates most substances can form glassy substances. • The process of rapid cooling is called vitrification.
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CIVE 2700 – Civil Engineering Materials, Winter 2007 3 CIVE 2700 – Civil Engineering materials, Winter 2007, 2.5 Introduction • When crystals form from a molten mass, the time temperature curve shows a plateau, which lasts for the duration of solidification (due to the deliberation of heat during crystallization; latent heat of fusion) Time Temperature Freezing or melting point CIVE 2700 – Civil Engineering materials, Winter 2007, 2.6 Single Component Systems • Temperature-time curves do not provide information on the different phenomena that take place during the solidification process. • Phase diagrams provide useful information about melting, casting, crystallization and other phenomena. • Phase diagrams are used to show phases present under different temperatures and pressures.
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CIVE 2700 – Civil Engineering Materials, Winter 2007 4 CIVE 2700 – Civil Engineering materials, Winter 2007, 2.7 Single Component Systems • Point A corresponds to ambient temperature and pressure indicating that the substance is a solid under ambient conditions with a ! crystal structure. • Raising the temperature to T b the solid changes to an " crystal structure, Point B (polymorphic transformation). At temperature T
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11 - CIVE 2700 Civil Engineering Materials, Winter 2007...

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