上海交通大学：《材料热力学》教学资源_2014课件_lecture 17 Phase diagram IV

Contents of Today S.J.T.0. Phase Transformation and Applications Page 1/34 Review previous Examples Ternary system Review of phase diagrams etc. SJTU Thermodynamics of Materials Fall 2011 X.J.Jin Lecture 17 Phase Diagram IV

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2011 © X. J. Jin Lecture 17 Phase Diagram IV Page 1/34 Contents of Today Review previous Examples Ternary system Review of phase diagrams etc

Summary of Binary Phase Diagrams S.J.T.0. Phase Transformation and Applications Page 2/34 ① ② ③ 4 I- ⑤ ⑥ ⑦ x 图6-25二元相图的7种基本类型 SJTU Thermodynamics of Materials Fall 2011 @X.J.Jin Lecture 17 Phase Diagram IV

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2011 © X. J. Jin Lecture 17 Phase Diagram IV Page 2/34 Summary of Binary Phase Diagrams

Ternary Phases Reaction in Binary Systems ww S.J.T.0. Phase Transformation and Applications Page 3/34 表6-1二元系的各种三相平衡反应 转变类型 反应式 图型特征 共晶转变 I-a+B 共析转变 Y=a+8 a 、B 共晶型 偏晶转变 h=h+a h a 熔晶转变 6=l+y Y 包晶转变 I+B-a a 包晶型 包析转变 Y+8=a B a 合晶转变 l+h=a a 、2 SJTU Thermodynamics of Materials Fall 2011 @X.J.Jin Lecture 17 Phase Diagram IV

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2011 © X. J. Jin Lecture 17 Phase Diagram IV Page 3/34 Ternary Phases Reaction in Binary Systems

相图的用处 S.J.T.0. Phase Transformation and Applications Page 4/34 处理系统是多种物质的复杂系统 -相律 一相图 说明系统在不同条件下以哪几相共存；当温 度、压力、组成改变时会出现什么相变化 各相存在的范围，相变发生的条件等 探索新材料 分析合金组织、化学成分、制定生产和热处理工艺的重 要依据！ SJTU Thermodynamics of Materials Fall 2011 X.J.Jin Lecture 17 Phase Diagram IV

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2011 © X. J. Jin Lecture 17 Phase Diagram IV Page 4/34 相图的用处 • 处理系统是多种物质的复杂系统 – 相律 – 相图 说明系统在不同条件下以哪几相共存；当温 度、压力、组成改变时会出现什么相变化 各相存在的范围，相变发生的条件等 探索新材料 分析合金组织、化学成分、制定生产和热处理工艺的重 要依据！

相图的用处2 S.J.T.0. Phase Transformation and Applications Page 5/34 区域熔炼提纯 M 液相 析出固溶体杂质的含 固溶体 量比平衡液相的少 20B 图5-15 区域熔炼示意图 SJTU Thermodynamics of Materials Fall 2011 @X.J.Jin Lecture 17 Phase Diagram IV

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2011 © X. J. Jin Lecture 17 Phase Diagram IV Page 5/34 相图的用处 2 区域熔炼提纯 析出固溶体杂质的含 量比平衡液相的少

相图的用处3 S.J.T.0. Phase Transformation and Applications Page 6/34 估算热力学数据，如 熔化热 -从相图上查出一定成 分的合金系统中，作 LT-T) 为溶剂的金属熔点降 XB 低了多少度，然后用 RTR 稀溶液凝固点下降的 依数性公式，即可估 算溶剂金属的摩尔熔 化焓 SJTU Thermodynamics of Materials Fall 2011 @X.J.Jin Lecture 17 Phase Diagram IV

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2011 © X. J. Jin Lecture 17 Phase Diagram IV Page 6/34 相图的用处 3 • 估算热力学数据，如 熔化热 – 从相图上查出一定成 分的合金系统中，作 为溶剂的金属熔点降 低了多少度，然后用 稀溶液凝固点下降的 依数性公式，即可估 算溶剂金属的摩尔熔 化焓 2 ( ) m m B RT L T T x − =

相图的用处4 S.J.T.0. Phase Transformation and Applications Page 7/34 Weight Percent Cedmium ·求出活度数据 列442℃ 一在两相共存区，某组 分在这两个共存相中 的化学势应相等 (cd) 4an（sln)=as ALomie Percent Cadmium Lp(sIn)=+RTIn am =M+RTIn ap AG=LBx(D)-H(s) T→Tm Solid->liquid AG=△Hm-TASm=△Hm(I- T SJTU Thermodynamics of Materials Fall 2011 ©X.J.Jin Lecture 17 Phase Diagram IV

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2011 © X. J. Jin Lecture 17 Phase Diagram IV Page 7/34 相图的用处 4 • 求出活度数据 – 在两相共存区，某组 分在这两个共存相中 的化学势应相等 D * ( ) ( ln) Bi Bi s μ s = μ Bi Bi Bi Bi l Bi (sln) RT ln a RT ln a * ( ) 0 μ = μ + = μ + ΔG = Bi l − Bi s T →Tm * ( ) * μ ( ) μ (1 ) m m m m T T ΔG = ΔH −TΔS = ΔH − Solid -> liquid

二元例题1 ww S.J.T.0. Phase Transformation and Applications Page 8/34 10.用相律判断下列相图是否正确？说出理由。 B B B B UB● (4) (1) (2) (3) 图中A及B是纯物质，l指液态，a、B及Y均是固熔体。 SJTU Thermodynamics of Materials Fall 2011 @X.J.Jin Lecture 17 Phase Diagram IV

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2011 © X. J. Jin Lecture 17 Phase Diagram IV Page 8/34 二元例题 1

Liquid Liquid S.J.T.0. Phase Transformation and A L+a L+B 29/34 L+a L+B B a+B a+B B A B A Mole fraction of B,xB→ Mole fraction of B,xB-> (a) (b) Liquid Liquid L+B 个 L+x L+Y a+L B+Y +B a+B B A B Mole fraction of B,xB→ Mole fraction of B,xB-> SJTU (c) (d)

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2011 © X. J. Jin Lecture 17 Phase Diagram IV Page 9/34

二元例题2b S.J.T.0. Phase Transformation and Applications Page 10/34 Molar Gibbs free energy of What is the most stable state solution,drawn at T and P of the system at an average constant for an a phase and composition of Xo? B phase. · Suppose the a-phase was somehow prevented from forming (i.e., consider the B-phase equilibrium under the a-phase constraint that the a-phase is absent).In this case,what would be the equilibrium state of the system with average composition X,？ SJTU Thermodynamics of Materials Fall 2011 @X.J.Jin Lecture 17 Phase Diagram IV

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2011 © X. J. Jin Lecture 17 Phase Diagram IV Page 10/34 二元例题 2b • What is the most stable state of the system at an average composition of X0? • Suppose the α-phase was somehow prevented from forming (i.e., consider the equilibrium under the constraint that the α-phase is absent). In this case, what would be the equilibrium state of the system with average composition X0? Molar Gibbs free energy of solution, drawn at T and P constant for an α phase and β phase