上海交通大学：《材料热力学》教学资源_2010课件 lecture 16 phase diagram 3

Contents of Today S.J.T.U. Phase Transformation and Applications Page 1/40 Review previous Spinodal Points Compounds etc. Applications of phase diagrams Conclusion Remarks Examples SJTU Thermodynamics of Materials Spring2008©X.J.Jin Lecture 17 Phase Diagram Ill

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2008 © X. J. Jin Lecture 17 Phase Diagram III Page 1/40 Contents of Today Review previous Spinodal Points Compounds etc. Applications of phase diagrams Conclusion Remarks Examples

Review of Today S.J.T.U. Phase Transformation and Applications Page 2/40 。Immiscibility ·Spinodal Points ·Compounds Summary of Binary Phase Ternary Phases Reaction in Binary Systems ·二元相图构成的规则 SJTU Thermodynamics of Materials Spring2008©X.J.Jin Lecture 17 Phase Diagram Ill

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2008 © X. J. Jin Lecture 17 Phase Diagram III Page 2/40 Review of Today • Immiscibility • Spinodal Points • Compounds • Summary of Binary Phase • Ternary Phases Reaction in Binary Systems • 二元相图构成的规则

Binary System S.J.T.U. Phase Transformation and Applications Page 3/40 Degrees of freedom available in the system(F): F=C-P+1 F=C-P+2 F:the number of system variables that we may freely vary,or arbitrarily fix C:components P:phase C=2 P=1,F=2 单相区 P=2,F=1 平衡线包围的两相区 P=3,F=0 三相平衡线 SJTU Thermodynamics of Materials Spring2008©X.J.Jin Lecture 17 Phase Diagram Ill

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2008 © X. J. Jin Lecture 17 Phase Diagram III Page 3/40 Binary System Degrees of freedom available in the system (F): F: the number of system variables that we may freely vary, or arbitrarily fix C: components P: phase = − PCF + 2 C = 2 0,3 1,2 2,1 == == = = FP FP FP −= PCF +1 单相区 平衡线包围的两相区 三相平衡线

S.J.T.U. Phase Transformation and Applications Page 4/40 单元系 二元系 ·F=C-P+2=3-P ·F=C-P+1=3-P ·两相共存F=1 ·两相共存F=1 一给定温度或压力，体 给定温度或压力，体 系就已确定，因为两 系如果要确定，必须 相均为纯物质 给定两相中的组成， 即浓度 一多相平衡条件给出， SJTU Thermodynamics of Materials Spring2008©X.J.Jin Lecture 17 Phase Diagram Ill

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2008 © X. J. Jin Lecture 17 Phase Diagram III Page 4/40 单元系 • F=C-P+2=3-P • 两相共存F=1 – 给定温度或压力，体 系就已确定，因为两 相均为纯物质 二元系 • F=C-P+1=3-P • 两相共存F=1 – 给定温度或压力，体 系如果要确定，必须 给定两相中的组成， 即浓度 – 多相平衡条件给出

L m& BA B GA-GK m哈 m唱 a+B 「吸=咀 (T=T) 相变点 ug=u G (B) Q ② ① 公切线 温度 A 磴 唱 B (a)单元系(A) b)二元系(A-B) 图4.1单元系和二元系的两相平衡条件 (a)单元系中自由能的交叉点是平衡温度；(b)二元系中公切线的切点 ①和②是平衡成分 T.Nishizawa SJTU Thermodynamics of Materials Spring 2008 ©X.J.Jin Lecture 17 Phase Diagram Ill

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2008 © X. J. Jin Lecture 17 Phase Diagram III Page 5/40 T. Nishizawa

S.J.T.U. Te a Phase Transformation and Applications 0 固液完全互溶 的体系 d T 5 G (a) (b) SJTU Thermodynamics of Ma 图6-9两组元完全互溶的相图

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2008 © X. J. Jin Lecture 17 Phase Diagram III Page 6/40 固液完全互溶 的体系

Sn-Bi S.J.T.U. Phase Transformation and Applications Page 7/40 Weight Percent Bismuth 3040 60 60 70 90 100 3001 0 Sn中溶有 271,A42*℃ B形成固 250 23j,0681C L 溶体 200 自由度2 150 1699℃ 1和 0.8 100 (Bi) 溶解度变化很 50- 大！ 13C (aSn) 0 0 20 30 90 80 100 Sn Atomie Percent Bismuth i SJTU Thermodynamics of Materials Spring 2008 ©X.J.Jin Lecture 17 Phase Diagram Ill

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2008 © X. J. Jin Lecture 17 Phase Diagram III Page 7/40 Sn-Bi Sn中溶有 Bi形成固 溶体 自由度2 溶解度变化很 大！

Spinodal Points S.J.T.U. Phase Transformation and Applications Page 8/40 Spinodal points A special significance in the study of phase transformations 1050 =)a-0 1000 950 XB 900 850 Spinodal a2 RT 800 line XAXB 750 2 w口000 700 c1+g2 650 600 0.25 05 0.75 A 8 一 Figure 9.15 The miscibility gap,showing spinodal line. SJTU Thermodynamics of Materials Spring2008©X.J.Jin Lecture 17 Phase Diagram Ill

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2008 © X. J. Jin Lecture 17 Phase Diagram III Page 8/40 Spinodal points A special significance in the study of phase transformations 02) 11 ( 2 2 =−+= ⎟⎟⎠⎞ ⎜⎜⎝⎛ ∂∂ ϖ B T BA M xx RT xG 2ϖ RT xx BA = Spinodal Points

S.J.T.U. Phase Transformation and Applications ge9/40 Gibbs free energy of mixing curve is concave downward In this region the solution may begin the process of decomposition into the equilibrium phases by incremental changes in composition without increasing the total Gibbs free energy of the system. To the left of the spinodal point The transformation is discontinuous △Gm Spinodal point 8→ Figure 9.16 The relation between Gibbs free energy of mixing and composition on either side of spinodal point. To the right of the spinodal point The transformation is continuous XB SJTU Thermodynamics of Materials Spring2o08©X.J.Jin Lecture 17 Phase Diagram Ill

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2008 © X. J. Jin Lecture 17 Phase Diagram III Page 9/40 Gibbs free energy of mixing curve is concave downward In this region the solution may begin the process of decomposition into the equilibrium phases by incremental changes in composition without increasing the total Gibbs free energy of the system. To the left of the spinodal point The transformation is discontinuous To the right of the spinodal point The transformation is continuous xB

存在溶解度间隙的相图 S.J.T.U. Phase Transformation and Applications Page 10/40 非理想 1050 1000 规则溶液 950 900 850 1 Spinodal a2 相律 T 800 line 750 700 1+c2 650 600 0.25 0.5 0.75 A B→ Figure 9.15 The miscibility gap,showing spinodal line. SJTU Thermodynamics of Materials Spring 2008 ©X.J.Jin Lecture 17 Phase Diagram Ill

Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2008 © X. J. Jin Lecture 17 Phase Diagram III Page 10/40 存在溶解度间隙的相图 非理想 规则溶液 相律