吉林大学《材料科学与工程基础》chapter10 Phase Diagrams2012.pptVIP

Chapter 10 Phase Diagrams Chapter 10Phase diagrams 第十章 相图 材料科学与工程(MSE)的整体概念材料科学基础的内容 Composition Synthesis Equilibrium Cooling （平衡冷却） Fig. Schematic representation of the development of microstructure during the equilibrium solidification of a 35 wt% Ni–65 wt% Cu alloy. composition C4 课外作业 读书思考 查出，并熟记Important Terms and Concepts的内容。 完成Learning Objectives中提及的任务。 读懂每个Example Problem，学会分析和计算程序，尤其是10.3和10.4 。 书面作业(下周交)： 10.17、10.32 10.44（自己查ZrO2-CaO相图，画在作业上分析） 10.53、10.65、10.69、10.70 Point f : ? All the ? phase will transform to pearlite cooling heating + Fe3C eutectoid ferrite Point e (Te): ? (0.022 wt% C) and ? (0.76 wt%C) No Virtual change ? ?+? ?+ heating cooling ? ?+Fe3C ? +P(eutectoid ferrite+Fe3C) At Te proeutectoid ferrite It will normally be present as a continuous matrix phase surrounding the isolated pearlite colonies. cooling Below Te Fig.10.32 Photomicrograph of a 0.38 wt% C steel having a microstructure consisting of pearlite and proeutectoid ferrite. 635?. Large, white regions correspond to the proeutectoid ferrite. For pearlite: The spacing between the ? and Fe3C layers varies from grain to grain some of the pearlite appears dark because the many close-spaced layers are unresolved at the magnification of the photomicrograph. SEM graph 3000? Shows microstructure of a plain carbon steel that contains 0.44 wt%C proeutectoid ferrite pearlite Dark layers: ferrite light layers: cementite During etching of the surface: The ferrite phase was preferentially dissolved Thus, the pearlite appears in topographical relief with cementite layers being elevated above the ferrite layers. 0.022 C0’ 0.76 C1’ ? composition (wt% C) Temperature Fig.10.33 a portion of the Fe-Fe3C phase diagram used in computations for relative amount of proeu- tectoid and pearlite microconstituents for hypoeut- ectoid(C0`) and hypereutectoid(C1`) compositions. Pearlite is the transformation product of austenite