材料的相变研究及其应用

Fe-C和Fe-X-C合金马氏体相变热力学的研究成果使结构钢的Ms温度能以热力学预测。建立了铜基合金及Fe-Mn-Si基合金马氏体相变热力学，为铜基和铁基形状记忆合金的成分和工艺设计提供基础。提出了含ZrO2陶瓷Ms温度的热力学计算方法，以及其母相晶粒大小影响Ms的正确表达式，对陶瓷的生产和工业应用都具有意义。修正马氏体变温相变动力学方程，显示低碳钢中影响碳扩散系数的合金元素影响残余奥氏体量，这有利于低碳马氏体组织钢的开发。GCr15轴承钢中残余奥氏体→马氏体的等温动力学研究显示：钢经淬火后，再进行等温处理以形成很少量的等温马氏体，再作回火，提高钢件的尺寸稳定性（经1000d后与淬火-回火比较，在接触疲劳寿命并不降低的条件下（达34%。研究了Ni-Ti、Cu-Zn-Al、Fe-Mn-Si基合金及ZrO2陶瓷的马氏体相变及其逆相变特征，揭示了影响这些材料形状记忆效应（SME）的一些因素，并指出了改善SME的途径，有利于这些材料的开发应用。贝氏体相变的热力学研究，观察到生长台阶，母相强化对相变影响的研究以及内耗测量结果，均显示贝氏体相变属扩散型机制。Cu-Zn-Al中加入阻碍Zn和Al扩散的合金元素可能提高形状记忆使用寿命。揭示CeO2-ZrO2中存在贝氏体相变，并与其出现脆性有关。Cu-Zn中β相有序化研究对有序化合金的应用具有实际意义。三元合金spinodal分解判据的建立，对借spinodal分解呈现高阻尼或高强度合金的开发颇具价值。由群论导出呈现晶体学可逆性的条件为形成单变体马氏体。应用孤立子于相变的形核-长大模型初见成效。

Studies on PhaseTransformations and Their Applications in Materials Engineering

The results of studies on thermodynamics of martensitic transformation in Fe-C and Fe-X-C alloys lead the Ms temperature in structural steels to be predicted. Establishing thermodynamics of martensitic transformation in Cu- and Fe-Mn-Si based alloys built the basis of composition and processing design for Cu- and Fe- based shape memory alloys. The thermodynamic approach for calculation of Ms in ZrO2 containing ceramics and corrected formula expressing the effect of parent grain size on Ms were suggested. The revised kinetics equation of a thermal martensitic transformation shows that alloying element varying the diffusion coefficient of carbon in low-carbon steels would affect the amount of the retained austenite and it will be beneficial for the exploitation of steels with microstructure of lath martensite. Research on the isothermal kinetics of the retained austenite→martensite in GCrl5 ball bearing (AISI 52 100) steel indicates that the dimensional stability (as comparison to specimen treated by traditioinal quenching and tempering) increases 34％ in specimen treated by an isothermal holding in order to form a few percent of isothermal martensite from the retained austenite after quenching and followed by normal tempering and the contact fatigue life is not reduced. Studies of characteristics of martensitic transformations and their reverse transformations in Ni-Ti, Cu-Zn-Al, Fe-Mn-Si based alloys and ZrO2 containing ceramics reveal the factors affecting the shape memory effect (SME) and indicate the way to improve the SME as well as the exploitation of these materials. Thermodynamics study of bainitic transformation, observation of the growth ledge, studies on the effect of parent strengthening on transformations and the results of internal friction measurements all display that the bainite formation is controlled by diffusion. Addition of alloying elements hindering the diffusion of Zn and Al in Cu-Zn-Al may improve the SME and its service life. There exists the hainitic transformatioin in CeO2-ZrO2 and it relates to the appearance of brittleness in ZrO2 containing ceramics. Research on the ordering of β phase in Cu-Zn is significant for the application of alloy with ordered phase. The presentation of the criterion of spinodal decomposition in ternary alloys may be valuable for the development of alloys exhibiting high damping capacity or high strength by means of spinodal decomposition. Group theory is successfully utilized in crystallography of phase transformation. The required condition for the appearance of crystallography reversibility derived from group theory is the formation of single variant martensite. It seems effective that the soliton is introduced in the nucleation and growth model in phase transformation.