材料热处理的进展和瞻望

Progress and Perspective in Materials Heat Treatment

概述材料热处理技术和原理的进展。钢中珠光体相变的晚近研究揭示 :α和Fe3 C与邻近晶粒γ1呈位向关系 ,但向γ2 晶粒生长 ;α和Fe3 C之间存在位向关系 ,由台阶长大 ;一个珠光体的领域中α或Fe3 C的分枝生长 ,形成另一领域。贝氏体相变存在切变和扩散两种机制 ,目前仍有分歧。马氏体相变的有些概念宜应更新 ,如Magee的动力学公式对低碳钢需加改进 ;有些成果须待利用 ,如GCr1 5(AISI 52 1 0 0 )钢残余奥氏体经等温马氏体形成 ,有利于钢件的尺寸稳定性。简述Al Cu合金时效技术和机制研究的进展以及系列时效合金的发现。介绍回火马氏体致脆的新机制———Fe3 C自马氏体析出和自残余奥氏体析出的相关过程 ,建议短时回火工艺及钢中加Ni以避免回火致脆。基于材料表面状态对疲劳寿命影响的认识 ,表面处理得以发展 ,在钢的渗碳中应用动态碳势控制能得到渗碳层碳浓度的理想分布。瞻望绿色热处理的推广 , 材料相变的理论和建模工作值得加以重视。简介以场变数描述显微组织 ,并根据相场理论作组织变化的模拟。

Progress in technology and theory of materials heat treatment is generally introduced. Late research on pearlitic transformation in steel revealed that there exist orientation relationships(OR) between α and γ 1 as well as Fe\-3C and γ 1 of neighbor grain but α and Fe 3C grow to the other grain γ 2. There also exists OR between α and Fe 3C and they grow by means of ledge. The branching of α or Fe 3C in a colony leads the formation of another colony. Debate on mechanism of bainite formation, i.e, it obeys shear or diffusional mechanism is still continuing. Some concepts of martensitic transformation ought to be altered, for example, the Magee's kinetics equation should be modified for low carbon steel. New results need to be utilized, such as the dimensional stability of GCr15 (AISI 52100) steel part would be improved by the formation of isothermal martensite from the retained austenite. Progress in ageing technique and research on mechanism of age hardening in Cu\|Al and developing a series of age hardening alloys is briefly presented. A new mechanism for embrittlement in tempered martensite )TME) is introduced, i.e, the related processes of Fe 3C precipitation from martensite and from retained austensite induce TME, and short time tempering process and addition of Ni element in steel are suggested in order to avoid tempered martensite embrittlement. Based on the recognization of effect the surface condition on fatigue life of materials, surface treatment develops consequently. An ideal carbon concentration profile in deep carburized layer can be obtained by using dynamic control techique for potential of carbon in carburization process. Perpective in green heat treatment is described. In addition, the theory and modeling in materials phase transformations are worthy to be emphasized. Description of microstructure through field variables and the simulation of structural change based of phase field theory are also briefly introduced.