Phase Transformations in Metals and Alloys
Phase Transformations in Metals and Alloys
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DOI：
10.1146/annurev.ms.03.080173.001551
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发表时间：
1973-08
期刊：
影响因子：
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通讯作者：
G. Meyrick;G. W. Powell
中科院分区：
文献类型：
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作者：
G. Meyrick;G. W. Powell
理解相变涉及对其发生的原因以及其发生的模式的理解。本文将不再探讨前者，只是注意到如果系统的自由能减少，则系统可以自发地经历相（或相）的变化。如果自由能增加，跃迁的产物不一定是属于平衡态的产物。一个总的变化可能直接产生平衡态，也可能经过一条由几个涉及亚稳相的转变组成的路径。这一点，再加上一个给定的变化可以通过一个以上的动力学机制产生模态竞争来完成的事实，赋予相变及其后果的研究以复杂性，使其如此有趣。相变由于其固有的魅力以及在材料应用中的性能控制中起着特别重要的作用而受到广泛的研究。从最近对该领域的一些调查（1-3）中可以看出，习惯上将表现出共同特征的变化组合在一起，以便以系统的方式对相变进行分类。分类的标准主要是形态特征，但也包括或暗示机械过程。这一过程导致了公认的群体名称的建立：1。连续沉淀，2.巨大的转变，3.不连续沉淀，4.马氏体转变，5.贝氏体相变; 6.有序-无序转换，和7.亚稳分解由于对本综述的长度的初始限制，这里将不考虑有序-无序变换和旋节分解，但Wayman（4）在本系列的前一卷中已经讨论过它们。连续沉淀的特征在于新相的晶界和晶内颗粒的形成，其通常具有结构，
Understanding a phase transformation involves an appreciation of the reasons for its occurrence and of the mode or modes by which it takes place. The former will not be explored herein beyond noting that a system can spontaneously undergo a change in phase (or phases) if by so doing its free energy is reduced. Provided a reduction in free energy ensues, the product of the transition need not be that pertaining to the equilibrium state. A total change may yield directly the equilibrium state or traverse a path composed of several tranformations involv ing metastable phases. This, combined with the fact that a given change can be accomplished by more than one kinetic mechanism generating modal competi tion, endows the study of phase transformations and their consequences with the complexities that render it so intriguing. Phase transitions have received exten sive investigation because of their inherent fascination and because they play a particularly important role in property control for material applications. As can be seen from some of the more recent surveys of the field (1-3) it is customary to group together changes that exhibit common characteristics in an effort to classify phase transformations in a systematic manner. Criteria involved in classification are predominantly of morphological character but also include, or imply, mechanistic processes. This process has led to the establishment of accepted group names: 1. continuous precipitation, 2. massive transformations, 3. discontinuous precipitation, 4. martensitic transformations, 5. bainitic trans formations, 6. order-disorder transformations, and 7. spinodal decomposition. Because of an initial restriction on the length of this review, order-disorder transformations and spinodal decomposition will not be considered here, but they have been discussed by Wayman (4) in a previous volume of this series. Continuous precipitation is characterized by the formation of grain boundary and intragranular particles of the new phase, which generally has a structure and