Crystallographic Study of Diffusion Phase Transformations for Martensites with Complex Structure

对于无扩散相变的结晶学有一个很好的现象学理论叫做马氏体相变，是由韦氏勒-利伯曼-里德和鲍尔斯-麦肯齐提出的。然而，仍有一些合金，其转变的晶体学尚未建立。本文的目的是对它们进行详细的研究，以获得马氏体相变的统一观点。我们在Ni-Al合金中发现了B2->14M（7R）转变，在Au-49.5at%Cd合金中发现了beta_2 (B2)->zeta_2'（三角）转变。首先，我们发现现象学晶体学理论适用于B2- >14m相变。对合金的自调节特性进行了研究，提出了一种新的基本形貌，称为“平行四边形形貌”，取代了之前提出的“金刚石形貌”。此外，在Ni-Al-Mn合金中，我们发现了新的马氏体组织，命名为10M（15M）和12M(36M)，这在其他合金中也没有发现。对于后一种Au-49.5at%Cd合金，我们确定了50年来未确定的zeta_2'马氏体结构。在beta_2->zeta_2’变换上，Ledbetter假设存在晶格不变剪切，Tadaki等人定义了存在。在本研究中，我们发现了两种类型的马氏体形态，即屋顶型和人字形型，其中前者具有晶格不变剪切，而后者则没有。因此，我们调和了两位研究者之间的巨大矛盾。从以上结果可以看出，如果正确选择晶格不变剪切，现象学晶体学理论甚至适用于具有复杂结构的马氏体。

There is a beautiful phenomenological theory for the crystallography of diffusionaless phase transformations called martensitic transformations, which were developed by Wechsler-Lieberman-Read and Bowles-Mackenzie. However, there still remain alloys, for which the crystallography of the transformations are still not yet established. It is the purpose of the present work to study them in detail, and to obtain the unified view for the martensitic transformations. We picked up B2->14M(7R) transformation in Ni-Al alloys and beta_2 (B2)->zeta_2'(trigonal) transformations in a Au-49.5at%Cd alloy as such cases. First, we found that the phenomenological crystallographic theory applies well for the B2->14M transformation. The self-accommodation of the alloy was also studied, and we proposed a new basic morphology called "the parallelogran morphology" instead of the previously proposed "diamond morphology". Furthermore, in Ni-Al-Mn alloys, we found new martensite structures designated as 10M(15M) and 12M(36M), which have not been found in other alloys either. For the latter Au-49.5at%Cd alloy, we determined the structure of the zeta_2' martensite, which have been undetermined for 50years. On the beta_2->zeta_2' transformation, Ledbetter assumed the presence of a lattice invariant shear, while Tadaki et al.deined the presence. In the present study, we found two types of martensite morphologies called roof-type and herring-bone type, in which the former has a lattice invariant shear while the latter does not. Thus, we reconciled the big inconsistency between the two researchers. from the above results, we conclude that the phenomenological crystallographic theory applies well even for the martensites with complex structures, if the lattice invariant shear is chosen correctly.