Crystallographic Study of Diffusion Phase Transformations for Martensites with Complex Structure

有一个美丽的唯象理论的无扩散相变称为马氏体相变的晶体学，这是由韦克斯勒-利伯曼-里德和鲍尔斯-麦肯齐发展。然而，仍然存在合金，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，并得到马氏体相变的统一观点。在Ni-Al合金中发现了B_2 → ~（14）M（~ 7 R）相变，在Au-49.5at%Cd合金中发现了β_2（B_2）→ zeta_2 '（三角）相变。首先，我们发现唯象晶体学理论适用于B2-> 14 M转变。研究了该合金的自适应性，提出了一种新的基本形貌，即平行四边形形貌，而不是以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10 M（15 M）和12 M（36 M），这在其他合金中也没有发现。对于后者Au-49.5at%Cd合金，我们测定了50年来未测定的zeta_2 '马氏体结构。在β_2->zeta_2'变换中，Ledbetter假设存在晶格不变切变，而Tadaki等人则认为存在晶格不变切变.在本研究中，我们发现两种类型的马氏体形态称为屋顶型和人字形，其中前者具有晶格不变的剪切，而后者没有。因此，我们调和了两个研究者之间的巨大矛盾。从以上结果可以看出，只要晶格不变量切变选取正确，唯象晶体学理论即使对结构复杂的马氏体也适用。

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.