Research on Phase Transformations and Microstructure Control with Emphasis of Grain Boundary Character of the Matrix

为了研究基体晶界特征对相变的影响，进行了以下两项实验研究。[1]研究了Ni-43%Cr合金晶界上BCC析出相的形态选择。当面心立方基体的晶界面在{111}面附近时，析出相的变体受到很大限制，并以{111}面为主导。另一方面，晶界平面远离{111}超过30度，未观察到主导变体。这些结果可以从晶界上形成的变体的成核活化能的观点来解释。[2]Fe-Ni-Mn合金中晶界作为马氏体形核中心的特征研究了马氏体体积分数小于0.01的相变初期晶界作为马氏体形核中心的特征。马氏体晶界的数量为15个，与总晶界（2504个）相比少得多。这表明，作为高效成核位点的晶界是高度有限的。ECP分析发现，作为形核点的晶界多为取向差角在12 °附近的小角晶界，其晶界面靠近{110}。

The following two experimental studies have been carried out to examine the effects of grain boundary character of the matrix on phase transformations.[1] Effect of grain boundary plane on the variant selection of grain boundary precipitates.Variant selection of BCC precipitates forming on grain boundaries was investigated in a Ni-43%Cr alloy. When the grain boundary planes of the FCC matrix is near {111} wthin 20 degrees, the variants of the precipites are highy limitted and the dominant variant is observed. On the other hand the grain boundary planes are far from {111} over 30 degrees, the dominant variant is not observed. These results can be explained from the viewpoint of activation energy for nucleation of the variants forming on the grain boundaries.[2] Character of grain boundaries acted as martensitic nucleation site in an Fe-Ni-Mn alloy.Character of grain boundaries acted as martensitic nucleation site was investigated in the initial stage of transformation where the volume fraction of martensite less than 0.01. The number of the grain boundaries with martensite was fifiteen and much fewer compared with the total baoundaries, 2504. This indicates that the grain boundaries as high potent nucleation sites is highly limited. It was found by ECP analysis that most of the grain boundaries acted as nucleation sites were low-angle boundaries with the misorientation angle near 12 degrees and the boundary planes of those were near {110}.