形变温度对FeMnSiCrNiC合金第二相方向性析出及记忆效应的影响

Effects of Deformation Temperature on the Directional Precipitation of Second Phase and SME in an FeMnSiCrNiC Alloy

摘要:

基于控制第二相方向性析出提高铁基合金形状记忆效应的构想，研究了不同形变温度对Fe13.53Mn4.86Si8.16Cr3.82Ni0.16C合金g/e界面（母相g与诱发马氏体e之间界面）的数量和结构及随后时效第二相析出的数量和方向性的影响，以及第二相析出的数量和方向性对马氏体相变和形状记忆效应的影响。扫描电镜分析显示，形变温度远高于Ms时，无g /e界面产生，时效后第二相析出少；形变温度接近Ms时，产生大量g /e界面，时效后析出第二相数量很多，且方向性良好；形变温度进一步接近Ms时，g /e界面交叉，导致时效后方向性的第二相也交叉。透射电镜分析显示，析出方向性Cr23C6第二相的合金再次进行预变形时，产生的应力诱发马氏体具有单一方向。原因在于方向性Cr23C6及其产生的应力场对马氏体相变产生约束作用，避免马氏体片之间的交叉，使其具有更好的可逆转变性。

Abstract:

Based on the principle that the aligned precipitation of second phase can improve shape memory effect (SME), the following effects were investigated, including the effects of different deformation temperatures on the amount and the structure of g /e interface, on the amount and orientation of the second precipitation phase after subsequent aging, and the effects of whick on the martensite transformation and SME. The SEM analysis shows that no g /e interfaces were produced after deformation at the temperature far higher than Ms , and few carbides precipitated after ageing. Much more g /e interfaces were produced after deformation at temperature near Ms , and much more directional carbides precipitated after ageing. With further decreasing the deformation temperature to Ms, some g /e interfaces intersected and carbides precipitated along different directions after ageing. TEM analysis shows that the thick stress-induced martensite plates had the uniform orientation in the 5% preformed alloys with orientationaly precipitated carbides. The reason is that Cr23C6 and strain fields produced by Cr23C6 will restrain martensite transformation and avoid the intersection among martensite plates thus remarkably improve the reversibility of stress-induced martensite.