Effects of Elastic Tensile and Compressive Stresses on Phase Transformations in Steels

为了获得贝氏体相变的组织控制信息和阐明贝氏体相变的机理，采用金相、显微和电阻率测量等方法研究了连续冷却过程中贝氏体相变的起始温度。（1）马氏体相变-在Fe-30 Ni和Fe-20 Ni钢中，拉伸应力促进相变。通过施加单位应力，Ms温度的增加与Patel和Cohen的理论值进行了比较。压应力的影响很小。在0.4C-4 Ni-0.25Mo钢中，拉应力和压应力的影响可以忽略不计。应力的影响为什么很小的原因仍然没有解决。看来今后有必要弄清楚Mo碳化物是否在冷却过程中析出，以及应力对相变的影响。（2）奥氏体→铁素体转变--在0.1C-5 Ni钢中，应力的影响较小。（3）贝氏体相变-在0.4C-2 Mo钢中，拉应力促进贝氏体相变，而压应力的影响很小。在0.4C-3 NI钢中，两种应力都促进相变，但拉应力的影响较大。观察到应力对贝氏体的长大也有影响。在0.01C-3 Mn-1Cr-0.0016B钢中，应力的影响太小而不能被注意到。在这种钢中，相变倾向于从表面区域发生并向内部区域生长。这种相变行为可能是由于应力对相变的影响很小。

In order to get information on microstructure controlling and elucidation of mechanism of bainitic transformation in steels, the starting temperature of the transformations during continuous cooling were examined through dilatometry, micrography and electric resistivity measurement.Results can be summarized as follows.(1)martensitic transformation---In Fe-30Ni and Fe-20Ni steels, the transformation is promoted by tensile stress. The increase in Ms temperature by the application of unit stress is comparing to the value from the theory by Patel and Cohen. The effects of compressive stress are small. In 0.4C-4Ni-0.25Mo steel, effects of tensile and compressive stresses are negligibly small. The reason why effects of stresses is very small has remained unsolved. It seems necessary in future to make clear whether Mo-carbide precipitates during cooling and affects the effects of stresses on the transformation.(2)austenite->ferrite transformation---In 0.1C-5Ni steel, effects of stresses are small.(3)bainitic transformation---In 0.4C-2Mo steel, tensile stress promotes the transformation, while effects of compressive stress are hardly recognized. In 0.4C-3NI steel, both stresses promote the transformation although the effects of tensile stress is larger. It is observed that stresses also affect to growth of bainite. IN 0.01C-3Mn-1Cr-0.0016B steel, effects of stresses are too small to be noticed. In this steel, the transformation tend to occur from surface region and grow to inner region. Such transformation behavior may be contributable to the very small effect of stresses on the transformation.