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利用EBSD技术对不同应变速率下单向拉伸高锰TRIP钢中的马氏体相变进行了观察,使用XRD数据计算了奥氏体(g),hcp马氏体(e-M)和bcc马氏体(a′-M)的体积分数,并对g→e-M和e-M→a′-M两阶段相变的变体选择进行了理论计算.结果表明,高速拉伸时TRIP行为仍然具有取向依赖性,这是由不同取向g晶粒内a′-M变体的机械功差异引起的.应变速率的提高促进e-M→a′-M转变,但总的马氏体转变量降低,即高速拉伸抑制了TRIP效应.TRIP钢静态拉伸时a′-M变体选择较强,动态拉伸时变体选择减弱.静态拉伸时,<111>g和<100>g晶粒内a′-M变体选择可用局部应力对变体做功来计算.高速拉伸时,需结合应力对a′-M变体做功大小及应变能、界面能来分析这些g晶粒内的变体选择规律.与1个a′-M变体单独出现相比,一对具有特殊取向关系的变体同时出现,可以降低变体的应变能,使得不利变体能够出现.
The martensitic transformations in uniaxially stretched high manganese TRIP steels with different strain rates were observed by EBSD technique. The XRD data were used to calculate the martensitic transformation of austenite (g), hcp martensite (eM) and bcc Marsh (A’-M) volume fraction, and the theoretical calculations were carried out on the choice of two-phase transitions of g → eM and eM → a’-M. The results show that the TRIP behavior is still oriented at high speed , Which is caused by the difference in mechanical work of a’-M variants in different orientation g grains.The improvement of strain rate promotes the transformation of eM → a’-M, but the total amount of martensitic transformation decreases, that is, high-speed drawing TRIP effect was restrained.TRIP steel static tensile a’-M variant selection is strong, dynamic tensile deformation options weakened.When static stretching, <111> g and <100> g grain a’- M Variant Selection The available local stress is used to calculate the work of the variant.When drawing at high speed, the work size and strain energy of a’-M strain need to be combined with the stress, and the interface can analyze the variation selection rules of these g grains. A pair of variants that have a particular orientation relationship appear concurrently with one a’-M variant alone, reducing the strain’s strain energy so that unfavorable variants can appear.