共析钢形变诱导珠光体相变及渗碳体动态球化

Deformation induced pearlite transformation and dynamic spheroidization in a eutectoid steel

利用热模拟压缩变形实验研究了共析钢过冷奥氏体形变诱导珠光体相变的组织演变规律,探讨了不同形变量、形变速率、形变温度对诱导珠光体相变的影响。结果表明,由于应力的施加使相变动力学提前,诱导相变能够迅速的在形变的过程中发生,不同形变条件下组织呈现出动态演变的规律。提高形变量,增加了组织内的位错密度和相变驱动力,加速了相变的发生和渗碳体球化的进程;对于扩散控制型相变,降低形变速率增长了形变作用时间,碳原子能够得到充分扩散,有利于得到球化组织;在A1~Ar1温度间变形,形变温度降低,过冷度增加,球化时间延长,得到的渗碳体颗粒更为细小。因此高形变量、低形变速率、低形变温度三者均有利于得到超细晶复相组织（α＋θ）。同时研究发现,在形变的过程中存在先共析铁素体沿奥氏体晶界形核析出。

The microstructure evolution of a eutectoid steel during the deformation induced pearlite transformation of undercooled austenite was investigated by uniaxial hot compression simulation experiment.The effects of different deformation degree,deformation rates and deformation temperature on the deformation induced pearlite transformation were explored.The results indicate that the induced pearlite transformation can occur rapidly during the deformation,for the stress accelerates phase transition.With the increase of the deformation degree,the dislocation density and phase transition driving force in the microstructure are improved,accelerating the occurrence of phase transition and the process of cementite spheroidization.For the diffusion-controlled phase transition,the deformation rates decrease to prolong the deformation time,so the carbon atoms can diffuse sufficiently to obtain spheroidized cementite.At lower deformation temperature fromA1 to Ar1,significant refinement of the fragmentation of cementite occurs due to the increase of supercooling and spheroidized time.The ultrafine microstructure of cementite particles can be obtained through the high deformation degree,low deformation rates and low deformation temperature.It is also observed that the pro-eutectoid ferrite nucleates along the austenite boundary in the process of deformation.