珠光体对ZG120Mn13钢拉伸断裂过程的影响

为探究珠光体降低高碳高锰钢机械性能的原因,本文采用金相组织分析、机械性能测试和断口微观形貌分析等实验方法,研究了奥氏体基体上含体积分数23%珠光体的ZG120Mn13高碳高锰钢的拉伸性能及其裂纹形核和扩展过程.结果表明:通过时效处理,在奥氏体基体上析出的条状、颗粒状以及沿晶界连续分布的珠光体将使ZG120Mn13钢的强度和塑性大幅度下降.机械性能的降低与其力学行为有关,当基体为单一奥氏体时,裂纹将在大量孪生变形后,在孪晶界、孪晶与晶界交界处形核,并沿孪晶界长大而相互连接、扩展.而奥氏体基体上存在珠光体时,裂纹主要在珠光体团内形核,并通过相邻珠光体间奥氏体的塑性耗竭、切断而得以扩展.

Effect of pearlite on the tensile fracture process of ZG120Mn13 steel

To investigate the reason why pearlite on austenite matrix of Hadfield steel would reduce its mechanical properties, the effect of pearlite on the tensile properties, crack nucleation and propagation process of ZG120Mn13 steel which contains volume fraction of 23% pearlite, was studied by metallography analysis, mechanical property testing and fracture morphology analysis. The strength and ductility of ZG120Mn13 steel can be decreased by the aging treatment that produced the pearlite colonies with the strips and granular-like,or continuously along grain boundaries of the austenites. The strength and ductility of the steel sharply decrease because of pearlite. The decrement of mechanical properties is related to the crack nucleation and propagation process during the deformation and fracture of the steel. When the steel is a single-phase austenite, the cracks nucleate mainly at twin boundaries, or junctions between twins and grain boundaries after a large number of twinning deformation, then grow up along twin boundaries and connected with each other. Whereas, when there are pearlite colonies on the austenite matrix, cracks nucleated mainly in the pearlite colonies, and these cracks were expanded even to rupture by plastic deformation and fracture of austenite between adjacent pearlite colonies.