The effect of the austenite grain refinement on the tensile and impact properties of cast Hadfield steel

This paper studied the effect of the austenite grain refinement on the tensile and impact properties of a cast Hadfield steel (12 % Mn, 1.2 %C and 0.65 % Si). The austenite grain refinement was obtained by hafnium inoculation. Microstructural characterization showed that the Hf-refined cast Hadfield steel featured a grain size of 600 µm, while the non-refined condition presented a grain size of 3000 µm. Mechanical test results indicated that the austenite grain refinement promoted an increase in the values of the yield stress (6%), the ultimate tensile strength (37%), the toughness (88%), the work-hardening coefficient (50%) and the Charpy absorbed energy (15%). Microscopic characterization of the fractured test-pieces indicated that the grain refinement increased the proportion of plastic deformation by the twinning mechanism and furthermore improved the values of the mechanical properties of the cast Hadfield steel considerably.本研究探讨了奥氏体晶粒细化（austenite grain refinement）对成分为12%Mn、1.2%C及0.65%Si的铸造哈德菲尔德钢拉伸与冲击性能的影响。本次通过铪（Hafnium）孕育处理实现奥氏体晶粒细化。显微组织表征结果显示，经铪细化的铸造哈德菲尔德钢晶粒尺寸为600 μm，未细化组试样的晶粒尺寸达3000 μm。力学性能测试结果表明，奥氏体晶粒细化可使试样的屈服强度提升6%、抗拉强度提升37%、韧性提升88%、加工硬化系数提升50%以及夏比冲击吸收功提升15%。断口试样的微观表征结果显示，晶粒细化提高了孪生（twinning）机制主导的塑性变形占比，进而显著改善了铸造哈德菲尔德钢的各项力学性能。