Si对超高强钢残留奥氏体回火稳定性与力学性能的影响

Effects of Si on tempering stability of retained austenite and mechanical properties of ultra-high strength steels

采用XRD、TEM等实验方法研究了Si含量对超高强钢回火过程残留奥氏体稳定性及其力学性能的影响。结果表明,Si对抑制回火脆性和提高回火抗力具有有益作用;Si抑制残留奥氏体的分解,随Si含量提高,回火过程逐渐出现逆转奥氏体;Si对提高碳分配作用显著,可增强残留奥氏体的稳定性。马氏体板条内部,Si与C原子相互排斥;而奥氏体内Si与C相互吸引。发现1.8%Si钢250℃回火后出现ε-碳化物;400℃回火后ε-碳化物明显粗化,导致回火脆性。对0.4%Si钢而言,导致回火脆性的是回火后出现的大量针状或长条状碳化物,确定这类碳化物为非ε-碳化物。探讨了Si对回火过程残留奥氏体分解及逆转奥氏体形成的作用机理。

Effects of Si content on tempering stability of retained austenite and mechanical properties of ultra-high strength steels were investigated by means of XRD,TEM and other experimental method.The results show that Si can supress temper embrittlement,improve temper resistance and hinder the decomposition of retained austenite.The reversed austenite is gradually appear with increasing Si content during tempering.Si has a significant effect on enhancing carbon partitioning and improves the stability of retained austenite.Si and C atoms are mutually exclusive in lath martensite,while they attract each other in austenite.The ε-carbide is found in 1.8% Si steel tempered at 250 ℃,and they get coarsened obviously leading to temper embrittlement.It is the acicular or lath carbide that lead to temper embrittlement,which is not ε-carbide,may be inferred as cementite and composite compounds.Mechanisms of effects of Si on the decomposition of retained austenite and the formation of reversed austenitee were discussed.