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用电子显微镜电子衍射和电子显微分析、X-射线衍射和俄歇谱研究了淬火和淬火并回火的含碳0.3%的低合金钢。在高压电子显微镜下对断口进行了研究。结果表明,在250～400℃回火时发生回火马氏体脆性主要是由于板条间残余奥氏体分解成 M_3C 薄膜和受其制约的显微组织引起的。加之板条内的ε-碳化物转变成魏氏组织型式的 Fe_3C,其断裂相对于原先的奥氏体是穿晶断裂,此种情况类似于上贝氏体。回火马氏体脆性(TME)不同于较高温度(约500℃)下的回火脆性(TE),且不受显微组织的影响。TE 是由于杂质(目前认为主要是硫)偏聚到原始奥氏体晶界,导致沿晶界的晶间断裂。两种失效可发生在同一钢种中,这取决于回火条件。
The low carbon steels containing 0.3% carbon, which were quenched and quenched and tempered, were investigated by electron microscopy and electron microscopy, X-ray diffraction and Auger spectroscopy. Fracture was studied under high pressure electron microscope. The results show that the brittleness of tempered martensite during tempering at 250-400 ℃ is mainly caused by the decomposition of residual austenite between the slabs into M_3C films and the microstructures controlled by them. In addition, the ε-carbides in the slab transform into Widmanstatten type Fe_3C, and the fracture is transgranular fracture relative to the original austenite, which is similar to the upper bainite. Tempered martensite brittleness (TME) differs from temper embrittlement (TE) at higher temperatures (about 500 ° C) and is not affected by microstructure. TE is segregated to the original austenite grain boundaries due to the impurities (currently thought to be mainly sulfur), resulting in intergranular fracture along the grain boundaries. Both failures can occur in the same steel, depending on the tempering conditions.