【摘要】 通过对Ｇ９９钢在不同回火温度下常规力学性能的测试、透射电镜观察和穆斯堡尔谱分析，研究了回火温度对微观组织和力学性能的影响．该钢具有很高的强度和很好的韧性．随回火温度的升高，抗拉强度和屈服强度分别在４３０℃附近和在４８０℃附近出现二次硬化峰．峰时效状态细小的Ｍ２Ｃ型碳化物弥散析出起到了重要的强化作用．Ｃｏ，Ｎｉ原子在板条马氏体中的均匀分布也可能是导致强度增加的因素．其优良的韧性主要归因于极细小的马氏体板条束、适量的逆转变奥氏体的出现．更多还原

【Abstract】 The influence of tempering temperature upon microstructure and mechanical properties of G99 was studied by measuring mechanical properties,TEM and Mssbauer spectroscopy. The steel G99 has ultrahigh strength and high fracture toughness. With increasing of tempering temperature,the tensile strength σ b and yield strength σ 0 2 showed secondary hardening peak at 430℃ and 480℃ respectively. Small needle shaped precipitates of M 2C carbides take an important strengthing effect. Well distributed Co and Ni atom in martensite may result in increase in strength. The good toughness results from the presence of very fine lath like martensite and suitable amount of reversed austenite.更多还原