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利用Thermo-Calc热力学软件、扫描电镜(SEM)、高分辨透射电镜(HRTEM)与物理化学相分析等试验手段,研究了时效处理对AM355高强不锈钢微观组织与力学性能的影响规律。结果表明,450℃时效4 h时,M23C6相析出,导致钢的强度达到峰值,而非均匀塑性变形能力与韧性却极低。时效温度在520~575℃时,(Cr,Mo)2N相析出,发生钢的二次强化,其屈强比达到峰值,塑性与韧性并没有降低,但由于逆转变奥氏体的增加及固溶强化效果的减弱使强度略有下降。时效温度在575~650℃时,逆转变奥氏体大量生成且沿原马氏体板条边界平行分布,极大程度地提高钢的均匀塑性变形能力,降低钢的非均匀塑性变形能力与强度,不会提高钢的韧性。时效温度在650~700℃时,逆转变奥氏体又重新转变为马氏体,此时钢中析出相较粗大,马氏体板条特征不明显,强度较低,钢的均匀塑性变形能力降低,其非均匀塑性变形能力升高,韧性略有降低。
The effects of aging treatment on the microstructure and mechanical properties of AM355 high strength stainless steel were studied by means of Thermo-Calc thermodynamic software, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and physicochemical phase analysis. The results showed that M23C6 phase precipitated at 450 ℃ for 4 h, leading to the peak of steel strength, while the non-uniform plastic deformation capacity and toughness were extremely low. When the aging temperature is between 520 and 575 ℃, the (Cr, Mo) 2N phase precipitates and the secondary strengthening of the steel occurs. The yield ratio reaches the peak value, and the ductility and toughness do not decrease. However, due to the increase of austenite and solidification The weakening of the solution strengthens the strength slightly. Aging temperature of 575 ~ 650 ℃, the large number of retrograde transformation of austenite and parallel distribution along the original martensite slab boundary, to a great extent to improve the uniform plastic deformation capacity of steel to reduce the non-uniform plastic deformation capacity and strength of steel , Will not improve the toughness of steel. Aging temperature of 650 ~ 700 ℃, the retrograde austenite and re-transformed into martensite, then precipitated relatively coarse steel, martensite lath characteristics are not obvious, lower strength, uniform plastic deformation capacity of steel Reduce its non-uniform plastic deformation increased, toughness slightly lower.