论文部分内容阅读
为了在镁合金表面获得远离平衡态的极端快速冷却结构,对AZ31B镁合金进行了在液氮环境下极端快速冷却的CO_2激光表面重熔处理,并对该重熔层的微观结构、性能和强化机制进行了分析研究。结果表明:远离平衡态结晶凝固的镁合金表面重熔层的晶粒高度细化,且晶粒大小基本均一。重熔层主要为α-Mg,以及沿晶界析出的极少量β-Mg_(17)Al_(12)。极端快速冷却条件获得的远离平衡态的重熔层的强化机制主要为细晶强化、超固溶强化和位错强化。在此强化作用下重熔层的显微硬度HV提高到1400 MPa,磨损失量比空气冷却条件下的少50%,耐磨性显著提高。该重熔层的冲击断口特征显示出了塑性变形的痕迹,故该镁合金表面的塑性和韧性也得到了改善。
In order to obtain an extremely fast cooling structure far away from the equilibrium state on the magnesium alloy surface, the AZ31B magnesium alloy was subjected to CO2 laser surface remelting which was rapidly and rapidly cooled in a liquid nitrogen environment. The microstructure, properties and strengthening of the remelted layer Mechanism analysis and research. The results show that the grains of the remelted layer far away from the equilibrium crystalline solidification are highly refined and the grain sizes are basically uniform. The remelted layers are mainly α-Mg and a very small amount of β-Mg_ (17) Al_ (12) precipitated along the grain boundaries. The strengthening mechanism of the remelted layer away from the equilibrium obtained by the extremely rapid cooling condition is mainly the grain refinement, the over-solid solution strengthening and the dislocation strengthening. Under this strengthening action, the micro-hardness HV of the remelted layer increases to 1400 MPa, the wear loss is 50% less than that in the air-cooled condition, and the abrasion resistance is remarkably improved. The impact fracture characteristics of the remelted layer show traces of plastic deformation, so the plasticity and toughness of the magnesium alloy surface are also improved.