Mg-15Gd-3Y挤压合金的时效强化

Aging strengthening of squeezed Mg-15Gd-3Y alloy

研究时效处理对挤压态Mg-15Gd-3Y合金显微硬度及力学性能的影响,采用透射电镜对时效析出相的形态进行分析。结果表明:225℃、14h时效时合金获得最高硬度,为135HV,此时,晶内弥散析出许多纳米β′亚稳相,且与基体有着良好的共格匹配性,使合金获得较高强度和硬度,同时塑性降低;在225℃、70h过时效作用下,纳米β′亚稳相原位长大成β稳定相,且与基体失去共格匹配性,降低合金的强度和硬度,同时塑性有所回升;合金的最高强度出现在200℃、100h时效处,此时,抗拉强度达到446.67MPa,合金中的β′亚稳相呈蠕虫状,沿亚晶界分布,有效地阻碍亚晶界和位错的运动,从而强化合金。

The effects of aging on the Vickers hardness and mechanical properties of the squeezed Mg-15Gd-3Y alloy were investigated,and TEM was used to observe the microstructure of the precipitates.The results show that a maximum hardness of 135 HV can be attained when aged at 225℃ for 14 h.The alloy exhibits good strength and hardness but poor plasticity due to the precipitation of the nanoscale β＇ metastable phase,which has good coherence with the matrix.The β＇ phase transforms into the β stable phase in-situ,and becomes incoherent with the matrix when aged at 225℃ for 70 h.This induces the decline of the strength and hardness,and somewhat the recovery of the plasticity.The alloy achieves a maximum tensile strength of 446.67 MPa when aged at 200℃ for 100 h,and the β＇ phase shows a shape of helminth and distributes along the subgrain boundaries.The β＇ phase baffles the movement of the subgrain boundaries and dislocation effectively,and strengthens the alloy.