热处理工艺对Mg-5Y-3Nd-1Gd-0.4Zr镁合金冲击韧性的影响

采用冲击实验研究了热处理工艺对Mg-5Y-3Nd-1Gd-0.4Zr镁合金U型缺口和无缺口试样的冲击韧性的影响,同时研究了时效时间对于时效态样品冲击性能缺口敏感性的影响。结果表明:固溶处理后合金的冲击韧性最高,断口形貌具有韧脆混合断裂特征,而时效后合金的冲击韧性迅速降低,断口形貌呈现脆性断裂的特征。这是由于固溶处理后合金的组织为单相组织,晶粒间和晶粒内协调性好,而时效处理后组织中析出大量第二相,在冲击变形过程中这些第二相阻碍位错运动,导致材料强度提高而韧性迅速降低。随着时效时间的延长,合金的室温缺口敏感性几乎不发生变化。当冲击温度提高到200℃时,缺口敏感性相对室温增加,这是由于存在缺口时,冲击过程几乎不发生塑性变形。提高实验温度,有缺口试样的冲击韧性增幅比无缺口试样的冲击韧性增幅要小的多,试样缺口敏感性也会增大。

Effect of heat treatment process on impact toughness of Mg-5Y-3Nd-1Gd-0.4Zr magnesium alloy

Effect of heat treatment on impact toughness of U-notch and non-notch specimen of Mg-5 Y-3 Nd-1 Gd-0.4 Zr magnesium alloy was studied by impact experiment,and the effect of aging time on notch sensitivity of impact performance of the aged samples was studied.The results show that the impact toughness of the alloy is the highest after solid solution treatment,the fracture surface morphology has the characteristics of ductile and brittle mixed fracture,but the impact toughness of the alloy decreases rapidly after aging treatment,and the fracture surface morphology presents the characteristics of brittle fracture.This is because the microstructure of the alloy after solid solution treatment is single-phase structure,the coordination between inter-grain and intra-grain is good,while a large number of second phases precipitate in the microstructure of the alloy after aging treatment,which hinder dislocation movement during impact deformation,resulting in the increase of strength and the rapid decrease of toughness of the alloy.With the increase of the aging time,the room temperature notch sensitivity of the alloy changes very little.When the impact temperature increases to 200℃,the notch sensitivity of the alloy increases relative to room temperature,which is due to the almost no plastic deformation during the impact process when there is a notch.When the experimental temperature is increased,the increment of impact toughness of the notch specimen is much less than that of the non-notched specimen,and the notch sensitivity of the specimen increases.