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综合运用OM、XRD、FEGSEM和HRTEM手段深入分析了Mg-6%Gd-2%Y(质量分数)(记为GW62)合金铸态、固溶态和时效态的显微组织特征及演变过程。GW62合金铸态组织主要由α(Mg)和呈不连续网状的Mg_5(Gd,Y)相组成,在紧邻Mg_5(Gd,Y)处有少量非平衡凝固相Mg_2(Gd,Y);对合金进行520℃固溶处理,随着固溶时间延长,半连续状Mg_5(Gd,Y)相尺寸逐渐缩小,直至溶解,并在晶界形成大量细小fcc结构的富稀土相Mg(Gd,Y)_2,明显阻止了α(Mg)晶粒的长大;合金在175~225℃时效处理时,175℃时效硬化效果最明显,时效析出过程包括:时效初期(4~32 h),过饱和α(Mg)析出β″相;快速析出期(32~100 h),α(Mg)析出β′相,100 h达到峰值时效,析出相为β″、β′相;过时效期区(>100 h),β′相尺寸逐渐增大,并转化成β_1和向稳定的β相转变。
The microstructures and evolutions of as-cast, solid solution and aged Mg-6% Gd-2% Y (denoted as GW62) alloys were comprehensively analyzed using OM, XRD, FEGSEM and HRTEM methods. The as-cast microstructure of GW62 mainly consists of α (Mg) and Mg_5 (Gd, Y) phases which are discontinuous, with a small amount of non-equilibrium solidified phase Mg_2 (Gd, Y) immediately adjacent to Mg_5 The results show that the size of the semidontinuous Mg_5 (Gd, Y) phase decreases gradually until it dissolves, and a large number of rare earth-rich Mg (Gd, Y) ) _2 obviously prevented the growth of α (Mg) grains. The aging hardening effect at 175 ℃ was the most obvious when the alloy was aged at 175-225 ℃. The aging precipitation process included: initial aging (4 ~ 32 h), supersaturation The β ’phase was precipitated by α (Mg), the β’ phase was precipitated by α (Mg) during the rapid precipitation (32-100 h), and the β ’phase was precipitated at 100 h. 100 h), β ’phase size gradually increased, and transformed into β_1 and to stable β-phase transition.