Ta/W比对一种粉末高温合金相组成和形貌的影响

Effect of Ta/W ratio on phase composition and morphology of a PM superalloy

提高Ta、W元素的含量是新型镍基粉末高温合金设计和研究的趋势。为了研究Ta、W元素交互作用对粉末高温合金组织的影响,设计了一种高(W+Ta)的粉末高温合金,在保持(W+Ta)的总量(7.5%,质量分数)和其他元素含量相同的情况下,合金的Ta/W比从4.0/3.5逐步下降到3.0/4.5。结果表明:Ta/W比的变化对合金的晶粒组织基本没有影响,对碳化物、γ′相的分布和含量影响不大,但强烈影响二次γ′相的形貌和尺寸。随Ta/W比的下降,二次γ′相的尺寸逐渐增大,形貌由近方形转变为不规则形状,甚至产生分裂趋势;γ′相和γ基体的晶格常数均减小,但γ基体晶格常数减小更多,导致合金γ′相/γ基体间错配度增大。W元素随着Ta/W比的降低从倾向分配在γ基体转变为分布在γ′相;除W外,Ta/W比对其他合金元素在γ′相/γ基体间的分配系数影响不大。

Increasing the content of Ta and W elements is the trend of the research and design of new nickel-based powder metallurgy(PM)superalloys.In order to study the effect of interaction of Ta and W elements on microstructure of PM superalloys,a high(W+Ta)powder superalloy was designed.The Ta/W ratio of the alloy gradually decreased from 4.0/3.5 to 3.0/4.5 under the condition that the total(W+Ta)content(7.5%,mass fraction)and other elements content were kept the same.The results show that the change of Ta/W ratio has no effect on the grain structure of the alloy,and has little effect on the distribution and content of carbides and γ′phase,but strongly affects the morphology and size of secondary γ′phase.With the decrease of Ta/W ratio,the size of secondary γ′phase gradually increases,the morphology changes from nearly square to irregular shape,and even has a splitting trend.The lattice constants of γ′phase and γ matrix decrease,but the lattice constants of γ matrix decrease more,resulting in the increase of mismatch between γ′phase and γ matrix.With the decrease of Ta/W ratio,W element changes from tendency distribution in γ matrix to distribution inγ′phase.Except for W,the Ta/W ratio has little effect on the partition coefficient of other alloy elements between γ matrix/γ′phase.