Effect of Sc content on microstructure characteristics and evolution of W phase in Al–Cu–Li alloys under as-cast and homogenization conditions
Journal of Materials Research and Technology(2023)
摘要
In this study, the effect of Sc content on the microstructural characteristics and phase evolution of an Al–Cu–Li alloy under as-cast and homogenization conditions was investigated. The results show the grain refinement effect was distinct when the content of Sc was 0.16 wt%. However, further increased in Sc content resulted in a limited decrease in grain size. Besides, In the 0.16Sc alloy, the flocculent phase with primary Al3(Sc,Zr) phase coexisting with W (Al8-xCu4+xSc) phase appeared, and in the 0.32Sc alloy, the additional blocky primary Al3(Sc,Zr) phase was observed. With the increased of Sc content, the proportion of primary Al3(Sc,Zr) and W phases gradually increased, and the number and size of Al2Cu and Ag-containing Al2CuMg phases at grain boundaries gradually decreased. Two different morphologies of the primary W phase, flocculent and long strip shaped, were revealed within the Sc-containing alloy. The formation of the core-shell structure formed by Al3(Sc,Zr) particles and W phase was generated by the peritectic-eutectic reaction (Liquid + Al3(Sc,Zr)→α-Al + W) and the long strip of W phase was generated by the eutectic reaction (Liquid→α-Al + Al2Cu + W). During the homogenization process, the Al2Cu and Ag-containing Al2CuMg phases were completely re-dissolved after the two previous stages of homogenization, and only a small amount of the spheroidal residual W phase persisted. A subsequent low temperature treatment was employed to allow the Sc atoms that had diffused into the Al matrix to precipitate as Al3(Sc,Zr) dispersoids, resulting in a higher number density of Al3(Sc,Zr) particles for more efficiently utilizing the Sc elements.
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关键词
alloys,microstructure characteristics,as-cast
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