Coherency loss of Al₃(Sc,Zr) precipitates by deformation of an Al-Zn-Mg alloy

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• 作者：M. Schö ; bel^a ; ^{michael.schoebel@tuwien.ac.at} ; P. Pongratz^b ; H.P. Degischer^a
• 关键词：Ll2 superstructure ; Coherent A3B precipitates ; Orientation relation ; Grain growth inhibition ; ECAP deformation
• 刊名：Acta Materialia
• 出版年：2012
• 期刊代码：1_13596454
• 类别：ms
• 出版时间：June, 2012
• 卷：60
• 期：10
• 页码：4247-4254
• 文件大小：1473 K

摘要

Al alloys with additions of Sc and/or Zr exhibit a reasonably stable grain structure due to a uniform distribution of coherent Al₃(Sc,Zr) precipitates that forms at temperatures >300 掳C. These precipitates are stable up to the solution treatment temperature and are able to pin subgrain and grain boundaries, inhibiting grain coarsening. The crystallographic structure of these precipitates presents a L1₂ superstructure coherent with the face-centred cubic Al matrix. Changes in the orientation relation between precipitates and the matrix are described in deformed, recovered and partially recrystallized samples of extrusions of AW7010 (AlZn6Mg2Cu2). The coherency of the intracrystalline Al₃(Sc,Zr) precipitates present in the extrusions is lost by severe deformation performed by an equal channel angular pressing process, which produced a fine-grained microstructure. The deformed sample recovers, forming a subgrain structure with restored coherency of the Al₃(Sc,Zr) precipitates. Rapid heating to 470 掳C causes partial secondary recrystallization, which transforms the precipitates within the recrystallized grains into incoherent groups of particles that maintain their original orientation with each other.