The effect of the chemical distribution on the mechanical properties of the Al-5.5wt%Si-5wt%Zn-0.2wt%Mg alloy after thixoforging and solution heat treatment

Materia

article

Gabriela Lujan Brollo¹  Cecília Tereza Weishaupt Proni¹  Eugênio José Zoqui¹ 

[1] Unicamp

关键词: thixoforming;    Al-Si-Zn-Mg alloys;    solution heat treatment;    solid solution strengthening;   

DOI  :  10.1590/S1517-707620220002.1316

学科分类：工程和技术（综合）

来源: Universidade Federal do Rio de Janeiro * Coordenacao dos Programas de Pos-Graduacao de Engenharia

【 摘 要 】

The effect of heat and strain during the semisolid processing route on the microstructural evolution and mechanical performance of the Al-5.5wt%Si-5wt%Zn-0.2wt%Mg alloy was evaluated. The as cast alloy was heated and partially melted to 588 °C (fs = 0.40), thixoformed (in an open die forged) and solution heat-treated (SHT) at 525 °C for 1 to 6 h. The microstructural evolution and chemical distribution (SEM-EDS) of the main alloying elements were evaluated at each step of the processing route. The SHT for 2.5 h after thixoforming showed to be adequate considering (a) the spheroidization of Si crystals, (b) the formation of Fe- and Mn-rich platelet-like particles in the eutectic phase, (c) the Mg dissolution from the Mg2Si conglomerates and (d) the homogeneous Zn diffusion along the entire part. As a consequence of the higher circularity of secondary particles, the possibility of crack formation and propagation under stress was minimized. The possible formation of solute clusters and GP zones containing Zn, Mg, Si and Cu was enabled due to the dissolution and diffusion of secondary elements during SHT, which increased the alloy’s mechanical strength. Larger Si crystals and the homogeneous spatial spread of Zn resulted in the hardness increase of the SHT alloy.

【 授权许可】

CC BY