Microstructural Analysis of Zr-Added 7075 Aluminum Alloy

What is it about?

The effect of zirconium (Zr) on the formation of precipitates in the 7075 aluminum alloy was investigated through an aging heat treatment. Four alloys were produced with Zr contents ranging from 0 to 0.355% by weight.

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Why is it important?

In the as-cast condition, it was observed that Zr promoted microstructural refinement, leading to a 48% reduction in the secondary dendrite arm spacing (SDAS) in alloy A4 containing 0.355 wt% Zr, compared to alloy A1 without Zr addition. The alloys containing Zr also exhibited the presence of the Al3Zr precipitate. After the solution heat treatment, the previously identified phases were retained in both the conventional and modified processes, although they exhibited reduced interconnectivity compared to the as-cast condition. Furthermore, after the aging treatment, nanometer-sized precipitates rich in Al3Zr and MgZn2 were identified and uniformly dispersed within the matrix, resulting in a significant increase in the hardness of the alloys.