Control of Dispersolds in 7475 Aluminum Alloy

Abstract:

7475 aluminium alloy is widely used in aerospace industry and military field. There are many dispersoid former elements in 7475 aluminium alloy, such as Mn, Cr, Ti, Zr and Sc. And the dispersoid configuration has important effect on the performance of alloy wrought. The characteristic of dispersoids in the semi-continuous casting ingot of 7475 aluminum alloy and the evolution of their distribution during rolling have been investigated. The size, shape and distribution of dispersoids are controlled by pre-treatment before homogenization. The results show that there are many coarse triangular, irregular block and spindly rod-like dispersoids which contain some of Cr and Mg and a little of Cu and Zn in the 7475 aluminum alloy which subject to conventional one-step homogenization treatment. The size and the distribution of the Cr-containing dispersoids is not uniform. The width of the coarse dispersoids is close to 1 micron and the length of the spindly rod-like dispersoids is more than 4 microns. There is no dispersoids in the center of the dendritic grains, but the nonuniform distribution of dispersoids is eliminated when the hot rolling reduction exceed 80%. The dispersoids can be significantly refined and homogenously distributed by pre-treated before the conventional one-step homogenized. The pre-treatment can stimulate the nucleation of Cr-containing dispersoids, narrow down the dispersoids free zone. The size of the dispersoids is dramatically reduced by pre-treated before the conventional homogenization, and the width of the coarse dispersoids and length of the spindly rod-like ones are less than 300 nm and 1 micron.

• Periodical: Materials Science Forum (Volume 941)
• Pages: 896-901
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.941.896
• Online since: December 2018
• Authors: Yi Ran Zhou, Lei Kang, Ce Heng Duan, Gang Zhao*, Ni Tian
• Keywords: 7475 Aluminum Alloy, Al₁₈Mg₃Cr₂ Phase, Dispersoids, Homogenization, Pre-Treatment

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