# Microstructural evolution of spray formed 7075 Al alloy

Jeyakumar, M and Kumar, S (2005) Microstructural evolution of spray formed 7075 Al alloy. In: Transactions of the Indian Institute of Metals, 58 (4). pp. 617-623.

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## Abstract

Spray deposition is a novel manufacturing process, which is currently being developed for producing near-net-shape preforms. Spray deposition involves the creation of a spray of droplets by a gas atomizer and the consolidation of these droplets on a substrate to create a preform. In order to maximize the metallurgical benefits of spray deposition, a thorough study of the solidification process is important. In this study, 7075 Al alloy is atomized by high velocity argon gas and atomized droplets are collected on the fixed copper substrate. The microstructure of over spray powder and the preform are studied. Spray atomization produces various sizes of droplets, ranging from 5 to 300 \mu m. A variety of microstructures are observed for different size of powders. Microstructural changes occur due to the difference in the cooling rates of the atomized droplets. The cooling rate of the fine droplets is high compared with coarse droplets. Generally the cooling rate of the droplet changes from 101 to 106 K$s^{-1}$. In the spray deposition the preform shows equiaxed grains, while the size of the grain changes from bottom to top of the preform. The grain size measurements at the bottom, centre and top of the preform gives 25, 40 and 20 \mu m respectively. This happens because of the fact that different portions of the preform experiences different cooling rates.The bottom and top of the preform have high cooling rate compared with the centre portion.

Item Type: Journal Article Copyright for this article belongs to Indian Institute of Metals. Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy) 20 Apr 2006 27 Aug 2008 11:34 http://eprints.iisc.ernet.in/id/eprint/4214