The Oxidation Behaviors of 7,050 Aluminum Strips During Semi-solid Powder Rolling and Mechanical Properties of Strips

摘要

Semi-solid powder rolling (SSPR) is a novel strip manufacturing process, which combines powder rolling with semi-solid rolling in one step. Based on the features of SSPR, powders were heated to the semi-solid temperature range and then rolled. Therefore, oxides will form during heating and rolling. The oxidation behavior of 7050 aluminum during SSPR was analyzed and the quantity, distribution and morphology of oxides are discussed. The effects of quantity, distribution and morphology of the oxides on the microhardness of strips under different conditions were studied. The results showed that the main factor influencing the quantity of oxides is the heating temperature. The mechanism of oxidation during SSPR was found to be diffusion controlled. In the heating stage, surface oxide films hinder the diffusion. In the rolling stage, surface oxide layers were broken and so the oxidation of aluminum alloy mainly took place in the rolling stage. The formed oxides are Al2O3 with a little of MgO showing an irregular morphology with a size of 2-3 A mu m. High bonding quality between the oxide particles and the matrix, as well as an uniform distribution of the oxides, leads to a higher microhardness of the SSPR-ed strips. But, the bonding quality between the oxide particles and the matrix is poor under conditions of low liquid fraction and some oxides distribute non-uniformly around the grain boundaries.

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