Post-heat Treatment Effects on Cold-Sprayed Aluminum Coatings on AZ91D Magnesium Substrates |
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Authors: | Hengyong Bu Mohammed Yandouzi Chen Lu Bertrand Jodoin |
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Affiliation: | 1. National Engineering Research Center of Light Alloy Net Forming, School of Materials Science and Engineering, Shanghai JiaoTong University, Shanghai, 200240, People??s Republic of China 2. Mechanical Engineering Department, University of Ottawa, Ottawa, ON, K1N 6N5, Canada
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Abstract: | Commercially pure aluminum (CP-Al) powder was deposited by the cold spray process onto AZ91D magnesium (Mg) substrates that had been subjected to three different heat-treatment conditions: namely, as-cast (F), homogenized (T4), and artificially aged (T6). The substrate hardness was measured to be 80.7?±?1.8, 73.7?±?4.0, and 103.6?±?7.4 HV0.025 for the F-, T4-, and T6-Mg alloy substrates respectively. Thick (~400???m) and dense (below 1% porosity) Al coatings have been obtained. After post-deposition heat treatment at 400?°C, the intermetallic Mg17Al12 (??) and Al3Mg2 (??) phases with different thicknesses were found to have formed at the coating/substrate interface depending on the holding time. While no significant thickness differences of the intermetallic layers were detected in the cases of F- and T6-AZ91D substrates, thicker layers formed on the T4-AZ91D substrate. It is believed that the higher Al concentration in the T4-AZ91D solid solution within the ??-Mg could diffuse and contribute more easily to the growth of the intermetallic phases. The hardness of the ??- and ??-phase was measured to be 260.5?±?10.7 HV0.025 and 279.6?±?13.7 HV0.025, respectively. Shear strength test results revealed lower adhesion strength after heat treatment, which is attributed to the presence of brittle intermetallic layers at the coating/substrate interface. |
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