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چکیده
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In the current work, Al-ZrB2 composite powders were made by a high-energy planetary mill and then consolidated into bulk samples by the equal channel angular pressing (ECAP) process. The effect of milling time (6, 12, 18, and 24 h) and ZrB2 ceramic reinforcement (1, 5, 10, and 15% by weight) on microstructural and mechanical properties of powder and bulk samples were evaluated. The results indicated that for up to 12 h, the composite powders experienced flattening and particle growth through cold welding. In 18 h, the fracturing mechanism resulting from large plastic deformation overcomes the cold welding and reduces the particle size. Al-10%ZrB2 bulk composites showed the best distribution of reinforcement between ECAP-processed samples. In reinforcement amounts greater than 10%, ZrB2 particles tended to agglomerate, which caused a decrease in the mechanical properties of the bulk sample. The experimental results obtained by measuring relative density implied that the Al-10%ZrB2 sample is the densest composite that has given an excellent response to ECAP. The hardness of the ZrB2 composite is increased by about 53% with the increase in ZrB2 from 1 to 15%. Moreover, the compressive strength results confirmed the addition of compressive strength by increasing ZrB2 up to 10%. In Al-15%ZrB2, due to the agglomeration of ZrB2, the compressive strength presented a downward trend, which was due to stress concentration in the agglomerated areas. The strong mechanical connection between the reinforcement and Al reduced the coefficient of friction in the Al-10%ZrB2 sample. So this sample displayed the lowest material loss in terms of wear volume and depth in the wear tests. Therefore, the Al-10%ZrB2 bulk composite prepared via 18 h of planetary milling and subsequent ECAP was the optimum sample.
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