Precessing of 2024 Al /W Composites Prepared by Powder Metallurgy

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Precessing of 2024 Al /W Composites Prepared by Powder Metallurgy Zhimin Yang1, Jian Yang1, Youyun Lian2, and Changhui Mao2 1 Advanced electronic Materials Institute, General Research Institute for Non-ferrous Metals, 2# XinJieKou Wai Street, Beijing, 100088, China, People's Republic of 2 General Research Institute for Non-ferrous Metals, Beijing, 100088, China, People's Republic of Abstract In this work, the 2024 Al/W composites were fabricated by powder metallurgy. W powders and gas-atomized 2024 Al aluminum powder were milled by ball milling with different milling parameters. The mean size of the 2024 Al alloy powders and W powders are 45 µm, 3 µm respectively. The content of W powders and Ta powders are 30 wt. %. The mixtures were consolidated by vacuum hot press under a pressure of 400MPa and then hot-extruded for a higher density. A T6 heat treatment was carried out for the samples, which consisted of solution treating at temperature 470-500 , water quenching and artificial aging at 190 for 8h. The microstructure of as-milled mixture powders and the composites were investigated by combination of X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). The results show the milling-energy is a key factor for the processing of the composite. For the samples with high energy milling, Al atoms dissolved into W lattice gradually and finally formed a W solution after 6 hours’ milling, which can cause the a large amount of precipitation of WAl12, WAl5 in the following hot pressing process. The precipitation of WAl12, WAl5 cause a hard uncompacted performs, which are difficult to be hot-extruded. With appropriate processing parameters, the Al/W composites were successfully fabricated. The YS, UTS and elongation of extruded composites are 165 MPa, 285 MPa and 11% respectively. The corresponding YS, UTS and elongation of the heat-treated composites are 400 MPa, 480MPa and 4% respectively. The microstructure and its relationship with the mechanical properties of the composites were investigated. The particles of nonuniform size and irregular shape can be seen randomly dispersed in the 2024 aluminum alloy matrix. Agglomeration or clustering of the particles was observed. The agglomeration is due to large difference of particle size between W particles and matrix alloy particles and the low milling energy used during the milling process. Fractographs indicate that the fracture occurred by a locally ductile mechanism. The agglomerations are clearly observed in the fracture surface. The influence of W particles on the tensile strength is two-sided. On the one hand, the well dispersed small W particles act as the reinforcement. The presence of hard W particles limits the deformation of the matrix and enhances the composite strength. On the other hand, the concentration of stresses cause de-cohesion of clustered W and the formation of the cracks in the cluster, which work as the fracture source and decrease the strength of the composite.