Spark Plasma Sintering and Upsetting of a Gas-Atomized/Air-Atomized Al Alloy Powder Mixture

Al-Zn-Mg-Cu alloy powder, Alumix 431D, was modified by replacing the native air-atomized pure Al particles with gas-atomized pure Al. Samples were sintered using spark plasma sintering (SPS), and upset forging was applied to the sintered samples by SPS. Densities over 98 and 99% of theoretical were obtained for the sintered and forged samples, respectively. Microstructural analysis and characterization of all samples were done using energy-dispersive spectroscopy and x-ray diffraction. Mechanical properties were evaluated using microhardness and flexural strength and strain measurements. The microhardness value of the T6 tempered sample was comparable to that of its wrought counterpart AA7075. Particle bonding after sintering was incomplete and reveals that composite oxide layer of Al-Zn-Mg-Cu alloy powder is difficult to disrupt, and it is necessary to apply a secondary process like forging to improve particle bonding. The loss in ductility following T6 tempering is ascribed to void formation due to the dissolution of the secondary phases, remaining undissolved precipitates, and a localized lack of cohesion between particles.

Al - Zn - Mg - Cu合金粉末（Alumix 431D）通过用气体雾化纯铝替代原生的空气雾化纯铝颗粒进行了改性。采用放电等离子烧结（SPS）对样品进行烧结，并对SPS烧结后的样品进行镦锻。烧结样品和锻造样品分别获得了超过理论密度98%和99%的密度。使用能谱分析和X射线衍射对所有样品进行了微观结构分析和表征。使用显微硬度、抗弯强度和应变测量对力学性能进行了评估。T6回火样品的显微硬度值与其锻造对应物AA7075相当。烧结后的颗粒结合不完全，这表明Al - Zn - Mg - Cu合金粉末的复合氧化物层难以破坏，有必要采用锻造等二次加工来改善颗粒结合。T6回火后延展性的损失归因于二次相溶解、剩余未溶解的析出物以及颗粒之间局部缺乏内聚力而形成的空隙。