科研之友
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摘要
Semi-solid powder forming (SPF) has been widely used to prepare metal matrix composites, during which powder breakage plays an important role in grain refinement and densification process. However, it is not easy to directly observe because of the complicated SPF process, resulting in few investigations. Therefore, based on semisolid compression of AA2024 porous materials, powder breakage behavior and mechanism were studied by introducing the continuity, capillary force, and Newtonian fluid and Roscoe-Einstein model in this work. The results indicate that when the continuity C-SS approximate to 1, the powders are not crushed, the liquid solidified as short-rod shapes distributing within a powder is regarded as small holes, and its influence is ignored. When C-SS = 0.384-0.608, the powders break up along grain boundaries partially occupied by liquid, with their solid-bonding being torn open, resulting in transgranular ruptures. Its breakage resistance is the combined force acted by the solid-bonding and liquid. When C-SS < 0.384, the solid grains are wrapped by liquid with few deformation resistances, regarded as a Newtonian fluid. The breakage resistance of semi-solid powders was calculated by the deduced mathematical equation, and it further confirmed the above results. The breakage coefficient representing the broken degree was calculated and then proved to be consistent with experimental results.
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单位广东技术师范学院; 西南石油大学
