位错对高体积分数SiCP/2024Al时效行为的影响

采用粒径为1μm的SiC颗粒,用挤压铸造法制备出体积分数为45 %的SiC_P/2024Al复合材料,研究了位错对高体积分数SiC_P/2024Al时效行为的影响。结果表明,复合材料中的高密度位错可以湮灭大量的淬火空位,这在一定程度上抑制了GP区的析出。但是,高密度位错的存在降低了其它析出相的热扩散激活能,促进了析出相形核;还能为原子的管道扩散提供通道,促进了溶质原子的扩散,加速析出相的长大,在宏观上表现为对时效行为的促进,使峰时效提前。高密度的位错为强烈依赖于位错等缺陷形核的θ'和S'相提供许多优先形核的场所,使复合材料中的形核密度增加,同时使析出相的尺寸减小,所以复合材料中的析出相呈现细小弥散的分布特点。 

EFFECT OF DISLOCATIONS ON THE AGING BEHAVIOR OF HIGH VOLUME FRACTION SiCP/2024Al COMPOSITE

2024 aluminum matrix composite reinforced by SiC particles with 45% volume fraction and 1 μm diameter was successfully fabricated by a squeeze-exhaust casting method. The effect of dislocations on the aging behaviors of SiCP/2024Al composite was investigated. The results showed that the high-density dislocations in the composite cause the annihilation of quenched-in vacancies, so the GP zone formation is suppressed to some extent. However, the high-density dislocations decrease the thermal diffusion activation energy for the other precipitate formation and accelerate the nucleation of precipitates. Moreover, the high-density dislocations can supply the pathway for pipe diffusion of solute and accelerate the growth of precipitates. So the aging behavior of composite is accelerated and the aging peak of composite appears earlier than that of 2024Al alloy. The high-density dislocations, as preferential nucleation sites for precipitates, bring about the tiny and dense precipitates in the composite.