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The extrusion of Al-Si alloy powders with different particle sizes allows manufacture of different products with unique microstructures and therefore with unique mechanical properties. The effects of powder size on the extrusion behavior and process defect of Al-18%Si alloy were studied by means of microscopy (optical, scanning electron) and density determination. The main objective of the work is to demonstrate the influence of the powder material characteristics on final density and quality of bar. The results show that the bigger the powder particles, the better the performance of cold compacting. The surface of alloy bar extruded from big particles has good quality without cracking. While the smaller the powder particles, the higher the density and the better the microstructure and mechanical properties. For practice application, the mixed powders are better than single powder. 相似文献
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以群体动力学模型为基础,在充分考虑合金的热物性参数、过饱和度以及第二相形核率变化的基础上,提出描述该合金快速凝固组织演变的数学模型,并结合A390合金进行计算。结果表明:随着雾化合金液滴尺寸的减小,平均冷却速度增加,而初生Si相长大时间减少,所析出初生Si相的尺寸及体积分数也不断减小;当粉末尺寸减小到某一临界值时,初生Si相消失,从而使不同尺寸粉末的微观组织发生很大的变化。计算结果与实验结果吻合较好,说明此提出的模型可以较好地预测过共晶Al-Si合金快速凝固组织的形成,从而为进一步研究高硅合金材料的组织演变奠定基础。 相似文献
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忆容器是一种具有记忆特性的基础电子器件,其电压-电荷关系与其所经历的历史有关,是记忆性器件的一种。电荷控忆容器的电容量不再是常数,而与其积累的电荷量有关,电荷-电压关系表现出非线性特性。研究一个三阶的电荷控忆容器电路,利用忆容器的非线性,在特定条件下该电路的动态特性非常复杂,仿真结果分析表明为一种混沌振荡。 相似文献
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