| Semi-solid metal process is a new near net shape technology. And its drip molding is compaction, high mechanical property, little machining and complex.Copper alloys are widely used in various industries, conventional casting of copper alloy is easy to produce the casting defects such as porosity, Shrinkage cavity and composition-segregation, and the short die life is a dead problem to die-casting of copper alloy. If the semi-solid casting technology be used to produce copper alloy, whic is expected to reduce the die temperature significantly and improve the die life, can reflect the advantages of semi-solid forming technology, it will exhibits an excellent prospect in the producing process of copper alloys. The ideal semi-solid ZCuSn10copper alloy was fabricated by strain induced melt activated (SIMA) method, the main research is as follows:Firstly, semi-solid ZCuSn10copper alloy was fabricated by SIMA including the multi-axial forging and remelting process. The effect of remelting temperature and holding time on the microstructure of semi-solid ZCuSn10copper alloy was investigated. With16%deformation, the semi-solid ZCuSn10copper alloy with uniform and spherical grains can be obtained at remelting temperature of900℃and the holding time of30min, the mean grain diameter of the alloy is64.7μm and the shape factor is1.65. But find that the deformation in the pre-deformation stage operation difficult, the deformation is not easy to control and not accurate, the rod billet forging process prone to fracture, this deformation methods can not achieve the preparation of semi-solid billet continuous, and the billet size also has its limitations.Secondly, semi-solid ZCuSn10copper alloy was fabricated by SIMA method which used cold rolling and hot rolling as pre-deformation methods. Results indicate that the semi-solid microstructure with fine grain diameter and good roundness and high liquid fraction can be obtained by SIMA method which used cold rolling and hot rolling as pre-deformation. But in the process of hot rolled, the billet is easy to crack and bend, the billet external complete, uniform deformation, to determine that the cold rolling is best predeformation mode to prepare semi-solid copper alloy billet.Once more, The paper study the process parameters which affect the microstructure of semi-solid ZCuSn10copper alloy billet was fabricated by cold rolling and remelting process detailly, including three main factors:the remelting temperature, holding time and the deformation. The results show that the best process parameters of using cold rolling as predeformation to prepare semi-solid copper alloy billet is that the copper alloy billet with22%deformation remelt at900℃for15～20min. Under the same remelting temperature and holding time, the larger of deformation, the less of solid fraction, around12%deformation is the threshold of the grain refinement of semi-solid copper alloy microstructure. But when the deformation increases from17%to22%, grain refinement trend gradually flatten out.Finally, The mechanism for the semisolid microstructural evolution of the ZCuSn10copper alloy fabricated by SIMA have been researched. During remelting processing, firstly, the copper alloy billet of the pre-deformation occurred the recrystallization to reduce internal stress, produced a large number of recrystallization grain boundaries. In the grain boundary and dendrite root, the liquid appearred firstly. Molten pool stay in the inner of grain is the combined result of dendrite arm. Broken dendrite gradually surrounded by liquid phase, and the first to make the dendrite sharp corners rounded, grains became lumpy. With the increase of holding time, deformation energy gradually released, and the amount of the liquid increased, the interface of grains with high energy easily melted and increasingly resulted in the spheroidization of the solid phases. Finally it is able to get the semi-solid organization with high roundness, fine grain, and high liquid fraction. |
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