【作者】 张永进；

【导师】 于思荣；

【作者基本信息】 吉林大学 ， 材料加工， 2006， 硕士

【摘要】 本文分别以AlSi3合金和SiCp/AlSi3复合材料为研究对象,采用SIMA半固态加工法,研究AlSi3合金和SiCp/AlSi3复合材料在半固态等温过程中的组织演变规律,为颗粒增强铝合金复合材料部件的SIMA半固态成型提供理论指导。研究发现经压缩变形后,AlSi3合金铸态组织由发达的无方向性的树枝晶转变为具有一定方向性的变形晶体。压缩形变量越大,AlSi3合金半固态晶粒平均等积圆直径越小,球化程度越高;但压缩形变量超过50%后,AlSi3合金晶粒尺寸变化不大。随等温保温时间的延长,AlSi3合金半固态晶粒尺寸逐渐增大,圆度提高,分形维数逐渐减小。建立了晶粒曲率对半固态晶粒周围液相质量传输及晶粒组织球化演变的影响的理论模型。为了在半固态等温处理过程中比较容易地获得细的球状晶粒,在上述理论分析基础上,对半固态等温处理前晶粒的原始状态提出了建议。对SiCp/AlSi3复合材料半固态等温组织演变的研究结果表明,随压缩形变量增大,SiCp/AlSi3复合材料基体半固态晶粒尺寸变小,圆度提高,分形维数降低。压缩形变量超过20%后,晶粒尺寸变化不明显。随半固态保温时间增加,晶粒尺寸呈增大趋势,晶粒圆度增加,分形维数减小。SiC颗粒体积分数越大,SiCp/AlSi3复合材料基体半固态晶粒越细小、均匀、圆整。随SiC颗粒尺寸增大,SiCp/AlSi3复合材料基体晶粒圆度减小,晶粒等积圆直径增大,分形维数变大。更多还原

【Abstract】 Particle reinforced metal matrix composites (MMCs), which are of many advantages such as better specific strength and specific modulus of elasticity, better wear resistance and corrosion resistance, and low thermal expansion coefficient, have broad application prospect in fields of aerospace, automobile and so on. For the forming of MMCs parts, up to now, there is not an ideal method which is suitable for casting ingots of MMCs serving as raw material, energy and material saving, mechanization, and volume production. So developing a new, energy saving method for MMCs parts forming near net shape has important significance. SIMA is a new semisolid process method, and has been applied more and more in recent years. But little report is found about processing particles reinforced MMCs parts with this method. The key of semisolid process is the preparation of semisolid slurry. This study serves AlSi3 alloy and SiCp/AlSi3 composites respectively as investigated objects, adopts SIMA semisolid process method, and investigates the microstructure evolution law of AlSi3 alloy and SiCp/AlSi3 composites in semisolid isothermal holding process, in order to providing theory guide for SIMA method semisolid forming of particles reinforced MMCs parts.First AlSi3 alloy was fabricated,and SiCp/AlSi3 composites was fabricated by mechanical stirring method.The microstructure evolution of AlSi3 alloy during semisolid isothermal experiment was studied. The effects of compression ratio and holding time on semisolid grain size,roundness,fractal dimension were analysed. The results show that as cast structure of AlSi3 alloy transfers from big and no directional dendrites更多还原