【作者】 侯文杰；

【导师】 谭建波；

【作者基本信息】 河北科技大学 ， 材料加工工程， 2010， 硕士

【摘要】 半固态流变成形的最大优势是工艺流程短、生产成本低,符合当今时代节能减排、绿色铸造的要求。近些年来已经成为了半固态成形技术的发展趋势。半固态流变压铸利用半固态合金熔体具有触变性的特点,能有效减轻甚至消除气孔缺陷,具有独特的优势,工业应用前景非常光明。本文利用倾斜板法制备半固态AlSi9Mg合金熔体,并流变压铸标准试样。研究了浇注温度、压射比压、压射速度、固溶处理工艺参数对半固态AlSi9Mg组织及性能的影响,分析了在沿程流动过程中初生固相组织演变规律。研究表明:浇注温度对半固态AlSi9Mg合金熔体的微观组织特征影响较大,在本试验条件下,合适的浇注温度为610~615℃,浇注温度为615℃时初生固相率为40.3%,初生固相的平均直径为22.4μm,圆整度为0.606。压铸压力对半固态AlSi9Mg微观组织和性能的影响较大,在本试验条件下,合适的压射比压为48~72MPa,压射比压为48MPa时试样的抗拉强度为233MPa,延伸率为4.5%,布氏硬度为76,冲击韧性为98kJ?m-2。其微观组织中初生固相率为27.3%,初生固相的平均直径为17.2μm,圆整度为0.662。压铸速度对半固态AlSi9Mg微观组织和性能的影响较大,在本试验条件下,合适的压射速度为1.5~2.0m/s,压射速度为1.5m/s时试样的抗拉强度为238MPa,延伸率为5.7%,布氏硬度为83,冲击韧性为134kJ?m-2。其微观组织中初生固相率为38.9%,初生固相的平均直径为22.7μm,圆整度为0.663。流变压铸试样各部位初生α-Al都为近球状晶粒,而非普通压铸的树枝晶。沿程流动时微观组织中圆整度变化很小,差异不超出0.1;初生固相率为波浪形曲线变化,变化值在20%左右;晶粒的平均直径在10~25μm内不规则变化。固溶处理工艺参数对流变压铸零件组织和性能有较大的影响。固溶处理温度对抗拉强度和延伸率有较大的影响。本试验条件下适宜的固溶处理工艺为固溶处理温度535℃,保温时间2h,水温80℃。在此固溶处理工艺参数下试样的抗拉强度305MPa,延伸率15.3%,布氏硬度107。更多还原

【Abstract】 The greatest advantage of semi-solid rheological forming process is that process flow short, low production costs, in line with the requirements of energy-saving and emission reduction. In recent years it has become a trend of semi-solid forming technology. Use of semi-solid alloy melt with thixotropic characteristic semi-solid rheo-die casting can effectively reduce or eliminate the porosity defects. Semi-solid rheo-die casting has unique advantages and its industrial application is very promising.In this paper, semi-solid AlSi9Mg alloy melt prepared by sloping plate. Then rheo-die casting and made it to standard samples. Pouring temperature, injection pressure, injection speed and parameters of solution heat treatment process are studied. Find how they affect the microstructure and mechanical property on AlSi9Mg semi-solid alloy. Microstructure evolution of the primary solid phase is analysed along alloy melt filling process.The experiments show that: pouring temperature have great influences on the microstructure of semi-solid AlSi9Mg alloy melt. In this experiment, suitable pouring temperature is 610~615℃. When pouring temperature is 615℃the primary solid fraction is 40.3%, the average diameter of primary solid phase is 22.4μm, roundness is 0.606.Injection pressure has great influences on the microstructure and mechanical properties of semi-solid AlSi9Mg alloy. In this experiment, suitable injection pressure is 48~72MPa. When injection pressure is 48MPa, the tensile strength of the sample is 233MPa, elongation percentage is 4.5%, Brinell hardness is 76, and impact toughness is 98kJ?m-2. In microstructure the primary solid fraction is 27.3%, the average diameter of primary solid phase is 17.2μm, roundness is 0.662.Injection speed has great influences on the microstructure and mechanical properties of semi-solid AlSi9Mg alloy. In this experiment, suitable injection speed is 1.5~2.0m/s. When injection speed is 1.5m/s, the tensile strength of the sample is 238MPa, elongation percentage is 5.7%, Brinell hardness is 83, and impact toughness is 134kJ?m-2. In microstructure the primary solid fraction is 38.9%, the average diameter of primary solid phase is 22.7μm, roundness is 0.663.At every transverse section of rheology die casting primary solidα-Al grains are nearly spherical, rather than ordinary die casting dendrite grains. Along alloy melt filling process the change of roundness in the microstructure is small, the difference does not exceed 0.1. Primary solid fraction has a wave-shaped change, and the value change is around 20%. The average diameter of grains is 10~25μm. It changes irregular. Solution treatment parameters have great influences on the microstructure and mechanical properties of rheology die casting. Solution treatment temperature has a significant impact on the tensile strength and elongation. In this experiment, the suitable solution treatment process for rheology die casting is that the solution heat treatment temperature is 535℃, holding time is 2h, water temperature is 80℃. Under this solution treatment parameters tensile strength of the sample is 305MPa, elongation percentage is 15.3%, Brinell hardness is 107.更多还原