【作者】 任林昌；

【导师】 阎峰云；

【作者基本信息】 兰州理工大学 ， 材料加工工程， 2012， 硕士

【摘要】 MgZnA1系镁合金由于具有高温性能较好、成本较低和较好的铸造性能等优势，被认为是一种具有发展前途的高温抗蠕变镁合金。本文以有色合金半固态成型技术为背景，研究开发了适合半固态触变成型的新型ZA52镁合金，并用Ca、Sr对其进行了细化，对细化后合金进行性能分析，优化了细化工艺；对细化后合金进行半固态处理，制备压铸浆料；最后进行压铸实验，对压铸件进行性能分析。首先主要对合金进行细化处理，结果表明：细化温度为760℃，浇注温度为700℃时，Ca、Sr加入量分别为0.2%和0.1%时细化效果比较好。经过细化剂Ca细化后，当加入量为0.2%Ca时，平均晶粒尺寸为85μm，铸态和T6后抗拉强度分别为为233MPa、279MPa，延伸率分别为12.4%、13.6%。经过细化剂Sr细化后，当加入量为0.1%Ca时，平均晶粒尺寸为96μm，铸态和T6后抗拉强度分别为为211MPa、246MPa，延伸率分别为11.8%、12.5%。经过Ca、Sr细化后的ZA52镁合金进行半固态处理后，保温温度为600℃和590℃保温时间50min时，得到的半固态浆料的球状组织圆整，均匀、细小。在半固态压铸最佳固相率范围（40%60%）内，考察了不同固相率、不同压射速度对压铸件性能的影响，结果表明：在此范围内，固相率越低铸件性能越好。压射速度较低或较高时，压铸件很容易形成缺陷，影响性能。当压射速度为3m/s时，压铸件力学性能较好为189MPa，压铸件的断裂方式以沿晶脆性断裂为主。更多还原

【Abstract】 Because of the good high temperature performance,low cost and good casting properties,Mg-Zn-Al magnesium alloy is considered to be a promising magnesium alloy with high temperature resistance to creep.Taking nonferrous alloy semi-solid forming technology for background, this paper study and develop the new type ZA52magnesium alloy,which is suitable for the of semi-solid forming, and refined by Ca, Sr, Then the properties of refined alloy is analyzed and the process is optimized; After semi solid material processing,prepare semi-solid slurry for die casting; After die casting experiments, the performance of die casting is analyzed.First, the alloy is refined, and the results show that:when refining temperature is760℃, pouring temperature is700℃, the amount of Ca, Sr is0.2%and0.1%respectively, refined effect of the alloy is better. After refined by Ca, when the content of Ca is0.2%, the average grain size for85μm, tensile strength of as-cast and T6processed were233MPa,279MPa, elongation rate were12.4%and13.6%. After refined by Sr, with the content0.1%Ca, the average grain size isr96μm, tensile strength of as-cast and T6processed were for211MPa,246MPa, elongation rate were11.8%and12.5%.After semi-solid treatment for refined ZA52magnesium alloy by Ca and Sr, heating temperature of600℃and590℃, holding time50min, solid state ball roundness of the organization, fine and smaller.In semi-solid casting best in steady rheological solid range (40%-60%) inside, study the different solid content, different injection speed on the influence on the performance of the die casting, the results show that in the range, the lower in steady rheological solid content, the better casting performance. Injection speed is lower or higher, die casting is very easy to form defects, impact performance. When the injection speed of3m/s, die casting mechanics performance is good for189MPa. the main fracture means of die casting is the intergranular brittle fracture primarily.更多还原