(1. 太原工业学院 机械工程系，太原 030008；
2. 晋中学院 材料科学与工程系，晋中 030600；
3. 哈尔滨工程大学 材料科学与化学工程学院，哈尔滨 150001；
4. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-0812, Japan；
5. 清华大学 机械工程系 摩擦学国家重点实验室，北京 100084)
摘 要: 采用光学显微镜(OM)、X射线衍射分析(XRD)、带有能谱仪(EDS)的扫描电子显微镜(SEM)、透射电子显微镜(TEM)和力学性能测试等方法，研究了压射速度和压射比压对RE(Ce和Y)、Sr和AlTiB复合变质的AZ91D压铸镁合金相机壳体毛坯件的微观组织和力学性能的影响。结果表明：随着压射速度和压射比压的增加，合金的强度先增大后减小、伸长率先减小后增加，由此得到优化的压铸工艺参数为浇铸温度680 ℃、压射速度6 m/s和压射比压90 MPa。RE、Sr和AlTiB复合变质显著细化AZ91D合金的α-Mg晶粒和Mg17Al12相，同时在基体中引入了细小弥散的TiB2、Al11Ce3、Al2Y和Al10Ce2Mn7相，它们的协同强化作用显著提升了合金的强度。因此，变质的合金获得了最优的力学性能：抗拉强度为287 MPa，屈服强度为196 MPa，伸长率为4.7%。
关键字: 压射速度；压射比压；微观结构；力学性能；Al-5Ti-B
（1. Department of Mechanical Engineering, Taiyuan Institute of Technology, Taiyuan 030000, China;
2. Department of Materials Science and Engineering, Jinzhong University, Jinzhong 030600, China;
3. Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001, China;
4. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-0812, Japan;
5. State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China）
Abstract:The influences of the injection speed and injection specific pressure on the microstructure and mechanical properties of the camera body of modified AZ91D die casting magnesium alloy with RE(Ce and Y), Sr and AlTiB was studied using optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) with energy dispersive spectrometer (EDS), transmission electron microscope (TEM) and mechanical properties test. The results show that the alloy strength increases, but the elongation decreases with increasing the injection speed and injection specific pressure, and thus the optimal die-casting parameter including casting temperature of 680 ℃, injection speed of 6 m/s and injection specific pressure of 90 MPa are obtained. Co-additions of RE, Sr and AlTiB into AZ91 alloy significantly refine α-Mg grains and Mg17Al12 phases, and introduce fine TiB2, Al11Ce3, Al2Y, and Al10Ce2Mn7 phases dispersed in the matrix, which generates a synergistic hardening effect to enhance strength. As a result, the modified alloy achieves optimal mechanical properties, such as the ultimate tensile strength of 287 MPa, yield strength of 196 MPa and elongation of 4.7%.
Key words: injection speed; injection specific pressure; microstructures; mechanical properties; Al-5Ti-B
