微量Ca对AZ91镁合金凝固组织和力学性能的影响

Effect of Trace Ca on Microstructure and Mechanical Properties of AZ91 Magnesium Alloy

利用光学显微镜、X射线衍射仪、扫描电镜研究了0.1%-0.5%的Ca添加量对AZ91镁合金的凝固组织和力学性能的影响。结果表明,添加微量的Ca后,合金的初生相粗化;随着Ca加入量的增加,初生相的尺寸变化不明显,第二相先细化后粗化,转折点为0.4%;加入0.5%的Ca时,发现新相Al2Ca;添加0.4%的Ca后,合金的固液转变温度区间变窄,共晶转变温度升高;随着Ca加入量的增加,力学性能有所提高,当加入0.4%的Ca时,综合力学性能达到最优,其抗拉强度和伸长率分别为261 MPa和14.8%,较未加Ca处理时提高了51%和691%。

Effects of Ca addition （0.1%- 0.5%） on solidified structure and mechanical properties of AZgl magnesium alloy were analyzed by OM （optical microscopy）, XRD （X-ray diffraction） and SEM （scanning electron microscopy）. The results show that primary phase in the AZ91 alloy is coarsened with adding trace Ca. With the increase of Ca addition, change of primary phase can be ignored, howev-er, second phase is refined firstly and then coarsened, where secondary phase size exhibits desirable with 0.4 % Ca addition. Alz Ca phase can be found with 0.5 % Ca addition. The solid-liquid transition temper- ature range of the alloy becomes narrow, and the eutectic transition temperature is increased with adding 0.4%Ca. With the increase of Ca addition, mechanical properties of the AZ91 magnesium alloy are increased. Comprehensive mechanical properties exhibit satisfied when Ca addition is 0.4 %, where tensile strength and elongation of the alloy reach 261 MPa and 14.8%, increased by 51% and 691%, respec- tively, compared with the alloy with absence of Ca addition.