凝固冷速与时效时间对CaMgSn形态的影响

针对CaMgSn形貌对Mg-Sn-Ca系合金的力学性能具有重要的影响,研究了慢冷、快冷及时效处理对CaMgSn组织形貌的影响规律.分别采用光学显微镜、扫描电镜、X射线衍射仪和维氏硬度计对比分析了不同处理条件对Mg-3Sn-2Ca-3Cu（质量分数/%）合金微观组织、相结构和硬度的影响.Mg-3Sn-2Ca-3Cu合金慢冷组织主要由α-Mg、CaMgSn、Mg2Ca、CuMg2和Mg2Sn构成,其中CaMgSn为粗大的棒状相;快冷及时效处理后,CaMgSn的形态发生了明显的改变,在时效48 h时,转变为近球状形貌.时效处理后,合金的维氏硬度得到了明显的提高,在时效48 h时达到最高值77.随时效时间延长,表现为硬度的降低和第二相与基体的脱离.

Effects of cooling rates of solidification and aging time on the morphologies of CaMgSn phase

Due to great effects of the morphologies of CaMgSn on the mechanical properties of Mg-Sn-Ca alloys,the influences of natural cooling,rapid quenching and aging treatment on the morphologies of CaMgSn were studied.Effects of different processing conditions on the microstructure,phase structure and hardness of Mg-3Sn-2Ca-3Cu alloy were comparatively investigated by optical microscopy,scanning electron microscope,X-ray diffraction and Vickershardness tester.The main phases of natural cooling alloy were α-Mg,CaMgSn,Mg2Ca,CuMg2 and Mg2Sn,where CaMgSn was coarse rod pattern;after rapid quenching and aging treatment,the obvious changes occurred on the morphologies of CaMgSn phase.After aging for 48 h,it turned spherical-like phase.Both the rapid quenching and aging treatment can cause the Vickershardness of the alloy increase.While aging for 48 h,the Vickershardness reaches the highest value of 77.With the aging time,the hardness was lower and the second phase departed from the matrix because of the weakened orientation relationship between the second phase and the matrix.