热历史对搅拌摩擦加工制备的AZ31镁合金微观组织和力学性能的影响。

Effect of Thermal History on Microstructures and Mechanical Properties of AZ31 Magnesium Alloy Prepared by Friction Stir Processing.

作者信息

Chai Fang, Zhang Datong, Li Yuanyuan

机构信息

National Engineering Research Center of Near-net shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510640, Guangdong, China.

出版信息

Materials (Basel). 2014 Feb 28;7(3):1573-1589. doi: 10.3390/ma7031573.

Hot-rolled AZ31 (Mg-2.57Al-0.84Zn-0.32Mn, in mass percentage) magnesium alloy is subjected to friction stir processing in air (normal friction stir processing, NFSP) and under water (submerged friction stir processing, SFSP). Thermal history of the two FSP procedures is measured, and its effect on microstructures and mechanical properties of the experimental materials is investigated. Compared with NFSP, the peak temperature during SFSP is lower and the duration time at a high temperature is shorter due to the enhanced cooling effect of water. Consequently, SFSP results in further grain refinement, and the average grain size of the NFSP and SFSP specimens in the stir zone (SZ) are 2.9 μm and 1.3 μm, respectively. Transmission electron microscopy (TEM) examinations confirm that grain refinement is attributed to continuous dynamic recrystallization both for NFSP and SFSP. The average Vickers hardness in the SZ of the NFSP and SFSP AZ31 magnesium alloy are 76 HV and 87 HV. Furthermore, the ultimate tensile strength and the elongation of the SFSP specimen increase from 191 MPa and 31.3% in the NFSP specimen to 210 MPa and 50.5%, respectively. Both the NFSP and SFSP alloys fail through ductile fracture, but the dimples are much more obvious in the SFSP alloy.

对热轧AZ31（镁含量为2.57%、铝含量为0.84%、锌含量为0.32%、锰含量为0.32%，质量百分比）镁合金在空气中进行搅拌摩擦加工（常规搅拌摩擦加工，NFSP）以及在水下进行搅拌摩擦加工（浸没式搅拌摩擦加工，SFSP）。测量了这两种搅拌摩擦加工工艺的热历史，并研究了其对实验材料微观结构和力学性能的影响。与常规搅拌摩擦加工相比，由于水增强的冷却效果，浸没式搅拌摩擦加工过程中的峰值温度较低，高温持续时间较短。因此，浸没式搅拌摩擦加工导致进一步的晶粒细化，搅拌区（SZ）中常规搅拌摩擦加工和浸没式搅拌摩擦加工试样的平均晶粒尺寸分别为2.9μm和1.3μm。透射电子显微镜（TEM）检查证实，常规搅拌摩擦加工和浸没式搅拌摩擦加工的晶粒细化均归因于连续动态再结晶。常规搅拌摩擦加工和浸没式搅拌摩擦加工AZ31镁合金搅拌区的平均维氏硬度分别为76 HV和87 HV。此外，浸没式搅拌摩擦加工试样的极限抗拉强度和伸长率分别从常规搅拌摩擦加工试样的191 MPa和31.3%提高到210 MPa和50.5%。常规搅拌摩擦加工和浸没式搅拌摩擦加工合金均通过韧性断裂失效，但浸没式搅拌摩擦加工合金中的韧窝更为明显。