Effect of Post-weld Heat Treatment on Mechanical Characteristics of AZ31 Magnesium Alloy Welded Joints

• 来源期刊: 武汉理工大学学报（材料科学版）（英文版）
• 年，卷（期）: 2017,（5）
• 页码范围: 1205-1212
• 页数: 8页
• 语种: 英文
• DOI: 10.1007/s11595-017-1732-5

摘要

Tungsten inert gas (TIG) welding was performed on 2.7 mm thick commercial extruded AZ31B magnesium alloy plates. We investigated the effect of post-weld heat treatment (PWHT) on the microstructure, mechanical properties and precipitated phase of the weld joints. The results showed that during the annealing treatment (200 ℃-1 h, 250 ℃-1 h, 300 ℃-1 h, 350 ℃-1 h, 400 ℃-1 h, and 450 ℃-1 h), the average grain size in the weld seam was the minimum after annealing at 400 ℃ for 1 hour, and then abnormally grew up after annealing at 450 ℃ for 1 hour. The mechanical properties enhanced when the joints were processed from 200 ℃-1 h to 400 ℃-1 h but sharply decreased with increasing annealing temperature. In contrast to the annealing treatment, solution treatment (250 ℃-10 h, 300 ℃-10 h, 350 ℃-10 h, 400 ℃-10 h, and 450 ℃-10 h) exhibited a better ductility but a slight deterioration in tensile strength. Especially speaking, no eutectic compounds (such as Mg17Al12) were observed in the weld seam. The supersaturated Al atoms were precipitated in a coarse spherical shape dispersed in the weld seam. The precipitated Al atoms dissolved in the matrix substances at the condition (400 ℃-1 h) or (250 ℃-10 h). The solution treatment caused grain coarsening and precipitated Al atoms dissolved in the weld seam substantially, which resulted in a drop in micro-hardness at the weld seam compared to the area of the annealed joints.