(1. 中南大学 材料科学与工程学院，长沙 410083;
2. 中南大学 教育部有色金属材料科学与工程重点实验室，长沙 410083;
3. 湖南工学院 机械工程系，衡阳 421002)
摘 要: 研究高低温循环热处理对EW94合金挤压−T6态板材组织与力学性能的影响。结果表明：在(−196 ℃, 12 h)+(RT, 12 h)制度下，循环热处理对合金的力学性能无明显影响；经(−196 ℃, 12 h)+(≤200 ℃, 12 h)循环热处理N(N≤15)次后，样品抗拉强度有所提高；经(−196 ℃, 12 h)+(200 ℃, 12 h)循环4次后，样品抗拉强度达到峰值，为413 MPa；经(−196 ℃, 12 h)+(250 ℃, 12 h)循环处理后，样品抗拉强度略有下降，伸长率略有提高；而经(−196 ℃, 12 h)+(300 ℃, 12 h)循环处理后，样品抗拉强度,急剧下降至307 MPa，但伸长率由2.8%提高到5.6%；随循环次数的增加，合金力学性能基本保持稳定。合金在高低温循环过程中的相变是影响其力学性能的主要因素。
关键字: 高低温循环；时效；析出相；断裂；伸长率
mechanical properties of EW94 magnesium alloy
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China;
3. Department of Mechanical Engineering, Hunan Institute of Technology, Hengyang 421002, China）
Abstract:The effects of high-low temperature cycle on microstructures and mechanical properties of EW94 alloy with extruded-T6 temper were investigated. The results indicate that there is no effect on the mechanical properties when the aged alloy is held at −196 ℃ and ambient temperature. There is some increment in ultimate strength of the alloy when it is treated by (−196 ℃, 12 h)+(≤200 ℃, 12 h) regime for N(N≤15) times, the maximum ultimate strength of 413 MPa is derived when the alloy was treated by (−196 ℃, 12 h)+(200 ℃, 12 h) for 4 times. There was some decrease in ultimate strength but some increment in elongation when treated by (−196 ℃, 12 h)+(250 ℃, 12 h). However, the ultimate strength abruptly decreases to 307 MPa and the elongation increases to 5.6% when the samples are treated by (−196 ℃, 12 h)+(300 ℃, 12 h), and the mechanical properties are stable at this level as the number of cycles increases. The phase transformation during the heat-treatment at alternate temperature is the key factor of the variation in mechanical properties.
Key words: high-low temperature cycle; ageing; precipitation; fracture; elongation
