Study of back-pressure on microstructure of AZ80 magnesium alloy in equal channel angular extrusion

• Main Authors: Lin, Yueh-Shien, 林岳賢
• Other Authors: Hsu, Ray-Quan
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/56063984408097369964

碩士 === 國立交通大學 === 機械工程系所 === 97 === Severe Plastic Deformation (SPD) is widely used to improve the mechanical properties of magnesium. The equal channel angular extrusion (ECAE) is the most simple and convenient technique in SPD. By using ECAE, we obtain a product which has the same cross section with original billet after extrusion .In addition, the force required in extrusion during ECAE process is usually not large, and we can control the microstructure of the billet by changing the die parameters. Our experiments show that low temperature extrusion can achieve in grain refinement, but the lowest extrusion temperature is limited by materials and dies. Imposing a back-pressure is useful for increasing the strain of billet to avoid the cracking on the billet surface by tensile stress. In order words, imposing a back-pressure is beneficial to compromise the extrusion temperature. In this study, the effect on the microstructure of magnesium alloy AZ80 of imposing the back-pressure was investigated. As a result, we found that imposing the back-pressure is helpful in extending the lowest extrusion temperature. At the same temperature, it makes the grain size larger with increasing back-pressure.