摘 要 鎂合金為最輕的結構金屬，因其具有良好的比強度、比剛性、導(散)熱性、制震性、電磁遮蔽性及材料回收性等優異的特性，廣泛應用於各種3C產業、汽車工業與自行車等需結構輕量化的工業上。故大量廢料及產品回收的問題日益凸顯，因目前業界所用的液相回收製程有著高污染、高耗能、高成本及高危險性等缺點，因此，本研究探討不同熱處理及熱機處理條件對其固相回收擠製材之機械性質及微結構的影響，找出鎂合金AZ91D固相回收的最佳製程參數。 研究結果顯示不同鎂合金AZ91D屑料狀態(新生、強制氧化及實際廢料)會影響固相回收製程後之機械性質。實際廢料>強制氧化料>新生料，抗拉強度由新生屑料274.3MPa分別提升8.5％及15.5％至297.7MPa及316.7MPa，主要原因為材料的氧化層在擠製過程中碎裂成強化相顆粒。 固相回收材以170 ℃時效處理，其尖峰時效為時效時間16hrs，其中新生料及強制氧化料之抗拉強度分別為371.1及382.3MPa。另AZ91D強制氧化料固相回收擠製材最佳之熱機處理製程為：軋前350℃退火處理+軋後400℃退火處理，此時抗拉強度為335.6MPa，降伏強度為233.5MPa，伸長率為8.1%。 Abstract Magnesium alloy is a kind of lightest structure metal. As it has strong tensile stress and toughness, good conductivity and vibration absorber, electromagnetic cover and easy material recycling, magnesium alloy could be the best choice for 3C products for Aircraft chamber and automobile non-structure requirement material. It becomes wildly used in 3C manufacturing, automobile industry and bicycle etc. light structural industries. Large dumping and product recycle problem becomes outstanding. The research work is to introduce how the solid-state magnesium alloy could be recycled. Various heat treatment approaches and different heat treatment conditions are selected to investigate into the alloy mechanical property and its microstructure performance. It is expected to find out the best result data to strengthen the magnesium alloy AZ91D solid-state recycle process. The result of research as following: (1) The actual waste magnesium alloy can be recycled by the solid-state recycle process and the tensile stress of this recycled material is 316.7MPa. (2) The peak aging is aged at 170℃ temperature and 16hrs, the ultimate tensile stress of specimen which oxidized at 300℃ is 382.3MPa. (3) The best parameter of TMT (Thermo Mechanical Treatment) process of solid-state recycle process is 350oC pre-crunched process plus 400oC pro-tempering heat treatment. The tensile stress could reach 335.6MPa, yield stress 233.5.2MPa and extension rate 8.1%.
