本研究採用熱輥軋及等通道彎角擠製來探討可細化鎂合金晶粒程度以及對機械性質的影響，並利用沖壓、吹氣成形法探討晶粒細化前後鎂合金鈑片之成形性。 在沖壓成形實驗中，未經輥軋鈑片成形性不佳，需要420℃的高溫及10分鐘的預熱時間才能使鈑片成功成形，而利用階段沖壓則可以降低成形溫度及預熱時間。 熱輥軋研究中，AZ31鎂合金2mm厚鈑片加熱至350℃持溫10分鐘後，一次輥軋50％，可細化晶粒10μm至4.7μm，降伏強度由161MPa提升至279MPa，同時伸長率也由14.2%提升至20.9%。熱輥軋後之鎂鈑經退火處理後，可使晶粒大小之分佈更平均，且伸長率再提升。 鈑片吹氣成形研究中，晶粒細化的確能有效提升鎂鈑之成形性，經熱輥軋後的AZ31鎂鈑在300℃及5x10-3~1x10-2應變速率範圍內，伸長率可達220%。 在等通道彎角擠製(Equal Channel Angular Extrusion, ECAE)部份，AZ31鎂合金以Φ=90o、250℃一道次擠製後再以200℃擠製三道次後，晶粒細化效果最佳，由9.5μm細化至2.6μm，而機械性質也相對的提升，其中降伏強度由169MPa增加至226MPa，伸長率則由18.7﹪提升至21.7%，再經由後續退火處理，材料伸長率更大幅度的提升至29.2%。 由於ECAE與熱軋之不同加工方式，使材料呈現不同之織構組織，因而使得ECAE製程後的AZ31及AZ61材料強度皆低於熱軋後異方性較高之材料。另外在高溫性質方面，由於AZ61加工後會在晶界處生成微細之析出物，這使得其高溫之延伸率優於AZ31鎂合金。 Magnesium alloy is the lightest metal that can be employed for structural use, and there have been many researches of grain refining on this material. We will investigate the different effects on mechanical properties between two grain refining methods--(1) Rolling and (2) ECAE (Equal Channel Angular Extrusion) process. Also, the formability of un-processed and processed materials would be conferred by punch and gas forming (punch-less) method as well. 2mm of AZ31 plate reduced 50% thickness by rolling single time with hot roller after preheating 10mins at 350℃, then we can have fine grain (<5μm) materials. Meanwhile, the better yielding strength (161->279MPa) and elongation (14.2->20.9%) can be achieved by this process. In addition, this process will improve the gas formability of Magnesium Alloy. The elongation of refined AZ31 specimen could reach 220% by gas forming at 300℃ and the strain rate range of 5x10-3~1x10-2. In ECAE experiments, after extruded one time at 250℃ and three times at 200℃ with channel angular of 90o, we could have smallest grain size decreased from 9.5 to 2.6μm. Equally, the strength and elongation of materials increased simultaneously after ECAE process. The ductility would have further great promotion after the post-annealing treatment. Because of different textures, both AZ31 and AZ61 materials with more strength can be achieved by rolling than ECAE process. This phenomenon is more apparent after post-annealing treatment. Besides, fine precipitations(<1μm) will exist at grain boundaries after processed, this is the reason why AZ61 materials have more ductility than AZ31 at high temperature. The results of this study might be used as referenced resources not only for the related academic research of Magnesium Alloy but also for the development of the real products in industry.
