本論文主旨在探討連續式CO2 雷射銲接製程對AZ31B與AZ61A鎂合金銲接性之影響，並與傳統氬銲製程進行比較，研究範圍為銲接參數對微觀組織、化學成份、機械性質及破壞形態等影響。
　　研究發現不同功率、銲接走速但入熱量相同時，會得到相同的銲透深度，深比則隨入熱量增加而增加。銲道中以掃瞄式電子顯微鏡(Scanning electron microscope , SEM)觀察發現AZ61A之析出物數量較AZ31B為多，且析出物尺寸隨入熱量增加而增加。而電子微探儀(Electron probe X-ray microanalysis , EPMA)成份定量分析顯示銲道有合金元素減少的情況，隨入熱量增加而元素損失也越多。於SEM下在AZ61A銲道邊緣發現有液化裂縫存在，能量分散光譜儀(Energy dispersive X-ray spectroscopy , EDS)掃瞄結果顯示微裂縫邊緣有鋁、鋅偏析的現象。
　　微硬度試驗結果雷射銲道有硬度提高的現象。而拉伸試驗中雷射銲道試片抗拉強度高於TIG試片，因為液化裂縫的影響導致兩種合金呈現不同的拉伸破壞形式。

Effects of welding heat input on CO2 laser weldability of AZ31B and AZ61A magnesium alloy extrusion sheet which has been investigated. CO2 laser beam welding was conducted on AZ31B and AZ61A magnesium alloy sheets at different welding speeds and input density. The depth-to-width ratio, mechanical property, microstructure, chemical component , and fractography, of the welds were evaluated using optical microscopy, tensile tests, hardness tests, energy dispersive X-ray spectroscopy, and electron probe for microanalysis, scanning electron microscope, and compared with TIG(tungsten inert gas) welding.
Results indicated that both the hardness and tensile strength of laser beam welding were higher than those of TIG welds. It was shown that both the volume of precipitates increased on welded metal while the increase of heat input, AZ61A got more precipitates than AZ31B. But welded metal lose of alloy element increased on increase of heat input. Liquation Crack and segregation of Al and Zn were found on the edge of laser welded bead of AZ61A, but not found in TIG welded bead or in AZ31B. Liquation Crack led to different tensile fractography on two alloys.

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