摘 要

本試驗用光學顯微鏡，掃描電鏡以及能譜分析對變形鎂合金AZ61ND:YAG脈沖激光焊接接頭微觀組織和缺陷進行了詳細的研究。結果表明:脈沖激光焊接焊接鎂合金AZ61能夠得到缺陷較少的焊縫，同時焊接線能量對微觀組織的變化和缺陷的形成有很大的影響。
實驗結果表明：熱影響區(qū)的寬度在焊接線能量較小時很窄，但是隨著線能量的增加熱影響區(qū)的寬度也隨著增加，而且在焊縫區(qū)還存在著具有一定寬度的層狀偏析。另外焊縫中也出現(xiàn)了熱裂紋和氣孔等缺陷：鎂合金AZ61的脈沖激光焊接焊縫對熱裂紋敏感性很強，幾乎每個焊縫都出現(xiàn)了不同程度的熱裂紋，而氣孔則主要為氫氣孔，并且隨著線能量的增加凝固裂紋減少液化裂紋增多氣孔也隨著減少，在焊接線能量為87J/mm時焊縫中缺陷較少。


關鍵詞：鎂合金，激光焊接，微觀組織

ABSTRACT

Optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to analyze the microstructure and defect of wrought AZ61magnesium alloy joint welded by ND:YAG pulse laser. The results show that defect-free welding seam of the AZ61magnesium alloy can be achieved by use of pulse laser welding and the welding heat input influenced the microstructure and the defect distribution of alloy joint greatly.
The experiments show that the width of the heat affect zone (HAZ) was narrow when the heat input was low while it increased with the increase of heat input. Layer-like segregations were presented in the weld seam. In addition, hot cracks and pores were formed in the weld seam. The presence of hot cracks almost in every weld seam indicated hot cracks were easy to form in AZ61magnesium alloy joint during pulse laser welding. The number of the hydrogen pores, which is the major pore formed in alloy joint, reduced with the increase of heat input in pulse laser welding. The best alloy joint with most few defects was obtained when the heat input of pulse laser welding about 87 J/mm.


Key words: magnesium alloy, laser welding, microstructure

目 錄

中文摘要 Ⅰ
ABSTRACT Ⅱ
1緒論 1
1.1鎂及鎂合金性能與應用前景 1
1.2 鎂合金加工（成型）技術的現(xiàn)狀與發(fā)展 3
1.3 激光技術及激光焊接 5
1.4 激光焊接技術發(fā)展趨勢和展望 6
2 實驗 9
2.1 實驗材料 9
2.2 實驗設備 9
2.3 實驗原理 11
2.3.1 激光焊接原理 11
2.3.2 掃描電子顯微鏡（SEM）及工作原理 13
2.4 實驗工藝及樣品的制備 14
2.4.1 實驗工藝 14
2.4.2 樣品的制備 15
3 實驗結果的分析及討論 16
3.1激光焊接焊縫成型分析 16
3.1.1 焊接接頭的宏觀結構 16
3.1.2 焊接接頭的微觀組織 17
3.1.3 線能量對微觀組織的影響 19
3.2激光焊接焊縫微觀組織缺陷分析 20
3.2.1 氣孔 22
3.2.2 裂紋 23
3.2.3 元素損耗 24
3.2.4 層狀偏析 25
3.3關于缺陷的預防的討論 25
4 結論 28
參考文獻 29