热输入对7A52铝合金光纤激光焊接头组织及性能的影响

Effect of welding heat input on structure and properties of fiber laser welded joints of 7A52 aluminum alloy

采用IPG公司生产的YLS-6000光纤激光器,对6mm厚热轧态7A52铝合金进行焊接,研究不同焊接参数对接头组织及性能的影响。结果表明,焊缝中心为均匀分布的"雪花"状等轴晶,组织为α-Al+T(Mg_3Zn_3Al_2),与母材相同,晶粒大小随热输入的增加而长大;随热输入增加,Mg,Zn元素的烧损逐渐加重;相同热输入下,高功率、高焊速能够降低Mg,Zn元素的烧损;母材硬度最高约为110HV左右,焊缝中心硬度最低,硬度从焊缝中心向两侧母材呈"U"型分布;适当增大焊接热输入,接头的冲击吸收能量和抗拉强度均有所提高;在相同热输入情况下,高功率、高焊速的接头冲击性能降低,抗拉强度有所提高,最大抗拉强度为341MPa,约为母材的69.8%,7A52铝合金光纤激光焊接头拉伸断口形貌呈韧-脆混合断裂。

6 mm thick hot rolled 7a52 aluminum alloy was welded by using fiber laser.The microstructures and properties of welded joints were studied at the same welding heat input with different welding parameters and different welding heat input.The result shows that the microstructure of welded joint consists of larger grain with equiaxed grain in the form of'snow'shape,the grain size was increased with the increase of welding heat input.With the increase of welding heat input,the loss of Mg element and Zn element were increased gradually.At the same welding heat input,high welding speed and high welding power can relatively reduce the burning loss of Mg and Zn elements.The results of hardness test showed that the microhardness of base metal is about 110HV and microhardness in fusion center zone is the lowest,and microhardness curve in the form of 'U'shape from weld center to the parent metal.With the increase of welding heat input,the joint can obviously improve the impact toughness and tensile strength.At the same welding input,the joint at high welding speed and high welding power input has lower impact toughness and higher tensile strength,the maximum tensile strength is 341.05 MPa,accounts for about 69.8% of the base metal.The tensile fractured surface of laser welded 7A52 aluminum alloy is plastic and brittle mixed fracture.