中文摘要：

采用CO2激光对高热裂倾向的ZK60高强镁合金挤压板材进行焊接,研究焊接工艺参数对焊缝成形特征及裂纹倾向的影响规律。结果表明：激光焦点位置设定在板材上表面时,焊缝可以获得最大的熔深和深宽比;焊接速度过高或过低均会导致焊缝深宽比的减小和热裂纹的产生,采用优化的焊接速度可得到成形形状良好且无裂纹的焊缝;激光深熔焊匙孔形成所需的功率密度阈值在0.99×105~1.23×105W/cm2之间,为了保证深熔匙孔的稳定,激光功率选择的下限应不低于750 W;而功率增大到一定值以后,焊缝的熔深不再增大,功率选择的上限应不高于750 W。高速焊接条件下,随着焊接速度的增大,焊缝热裂倾向增大,且开裂形式逐渐由横向裂纹向纵向裂纹转变。

英文摘要：

The high cracking susceptible ZK60 magnesium alloy plates were welded by CO2 laser beam.The effects of welding parameters on the appearance and cracking tendency of the welds were studied.The results show that weld with maximum penetration and aspect ratio can be obtained when the position of focal point is adjusted on the top surface of the plate.Too higher or too lower welding speed deteriorates aspect ratio and leads to the occurrence of hot cracking.Under optimum welding speed range,the weld with high aspect ratio and free of cracking can be manufactured successfully.The threshold power density for deep penetration mode welding of ZK60 alloy is approximately between 0.99×105 and 1.23×105 W/cm2,thus the minimum laser power to sustain is about 750W,and the upper limit of recommend laser power for welding should be lower than that results in maximum penetration deep.Under the condition of higher welding speed,ZK60 alloy presents stronger cracking tendency and morphologies of cracks evolve from transverse to longitudinal with the welding speed increasing further.