基于响应面设计发现2195铝锂合金薄板单面搅拌摩擦焊接的最佳工艺参数，并发现当转速越高焊速越低时，焊接接头的抗拉强度越高。实验结果表明：单面搅拌摩擦焊接中，针长为板材厚度的2/3长度时，焊缝根部出现未焊接缺陷，焊接接头的断裂形式介于脆性与塑性断裂之间，接头抗拉强度较差。在单面焊接最佳工艺参数的基础下，双面搅拌摩擦焊接能克服单面焊接中存在于焊缝根部的未焊接缺陷。通过设置不同的刀具下压量，当搅拌头转速为1600 r/min，进给速度为150 mm/min，下压量为0.1 mm时，双面焊接能将焊接接头的抗拉强度提高约10%，焊接接头的伸长率提高10%。双面搅拌摩擦焊接中前进侧的材料流动明显，焊接接头的断裂形式为塑性断裂。在双面焊接中，由于坯料受到了二次搅拌和加热，焊接区的材料软化加剧。相较于单面焊接，双面焊接接头处的显微硬度进一步降低。

Based on the response surface design， the optimal process parameters for single-side friction stir welding（FSW） of 2195 Al-Li alloy sheets are studied. It is found that the higher the rotation speed and the lower the welding speed， the higher the tensile strength of the welded joint. The results show that in the single-side FSW， when the pin length is 2/3 length of the thickness of the plate， the root of the weld appears unwelded defects， the fracture form of the welded joint is between brittle and plastic fracture， and the tensile strength of the joint is poor. Based on the optimum process parameters of single-sided welding， double-sided FSW can overcome the unwelded defects at the root of single-sided welding. Under different tool pressures， when the stirring head speed is 1600 r/min， the feed speed is 150 mm/min， and the pressure is 0.1 mm， the double-sided welding can improve the tensile strength of the welded joint by about 10% and the elongation of the welded joint by 10%. In two-sided FSW， the material flow on the forward side is obvious， and the fracture mode of the welded joint is a plastic fracture. In double-sided welding， the plate is subjected to secondary stirring and heating， resulting in increased softening of the material in the welding area.The microhardness of the double-sided welded joint is further reduced than that of the single-sided welding.