基于搅拌摩擦加工的汽车钛合金组织与性能研究

Study on the microstructure and mechanical properties of the automotive titanium alloy based on friction stir processing

采用不同的主轴旋转速度和行进速度对铸态Ti8LC汽车钛合金进行了搅拌摩擦加工改性试验,并测试和对比分析了合金试样的显微组织和力学性能。结果表明,改性后合金内部晶粒明显细化、组织分布均匀性得到改善、力学性能显著提高。在轴肩下压量0.2 mm和主轴倾斜角度2.5°不变的情况下,随主轴旋转速度从200 r/min增大到400 r/min或行进速度从30 mm/s加快到90 mm/s,改性钛合金试样的晶粒先细化后粗化、力学性能先提高后下降。主轴旋转速度300 r/min,行进速度60 mm/s时改性钛合金试样的力学性能最佳,抗拉强度和屈服强度分别为1 046、729 MPa,延伸率为12.7%;与铸态Ti8LC汽车钛合金相比,改性后试样的抗拉强度和屈服强度分别增大118、125 MPa,其增幅分别达12.7%、20.7%。

In this investigation, the friction stir processing(FSP) method was used to modify the surface layer of an as-cast Ti8LC automotive titanium alloy using different spindle rotation speeds and travel speeds. In addition, the microstructure and mechanical properties of the alloy samples were tested and compared. The results show that the internal grains of the alloy are refined, and the uniformity of microstructure distribution and the mechanical properties are improved after FSP modification. When the shoulder depression is 0.2 mm, and the spindle inclination angle is 2.5°, the spindle rotation speed increases from 200 r/min to 400 r/min or travel speed from 30 mm/s to 90 mm/s. Meanwhile, the grains of FSP alloy samples are refined first and then coarsened, and the mechanical properties are improved first and then decreased. The best mechanical properties of the modified alloy samples can be obtained with the spindle rotation speed of 300 r/min and the travel speed of 60 mm/s. The tensile strength, yield strength and elongation are 1 046, 729 MPa and 12.7%, respectively. Compared with the as-cast Ti8LC automotive titanium alloy, the tensile strength and yield strength of FSP modified alloy samples are increased by 118 MPa and 125 MPa(with a 12.7% and 20.7% amplitude), respectively.