水下多道次搅拌摩擦加工对纯铜微观组织和力学性能的影响

Effects of Underwater Multi-pass Friction Stir Processing on Microstructure and Mechanical Properties of Pure Copper

目的分别在空气中和水中对铜板进行单道次和多道次搅拌摩擦加工(FSP),以此探究冷却介质和加工道次对纯铜微观组织和力学性能的影响。方法选择厚度为3mm的T2纯铜板分别在空气中进行1~2道次加工,在水下进行1~4道次加工。使用光学显微镜、显微硬度检测、扫描电子显微镜和拉伸试验机对加工后的试样进行微观组织和力学性能检测。结果与空气中的搅拌摩擦加工相比,水下搅拌摩擦加工试样的表面质量更好;空气中搅拌摩擦加工试样的晶粒尺寸比母材的晶粒尺寸大,水下搅拌摩擦加工(SFSP)可以有效细化晶粒,并且随着加工道次的增加,晶粒尺寸逐渐增大,其中,1道次水下搅拌摩擦加工纯铜的晶粒尺寸最小(3.93μm)。显微硬度检测和拉伸试验结果表明,与空气中搅拌摩擦加工试样相比,水下搅拌摩擦加工试样的屈服强度和硬度更高,但随着加工道次的增加,样品的屈服强度和硬度都会有所降低。结论水下多道次搅拌摩擦加工可以减小纯铜的晶粒尺寸,提升纯铜的力学性能。

The work aims to investigate the effects of cooling medium and number of passes on the microstructure and me-chanical properties of pure copper by single and multi-pass friction stir processing(FSP)in air and water,respectively.T2 pure copper plates with a thickness of 3 mm were processed one to two passes in the air and one to four passes in the water.The mi-crostructure and mechanical properties of the processed samples were measured with an optical microscopy,a microhardness tester,a scanning electron microscope and a tensile tester.Compared with air friction stir processing,the surface quality of sam-ples after underwater friction stir processing was better.The grain size of the sample processed by friction stir in air was larger than that of the base metal.The grain size of the sample processed by friction stir under water(SFSP)could be effectively re-fined,and the grain size increased gradually with the increase of the number of processing passes.Among them,the grain size of pure copper processed by friction stir under water for one pass was the smallest(3.93μm).The results of microhardness test and tensile test showed that the yield strength and hardness of the samples processed under water were higher than those in air,but the yield strength and hardness of the samples would decrease with the increase of the number of processing passes.The grain size of pure copper can be reduced and the mechanical properties of pure copper can be improved by underwater multi-pass fric-tion stir processing.