摘要
In friction stir welding(FSW), pin profile has more influence on material flow especially in welding of dissimilar materials with different yield strengths. In the dissimilar welding of aluminium and copper, the material flow behaviour is complex to understand and thus a study is needed to reveal the mechanism of flow behaviour and the resultant mechanical properties. Three pin profiles, whorl pin profile(WPP), plain taper pin profile(PTP) and taper treaded pin profile(TTP) were chosen. The effects of pin profile on the microstructure, microhardness and tensile properties were studied. Optical microscope, scanning electron microscope, X-ray diffraction and EDS analysis were used to characterize the microstructural features. Among the three pin profiles, PTP profile results in defect-free stir zone and maximum joint properties of yield strength of 101 MPa, tensile strength of 116 MPa and joint efficiency of 68% compared with the other pin profiles. However, the microhardness plots are more or less identical for all the pin profiles but follows fluctuating trend. This is attributed to the heterogeneous distribution of hard Cu particle. The superior joint properties are mainly attributed to the defect-free stir zone formation and dispersion strengthening.
在搅拌摩擦焊中,搅拌头的外形对材料流有很大的影响,特别是对具有不同屈服强度的异质材料。在铝和铜的异质焊接过程中,材料流行为复杂难懂,因此揭示流变行为和力学性能相当重要。选择了3种不同外形的搅拌头:螺纹搅拌头(WPP)、平锥形搅拌头(PTP)、锥针形搅拌头(TTP),研究搅拌头的外形对材料显微结构、显微硬度和拉伸性能的影响。采用光学显微镜、扫描电子显微镜、X-射线衍射和EDS表征材料的显微组织。在这3种不同外形的搅拌头中,PTP搅拌头能产生无缺陷搅拌区,并得到力学性能良好的接头,其屈服强度为101 MPa,拉伸强度为106 MPa,焊接效率为68%。然而,对于所有的不同外形的搅拌头,其显微硬度曲线大致相同,但都遵循波动趋势,这归因于铜颗粒的不均匀分布。优良的接头性能归因于无缺陷搅拌区的形成和弥散强化。
