마찰교반 점용접을 이용한 Al 합금의 접합성 평가

Abstract

In an attempt to optimize the friction spot joining process of Al alloys for automotive (Al 5052-H32 and Al 6111-T4, thickness 1mm), effects of joining parameters such as tool rotating speed, plunging depth and dwelling time on the weld joints properties were evaluated. Experimental tests were carried out for Al plates with lap joint. A wide range of joining conditions could be applied to join Al alloys for automotive without defects in the weld zone except for certain welding conditions with an insufficient heat input. The microstructures and hardness variations in the weld regions are discussed. The microstructures of welds, which corresponds to the pin hole, have dynamic-recrystallized grain similar to the stir zone in FSW weld. In hardness distribution, minimum hardness region was located about 6mm away from the weld center, corresponding to the shoulder radius of the tool. For each weld the results from tensile-shear tests are also presented. For sound joints without defects, tensile shear failure load of weld joints was approximately 230% higher than acceptable criteria of tensile shear strength in electrical resistance spot-welded joints for aluminum (MIL-W-6858D).