EFFECT OF PROCESS PARAMETERS ON FRICTION STIR LAP WELDED 304 STAINLESS STEEL AND 5052 ALUMINIUM ALLOYS

摘要

Joining of two different materials like aluminium and steel is a challenging task because of the vast differences in their physical, mechanical and chemical properties. Friction stir welding is a solid-state joining technique which is successful in joining dissimilar materials. In this study, the tool made with Tungsten-Rhenium with a pin length of 4.1 mm is used to weld 4 mm stainless steel and 2 mm aluminium plates in lap configuration with steel as the top plate. The process parameters used in the study are tool rotational speeds between 800 rpm and 1200 rpm, traverse speed ranging from 20 mm/min to 40 mm/min, penetration depth of 4.1 mm to 4.3 mm with a varying tilt between from 0°and 2.5°. The Aluminium is melted during the process because of the high temperature and is thrown out in the form of flash resulting in the formation of defects and a cup like structure at the weld zone. Microstructural analysis confirmed that formation of a sound joint without defects was impossible. The mechanically stirred zone consists of a thin intermetallic layer at the interface of aluminium and steel plates. The thickness of the intermetallic layers formed were between 5 /μm and 20 /μm. The maximum shear strength of 2.7 kN was achieved with tool rotational speed of 1000 rpm, penetration depth of 4.3 mm and welding speed of 30 mm/min when the angle was tilted at 0°. It is evident from the experiments that the joints achieved were not defect free because of improper mixing of the material.