Microstructural and Mechanical Properties of Dissimilar Aluminium Alloys by Friction Stir Welding

Abstract

In the present study, the dissimilar aluminium alloys AA 2014-T651 and AA 7075-T651 of 16 joints was successfully joined with (four welding speeds (50, 60, 70, 80 mm/min), four rotational speeds (900, 1000, 1100, 1200 rpm), four different weld tool profiles (T1=12/4, T2=15/5, T3=16/4, T4=20/5 in D/d ratio) by friction stir welding machine. In the optical microstructure and SEM very fine equiaxed grains are formed in the stir zone. The maximum hardness value is 150 HV obtained in the weld nugget area of the specimen 2 under the conditions of 900 rpm, 70 mm/min for T3 profile. Compare to other tool profiles T3 profile attained maximum hardness value. The minimum hardness value is attained for the specimen 13 for the tool profile T1 was 103 HV compared to all tool profiles. In post weld heat treatment conditions, hardness values were decreased compare with as weld conditions due to over heating followed by ageing. The maximum joint efficiency attained is around 90 to 95% with T2 and T3 profiles at rotational speed of 1000 rpm, 1200 rpm and welding speed of 60, 70 mm/min. The T1 profile attained least joint efficiency of 69.5 % at 900 rpm, 50 mm/min, since it has very less shoulder diameter or contact area and maintain a D/d ratio is 3.