Mechanical Properties and Residual Stress Measurement in the Friction Stir Welding Process of Al 6061-T6 Plates with Copper and Brass Interlayer

Abstract

Friction stir welding was used to join 6061-T6 aluminum plates with and without the addition of commercial pure copper and brass alloy (CuZn30) interlayers. The effects of these interlayers on mechanical properties, and residual stress distribution were analyzed. Tensile and microhardness tests were conducted to evaluate mechanical performance, while residual stress was measured using the contour method. Welding was performed at rotational speeds of 900 and 1120 rpm and feed rates of 25 and 50 mm/min. Results showed a 54% increase in yield strength in the no-interlayer condition and a 35% increase with a copper-interlayer compared to the base metal. The highest hardness, 158 Vickers, was recorded in the brass-interlayer joint. Residual stress analysis revealed that stresses were tensile near the weld center and compressive in the base metal. Longitudinal residual stresses were generally higher than transverse stresses. The brass interlayer led to the highest residual stress distribution, followed by the copper interlayer, indicating the interlayer’s role in increasing residual stress in friction stir welding.