Static and Fatigue Properties of Rotary Friction Welded Dissimilar AA7075/AA5083 Aluminium Alloy Joints at Various Rotational Speeds

Abstract

In the present study, dissimilar rotary friction welding of AA7075/AA5083 aluminium alloy rods having diameter of 15 mm was conducted at various rotational speeds in the range of 370 to 2500 rpm. The aim of this research is to gain the best weld mechanical properties in particular weld tensile strength and fatigue performance. Several experiments were carried out including macro and microstructural examinations, microhardness measurements, tensile tests and fatigue tests combined with residual stress measurements. Results show that at higher rotational speeds, typically 540 rpm or above, the dissimilar AA7075/AA5083 rotary friction weld joints reveal static fracture in the AA5083 base metal side indicating the joint efficiency is more than 100%. It seems that the best weld joint is achieved at the rotational speed of 1200 rpm in which the friction heat is sufficient to form metallurgical bonding without causing excessive flash and burn-off shortening. In such a condition, the fatigue strength of the weld joint is slightly higher than its AA5083 base metal but it is lower compared to another AA7075 base metal. It is confirmed that the crack origin is observed at the interface followed by fatigue crack growth towards AA5083 side and the growth of crack seems to be controlled by microstructure and residual stress.