The influence of tool traverse speed on the low cycle fatigue properties of AZ31 friction stir welded joints

This paper describes the basic low cycle fatigue properties of AZ31 friction stir welded joints obtained by different welding velocities: 150, 300, 600, and 900 mm/min with the constant value of 1600 rpm tool rotation speed. The performed LCF tests at various strain amplitudes: 0.25, 0.35, 0.5 (for R=-1) together with fractography analysis allowed to state that the value of welding velocity has no significant impact on the LCF behavior of AZ31 FSW in the investigated range. The tests also revealed that the AZ31 FSW joint is characterized by three stages of fatigue life: a very short period of cyclic hardening (up to 100 cycles), cyclic stabilization, and a relatively long period of cyclic softening until failure. All joints are free of imperfections and tend to fail in the heat-affected zones.