LAUSR

Abstract Fine eQuiaxed Zone (FQZ) close to the fusion line is a common and unique microstructural feature for fusion welded high-strength Al alloys particularly when containing Zr element. It is well believed that the presence of FQZ can degrade the fatigue cracking resistance and tensile strength of the joints. Thus, a thorough knowledge on the formation and microstructure due to FQZ and resultant softening and failure mechanisms is necessary to be well understood on the damage tolerance and structural integrity of fusion welded joints. Current paper reviews the relevant aspects mentioned above as an important reference to be capable of correlating the microstructural response with service performance. Some potential solutions to coordinate the FQZ are therefore discussed. Furthermore, few papers up to date have focused on the fatigue and fracture mechanisms related with FQZ inside high-strength Al alloy fusion welds. By combining conventional characterization and numerical modelling approach, the high-resolution synchrotron radiation X-ray computed microtomography shows great potential in revealing the competition mechanism between FQZ and welding defects on the cracking behavior.