Authors: Naveed Akhtar; Su Jun Wu
Addresses: School of Material Science and Engineering, Beihang University, Beijing 100191, China ' School of Material Science and Engineering, Beihang University, Xue Yuan Road, Hadian District, Beijing 100191, China
Abstract: Development of idiosyncratic microstructure as a result of laser beam welding (LBW), and joint efficiency along with fatigue behaviour was investigated in an aluminium-lithium alloy. In this experiment rolled sheet of 2 mm thickness was used to fabricate butt joints via LBW technique. Five selected joints were analysed to observe the microstructural changes, mechanical and fatigue properties, and fracture mechanisms in the weld zone. Tensile test results showed that the LBW joints exhibited ∼21-30% reduction in UTS. However, a delayed fatigue crack initiation was observed inside the weld fusion zone, which was attributed to the freshly developed unique microstructure. A transgranular fatigue was detected in the near-threshold region, whereas, ductile striations during stage II, and intergranular dimpled fracture in the final stage. A fairly good fatigue life of the laser beam weld could be credited to the unique microstructural arrangement inside the fusion zone.
Keywords: laser beam welding; LBW; aluminium alloys; lithium; fatigue crack growth rate; fracture toughness; microstructure; mechanical properties; laser welding; butt joints; tensile testing; crack initiation; weld fusion zone; transgranular fatigue; ductile striations; intergranular dimpled fracture.
International Journal of Microstructure and Materials Properties, 2015 Vol.10 No.5/6, pp.350 - 365
Received: 27 Aug 2015
Accepted: 23 Oct 2015
Published online: 28 Feb 2016 *