Original Article

Microstructural investigations on laser welded Al-30wt.% B₄C composite

Institute of Materials, China Academy of Engineering Physics, Mianyang 621908, China

^* e-mail: lyjcaep@163.com
^** e-mail: pxx3751@163.com

Received: 16 September 2022
Accepted: 6 January 2023

Abstract

In order to tailor the microstructures and mechanical properties of laser welded Al-B₄C composite, it is necessary to elucidate the chemical reactions between B₄C reinforcement and Al matrix during laser welding process. In this study, 3 mm thick Al-30wt.% B₄C plates were laser welded using different parameters. Then the microstructure, reaction products, tensile properties and fracture surface of welded joint were studied. The results show that the reaction products of the weld zone can be controlled by varying the welding energy input, but the full penetration welded joint requires high energy input (120 KJ/m in this paper). For the full penetration welded joint, all B₄C particles and part Al matrix react to form irregularly particle-like AlB₂C₂ and coarse needle-like Al₄C₃ phases, the joint efficiency is 67%. The failure mechanism of AlB₁₂C₂ is cleavage fracture, and the failure mechanism of Al₄C₃ is interfacial decohesion and pull out. The interfacial decohesion between Al₄C₃ and Al matrix results in crack initiation due to their weak bonding interface. The cracks propagate, connect and penetrate the brittle AlB₁₂C₂ phase and eventually lead to brittle fracture of the joint.