In situ study on fracture behaviors of SiC/2A14Al composite joint： Co-construction of microstructure and mechanical properties via laser welding

Abstract

SiC p /Al matrix composite (SiC p /AMCs) has been widely used in aerospace field of structural frames, but it is difficult to realize the lightweight connection of complex structural parts. Understanding the fracture mechanism from the source will provide a decisive insight into the preparation (e.g. additive manufacturing) and processing (e.g. welding) of new high strength lightweight aluminum matrix composite. In this work, the fracture characteristics and the correlative damage mechanisms near fracture crack tip in a notorious SiC/2A14Al joint was conducted by in-situ scanning electron microscopy tensile test and transmission electron microscopy . The sandwich eutectic microstructure Mg 2 Si–Al–AlCu of clean interface and micron scale heterogeneous heterostructure inhibited the crack propagation . The sandwich eutectic microstructure disperses the extra stress caused by deformation, and the dislocation multiplies and moves at the interface of Mg 2 Si–Al and Al–AlCu phase, which slows down the stress concentration at the interface and avoids catastrophic crack propagation. Based on the fracture crack initiation source characterization of the joint, a rapid solidification process strategy was designed to further improve the mechanical properties of the joint, and the joint with tensile strength of 255 MPa was successfully prepared. Under the premise of ensuring full penetration and the same heat input, it is easier to obtain satisfactory tensile strength with high laser power - high velocity welding parameters, which is due to the suppression of the Al 4 C 3 . This work can be regarded as a breakthrough in the research of high strength aluminum matrix composites guided by reverse failure analysis strategy.