Investigation on microstructure and mechanical properties of in-situ TiB2/Al–Cu–Mg composite profile fabricated by porthole die extrusion

Abstract

A comparative study was conducted on 2024 Al and in-situ TiB2/2024 Al composite extruded by porthole die. The evolution of microstructure from as-cast billet to extruded profile, and the response of mechanical properties were examined. The result showed that the grain sizes of the as-cast 2024 Al and TiB2/2024 Al were 95.6 and 38.5 μm, which indicates a strong refining effects of TiB2 particles during solidification. The extruded profile is divided into the welding zone with fine equiaxed grains and matrix zone with coarse elongated grains, and the grain size in both zones were refined in the extruded TiB2/2024 Al. The nanosized Al9Fe0.84Mn2.16Si and TiB2 as well as some coarse particles were observed, and large number of dislocations formed in the matrix zone due to the severe deformation and slight recrystallization. Compared to the extruded 2024 Al, both the hardness and wear resistance were enhanced in extruded TiB2/2024 Al. Moreover, the matrix zone always owned higher hardness and better wear resistance than the welding zone. The ultimate tensile strength of extruded 2024 Al and TiB2/2024 Al are 255.6 and 263.6 MPa, and the elongation of them are 18.6% and 19.2%. It implies that TiB2/2024 Al can achieve good welding quality during the porthole die extrusion, which will not cause the loss of mechanical properties.