Advanced heat treated die-cast aluminium composites fabricated by TiB2 nanoparticle implantation

Abstract

The global carbon emission reduction strongly requires high strength lightweight die-cast aluminium alloys in industry. Here die-cast AlSiMgMn–TiB2 composites with advanced mechanical performance were fabricated by the implantation of TiB2 nanoparticles. Super vacuum assisted high pressure die casting was applied to enable the T6 heat treatment of the composites, and the super vacuum of 20 mbar was achieved in the limited evacuation time of 1.6 s. The composites demonstrated good die castability within the addition of 3.5 wt% TiB2, while the composites could not fill into the chill vent with the addition of >3.5 wt% TiB2. The composite with 3.5 wt% TiB2 nanoparticles delivered the high hardness of 150.2 kg/mm2, yield strength of 351 MPa, tensile strength of 410 MPa, and the industrially applicable good ductility of 5.2%, after T6 heat treatment. The strengthening of the T6 heat treated composite was a result of both TiB2 nanoparticles and nanoscale β′′ precipitates that had coherent interfaces with α–Al matrix, i.e., Al(11-1)//TiB2(0001), Al[011]//TiB2[11-20], Al[320]//β″(a-axis), Al[1-30]//β″(c-axis) and Al(020)//β″(b-axis). The T6 heat treated composite reinforced by 3.5 wt% TiB2 showed ductile fracture.