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.
Highlights
High pressure die casting (HPDC) is a near-net shape manufacturing process in which the molten die-cast metal is injected into a metal dieX
The world-wide consensus of the reducing of carbon emission strongly motivates the lightweight of automobile, which requires the die-cast aluminium alloys to be able to provide higher strength, for the achieving of the structural weight saving through the use of the thinner wall components basing on stronger alloys [8]
The super vacuum of 20 mbar was achieved in the die cavity in limited evacuation time of 1.6 s under the super vacuum assisted high pressure die casting, for the fabrication of the composites
Summary
High pressure die casting (HPDC) is a near-net shape manufacturing process in which the molten die-cast metal is injected into a metal die. The as-cast strengths of the currently available die-cast automotive aluminium alloys are usually low, with a yield strength of ~130–170 MPa [9,10]. It is hard to meet the requirement of higher strength die-cast automotive aluminium alloys basing on the currently available alloys. Few literatures reported the particle reinforcement of the die-cast aluminium alloys under HPDC [25]. The latest developed frontier super vacuum assisted HPDC process can achieve a cutting-edge vacuum [27], and it could largely decrease the gas porosities in HPDC castings and enable the further strengthening of the diecast aluminium alloys through heat treatment. Al–Si–Mg–Mn die-cast aluminium alloys have been widely used in automotive industry for the manufacturing of high integrity castings due to excellent combinations of castability, strength, ductility and corrosion resistance [9,11,28]. Super vacuum assisted HPDC was applied to enable the heat treatment of the composites
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