Microstructure and properties of as-cast Al-4.5Cu-1.5Mg alloy refined with Ti-supported TiC nanoparticles via ultrasonic-assisted addition

摘要

A novel Ti-supported TiC nanoparticle (NP) refiner (TiC/Ti) was fabricated by high-energy ball milling and successfully introduced into molten Al via ultrasonic assistance. The effects of the refiner on the microstructure and mechanical properties of the as-cast Al-4.5Cu-1.5Mg alloy were investigated, and the refinement mechanism was discussed. With the addition of 0.2 wt% TiC/Ti refiner, the microstructure of the as-cast Al-4.5Cu-1.5Mg alloy was transformed from coarse dendritic crystals to fine grains, and the average grain size of a (Al) decreased from 415 pm to 88 gm. During the refinement process, the uniformly distributed TiC NPs or small clusters promoted the nucleation of alpha (Al) on the surface of TiC along the specific orientation Al (111)//TiC (111) and Al (-111)//TiC (-111), which further resulted in the refinement of the grains, the increase in solute Cu/Mg atoms in alpha (Al) and the improvement of the intergranular eutectic (alpha (Al) + theta (Al2Cu) + S (Al2CuMg) and block theta (Al2Cu)) phases. These microstructural improvements enhanced the Vickers hardness, yield strength and tensile strength of Al-4.5Cu-1.5Mg to 102 HV, 125 MPa and 249 MPa, which were 13.4%, 68.9% and 39.8% greater than those of the unrefined alloys, respectively.