Effect of Cu and Ni on the mechanical properties and fracture behavior of Al–Si–Mg cast alloys

Chem. Met. Alloys 7 (2014) 154-159

https://doi.org/10.30970/cma7.0281

Abul HOSSAIN, A.S.W. KURNY

The effect of addition of Cu or Ni on the microstructure and mechanical properties of an
Al-6Si-0.5Mg alloy was investigated. The alloys were cast into pre-heated metal moulds, homogenized (24 h at 500°C), solution-treated (2 h at 540°C) and aged for 1 h at temperatures of up to 300°C; the age-hardening stages were monitored by hardness measurements. Tensile properties of the aged alloys were evaluated at nominal strain rates of 10^-3 s^-1. The yield strength and fracture strength of the alloys were found to increase with increasing ageing temperature and to be maximum in the peak-aged condition (1 h at 225°C), whereas the ductility and impact toughness decreased with increasing ageing temperature. The addition of 2 wt.% Cu to the Al-6Si-0.5Mg alloy resulted in an increase of the hardness and tensile strength and substantial reduction of the ductility and fracture toughness. The fracture toughness of the Al-6Si-0.5Mg-2Ni alloy, containing 2 wt.% Ni, was lower for all ageing treatments and lowest at the peak-aged condition. SEM fractographs of broken specimens showed both ductile and ductile-brittle fracture behavior.

Microstructure of a solution-treated Al-6Si-0.5Mg cast alloy (Alloy-1)

Keywords

Al-6Si-0.5Mg alloy / Microstructure / Tensile strength / Fractograph