Effect of Ti-B addition on the variation of microporosity and tensile properties of A356 aluminium alloys

The variability in the tensile properties of A356 aluminium alloys due to the addition of a Ti-B alloying element was investigated, including the defect susceptibility of the tensile properties to variations in microporosity, as well as the overall grain size, microporosity, and tensile properties of as-cast and T6-treated alloys. The test specimens were fabricated via gravity casting by the addition of the Al-5Ti-1B master alloy to the A356 alloy melt. The optimal range of the Ti contents for grain refinement and microporosity reduction was 0.06-0.15 wt% Ti and was maintained, even in T6-treated alloys. The ultimate tensile strength and elongation at the optimal range of Ti contents increased by 50 MPa and 3%, respectively, compared to alloys without Ti. The defect susceptibility of tensile properties to variations in the microporosity was improved using the optimal Ti content, and the maximum values of the tensile properties under defect-free conditions also increased. The constitutive description of the empirical relationship of defect susceptibility suggested that the observed improvement in defect susceptibility in the optimal range of Ti contents was mainly due to an increase in the strain-hardening exponent.