Quality Index of Tensile Properties on Microporosity Variation in A5052 Aluminium Alloy

The present study aims to estimate the variability in the tensile properties of the A5052 aluminium alloy processed through ultra-high-density sonication. An in-depth look at the quality index of the tensile properties to microporosity variations through a quantitative description based on a modified constitutive model for tensile instability. The test specimens were prepared as billets of 4 inches in diameter via gravity casting using a pilot-scale melt amount (30 kg) under the ultrasonic frequency of 20 kHz (4.4 kW). The ultimate tensile strength and yield strength of the as-cast A5052 alloy were increased by approximately 40 MPa and 10 MPa due to effective grain refinement through sonication compared to those of specimens without sonication. In addition, the nominal value of fracture elongation also exhibited a remarkable improvement of more than 5% by reducing the microporosity through degassing of the melt during sonication. The ultra-high-density sonication treatment using a Ti-horn to aluminium melt clearly maximised the effect of grain refinement by heterogeneous nucleation of foreign nuclei and fragmentation of dendrites, simultaneously with the degassing action accompanying the melt convection provided by ultrasonic excitation. The dependence of the tensile properties on the microporosity variation can be expressed in terms of a quality index chart, which considers the porosity level, the distribution of micro-voids, and the strain hardening exponent through the modified constitutive model.