Effect of heat treatment on modulus hardening and phase transformation in experimental 7xxx stir-cast alloy from recycled beverage cans

Abstract

The astronomic growth in drinking beverage cans waste calls for an innovative conversion of this huge resources to aerospace and automobile applications. Unfortunately, the can-to-can cycle has been maintained for decades. Past studies nosedived in converting Recycled Beverage Cans (RBCs) to experimental 7 series alloys. Literature on evaluating the consequence of heat treatments on formation of hardening compounds and modulus of this novel alloy is scarce. The aim of this study is to investigate compounds, phase formations and the effect of the duo on the modulus hardening of the experimental Al-Zn-Mg-Cu alloy cast from RBCs after heat treatments. Weight percent (wt. %) of Zn was varied at 4, 4.5 and 5; annealing at 350, 380 and 413 °C; artificial ageing temperature and time were equally varied at 100, 120 and 145 °C and 5, 10.5 and 15 hrs respectively. The highest modulus of 566.0 MPa was observed in an alloy of 5 wt% Zn, annealed at 350 °C, 100 °C T6- temperature and 6 hrs soaking time. When the annealing temperature and wt. % Zn were increased to 380 °C and 4.5 wt%, the modulus was 170.0 MPa. Simples artificially aged at 120 °C and 100 °C, when time was held at 10.5 hrs recorded a peak modulus of 137.3 MPa and least of 127. 8 MPa. The maximum obtainable hardness of 151.6 Hv was observed in an alloy with 4 wt% Zn, 145 °C T6-Temperature and aged for 15 hrs. Al, FCC (ICDD 004-0787), Zn (ICDD = 004-0831) were among identified phases. Simulations to predict the mushy zones of this alloy and other properties, the introduction of graphene in RBCs for property enhancement are opinions open to further investigations.