The effect of temperature on the mechanical properties and forming limit diagram of aluminum strips fabricated by accumulative roll bonding process

Abstract

Accumulative Roll Bonding (ARB) process is a new, low-cost, and applied method for obtaining nano/ultrafine-grained materials along with improvements in mechanical properties. The primary goal of this study was to investigate the effect of increasing temperature on mechanical properties and formability of Al 1050, fabricated by the ARB process. The present work also aims to study the feasibility of increasing temperature as an approach for solving the ductility problem of ultrafine-grained Al 1050, although some strength of the material might be sacrificed. So, the quantitative and qualitative analysis of the effect of temperature increase on mechanical properties and formability has been done. In this article, the ARB process has been performed at four different temperatures (i.e., 25℃, 100℃, 200℃, and 300℃) to the fifth cycle without lubrication. After the production of samples, the investigation of mechanical properties such as micro-hardness, yield strength, and ultimate tensile strength after each pass of the ARB at different temperatures has been accomplished. The results presented that by applying the ARB process at a specific temperature, the micro-hardness values and mechanical properties of the samples enhanced, while elongation to fracture decreased. Also, at the end of the first pass, the amount of elongation and level of the forming limit diagram (FLD) was sharply reduced, but in subsequent passes, it would increase at low rates. The tensile strength also improved at a lower rate than the first cycle. At ambient temperature, the best mechanical properties after the fifth cycle were obtained, which tensile strength and elongation were recorded as 210.1MPa and 14.2%, respectively. By increasing temperature, the tensile strength and micro-hardness of the samples were slightly lower than the ambient temperature; however, elongation and consequently, forming limits of the samples were improved. At 100°C, no significant changes were observed in the mechanical properties and the formability of specimens compared to the ambient temperature. While the highest difference was at 300°C, which elongation and FLD0 relative to ambient temperature increased by about 38.1% and 87%, respectively.