The effect of temperature and strain rate on elongation to failure in nanostructured Al-0.2wt% Zr alloy fabricated by ARB process

A nano/ultra-fine grain Al-0.2wt% Zr alloy was produced by accumulated roll bonding (ARB) processafter 10 cycles. The fraction of high angle grain boundaries increased from 8% to 65.4% during 10passes during ARB process. This alloy was subjected to tensile test at different temperatures (523,573and 623 K) and strain rates (0.1 and 0.01 s-1). The optimum condition of temperature and strain rate of623k and 0.01s-1 was achieved for maximum elongation to failure, leading to 100% elongation,although maximum elongation was achieved at higher strain rate and maximum chosen temperature.In fracture surfaces after the test, dimples in higher temperature were deeper, bigger, and longer thanlow temperature. Because of presenting the superplasticity character at elevated temperature andhigher strain rate, there was no evidence of necking after failure

Analysis of Strengthening Mechanisms in an Artificially Aged Ultrafine Grain 6061 Aluminum Alloy

The current study adopted a quantitative approach to investigating the mechanical properties, and their relationship to the microstructural features, of precipitation-strengthened 6061 aluminum alloy processed through accumulative roll bonding (ARB) and aging heat treatment.  To serve this purpose, the contributions of different strengthening mechanisms including grain refinement, precipitation, dislocation and solid-solution strengthening to the yield strength of five-cycle ARB samples processed under pre-aged (ARBed) and aged (ARBed+Aged) conditions were examined and compared. Microstructural characterizations were performed on the samples through the transmission electron microscope (TEM) and X-ray diffraction (XRD). Also, the mechanical properties of the samples were investigated through the tensile test. The obtained results showed that an equiaxed ultrafine grain structure with nano-sized precipitates was created in the both ARBed and ARBed+Aged samples. The grain refinement was the predominant strengthening mechanism which was estimated to contribute 151 and 226 MPa to the ARBed and ARBed+Aged samples, respectively, while the dislocation and Orowan strengthening mechanisms were ranked second with regard to their contributions to the ARBed and ARBed+Aged samples, respectively. The overall yield strength, calculated through the root mean square summation method, was found to be in good agreement with the experimentally determined yield strength. It was also found that the presence of non-shearable precipitates, which interfered with the movement of the dislocations, would be effective for the simultaneous improvement of the strength and ductility of the ARBed+Agedsample