Hot workability of cast and wrought Ni-42Cu alloy through hot tensile and compression tests
(1. Department of Materials Science and Technology, Sharif University of Technology, Tehran 11365-8639, Iran;
2. Metallic Materials Research Center, Maleke Ashtar University of Technology, Tehran 1774-15875, Iran;
3. Department of Materials Science and Engineering, Hamedan University of Technology, Hamedan 6516913733, Iran)
2. Metallic Materials Research Center, Maleke Ashtar University of Technology, Tehran 1774-15875, Iran;
3. Department of Materials Science and Engineering, Hamedan University of Technology, Hamedan 6516913733, Iran)
Abstract: In order to analyze the flow behavior and workability of Ni-42Cu in cast and wrought conditions, hot deformation tests were performed at temperatures and strain rates within the ranges of 900-1150 °C and 0.001-1 s-1, respectively. Tensile tests showed a “hot ductility trough” at 950 °C for both alloys. The drop in hot ductility was more considerable in the cast alloy because of the sluggish dynamic recrystallization. The hot ductility drop and grain boundary cracking, particularly in the cast alloy, were attributed to the segregation of detrimental atoms to the boundaries. It was shown that the hot ductility of the wrought alloy could be improved with increasing strain rate. It was associated with increasing the fraction of dynamic recrystallization at higher strain rates. This finding corroborated the change in the mechanism of dynamic recrystallization with strain rate. The strain rate sensitivity and instability parameters calculated for the wrought alloy showed that the material is prone to strain localization at low temperatures, i.e., 950-1050 °C, and high strain rates of 0.1 and 1 s-1. Based on the tensile and compression tests, the best temperature range for a desirable hot workability was introduced as 1050-1150 °C.
Key words: Ni-Cu alloy; hot ductility; mechanical properties; dynamic recrystallization; hot compression; formability