Effects of temperature and strain rate on tensile deformation behavior of superalloy UNS N10276

Abstract

Tensile deformation behavior of nickel-base superalloy UNS N10276 was investigated in a wide temperature range of 200–1000°C with intervals of 50°C, employing the strain rates of 5 × 10−5, 3 × 10−4 and 3 × 10−3s−1. Various types of serrations as one of manifestations of dynamic strain aging (DSA) were observed in this alloy. Normal Portevin-Le Chatelier effect (PLE) was observed at temperatures lower than 600°C, while inverse PLE was noticed at temperatures above 600°C. The average activation energy for serrated flow was determined to be 132kJ/mol in the normal PLE regime, which was in line with migration of Mo through pipe diffusion in a Ni matrix. Negative strain rate sensitivity was observed in the DSA regime in this alloy. Yield strength increased with increasing temperature at strain rates of 5 × 10−5 and 3 × 10−4s−1 in the temperature range of 650–850°C, which was mainly related to the formation of M6C carbides at the grain boundary as well as to the enhanced DSA effect during tensile deformation. Typical intermediate temperature embrittlement (ITE) was observed in this alloy. The elongation had high values and remained almost unaffected by the temperature until 500, 600 and 650°C for 5 × 10−5s−1, 3 × 10−4s−1 and 3 × 10−3s−1, respectively. This alloy showed the minimum elongation at 700°C irrespective of strain rates employed, whereas the reduction in area (RA) exhibited the minimum at 700°C for 5 × 10−5s−1, 750°C for 3 × 10−4s−1 and 800°C for 3 × 10−3s−1, respectively. The lower limit of temperature at which intergranular brittle failure happened was reduced with decreasing strain rate. Additionally, it was found that reducing strain rate expanded the brittle temperature spectrum of the alloy.