Analysis of Hot Anisotropic Tensile Flow Stress and Strain Hardening Behavior for Inconel 625 Alloy
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JMEPEG https://doi.org/10.1007/s11665-019-04475-4
Analysis of Hot Anisotropic Tensile Flow Stress and Strain Hardening Behavior for Inconel 625 Alloy C. Anand Badrish, Nitin Kotkunde, Gauri Mahalle, Swadesh Kumar Singh, and K. Mahesh (Submitted November 29, 2018; in revised form September 12, 2019) In this study, hot deformation behavior of Inconel 625 alloy has been investigated from room temperature to 700 °C at an interval of 100 °C with slow strain rates (0.0001-0.1 s21). Flow stress behavior is significantly influenced by temperature and strain rate changes. Dynamics strain aging behavior has been reported from 300 to 700 °C. Various mechanical properties, namely tensile strength, % elongation, strain rate sensitivity and strain hardening capacity (Hc), have been studied over wide range of temperatures and strain rates. Hc values remarkably improved at higher temperatures which indicate an excellent combination of strength and ductility. Additionally, various anisotropic material parameters, namely Lankford coefficient, normal, planer and in-plane anisotropy and anisotropic index, were evaluated. Furthermore, hardening behavior of Inconel 625 alloy has been analyzed by various flow stress equations like Hollomon, Ludwik, Swift and Voce. Two-stage strain hardening behavior has been noticed at all temperatures. Ludwik and Swift equations represent poor prediction capability at lower strain region. Based on statistical parameter comparison, Voce equation prediction capability is found best in agreement with both strain regions. Finally, the fracture morphology of post-tensile specimens has been studied, indicating ductile– brittle fracture with dimples. Keywords
anisotropic material properties, fracture morphology, inconel 625 alloy, strain hardening, tensile flow stress
1. Introduction Understanding flow stress and strain hardening behavior is an essential prerequisite for improving conditions suitable for material processing and ensuring safe performance during working. Presently, higher performance requirements and safety concerns have enforced the selection of high strength and lighter-yet-safer superalloys for aerospace and automotive industries. Moreover, superalloys are studied to replace conventional metals to improve performance in many critical applications. Ni-Fe-Cr-based superalloys, because of their excellent mechanical properties at elevated temperature, are gaining special attention (Ref 1). Since the introduction of NiFe-Cr alloys in early 1960s, these alloys in relatively shorter time became indispensable materials for nuclear reactors, aircraft structures, gas turbines and marine applications (Ref 2). These superalloys are suitable mainly for service in hightemperature environment, to withstand severe mechanical condition, and to remain resistant to thermal shock, corrosion and creep. One of the popular Ni-based superalloys is Inconel 625 alloy, mostly used in chemical processing, modern aircraft
C. Anand Badrish, Nitin Kotkunde, and Gauri Mahalle, Department of Mechanical Engineering, BITS Pilani
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