Study of the Dynamic Recrystallization Process of the Inconel625 Alloy at a High Strain Rate

Abstract

High-temperature compression and electron backscatter diffraction (EBSD) techniques were used in a systematic investigation of the dynamic recrystallization (DRX) behavior and texture evolution of the Inconel625 alloy. The true stress–true strain curves and the constitutive equation of Inconel625 were obtained at temperatures ranging from 900 to 1200 °C and strain rates of 10, 1, 0.1, and 0.01 s−1. The adiabatic heating effect was observed during the hot compression process. At a high strain rate, as the temperature increased, the grains initially refined and then grew, and the proportion of high-angle grain boundaries increased. The volume fraction of the dynamic recrystallization increased. Most of the grains were randomly distributed and the proportion of recrystallized texture components first increased and then decreased. Complete dynamic recrystallization occurred at 1100 °C, where the recrystallized volume fraction and the random distribution ratios of grains reached a maximum. This study indicated that the dynamic recrystallization mechanism of the Inconel625 alloy at a high strain rate included continuous dynamic recrystallization with subgrain merging and rotation, and discontinuous dynamic recrystallization with bulging grain boundary induced by twinning. The latter mechanism was less dominant.

A Mechanism for the Evolution of Hot Compression Cracking in Inconel 625 Alloy Ingot With Respect to Grain Growth

“…One report indicates that the completed DRX temperature of the Inconel 625 superalloy is approximately 1100 C at a high strain rate. [5] As shown in Figure 4b, the temperature at which the crack appears during the simulated thermal compression process is about 1190 C, which again indicates that the DRX grain growth behavior is inextricably related to the crack initiation. This is consistent with the crack initiation temperature during the hot extrusion of the Inconel 625 alloy pipe.…”

“…All cutting samples were ground and polished to a smooth surface, and then electrolytically polished with a solution of 20 mL H 2 SO 4 þ 80 mL methanol. [5] Figure 1c shows the typical morphology of the hot crack at 1200 C and a strain rate of 10 s À1 . A large crack initiated at the edge of specimen and smaller secondary microcrack initiations were adjacently present.…”

“…It is commonly accepted that the DDRX nucleation mechanism, characterized by progressive GB bulging, occurrs at high temperature and strain rate. [1,5,8,13,15] As shown in Figure 7a, many tiny DRX grains are interspersed with some bulged GBs. The bulging GBs usually possess high local orientation or strain gradients, and, thus, are potential sites for DDRX nucleation.…”

“…Inconel 625, a typical industrial nickel-based superalloy, has been widely used in the aviation, nuclear, and shipyard industries as a high-temperature airtight pipe material because of its excellent mechanical and oxidation resistance and anticorrosion properties under elevated temperatures and high pressure. [1][2][3][4][5][6] Currently, the formation of high-temperature alloy sealed pipe is typically dependent on thermal processing, especially hot extrusion techniques. During hot forming processes, materials dynamically undergo severe plastic deformation and microstructural changes, which are closely related to the dynamic recrystallization (DRX) process.…”

The Effect of the Strain Rate on the Fretting Wear Properties of Thermally Compressed Inconel 625 Alloy

“…Therefore, Inconel 625 has been used in aerospace, chemical, nuclear, and other fields that require operation at high temperatures. [ 2,3 ] Typical applications include the container of Japan's JT‐60 nuclear fusion reactor [ 4 ] and components of the thermal power generator boiler (namely the main steam pipe, superheater, container, and water‐cooling pipe). However, the vibration caused by the flow of the gas–liquid medium in a pipeline or container and the relative microlevel movements of the contact interfaces due to mechanical fastening often cause fretting wear in these applications.…”