Effects of Cold Rolling and Annealing Conditions on Recrystallization and r-value in Invar Alloy

Evolution of Microstructure, Mechanical Properties and Residual Stress of a Cold Rolled Invar Sheet Due to Heat Treatment

“…It can be observed that the curves for the specimens annealed at 400 • C and 500 • C are comparable to the curve for the cold-rolled specimen. This indicates that a lack of recrystallization, as well as a negligible level of recovery, took place when annealed for 35 s under 500 • C. The lack of recrystallization is understandable, since the recrystallization temperature of Invar is typically above 650 • C, depending on the cold rolling reduction [18]. Furthermore, evidence of recovery in terms of hardness may occur above 600 • C for Invar alloys, depending on the cold rolling reduction [19], which explains why no notable indication for recovery in terms of tensile strength was observed for the specimen annealed at 500 • C. The specimen annealed at 700 • C experienced a small decrease in strength, accompanied by a moderate increase in ductility (Figure 5).…”

“…It is known that the underlying factors that contributes to changes in the mechanical properties of a material can readily affect the residual stress of the material. In particular, heat treatment based metallurgical processes such as recovery and recrystallization can not only change the mechanical properties of an alloy, but also release residual stress in the alloy [16][17][18][19][20][21][22]. However, unwary heat treatment should be avoided because these processes, which are central to the alleviation of cold rolling induced residual stress in Invar sheets, can result in undesirable changes in the microstructures and mechanical properties of the sheets.…”

Recrystallisation-assisted creep of an austenitic Fe-Ni alloy under low stresses after hot deformation

“…From the reported electron backscatter diffraction (EBSD) maps, only the high temperature, low strain rate conditions were found to lead to continuous dynamic recrystallisation; post-dynamic and static recrystallisation phenomena were not addressed in their paper. The static recrystallisation behaviour and mechanisms of the Fe-36%Ni alloy family have been widely characterised after cold working and annealing at temperatures between 600°C and 900°C [35][36][37]. In particular, heavy cold rolling has been shown to favour early nucleation of recrystallised, cubeoriented grains from the strongly recovered cube-oriented grains of the deformed microstructure [37].…”