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Effects of negative roll gap rolling and pulsed current annealing on microstructure and properties of Invar 36 alloy thin strip

Year: 2025

Type: article

Abstract: In this study, high-performance Invar 36 alloy thin strips were successfully fabricated by negative roll gap cold rolling and pulsed current annealing. The microstructure evolution and texture development of Invar 36 alloy thin strips under different rolling reduction ratios and pulsed current annealing parameters were systematically investigated. The results indicate Negative roll gap cold rolling leads to a significant increase in strength and a sharp decrease in ductility as the cold rolling reduction ratios rise. At a 90% reduction, the sample reaches a tensile strength of 820 MPa and a hardness of 283 HV. This is attributed to the increased dislocation density, the formation of low-angle grain boundaries (LAGBs) and deformation twins, and the development of strong crystallographic textures including copper-type {112}<111>, brass-type {110}<112>, and S-type {123}<634>. Pulsed current annealing significantly enhances the ductility of rolled thin strips while concurrently reducing their strength. This improvement is attributed to dynamic recovery, recrystallization and the development of a strong cubic texture {100}<001>, driven by high-energy pulsed current induced thermal and non-thermal effects. High-strength-ductility Invar 36 alloys, including a 0.5 mm-thick thin strip with a tensile strength of 650 MPa, yield strength of 575 MPa, and fracture elongation of 5.9%, as well as a 0.1 mm-thick ultra-thin strip with a tensile strength of 600 MPa, yield strength of 520 MPa, and fracture elongation of 5.8%, were successfully fabricated using a combined approach of negative roll gap cold rolling with 50% and 90% reductions followed by pulsed current annealing for only 40 seconds.

Source: Journal of Materials Research and Technology

DOI: 10.1016/j.jmrt.2025.04.231