Effect of Aging Treatment Conditions on the Microstructure and Strength of Fe-36Ni Based Invar Alloy

摘要

Strengthening method for the Fe-36Ni based Invar alloy for power transmission wire was investigated in this study. High strength of 1300 MPa could be obtained in this alloy through solution hardening, precipitation hardening and strain hardening by cold working. Phase equilibrium of the Invar alloy was calculated using FactSage, revealing that thermodynamically stable phases are Mo{sub}2C, MoC, M{sub}23C{sub}6-type FeCrMo carbide, and M{sub}6C-type FeMo carbides. Aging treatments were carried out at temperatures ranging from 400 to 900°C for time intervals from 3 min to 30 hrs. Peak aging condition was obtained as 400°C and 1 hr. With temperature increased, peak hardness was decreased abruptly. Microstructure observation was conducted by optical microscopy, scanning electron microscopy, and transmission electron microscopy. By using the result from aging treatment, high strength above 1300MPa was obtained in the cold rolled Invar alloy plate.