Fe–Ni Invar alloy reinforced by WC nanoparticles with high strength and low thermal expansion

Abstract

Invar is a solid solution alloy that offers high-dimensional stability. It is challenging for traditional methods to strengthen Invar alloys without a significant increase in the coefficient of thermal expansion (CTE). In this work, WC nanoparticle-reinforced Invar nanocomposite was manufactured. The microstructures, mechanical properties, and thermal expansion behavior were investigated. It was found that the Invar alloy was effectively strengthened by WC nanoparticle reinforcement without significant elevation of its CTE. The Invar–WC nanocomposite exhibits an enhanced yield and tensile strength of 440 and 795 MPa, an increase of 60% and 77% from commercial Invar alloy, and a moderate ductility of 22.7% in annealed state. In cold-rolled state, The Invar–WC nanocomposite exhibits a high tensile strength of 1050 MPa, an increase of 46% from commercial Invar alloy, while retaining 4.5% ductility. A record low CTE value of 2.61 × 10−6/°C and an enhanced Young’s modulus of 185 GPa, up from 140 GPa, were also achieved. It was found that WC leads to a lower CTE at higher temperature compared to unreinforced Invar.