Microstructure and Properties of High-strength Invar Alloy with Co-addition of Mo, Al and Ti Alloying

The effects of aging treatment and cold rolling on microstructure, mechanical properties and coefficient of thermal expansion of high-strength Invar alloy added with Ti, Al and Mo were studied. The results show that the matrix is single-phase austenite. Mo dissolves in the matrix, and Ti and Al form (Ti, Mo)C carbides and Ni₃(Al, Ti) γ' phase. With the aging temperature increasing from 660 ℃ to 820 ℃, the strength of investigated alloy increases first and then decreases. When aged at 700 ℃, the strength of the alloy can be further improved by prolonging the aging time. Considering practical production conditions, the optimal aging parameter is 700 ℃ and 12 hours. The strength of the investigated alloy increases obviously after cold rolling. When the deformation is 85%, the yield strength is 1154 MPa and the tensile strength is 1301 MPa. The addition of alloying elements raises the coefficient of thermal expansion, which increases further after aging treatment and cold rolling