Effect of Aging Treatment on the Microstructure and Properties of the Low Expansion Invar Alloy Strengthened by Elements Ti and Al

The high‐performance Invar alloy is a promising candidate for high‐capacity conductors in next‐generation power transmission. The primary objective of this study is to investigate the mechanical and physical properties of the Invar alloy strengthened by elements Ti and Al under various aging treatments. The main findings are as follows: before aging treatment, the geometrically‐necessary dislocations introduced by cold drawing primarily accumulate at grain boundaries and dislocation strengthening provides a strength contribution of 184 MPa. After aging treatment, the specimen undergoes recovery, with a decrease in dislocation density. Meanwhile, fine and uniform Ni 3 (Al, Ti) phases precipitate throughout matrix. The strength increment of the aged specimen due to precipitation strengthening reaches 659 MPa. Subsequently, the specimen after being aged at 680 °C for 2 h demonstrates excellent mechanical properties, achieving a yield strength of 1281 MPa, a tensile strength of 1395 MPa, and an elongation of 6.7%. In addition, the aged specimen shows an increase in the coefficient of thermal expansion compared to the cold‐drawn specimen which is attributed to a reduction in defects and the precipitation of γ′‐Ni 3 (Al, Ti) phase.