Research on the Effects of Combined Addition of Ce and Zr on the Microstructure and Properties of Fe–36Ni Invar Alloy

To develop Invar alloys with both high strength and low coefficient of thermal expansion (CTE), this study introduces a novel combined addition approach involving cerium (Ce) and zirconium (Zr). It systematically investigates the impacts of Ce and Zr on the microstructure, mechanical properties, thermal expansion behavior and corrosion resistance of Fe–36Ni Invar alloy. Compared to alloys containing a single addition of either Ce or Zr, the combined‐treated alloy exhibits a finer grain size. The low‐angle grain boundary fraction and dislocation density of the combined‐treated alloy are comparable to those of the alloy with an equivalent amount of Zr added individually. The Fe–36Ni Invar alloy, treated with a combination of Ce and Zr, exhibits excellent comprehensive mechanical properties (yield strength: 408 ± 4 MPa, tensile strength: 508 ± 6 MPa, elongation: 33.6 ± 1.4%). It also achieves a lower CTE of (0.58 ± 0.10) × 10 −6 °C −1 over the temperature range of 20–100°C. The grain refinement, matrix purification, and potential supplementary effect of dislocation‐associated residual stress collectively contribute to the alloy in attaining the minimum CTE. Moreover, the addition of Ce effectively mitigates the detrimental impact of Zr on corrosion resistance by reducing pitting initiation sensitivity and optimizing passivation film characteristics.