Zero thermal expansion in non-stoichiometric and single-phase (Hf,Nb)Fe2.5 alloy

Zero thermal expansion (ZTE) alloys are dimensionally stable under the influence of heat, which is critical in high-precision components but remains rare among single phase materials. This work reports a single phase and nearly isotropic ZTE alloy (Hf0.8Nb0.2)Fe2.5 over a wide temperature range of 5–460 K (αl ≈1.07 × 10−6 K−1) via non-stoichiometric regulation. The introduction of excess Fe breaks the dual-phase nature of parent alloy, extends the magnetic ordering temperature, and induces a spin reorientation. The evolution of magnetic structure versus temperature gives rise to the ZTE behavior. The design concept of changing the internal magnetic interaction through non-stoichiometric regulation provides support for the discovery of novel ZTE materials.