Structure and properties of precipitation-hardened Сu–Ni–Mn–Fe binders for composite coatings

Abstract

The structure and properties of Сu–Ni–Mn–Fe alloys within the concentration range of 19.3–21.0 % Ni, 19.5–20.5 % Mn, 0.6–2.7 % Fe, Cu – the balance (in wt. %) were studied in this work. Quantitative metallographic, X-ray, and differential thermal analyses were applied. Two α-Cu solid solutions that differ in composition and microhardness were revealed in the structure of the investigated Сu–Ni–Mn–Fe alloys. These solutions were formed at 1010 ± 10 °С and 890 ± 10 °С, correspondingly. Besides, hardening NiMn phase was precipitated at 405 ± 15 °С due to ageing. In the Сu–Ni–Mn–Fe alloys annealed at 900 °С for 60–750 hours, the volume fraction and size of NiMn precipitates increased with increasing holding time. When iron content was raised from 0.6 up to 2.7 wt. %, the amount of NiMn precipitates increased, especially during first 60 hours of annealing at 900 °С. Brinell hardness of the Сu–Ni–Mn–Fe alloys with higher iron contents increased by 10 НRB on average. At that, as test temperature was raised up to 400 °С, tensile strength decreased by ~1.3 times and elongation dropped markedly by ~10 times. The investigated Сu–Ni–Mn–Fe alloys containing up to 2.7 wt. % may be applied as binder materials for composite coatings provided that working temperature does not exceed 400 °С.