Microstructure Evolution and Mechanical Behavior of Cu-7ni-7al-4fe-2mn Alloy Via a Quenching-Aging Heat Treatment

The effects of solution and aging treatment on the microstructure and mechanical properties of Cu-7Ni-7Al-4Fe-2Mn alloy were studied by means of optical microscope(OM), scanning electron microscope(SEM), transmission electron microscope(TEM) and an electronic tensile testing machine. The results show that the microstructure of the as-cast alloy is mainly composed of an α-Cu matrix, Fe3Al particles and NiAl phase distributed at the grain boundaries. After solution treatment, the distribution of bean-shaped Fe3Al particles in the microstructure of the alloy is more uniform than that of the as-cast state, and the larger square Fe3Al phase is redissolved and disappears. During the aging process, the NiAl phase is continuously precipitated in the grains. The strength and hardness of the alloy first increase and then decrease with the extension of the aging time. After aging treatment at 500 °C×6h, the hardness of the alloy is 231.4 HV, and the tensile strength is 538.5MPa. The hardness is 78.8% higher than that of the as-cast state, and the tensile strength is 41.9% higher than that of the as-cast state.