Abstract:Cu-Ni-Mn alloy is a kind of copper alloy with high strength and high elastic modulus. Due to its excellent mechanical, corrosion resistance and wear resistance, Cu-Ni-Mn alloy has rich application value in mining machinery, ocean engineering and other fields. In this paper, the microstructure transformation and precipitation behavior of Cu-20Ni-20Mn alloy were studied, and the influence mechanism of Hf element on the microstructure and properties of Cu-20Ni-20Mn alloy was revealed by adding Hf element as the fourth component. The results showed that the as-cast structure of Cu-20Ni-20Mn-xHf alloy changed from dendrite to equiaxed crystal after solution treatment, and incomplete recrystallization occurred during hot rolling, and the mechanical properties were gradually improved. The precipitation mechanism of the alloy in the aging process changed with the increase of temperature, and changed from discontinuous precipitation to continuous precipitation at 350~450 ℃. The addition of Hf element had a certain inhibition effect on the discontinuous precipitation during the aging process of Cu-20Ni-20Mn alloy, and the inhibition effect was gradually increased with the increase of Hf element content in the experimental range. The peak hardness of Cu-20Ni-20Mn alloy could be maintained at HB 320 at the experimental temperature (350~450 ℃), and the addition of 0.6%Hf could increase the hardness of the alloy at low temperature aging, HB 5.1 at 350 ℃, HB 8.1 at 400 ℃, but the peak hardness did not increase significantly at 450 ℃.