Nanophase transformation and strengthening- Toughening mechanism of the Cu-15Ni-8Sn alloy during aging

The Cu-15Ni-8Sn alloy ingot was prepared in the medium-frequency induction melting furnace. The hot extruded alloy was treated by solid solution at 840 degrees C for 60 min and aging at 400 degrees C for different times (0 mi & ntilde;480 min). The effect of aging time on the evolution of the nanophase of Cu-15Ni-8Sn alloy and the strengthening-toughening mechanism were studied. The results show that at the beginning of aging, the alloy undergoes spinodal decomposition, the wavelength of the modulated structure is approximately 3 similar to 7 nm, the ordered phase transformation of D0(22) and L1(2) occurs simultaneously, and the ordered phase size is approximately 5 nm. With the extension of aging time, the modulated structure became coarser, and the wavelength of the modulated structure increased to 5-9 nm. At the same time, the D0(22) ordered phase changed to the L1(2) ordered phase, and a continuous distribution of elliptical discontinuous precipitation appeared at the grain boundary. The ratio of the long and short axes of the discontinuous precipitation was approximately 4.7. In the late aging period, the D0(22) ordered phase was basically transformed into the L1(2) ordered phase, and discontinuous precipitation, which is incompatible with the matrix, extended into the crystal. After 120 min of aging at 400 degrees C, the hardness, strength, and elongation of the alloy are 105.4 HRB, 839.8 MPa and 9.6 %, respectively. The peak-aging states D0(22) and L1(2) coexist in an orderly phase at the nanoscale, and this nanoscale strengthening phase is completely integrated with the matrix, which improves the strength and toughness of the alloy. The research results can provide support for the development of high-performance copper alloys in the ocean.(c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The effect of aging time on the evolution of nanophase and strengthening-toughening mechanism of Cu-15Ni-8Sn alloy was studied. It was found that with the extension of aging time, the modulated structure became coarser, and there was a transformation of ordered phases and appearance of discontinuous precipitation. After 120 min of aging, the alloy exhibited improved hardness, strength, and elongation.