Research on cross-scale precipitation regulation and its impact on properties in Cu-4Ti-1Ni alloy
摘要
In this study, Cu-4Ti-1Ni alloy was fabricated through a "pre-aging-cold rolling-re-aging" process, and the microstructure evolution and the mechanism of mechanical and electrical property regulation during the multi-stage process were systematically investigated. Transmission electron microscopy (TEM) analysis revealed that during the 450 °C pre-aging for 4 h, in addition to the retention of the primary NiTi phase, the alloy matrix also precipitated nanoscale β′-Cu4Ti phases, which were uniformly distributed and provided stable nucleation cores and strain energy storage for subsequent deformation and re-precipitation processes. The high-density dislocations introduced by cold rolling interacted with the fine β′-Cu4Ti precipitates and NiTi phases formed during pre-aging, creating a dislocation entanglement network and promoting re-precipitation at the interfaces. After the final aging, the alloy achieved a multi-level microstructure consisting of nanoscale β′-Cu4Ti phases (with an average size of approximately 4.96 nm) uniformly distributed in the Cu matrix and microscale NiTi phases. This multi-level microstructure not only significantly enhanced the alloy’s strength to 1168 MPa through the synergistic effect of precipitation strengthening and dislocation pinning, but also reduced the Ti solute concentration in the matrix, increasing the conductivity to 15.07%IACS. The research indicates that the β′-Cu4Ti nanoscale precipitates formed in the early pre-aging stage, together with the NiTi primary phase, jointly constructed the microstructural refinement and performance optimization basis for subsequent stages, revealing the strengthening mechanism of multi-scale precipitation-dislocation interaction in the Cu-Ti-Ni system.