Abstract
This work analyzed experimentally and numerically the growth kinetics of β′ precipitation of a Cu–4 wt%Ti alloy after aging at 400, 500, and 600 °C for times from 0.0166 to 200 h. Results indicated that the precipitation process is almost controlled by nucleation and growth during aging at 400 °C, originating a slow growth kinetics of precipitation. In contrast, the coarsening of precipitates dominates the precipitation process during aging at 500 and 600 °C. The interfacial energy of interface between the α matrix phase and β′ precipitates was determined to be about 0.1135, 0.0980, and 0.0725 Jm−2 for aging at 400, 500, and 600 °C, respectively. These values suggest a coherent interface, which is in agreement with the flat faces of β′ cuboid precipitates. Calculated Time–Temperature–Precipitation diagram for the β′ precipitation indicated good agreement with experimental results. Precipitation hardening was higher for the slower growth kinetics of precipitation.
Highlights
Cu-Ti alloys are prone to have precipitation hardening after isothermal aging for alloy compositions of about 1-5wt.% Ti1-4
The mechanical strength of Cu-Ti alloys has been improved either by the addition of a third alloying element such as Chromium, zirconium, carbon, nitrogen or hydrogen[9,10,11] or by using cold work previously to the aging treatment[12,13]. In the former case, the precipitation sequence was similar to that observed in the binary alloy; the presence of a different precipitates such as titanium chromide, nitride, carbide or hydride was reported to occur during aging[9,10,11]
The temporal evolution of precipitation of βphase in the Cu-rich α phase matrix is illustrated in the Bright-Field (BF) Transmission Electron Micrographs corresponding to the Cu-4wt.%Ti alloy aged at 400, 500 and oC for different times, as shown in Figs. 1-3, respectively
Summary
Cu-Ti alloys are prone to have precipitation hardening after isothermal aging for alloy compositions of about 1-5wt.% Ti1-4. The mechanical strength of Cu-Ti alloys has been improved either by the addition of a third alloying element such as Chromium, zirconium, carbon, nitrogen or hydrogen[9,10,11] or by using cold work previously to the aging treatment[12,13]. In the former case, the precipitation sequence was similar to that observed in the binary alloy; the presence of a different precipitates such as titanium chromide, nitride, carbide or hydride was reported to occur during aging[9,10,11]. The cold work, used after solution treatment and quenching, has been reported[12,14] to promote the precipitation of titanium on dislocations and to inhibit the precipitation of the β Cu4Ti and β Cu4Ti phases during aging
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