Precipitate stability in Cu–Ag–W system under high-temperature irradiation

The kinetics of precipitation was investigated in the ternary Cu alloy, Cu83.5Ag15W1.5 during irradiation with MeV Kr ions at elevated temperatures. The alloy was prepared as a solid solution by physical vapor deposition and then irradiated at room temperature to create a high density of nano-sized W precipitates. These precipitates served as effective sinks for point defects during subsequent elevated-temperature irradiation, suppressing radiation-enhanced diffusion. As a consequence the size of the Ag precipitates formed during elevated-temperature irradiation was stabilized below 20 nm, up to temperatures in excess of 300 °C, thus significantly extending the regime for “compositional patterning” above 175 °C, found for Cu85Ag15. For higher temperature irradiations (above 400 °C), the role of the W precipitates in stabilizing the size of the Ag precipitates switched from simply acting as point-defect sinks to serving as pinning sites for the Ag precipitates. At 500 °C, the average Ag precipitate diameter is ∼30 nm compared to ∼300 nm in the Cu85Ag15 binary alloy. Rate theory calculations and kinetic Monte Carlo simulations are employed to illustrate how this transition takes place.

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