THE INFLUENCE OF PROLONGED ANNEALING ON THE STRUCTURE AND PROPERTIES OF THE DEFORMED Cu-8at.%Pd ALLOY


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Abstract

The authors discovered the lack of literature sources on the structure and mechanical-and-physical properties of copper alloys with the palladium content of less than 10 at. %. It is determined that in the “copper corner” of the common Cu-Pd phase diagram, the temperature-concentration boundary between the disordered FCC-phase and the ordered L12-type phase was drawn without the relevant experimental support. At the same time, these alloys are attractive as the basis for the development of high-strength conductive materials.

The authors studied the evolution of the structure, microhardness, and specific electrical resistivity in the process of prolonged annealing of the Cu-8at.%Pd alloy. The increase of microhardness and specific electrical resistivity of pre-deformed samples after thermal processing at 250 °C and 300 °C was detected. It is shown, that the prolonged low-temperature annealing of the alloy with slow cooling leads to the increase of its specific electrical resistivity. The authors conclude that all the observed anomalies of properties are explained by the formation of the ordered L12 phase nuclei in the deformed matrix. The results of the study confirm that the preliminary deformation accelerates significantly the processes of atomic ordering. However, the rate of atomic ordering is extremely low: to determine a new phase using the structural methods, the low-temperature annealing for several months is necessary.

Based on the results of the study, it was concluded that the critical temperature of the order-disorder phase transformation in the alloy under the study is approximately 340 °C. Since the temperature boundary of phase transformation for the alloy of tested concentration was drawn on the common Cu-Pd phase diagram at 400 °C, the authors concluded as well, that the “copper angle” on phase diagram needs to be refined.

About the authors

Alina Evgenievna Kostina

M.N. Mikheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, Yekaterinburg

Author for correspondence.
Email: kostina_a@imp.uran.ru

graduate student, research engineer of Strength Laboratory

Russian Federation

Aleksey Yurievich Volkov

M.N. Mikheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, Yekaterinburg

Email: volkov@imp.uran.ru

PhD (Engineering), Head of Strength Laboratory

Russian Federation

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