STAGES OF MECHANICAL ALLOYING IN SYSTEMS WITH DIFFERENT SOLUBILITY CU-ZN AND AU-CO IN THE CASE OF COLD AND LOW-TEMPERATURE DEFORMATION BY TORSION UNDER PRESSURE

摘要

Methods of X-ray structural analysis and durometry, as well as electron microscopy were used to identify the stages of mechanical alloying in the case of torsion under high quasi-hydrostatic pressure on Bridgman anvils in the Cu-Zn and Au-Co systems that have different mutual solubility and enthalpy of mixing. It was established that decrease in temperature of mechanical alloying from room temperature (cold deformation) to the boiling temperature of liquid nitrogen (80 kappa, low-temperature deformation) has a considerable impact on mechanical alloying at different processing stages and on characteristics of an alloy synthesized by deformation. In the Cu-Zn system, when the ratio of powder components corresponds to the solid solution of alpha-brass in equilibrium state, as deformation increased, one observed consecutive change of evolution stages of the powder mix to the state of copper-based solid solution. At the same time, when processing temperature decreases, larger deformation is required to achieve analogous structural changes. In the Au-Co system characterized by absence of solubility at room and lower temperatures, one also observes the stages of powder mix evolution with the increase in deformation. However, complete dissolution occurs in the case of processing at 80 kappa, while larger deformation is required in the case of increase in mechanical alloying temperature. The paper examines possible mechanisms of solid solution formation in the system of components that are mutually insoluble under equilibrium conditions.