The study of influence of temperature and speed conditions on the mechanical properties of bioresorbable Zn–4Ag–Cu zinc alloy during equal-channel angular pressing

Abstract

Recently, innovative medical techniques for restoring lost functions of patients have been actively developed, in which the use of bio-soluble (bioresorbable) materials is of particular importance. Such materials include alloys based on Mg, Fe, and Zn, and can significantly reduce the cost of surgical operations and shorten the duration of treatment. However, these metals have such disadvantages as insufficient strength and increased fragility to be used in medical implants. Therefore, increasing the mechanical characteristics of bioresorbable alloys is an urgent problem. In this work, the authors solve this problem using an advanced method of plastic treatment – severe plastic deformation (SPD), which, due to active initial structure refinement to nano- and ultrafine state, allows effective improvement of the mechanical strength of metal materials. The authors used the most effective and well-spread SPD method –equal-channel angular pressing (ECAP). The paper presents the results of computer ECAP research of Zn–4Ag–Cu zinc alloy at different deformation rates (0.4 and 7.8 mm/sec) and temperature conditions (150, 200 °C) chosen based on equipment performance potential and conditions to ensure thermal stability of the structure. The patterns of distribution of accumulated deformation degree, deformation rate, average stress values, and temperature-force conditions are obtained. According to the results of computer modeling, the authors recommended carrying out ECAP processing at the temperature of 150, 200 °C and a speed of 0.4 mm/s, which ensures a uniform thermal field at the deformation zone. During the experimental work according to the selected modes, the authors obtained samples after four ECAP cycles, which had advanced mechanical properties improving performance characteristics. The increased strength will allow minimizing the implants’ sizes ensuring less trauma during their installation and faster dissolution in the physiological environment of the body when retaining functionality.