Effect of ECAP and volume ultrasonic treatment on the corrosion resistance of magnesium

Abstract

Magnesium and its alloys are promising materials for manufacturing bioresorbable implants. Various combinations of thermo-mechanical processing are used to improve the mechanical properties and corrosion resistance of magnesium alloys, forming the necessary structural state, which, in turn, requires determining the influence of various structural factors (grains, grain boundaries, dislocations, second-phase particles, etc.) on the complex properties of 'strength - corrosion resistance'. In this study, an experiment was conducted to determine the influence of structural changes in pure magnesium on mechanical properties and corrosion resistance in a physiological environment after deformation using equal channel angular pressing (ECAP) and post-deformation ultrasonic treatment. It was found that ECAP and subsequent ultrasonic treatment lead to a twofold increase in the yield strength of magnesium from 30 to 60 MPa. The increase in microhardness after ECAP is 50 MPa, while ultrasonic treatment results in an increase in microhardness by 230 MPa. After deformation, corrosion resistance changes significantly: ECAP reduces the corrosion rate compared to the initial state of magnesium by approximately 7 times, to values of 7 mm/year. Subsequent volume ultrasonic treatment does not lead to significant changes in the corrosion rate, which in this case was 10 mm/year.