Study On Effect Of High Strain Rate Rolling On The Bio-corrosion Of Magnesium Alloys And The Influence Mechanism

Magnesium alloys can be used as blood vessel stents and bone implant material with the advantage of mechanical compatibility, biocompatibility and biodegradability, etc. As medical materials, magnesium alloys need both higher corrosion resistance and great mechanical properties, and these requriements can be attained by grain refinement. At present, there are very few reports about the bio-corrosion behavior of fine-grained magnesium alloys produced by high strain rate rolling. The effect of high strain rate rolling on the bio-corrosion behavior of magnesium alloy sheets and the action mechanism were systematically investigated in this paper. The main research results are as follows:(1) The corrosion regularitise of the as-rolled samples are different from those of the as-cast. The corrosion rates of the as-rolled magnesium and its alloys soaked in 0.9% NaCl and Hank's solution decrease with the increasing soaking time. Compared with the plates preprared by conventional rolling, the high strain rate rolled plates show better corrosion resistance with lower average corrosion rate, higher polarization potential, and lower corrosion current density. At the same time, it shows slighter decline in tensile strength after soaked in Hank's soltution for a long time. Take ZK60 alloy soaked in Hank's solution for 15 days for example, the average corrosion rate of the high strain rate rolled plate and the conventional rolled plate are 0.29mg·cm-2·d-1 and 0.31mg·cm·d-1 respectively. The decline extents in tensile strength of high strain rate rolled plate and conventional rolled plates are 20% and 23%, respectively.(2) Compared with conventional rolling, the high strain rate rolling process increases the volume fraction of DRX and refines grains. Take ZK60 alloy for example, the average grain size of high strain rate rolling plates is 3 ?m and the volume fraction of DRX is above 90%; the average grain of conventional rolling plates is 8?m and the volume fraction of DRX is about 60%.(3) Compared with the conventional rolling plates, the high strain rate rolling plates have finer grains, higher content of DRX, lower twinning density, relatively big residual phase particles, higher density of nano-sized precipitate, lower residual stress and relatively stronger basal texture.(4) High strain rate rolling can improve the corrosion resistance of ZK60 alloy, which can be ascribe to finer grains, higher content of DRX, lower twinning density and dislocation density, relatively big residual phase particles, higher density of nano-sized precipitate and stronger basal texture.