Corrosion behavior of Mg-6Bi-2Sn alloy in the simulated body fluid solution: The influence of microstructural characteristics

The corrosion behaviors of as-cast and as-rolled Mg-6Bi-2Sn alloys were investigated in the simulated body fluid solution, and the influence of the microstructural characteristics on the corrosion properties were discussed. The as-cast alloy mainly consists of alpha-Mg and Mg3Bi2 phases, while a new Mg2Sn phase can be observed in as-rolled one. In addition, the average dendrite arm spacing and average second phase particle size of the as-cast alloy was 27.23 +/- 2.14 mm and 9.89 +/- 0.76 mm, respectively. After rolling, remarkable grain refinement and uniform distribution of second phase particles could be achieved with the average size of grains and second phase particles being 11.28 +/- 1.12 mm and 1.84 +/- 0.08 mm, respectively. The electrochemical and immersion tests results indicated that the as-rolled alloy have a lower corrosion rate than the as-cast one. The remarkably deceased corrosion rate of as-rolled Mg-6Bi-2Sn alloy in simulated body fluid solution is mainly attributed to refined grain size, finely dispersed secondary phase particles, favorable crystal orientation and the formation of passivity film. (C) 2017 Published by Elsevier B.V.