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The effect of microstructure on the stress corrosion behavior of Mg-Sn alloys was investigated using a bent-beam method. The effects of an Mg 2 Sn phase and Sn in the matrix on stress corrosion were investigated. Mg 2 Sn phase mainly formed at the grain boundary. The volume fraction of the Mg 2 Sn phase increased with increasing Sn content, and the morphology of Mg 2 Sn changed from spherical to a semi-continuous network. The average volume fractions of Mg 2 Sn phase increased from 0.07 ± 0.02% to 5.06 ± 0.92% as the Sn content was increased from 2 to 8 mass%. An increase in the amount of Mg 2 Sn phase increased the pit density, whereas dissolution of the Mg 2 Sn phase into the matrix resulted in decreased pit density. An intergranular cracking mode was observed. The solution heat treatment dissolved the Mg 2 Sn phase and eliminated the micro-galvanic corrosion due to Mg 2 Sn, thereby delaying crack initiation also enhancing stress corrosion resistance. Mg-8%Sn sample through solution heat treatment showed the best stress corrosion resistance.

In this work, the stress corrosion behavior of Mg-2 mass% Sn alloy in simulated body uid solution was systematically investigated to determine its performance in a physiological environment. The effect of equal-channel angular extrusion (ECAE) on stress corrosion behavior of Mg-2 mass% Sn alloy was investigated using three-point bending test. ECAE process changed both grain size and Mg 2 Sn second phase distribution. The average grain size under homogenization annealing condition (about 123.61 μm) was signi cantly reduced to 34.32 μm after four ECAE passes. Mg 2 Sn phase formed more uniformly both in the grains and along the grain boundaries with ECAE process. The average volume fraction of Mg 2 Sn phase increased with increasing passes. The microstructure became more homogeneous with further ECAE passes. In bent-beam stress corrosion test, the average crack depths of samples underwent ECAE process were signi cantly lower than that of sample under homogenization annealing condition. This showed that the ECAE process could reduce crack propagation rate. The enhancement of stress corrosion resistance is attributable to uniform second phase distribution and grain re nement via ECAE process.