Browsing by Author "Chang, Pei-Shan"

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Effect of Microstructure Factors on Stress Corrosion Behavior of Mg-xSn Alloys (x=2, 5, 8 mass%)
(2016)
Chang, Pei-Shan
;
Chen, Chun-Hung
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Chao, Chuen-Guang
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交大名義發表
;
材料科學與工程學系
The effect of microstructure on the stress corrosion behavior of Mg-Sn alloys was investigated using a bent-beam method. The effects of an Mg2Sn phase and Sn in the matrix on stress corrosion were investigated. Mg2Sn phase mainly formed at the grain boundary. The volume fraction of the Mg2Sn phase increased with increasing Sn content, and the morphology of Mg2Sn changed from spherical to a semi-continuous network. The average volume fractions of Mg2Sn 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 Mg2Sn phase increased the pit density, whereas dissolution of the Mg2Sn phase into the matrix resulted in decreased pit density. An intergranular cracking mode was observed. The solution heat treatment dissolved the Mg2Sn phase and eliminated the micro-galvanic corrosion due to Mg2Sn, thereby delaying crack initiation also enhancing stress corrosion resistance. Mg-8% Sn sample through solution heat treatment showed the best stress corrosion resistance.
Stress Corrosion Behavior of Mg-2 mass% Sn Alloy by Equal-Channel Angular Extrusion
(2017-01-01)
Chang, Pei-Shan
;
Chao, Chuen-Guang
;
Liu, Tzeng-Feng
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材料科學與工程學系
;
Department of Materials Science and Engineering
In this work, the stress corrosion behavior of Mg-2 mass% Sn alloy in simulated body fluid 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 Mg2Sn second phase distribution. The average grain size under homogenization annealing condition (about 123.61 mu m) was significantly reduced to 34.32 mu m after four ECAE passes. Mg2Sn phase formed more uniformly both in the grains and along the grain boundaries with ECAE process. The average volume fraction of Mg2Sn 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 significantly 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 refinement via ECAE process.