Papers by Author: Tien Yin Chan

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Authors: Tien Yin Chan, De Xing Wang, Hua Jun Chang, Chia Liang Chen
Abstract: Defects of components as a result of entrapped gases during an injection process could be minimized with the utilization of a gas-permeable metal die material in the mold, due to its excellent permeability of air. Conventional gas-permeable die materials employ low temperature sintering of loosely packed steel powders with or without the addition of pore-forming polymers, whose microstructures are usually weak and their gas permeability values are also low. In this study, gas-permeable metal die materials are developed using tool steel powder, packed in a mold having the insertion of orthogonally arrayed polymer wires. Linear gas-permeable channels in orthogonal array are thus developed by the burning out of the polymer wires, which yield a large value of air permeability. The value of air permeability can be adjusted by changing the diameter and number density of the polymer wires. The tool steel powder can be made fully dense by supersolidus liquid phase sintering, yielding a microstructure with a wear resistance value much larger than that of the conventional gas-permeable die material.
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Authors: Woei Shyan Lee, Tien Yin Chan
Abstract: The effects of the content of molybdenum on the dynamic properties of tungsten heavy alloys were investigated.Increase in mechanical properties was observed in molybdenum-added tungsten heavy alloys, due to the refined microstructure. On the other hand, decrease in mechanical properties was also observed in the alloys with high molybdenum concentrations, due to the decreased strength of the matrix phase and the precipitation of an intermetallic phase. Hopkinson bar dynamic test under strain rates ranging from 2000 s-1 to 8000 s-1 at room temperature revealed that the flow stress of tungsten heavy alloys depended strongly on the strain, strain rate, and the content of molybdenum. The variation of flow stresses was caused by the competition between work hardening and heat softening in the materials at different strain rates. The high temperature strength of the matrix phase was increased by the addition of molybdenum, which enhanced the strength of the tungsten heavy alloys in high strain rate test.
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