In order to improve the performance of plaster molds for investment casting,a diverse content of glass fiber and polypropylene(PP)fiber was incorporated into the slurry for the preparation of a fiber-reinforced mold.T...In order to improve the performance of plaster molds for investment casting,a diverse content of glass fiber and polypropylene(PP)fiber was incorporated into the slurry for the preparation of a fiber-reinforced mold.The green and fired bending strengths,thermal expansion properties,permeability,and thermal shock resistance of the mold were examined,and the scanning electron microscope(SEM)with energy dispersive spectrometer(EDS)was applied for the observation of fracture morphology.With appropriate content,the introduction of glass fiber was proved to increase the green bending strength and fired bending strength,restrain the thermal expansion and improve the thermal shock resistance of the mold,while the polypropylene fiber added was able to raise the green bending strength and the permeability,reduce the thermal expansion and heighten the thermal shock resistance as well,though the fired bending strength would be weakened slightly.Evenly distributed fibers were capable of enhancing the mechanical properties of the matrix,but agglomerations and bundles of fibers resulting from excessive addition had a negative impact.Meanwhile,it was also manifested that micropores left by ablative polypropylene fibers could improve the permeability and reduce the thermal expansion of the mold,and the fired bending strength would be decreased slightly by the deterioration of continuous structure.Three different ratios of hybrid fiber were employed in plaster molds,which can meet altered requirement of castings.The samples modified with hybrid fiber possessed lower thermal deformation,higher air permeability,and better resistance of thermal shock,while the mechanical strength was equal to the fiber free sample or slightly increased.展开更多
文摘In order to improve the performance of plaster molds for investment casting,a diverse content of glass fiber and polypropylene(PP)fiber was incorporated into the slurry for the preparation of a fiber-reinforced mold.The green and fired bending strengths,thermal expansion properties,permeability,and thermal shock resistance of the mold were examined,and the scanning electron microscope(SEM)with energy dispersive spectrometer(EDS)was applied for the observation of fracture morphology.With appropriate content,the introduction of glass fiber was proved to increase the green bending strength and fired bending strength,restrain the thermal expansion and improve the thermal shock resistance of the mold,while the polypropylene fiber added was able to raise the green bending strength and the permeability,reduce the thermal expansion and heighten the thermal shock resistance as well,though the fired bending strength would be weakened slightly.Evenly distributed fibers were capable of enhancing the mechanical properties of the matrix,but agglomerations and bundles of fibers resulting from excessive addition had a negative impact.Meanwhile,it was also manifested that micropores left by ablative polypropylene fibers could improve the permeability and reduce the thermal expansion of the mold,and the fired bending strength would be decreased slightly by the deterioration of continuous structure.Three different ratios of hybrid fiber were employed in plaster molds,which can meet altered requirement of castings.The samples modified with hybrid fiber possessed lower thermal deformation,higher air permeability,and better resistance of thermal shock,while the mechanical strength was equal to the fiber free sample or slightly increased.
