Authors: Xiao Wei Zhuang, Shou Hai Li, Yu Feng Ma, Wei Zhang, Yu Zhi Xu, Chun Peng Wang, Fu Xiang Chu
Abstract: The phenolic(PF) foams were prepared used low-temperature foaming and curing method. The optimum low-temperature foaming processing technology conditions and material proportioning were described below. The curing temperature was 40 °C, the amount of foaming agent iso-pentane was 8-10wt.%, tween-80 dosage was 6-7wt.%, the amount of composite curing agent was 15-18wt.%.The effects of low-temperature foaming on mechanical properties, heat insulation, fire-retardant, foam hole form and micro-structure were discussed. 40°C and 70°C curing PF foam performance comparison results showed that low-temperature curing technology slightly affect the fire-retardant properties of PF foam. And excellent overall performance PF foam were prepared with 40°C foaming technology, the foam hole morphology structure, toughness and strength of PF foam were better. In addition, the low-temperature curing PF foam had more even foam hole distribution, more regular foam hole structure, more clean foam hole arrangement.
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Authors: Roger Pelletier, Louis Philippe Lefebvre, Eric Baril
Abstract: Discontinuous reinforced titanium matrix composites have generated significant interest due to their compelling properties such as their specific strength and wear resistance at room and elevated temperatures. For these reasons, these materials have been considered in various applications such as automotive (valve components), aerospace (engine components) and medical devices (implants). Metal injection molding (MIM) has proven to be an efficient near net-shape technology suitable for high volume manufacturing of parts having complex geometries. The MIM technology is particularly attractive for producing composites as the metallic matrix does not go through the liquid state. This helps minimizing the segregation of the hard particles. MIM also reduces the needs for machining. However, the production of titanium components with the MIM process has its own challenges and limitations, such as presence of porosities and coarser microstructures compared to wrought products. The present work introduces the results obtained during the development of a MIM route for producing Ti6Al4V-5wt%TiC composites. The feedstock developed is wax-based and incorporates a pre-alloyed metal powder. The microstructure, mechanical properties at room and elevated temperatures, the wear resistance and the thermal diffusivity of the composites have been characterised. Properties are compared with those of a Ti6Al4V MIM material produced with the same feedstock and process but without TiC as well as with those of wrought Ti6Al4V reported in the literature. The presence of a small amount of TiC promotes densification and grain size refinement and affects the surface finish of the sintered components. Tensile properties of the composites are comparable or better than those of wrought Ti6Al4V (ASTM F1472). Improved mechanical properties compared to unreinforced material are associated to the higher density, finer grain size as well as solution strengthening of the titanium matrix.
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