The effect of thixoforming process on morphologies of silicon particles that affect fracture mode of A356 alloy was investigated.Microstructure and fracture surfaces of thixoformed samples were investigated by image a...The effect of thixoforming process on morphologies of silicon particles that affect fracture mode of A356 alloy was investigated.Microstructure and fracture surfaces of thixoformed samples were investigated by image analyzing technique and scanning electron microscopy.A new combination parameter, called silicon density ratio (SDR) index, was introduced.SDR index approximates the collective effects of morphological characteristics of silicon particles on microstructure transparency of alloy in crossing the dislocation.It is suggested that samples with lower SDR index have superior mechanical properties, especially elongation, and consequently intergranular fracture mode.On the contrary, samples with higher SDR index have inferior mechanical properties and fracture path tends to propagate along the cell boundaries leading to transgranular fracture.展开更多
The rheological behavior and gelcasting of composite suspensions of SiC and synthesized Al 2O 3-Y 2O 3-La 2O 3 powder as sintering aid were investigated. It was found that the rheological behavior of SiC particles cou...The rheological behavior and gelcasting of composite suspensions of SiC and synthesized Al 2O 3-Y 2O 3-La 2O 3 powder as sintering aid were investigated. It was found that the rheological behavior of SiC particles could be modified with a slightly oxidized surface that was similar to silica in colloidal behavior. The smaller the particles were, the more similar to silica the SiC powder was. The pH value of Al 2O 3-Y 2O 3-La 2O 3 synthesized powder slurry at isoelectric points (IEP) is higher than that of SiC powder. The dispersant PAA-NH 4 changes the IEP of both SiC and Al 2O 3-Y 2O 3-La 2O 3 powder slurry to higher pH values. The experimental results indicate that the composite suspension could possess satisfactory stability and lower viscosity at pH =10.1 and PAA-NH 4 as dispersant. The optimum solid loading was 550 0 in volume. Machinable green bodies with uniform complex shape are gained after molding.展开更多
文摘The effect of thixoforming process on morphologies of silicon particles that affect fracture mode of A356 alloy was investigated.Microstructure and fracture surfaces of thixoformed samples were investigated by image analyzing technique and scanning electron microscopy.A new combination parameter, called silicon density ratio (SDR) index, was introduced.SDR index approximates the collective effects of morphological characteristics of silicon particles on microstructure transparency of alloy in crossing the dislocation.It is suggested that samples with lower SDR index have superior mechanical properties, especially elongation, and consequently intergranular fracture mode.On the contrary, samples with higher SDR index have inferior mechanical properties and fracture path tends to propagate along the cell boundaries leading to transgranular fracture.
文摘The rheological behavior and gelcasting of composite suspensions of SiC and synthesized Al 2O 3-Y 2O 3-La 2O 3 powder as sintering aid were investigated. It was found that the rheological behavior of SiC particles could be modified with a slightly oxidized surface that was similar to silica in colloidal behavior. The smaller the particles were, the more similar to silica the SiC powder was. The pH value of Al 2O 3-Y 2O 3-La 2O 3 synthesized powder slurry at isoelectric points (IEP) is higher than that of SiC powder. The dispersant PAA-NH 4 changes the IEP of both SiC and Al 2O 3-Y 2O 3-La 2O 3 powder slurry to higher pH values. The experimental results indicate that the composite suspension could possess satisfactory stability and lower viscosity at pH =10.1 and PAA-NH 4 as dispersant. The optimum solid loading was 550 0 in volume. Machinable green bodies with uniform complex shape are gained after molding.
