Significant progress has been made in recent years in understanding and modelling the rheology of semi-solid metals.These models show the effects of the microstructure in terms of size and morphology of globules on th...Significant progress has been made in recent years in understanding and modelling the rheology of semi-solid metals.These models show the effects of the microstructure in terms of size and morphology of globules on the material response.More recently it has been shown that semi-solid metals can behave as compacted granular materials such as sand.A particular signature of such deformation is that the deformation becomes concentrated into shear bands which are 10-20 grains wide.Such bands have also been observed in a range of cast products.Recently, it has been clearly shown that shear bands in high pressure die cast (HPDC) products are also the results of Reynolds dilatancy.Shear bands are also known to be a common feature in semi-solid metal products.The segregation banding in semi-solid metal (SSM) material and its dependence of plunger velocity were investigated.Shaped castings were made with the RHEOMETALTM process with a range of different plunger velocities.The microstructural characteristics were investigated, with a particular emphasis on shear bands.It is shown that ingate velocities influence the location and characteristics of the shear bands.展开更多
The microstructure and tensile properties were investigated in a thick-walled section （approximately 45 mm×43 mm） of a rheocast component produced by the RheoMetalTM process. Due to the long solidification peri...The microstructure and tensile properties were investigated in a thick-walled section （approximately 45 mm×43 mm） of a rheocast component produced by the RheoMetalTM process. Due to the long solidification period of such components, it is expected that the A1-Si eutectic formed will be coarse. Therefore, sodium （Na） was used as a modifying agent to reduce the coarseness of the eutectic. Tensile test bars were machined from three different sets of materials： 1） non-modified melt, 2） modified melt cast directly after Na addition, and 3） modified melt cast 30 min after Na addition. The alloy used was a secondary AlSi6Cu2.5 alloy （STENAL Rheol）, specially developed for rheocasting. The material was studied in the as-cast condition as well as after a T6 heat treatment. The results show that the Al-Si eutectic is significantly refined by the Na addition, even after a fading time of 30 min. However, it is observed that the Na modification generally has a detrimental effect on the mechanical properties, despite the structure refinement. This is especially true in the T6 heat treated condition, where the yield strength is reduced by more than 30%. Some possible mechanisms for the degradation of mechanical performance are discussed.展开更多
文摘Significant progress has been made in recent years in understanding and modelling the rheology of semi-solid metals.These models show the effects of the microstructure in terms of size and morphology of globules on the material response.More recently it has been shown that semi-solid metals can behave as compacted granular materials such as sand.A particular signature of such deformation is that the deformation becomes concentrated into shear bands which are 10-20 grains wide.Such bands have also been observed in a range of cast products.Recently, it has been clearly shown that shear bands in high pressure die cast (HPDC) products are also the results of Reynolds dilatancy.Shear bands are also known to be a common feature in semi-solid metal products.The segregation banding in semi-solid metal (SSM) material and its dependence of plunger velocity were investigated.Shaped castings were made with the RHEOMETALTM process with a range of different plunger velocities.The microstructural characteristics were investigated, with a particular emphasis on shear bands.It is shown that ingate velocities influence the location and characteristics of the shear bands.
文摘The microstructure and tensile properties were investigated in a thick-walled section （approximately 45 mm×43 mm） of a rheocast component produced by the RheoMetalTM process. Due to the long solidification period of such components, it is expected that the A1-Si eutectic formed will be coarse. Therefore, sodium （Na） was used as a modifying agent to reduce the coarseness of the eutectic. Tensile test bars were machined from three different sets of materials： 1） non-modified melt, 2） modified melt cast directly after Na addition, and 3） modified melt cast 30 min after Na addition. The alloy used was a secondary AlSi6Cu2.5 alloy （STENAL Rheol）, specially developed for rheocasting. The material was studied in the as-cast condition as well as after a T6 heat treatment. The results show that the Al-Si eutectic is significantly refined by the Na addition, even after a fading time of 30 min. However, it is observed that the Na modification generally has a detrimental effect on the mechanical properties, despite the structure refinement. This is especially true in the T6 heat treated condition, where the yield strength is reduced by more than 30%. Some possible mechanisms for the degradation of mechanical performance are discussed.
