The microstructure formation and grains refinement of two Mg-based alloys,i.e.AZ31 and AZ91D,were reported using an electromagnetic vibration(EMV) technique.These two alloys were solidified at various vibration freque...The microstructure formation and grains refinement of two Mg-based alloys,i.e.AZ31 and AZ91D,were reported using an electromagnetic vibration(EMV) technique.These two alloys were solidified at various vibration frequencies and the microstructures were observed.The average size of grains was quantitatively measured as a function of vibration frequencies. Moreover,the grain size distribution was outlined versus number fraction.A novel model was proposed to account for the microstructure formation and grain refinement when considering the significant difference of the electrical resistivity properties of the solid and the liquid during EMV processing in the semisolid state.The remarkable difference originates uncoupled movement between the mobile solid and the sluggish liquid,which can activate melt flow.The microstructure evolution can be well explained when the fluid flow intensity versus vibration frequency is taken into account.Moreover,the influence of the static magnetic field on texture formation is also considered,which plays an important role at higher vibration frequencies.展开更多
The effect of the cooling slope on the structure of Zr-based metallic glass matrix composites was investigated by changing the cooling slope.The synthesis of bulk metallic glass composites was made by a process combin...The effect of the cooling slope on the structure of Zr-based metallic glass matrix composites was investigated by changing the cooling slope.The synthesis of bulk metallic glass composites was made by a process combining cooling slope casting and Cu mold casting for Zr66.4Nb6.4Cu10.5Ni8.7Al8 alloys.The results show that the semisolid slurry which consists of the spheroidal or rosette-type BCC crystals and the liquid phase which forms metallic glass phase can be formed by the cooling slope process in this alloy system.However,the semisolid slurry cannot reach to the mold.It is considered that higher viscosity of the liquid phase which forms metallic glass phase causes this result.Thus,parameters of the cooling slope have to be examined further.展开更多
文摘The microstructure formation and grains refinement of two Mg-based alloys,i.e.AZ31 and AZ91D,were reported using an electromagnetic vibration(EMV) technique.These two alloys were solidified at various vibration frequencies and the microstructures were observed.The average size of grains was quantitatively measured as a function of vibration frequencies. Moreover,the grain size distribution was outlined versus number fraction.A novel model was proposed to account for the microstructure formation and grain refinement when considering the significant difference of the electrical resistivity properties of the solid and the liquid during EMV processing in the semisolid state.The remarkable difference originates uncoupled movement between the mobile solid and the sluggish liquid,which can activate melt flow.The microstructure evolution can be well explained when the fluid flow intensity versus vibration frequency is taken into account.Moreover,the influence of the static magnetic field on texture formation is also considered,which plays an important role at higher vibration frequencies.
文摘The effect of the cooling slope on the structure of Zr-based metallic glass matrix composites was investigated by changing the cooling slope.The synthesis of bulk metallic glass composites was made by a process combining cooling slope casting and Cu mold casting for Zr66.4Nb6.4Cu10.5Ni8.7Al8 alloys.The results show that the semisolid slurry which consists of the spheroidal or rosette-type BCC crystals and the liquid phase which forms metallic glass phase can be formed by the cooling slope process in this alloy system.However,the semisolid slurry cannot reach to the mold.It is considered that higher viscosity of the liquid phase which forms metallic glass phase causes this result.Thus,parameters of the cooling slope have to be examined further.
