Semi-solid technology refers to the use of heating materials to a semi-solid state to form a semi-solid structure in which the solid phase and the liquid phase are uniformly mixed. The solid phase rate is controlled by adjusting the heating temperature and time, and processing is performed in this state. Methods. The microstructure after semi-solid treatment has good grain morphology, the technical requirements are not high in the control process, the metal is not easy to burn, and the energy consumption is low, which greatly improves the utilization rate of the alloy.
Semi-solid alloys have rheological and thixotropic properties
Rheology refers to the flow and deformation of an alloy under external force in a state of being heated to a semi-solid state. For all fluids, when relative motion occurs inside them, friction is generated, which hinders the deformation. The amount of friction depends on the rate of change of speed. Newton has analyzed the relationship between the two. As the rate of change of velocity increases, the frictional force increases accordingly. However, in all cases, the two are proportional to each other. If the temperature changes, the viscosity of the material will follow. The change, then the relationship between the two is nonlinear.
The thixotropy macroscopically shows the influence of the shear force on the fluid viscosity of the fluid alloy during the flow. The viscosity of the fluid is greater than the viscosity when the force is not applied. The fluid has two states at a certain temperature: a gel state and a sol state. In the final analysis, thixotropy is the transformation between two states, which is a reversible process. The evolution of the conversion process depends on time and mechanical strength.