Investigation of semi-solid metal processing route

Abstract

Two main objectives were complete during this work. One was the design and construction of a high temperature capillary viscometer and the second was the modelling of semi-solid metal flow with a view to aiding the design and providing data for comparison purposes. The high temperature capilla ry viscometer has been constructed and has been used for preliminary testing. This device will be used to measure the viscosity of semi-solid metals under high temperature and shear rate conditions, similar to those found in industry. The capillary viscometer is a single point system that can be used to calculate the v isco s ity b y measuring the flow rate and pressure difference between the two end o f the capillary tube as the v isco s ity directly proportional to the pressure drop and inversely proportional to the flow rate. Design criteria included a requirement for a highly controllable temperature up to 800 °C, injection shear rates above 10 ,0 0 0 s '1, and controllable injection profiles. A 2D , two phase theoretical unsteady state model using a computational fluid dynamics (CFD) software F LU E N T was developed. This was used to evaluate the v isco s ity o f semi-solid metals passing through the designed capillary viscometer at injection speeds o f 0.075, 0.5, and 1 m/s. The effects o f fractions solid (fs) o f the metal from 0 .25 to 0.50 were also investigated. Strong correlations between these parameters and the resulting v iscosity were noted for the power law viscosity equations which were used to develop the Fluent models