Search

The controlled application of macroscopic shears to solidifying melts containing alignable constituents provides for the management of fibres in, and the production of components to close tolerances. Shear controlled orientation technology (SCORTEC) may be applied to the thermoplastic and thermoset matrix composites, and to ceramic and metal matrix composites processed with the aid of sacrificial polymer binders. The principles of SCORTEC as applied to moulding and extrusion processes will be described, together with examples of typical property enhancement possible, and potential fields of application.

(1992). Application of Shear Controlled Orientation Technology to Powder Injection Moulding. Powder Metallurgy: Vol. 35, No. 2, pp. 107-112.

A Polypropylene based organic vehicle was used to injection mould commercial Purity aluminium powder. The test bars produced were heated, according to near optimum temperature-time schedules, in both static air and flowing nitrogen to remove the organic vehicle. Heating was interrupted at different temperatures to measure shrinkage and strength of the test bars. Shrinkage caused by the removal of organic vehicle increases the volume percentage of aluminium in the test bars and this results in an increase in their strength but the packing efficiency attained is well below the maximum value.

A polypropylene-based binder system was used to injection mould test bars containing 65 vol % aluminium powder. Specimens, 3 and 6 mm thick, made from these bars were used for pyrolytic binder removal experiments in static air and nitrogen. The development of a carefully defined experimental procedure for the determination of the heating rate at which binder removal can be carried out at a given temperature without the creation of macro defects is fully described. The use of isothermal heat treatments during pyrolysis are also considered and results are presented as temperature-heating rate diagrams for each atmosphere and thickness investigated. These diagrams show a lower and an upper boundary. Defect formation occurs if the temperature-heating rate relationship lies between the boundaries. Near optimum binder removal schedules deduced from each diagram have been experimentally verified.