DIRECTIONAL PRESSURE QUENCH CASTING OF ALUMINUM-ALLOYS

A novel method of casting is described in which liquid metal in permea ble moulds is subjected to high ambient pressure and quenching simulta neously A small pressure quenching chamber was used and shapes of two different geometries cast into sand moulds. Two non-heat treatable all oys, LM6M and LM21M, comprised the raw material. The results show that increasing ambient pressure alone up to a value of 2 MPa (20 bar) can reduce porosity of castings, has a limited effect on tensile strength , and little effect on dendrite arm spacing. Casting under pressure wi th quenching increased tensile strength by up to 30% compared with con ventional castings and virtually eliminated porosity. The dendrite aim spacing is also considerably reduced. Pressure quench casting is a po tentially inexpensive means of improving the mechanical and microstruc tural properties and integrity of a wide range of aluminium alloys mad e by existing sand casting methods. For heat treatable alloys it of of fers the possibility of solution treating in the mould, thus eliminati ng one operation in a production process.