Comparison of fibres for creep strengthening of zinc-aluminium foundry alloys

A comparative evaluation is made of a variety of possible fibrous reinforcements for strengthening zinc-aluminium foundry alloys. The composites are processed by squeeze casting, using preforms of alumina, carbon, stainless steel or low carbon steel fibres. A drastic improvement of the creep strength is achieved with the use of alumina or steel fibres. However, an acceptable level of fracture toughness is maintained only in the composites reinforced with steel fibres. This property results from the low interface adhesion which allows bridging of the crack by the fibres. Low carbon steel fibres do not exhibit more interface reaction than stainless steel fibres. It is concluded that low carbon steel fibres provide a better compromise when taking into account the creep strength, the fracture toughness and the cost of the composite.