Squeeze casting of high-strength aluminium wrought alloy AA7010

Abstract

Historically, the 7000 series alloys were developed for high-strength wrought-form applications and are, therefore, unsuitable for conventionally produced castings. However, in this study it is shown that using the squeeze casting process, porosity-free, fine equiaxed grain components of AA7010 composition can be produced successfully. In the first part of this study, the cast structure of aluminium alloy AA7010 solidified under pressure is examined. The results show that the effect of pressure-induced undercooling on the grain structure of the alloy is insignificant. The effect of pressure on the grain structure was detectable only when the melt temperature was well above the liquidus temperature at the time of pressure application. However, a porosity free, fine equiaxed grained structure having an average size of 70 μm was obtained when the alloy was pressurized at a temperature between its liquidus and solidus temperatures. The second part of the study compares the tensile properties of the squeeze cast AA7010 alloy and its wrought product counterpart. The results show that the squeeze cast fully heat-treated alloy exhibits tensile properties between those of the longitudinal and short transverse properties of the wrought material. Unlike the wrought material, in which the grain structure is not fully controllable, squeeze cast material can be produced having isotropic behaviour. It can be argued, therefore, that from this point of view, squeeze castings are better than their wrought counterparts.