The influence of Al3Zr precipitation on the superplastic behaviour of aluminium alloys

The development of a fine distribution of Al3Zr precipitates is essential to confer superplastic properties in a number of industrial and experimental aluminium alloys. In this paper the influence of a number of production variables on the development of the Al3Zr dispersions in both AA2004 and Al-4Mg-Zr alloys is investigated. Microsegregation leads to a heterogeneous distribution of supersaturated zirconium after solidification. Under certain processing conditions this can lead to the formation of precipitate free zones which are detrimental to SPF performance. An intermediate temperature hold (360degreesC) can strongly influence the final dispersion and in turn can reduce the detrimental effect of the precipitate free zones. Other key factors that influence the Al3Zr distribution (such as zirconium content, heating rate and hold times) are also discussed.