THE DEVELOPMENT OF 8090 AND 8091 ALLOY EXTRUSIONS

Abstract
This paper focuses attention on the manufacturing, mechanical properties, and microstructural aspects of 8090 and 8091 alloys in the extruded form. The paper draws upon the experience of commercially extruding the alloys at Alcan High Duty Extrusions and upon the results of extrusion trials carried out by Alcan International. These trials dealt with specific aspects of extrusions, in particular to show the interplay between the various process parameters involved in fabricating extruded product suitable for aerospace application. The paper will show how such factors as extrusion conditions (preheat temperature and extrusion speed, extrusion ratio, aspect ratio) and final thermomechanical treatments (stretching and ageing) influence the alloy's microstructure. The variation in mechanical properties, in particular strength and fracture toughness, will be discussed in terms of the microstructures observed. Emphasis is placed on examining the similarities and differences between the behaviour of thin (2 mm) and thick (25 mm) extrusions.