Mechanical Properties Improvement of Al–Li 8090 Alloy by Using the New Proposed Method of Directional Quenching

Abstract

Due to having low density as well as high specific modulus and fatigue toughness, Al–Li alloys have been targeted as an advanced material for using in aerospace applications. In the current investigation, a new heat treatment method namely as directional quenching process is proposed to improve the mechanical properties of the Al–Li 8090 alloy, the results of which are compared with those of T6 and T8 aging heat treatment techniques. For this purpose, aging process at 170 °C is conducted in all of the three heat treatment methods, but the solutionizing treatment and quenching are performed along a specific direction in the introduced directional quenching method. The mechanical properties and fracography of cross-sectional fracture pattern of the heat treated samples are studied corresponding to the various heat treatments. Based on the obtained results, it is found that in comparison with the two conventional T6 and T8 heat treatment methods, the proposed directional quenching technique has the capability to increase simultaneously both of the ductility and strength of Al–Li 8090 alloy. Also, according to the performed finite element based thermal stress analysis, it is observed that a uniform distribution and high volume fraction of strengthening δ′ (Al3Li) precipitates are acquired via the directional quenching technique. The proposed heat treatment technique of directional quenching