Abstract
This paper investigated the cooperative effects of Li addition and warm Equal Channel Angular Pressing (ECAP) on improving the mechanical properties of an Al-Mg-Li alloy for further weight reduction. The results showed that more Li addition could obviously refine the grains of the as-cast alloy and reduce its density value to only 2.37 g/cm3 when Li content reached 2.5% (about 12.6% lighter than commercial Al alloys). It also had a pronounced influence on the precipitations in the Al-5.5Mg-xLi-0.1Zr alloy, i.e., the number density and size of Al2MgLi and δ’-Al3Li phases. The yield strength of the as-cast alloy was increased with increasing Li, but the elongation deteriorated due to primary network intergranular Al2MgLi and more δ’ particles in the high Li-containing alloy. The warm multi-pass ECAP process was found to simultaneously improve the strength and ductility of the Al-Mg-Li alloys, and greatly alleviate the detrimental effect of Li addition on the elongation, thereby making the ultrafine-grained (UFG) alloys, a good combination of lightweight and high performance, very attractive for aerospace applications for much higher specific strength than both Al matrix composites and Mg alloys.
Highlights
Since weight reduction has been considered as a more and more important contributor to performance and operating cost associated with fuel efficiency, the strength/weight ratio has become the prime driver for designers to select materials for aerospace systems [1]
It is well known that Al-Mg-Li alloys, as one of the industrially used categories of Al-Li alloys, have the lowest densities available for a commercial aluminum alloy
For the ECAPed alloys, the effect of Li addition on the microstructure of Al-Mg-Li alloys is greatly weakened by severe plastic deformation
Summary
Since weight reduction has been considered as a more and more important contributor to performance and operating cost associated with fuel efficiency, the strength/weight ratio has become the prime driver for designers to select materials for aerospace systems [1]. Under such circumstances, aluminum-lithium alloys, with lower density, higher strength, and better stiffness than conventional aluminum alloys, are considered as promising structure materials to reduce cost in the aerospace industry [2,3]. High Mg contents (>4 wt%) tend to favor the formation of the equilibrium cubic phase
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