Mechanical Properties of a Novel High-Strength Aluminum-Lithium Alloy

Abstract

As a heat treatable aluminum alloy to be used in T6 and T8 temper, belongs to Al-Cu-Li system, a novel high-strength aluminum-lithium alloy 2A97 was developed. In order to improve the relationships of strength and ductility and fracture toughness, and to urge the applications in the aeronautical and aerospace industries, the effects of normal heat treatments and thermomechanical heat treatments on the mechanical properties and fracture toughness were investigated by Transmission Electron Microscope(TEM), Scanning Electronic Microscope (SEM), tensile test, and fracture toughness test. The results show that for the alloy aged at 135 °C for 24 h after quenching and 4 percent plastic deformation, its microstructures are strengthened by strain hardening and precipitation hardening, consisting of fine T1phase, θ″/θ′ phase and δ′ phase densely and homogeneously distributed in the matrix. It yields optimum relationship of strength and ductility, fracture toughness, its σ0.2, σband δ5are 454 MPa, 536 MPa, and 11.8%, respectively. It yields 43.5 MPa·m1/2of Kqvalues higher than that of 42.5 MPa·m1/2 in T6 temper. The fracture morphologies of impact tensile samples of fracture toughness test and normal tensile test were observed, indicating the dominance of intergranular failure and subintergranular failure with some dimples and trangranular failure.

Strengthening mechanisms, deformation behavior, and anisotropic mechanical properties of Al-Li alloys: A review

“…Thus, the relations of the orientation, shape, size and distribution of the strengthening phases within the alloy matrix are vitally important. The main characteristics that affect the mechanical properties of previous generation Al-Li alloys and lead to anisotropy in the tensile properties are summarized in Table 5 [109] , [110] , [111] , [112] , [113] , [114] , [115] , [116] , [117] , [118] , [119] .…”

Production methods of ceramic-reinforced Al-Li matrix composites: A review

“…However, this alloy has some problems such as yielding low fracture toughness and ductility in T8 temper while possessing high tensile strength, and yielding a fracture toughness and high ductility in T6 temper while having low strength. Investigations revealed that the fracture toughness and ductility were enhanced in this alloy by 4% deformation after under aging at low temperatures [41].…”

“…Age hardening response is additional advantage of Al-Li alloys [22]. Yuan et al [41] investigated the influence of thermomechanical and normal heat treatments on the fracture toughness and mechanical properties of a new generation of aluminum-lithium alloy (2A97). They aimed to enhance the relationships of fracture toughness, ductility, and strength to make them proper candidates for applications in the aeronautical industries.…”

Improving the properties of aluminum-lithium composites in aerospace applications: review

“…Few of the strengthening phases were found in Al-Cu-Li alloys include δ´(Al 3 Li), T1(Al2CuLi), and θ´(Al 2 Cu). Factors such as thermo-mechanical processing, corrosion resistance, composition, microstructure, heat treatment, and manufacturing techniques impact the mechanical properties of Al-Li alloys used in the past [75][76][77][78][79][80][81][82][83][84][85].…”