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Al–Cu–Li Alloys: Phase Composition, Texture, and Anisotropy of Mechanical Properties

Friday (10.11.2017)
10:35 - 10:55
Part of:

One of the serious problems of the use of aluminum-lithium alloys is expressed anisotropy of the properties, which is associated with the peculiarities of the formation of the texture and the phase composition of sheets of medium-strength alloy 1441 (1,8Li-1,8Cu-0,9Mg) and high-strength alloy 1469 (1, 3Li-3,8Cu-0,5Mg), which are regarded as promising for use in GLARE and in the hybrid laminated upper and lower wing panels. Thin sheets of 0.3 mm thick 1141 alloy and 1,5 mm 1469 alloy obtained for rolling of "KUMZ", then they are subjected to heat treatment: quenching, extension deformation with 1.5 -2.0% and the two-step aging treatment. With Scherer equation of particle sizes of these phases is estimated at ~ 3 and ~ 40 nm, respectively, for δ'- and T1-phases. Both intermetallic phase coherent matrix, as evidenced by the intensity and corresponding reflections intermetallic matrix based on the known orientation relationships. Measuring the amount of intermetallic phases in alloys on the basis of the measurement period of the lattice of the solid solution we have shown that the alloy number 1469 δ'-phase ranges 7.3-8.1%, and T1-phase 5,0-5,9%, and in 1441 alloy δ'-phase within 18,2-18,5%, and T1-phase 0-0.4%. The B-1469 alloy strength properties at 160-200 MPa higher than that of alloy 1441. Quantitative characteristics of the phase composition revealed that the reinforcing effect of the phase T1 4-4.5 times higher than the δ'-phase. The strength and yield strength in the longitudinal direction of 1469 alloy by 5% higher and the alloy 1441 to 5% lower than in the transverse direction. For an explanation of the reasons for a anisotropy of the strength properties of alloys in sheets counted Sachs factors. It is shown that to explain the anisotropy of the alloy must be taken into account slip deformation on the {111} <110> to the solid solution, slip on the system {001} <110> for an ordered δ'- phase and basal slip for hexagonal T1-phase. This model can explain such that only for the alloys Al-Cu-Li c texture "brass" occurs most pronounced anisotropy properties, such that when texture in other aluminum alloys prevents abnormal anisotropy.

Prof. Dr. Sergey Betsofen
Moscow aviation Institute