Structure and Properties of Sheets from New Al–Mg–Si Alloy V-1381

Abstract

A new series 6xxx Al-Mg-Si alloy is developed with grade V-1381. The influence of the composition and modes of heat treatment on the mechanical and corrosion properties of sheets with a thickness of 1 and 3 mm manufactured at the All-Russian Scientific Research Institute of Aviation Materials (VIAM) is investigated. The average properties of the sheets are as follows: the ultimate tensile strength is σ B = 410 MPa, the yield strength is σ 0.2 = 360 MPa, the elongation is δ = 11.5%, the fatigue crack growth rate is (dl/dN) = 0.59 mm/kcycle at ΔK = 18.6 MPa m 1/2 , the intergranular corrosion is IGC ≤ 0.15 mm, and the exfoliation corrosion (EXFC) is 4 points. It is found out that the sheets are structurally recrystallized, the main strengthening phase is the matrix-coherent β'(Mg 2 Si) phase evenly distributed with a high density across the volume of grains. Another observed process is the heterogeneous origin of the β′ phase on dislocations and dispersoids. The dispersoids observed in the tested specimens have various morphologies. The grain boundaries have emission-free zones 15-20 nm in width. The temperatures and heat values of phase transformations in ingots and sheets are determined, including the measurement of liquidus and solidus points. The sheet weldability is evaluated by automatic argon-arc welding, and critical strain rate V cr of the weld metal during crystallization is determined at which this metal is not covered with cracks. A laser welding mode has been developed to ensure optimal formation of the geometric parameters of the weld.