Structure and properties of the casted tape from alloy D16 in the technological chain "roll casting - hot rolling - heat treatment"

Abstract

At the experimental installation of two-roll casting, physical and technological parameters were developed to ensure a sustainable process of obtaining a sheet blank of metal of small thickness. Improving the technology of roll casting allowed for the first time in metallurgical practice to obtain a cast tape with a thickness of 2-3 mm from a wide-interval (˃130°C) aluminum alloy D16. The influence of hot deformation and heat treatment on the evolution and quantitative characteristics of the structure, as well as the properties of the obtained sheet blanks at each stage of the technological chain "roll casting - hot rolling - heat treatment" is studied. It was found that the microstructure of the aluminum alloy D16 in the cast state after roll casting is represented by a-Al dendrites of solid solution of different degrees of branching and intermetallics. Plastic deformation in the process of hot rolling leads to the orientation of the primary a-Al crystals in the rolling direction and to reduce their size in the plane perpendicular to the surface of the sheet. Increased compression to significant values (ε ≥87.5%) causes the formation of a line-type microstructure, and the number of intermetallics in the structure decreases monotonically, which is due to their partial dissolution in solid aluminum solution. Heat treatment after deformation helps to reduce the size and shape of intermetallics, especially during hardening with aging. The nature of changes in the size and shape of the dendritic cells a-Al from the heating of the alloy D16 after its deformation indicates a probable recrystallization process. The evolution of the structure of cast tape from this alloy, which occurs under the influence of technological factors "roll casting - hot rolling - heat treatment", significantly affects the level of their mechanical properties (short-term strength and elongation). The highest level of short-term strength is achieved by compressing ε = 50% (from σв ≈ 200 MPa in the cast state to σв ≈ 450 MPa). The elongation with increasing degree of deformation also increases significantly (from δ = 0…2% in the cast state to δ = 20…22% after rolling and heat treatment), which is associated with a decrease in the size and shape of the crystals of both solid solution of a-Al and intermetallic phases. The obtained mechanical properties of the D16 alloy belt exceed the existing analogues and are much higher than the requirements of the standards.

Keywords

• structure
• properties
• roll casting
• cast tape
• rolling
• heat treatment.