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The phenomenon of restrained stress-induced preferential orientation of S′ precipitates is investigated using a single-crystal of Al–1.23Cu–0.43 Mg alloy. Al–1.23Cu–0.43 Mg single-crystal specimens are subjected to stress aging, and the microstructure is analyzed by transmission electron microscopy (TEM). It is found that the stress-induced preferential orientation of S′ precipitates is restrained owing to the dislocations produced by a higher stress. The effect of dislocations on the oriented precipitates depends on the total length of the intersection lines for precipitate habit planes and dislocation glide planes. This investigation not only provides important insight into solving the anisotropy problem attributed to precipitation strengthening, but also offers a benchmark for choosing the appropriate stress range in manufacturing of Al–Cu–Mg alloys. [ABSTRACT FROM AUTHOR]

Highlights: [•] Aluminizing treatment decreased the creep strength of superalloy. [•] Long-term exposure deteriorated the creep strength of coated superalloy. [•] Surface orientation affected the creep lifetime of coated superalloy. [•] Fracture deformation mechanism in coated superalloy was discussed. [Copyright &y& Elsevier]

Abstract: By means of the stress–strain finite element method (FEM) in elastic–plastic regime, the influences of the applied stress on the distribution of von Mises stress and evolution of shape regularity of γ′ phase in a [011] oriented single crystal nickel-based superalloy are investigated. Results show that, after full heat treatment, the microstructure of [011] oriented single crystal superalloy consists of the cuboidal γ′ phase embedded coherently in the γ matrix phase, and on (100) plane aligned regularly at angle of 45° relative to the [011] orientation. During compressive creep, the cuboidal γ′ phase is transformed into the mesh-like lamellar rafted structure on (100) plane. Therefore, the changes of the lattice strain, the strain energy density and interfacial energy are thought to be the driving forces of the element diffusion and γ′ phase directional growth. During compressive creep, the lattice contraction occurs on (100) plane of the cuboidal γ′ phase along [001] and [010] directions, whose extruding effect may repel Al, Ti atoms with bigger radius. Therefore, the expanding strain of lattices along [100] direction on (010) and (001) planes of the cuboidal γ′ phase may trap Al, Ti atoms to promote the directional growth of γ′ phase on (100) plane along [001] and [010] directions, which is thought to be the main reason for the γ′ phase growing directionally into the mesh-like lamellar structure. [Copyright &y& Elsevier]