Showing papers on "Equiaxed crystals published in 1969"

Hot‐Working of Aluminum Oxide: I, Primary Recrystallization and Texture

Abstract: Polycrystalline aluminum oxide was hot-worked at 1750° to 1950°C and at stresses <21, 000 psi using a press-forging technique. No ductility problems were encountered, and maximum true strains and strain rates of -1.25 and 0.2/min, respectively, were observed. Deformed samples often showed grain elongation in addition to a marked basal crystallographic texture, which suggested that basal slip was the predominant deformation mode. However, nonbasal slip, grain boundary sliding, and diffusional deformation were all thought to contribute to the ductility. Primary recrystallization occurred during or after the deformation and resulted in equiaxed microstructures, although the basal texture was retained. Because of a severe shear strain gradient during deformation, nonuniform microstructures were usually obtained, and this provided a means for growing single crystals by strain anneal. Although no conclusions can be drawn concerning the origin of the recrystallization texture, it is suggested that pores are preferential sites for recrystallization nuclei. MgO in solid solution (1/4%) retarded primary recrystallization.

Orientation Dependence of Work-Hardening in Iron Single Crystals

Abstract: Iron single crystals with various tensile axes near the [100]–[110] line were extended in the temperature range 153°K to 473°K. The crystals which had their tensile axis within about 10 degrees from the [100] axis showed large work-hardening at low temperatures and the crystals with other orientations showed small work-hardening. It was confirmed from the rotations of tensile axis that four slip systems operated in the [100] type crystals and two systems in the [110] type crystals at low temperatures. At high temperature (473°K), the [100] type crystals showed long and linear work-hardening in the latter stage of deformation and large elongations more than 100%, but the crystals near the [110] axis showed small work-hardening in the latter stage and also small elongations.