The (110) [001] secondary recrystallization in Al-killed steel has been studied. Hot-rolled specimens are pre-annealed, cold-rolled, decarburized and isothermally annealed at 1163 K. The secondary recrystallization occurs during final isothermal anneal in the specimens which have been annealed prior to cold-rolling in the condition of a certain range of temperature and time. By the prior anneal, AlN precipitates as a dispersed second phase. The precipitated AlN particles inhibit the normal grain growth and thus induces the secondary recrystallization. The prior anneal also permits the occurrence of the (110) [001] component in the primary recrystallized texture, which grows into the secondary recrystallization grains during final isothermal anneal. The phenomenon is discussed from the viewpoint of dispersed precipitates comparing with the reported behavior in Al-killed steel and 3% Si–Fe.

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In order to clarify the effect of high hydrostatic pressure on the brittle fracture stress, the three-point bending tests have been carried out for an Fe–Cr alloy (σ phase) containing about 47%Cr and 0.7%Si at atmospheric pressure and under 800 MPa at temperatures up to 1200 K. In the temperature range from room temperature to 1140 K, the specimens remained in the σ phase and the transgranular cleavage fracture occurred under both pressures. By scanning electron microscopy, the fracture surface was found to comprise the river pattern and the Wallner lines. The fracture stress at atmospheric pressure increased gradually with increasing temperature to about 1000 K and increased rapidly at higher temperatures. The same tendency was observed in the tests under 800 MPa but the fracture stress under 800 MPa was always higher than that at atmospheric pressure, and the difference between these stresses became larger at temperatures higher than about 1000 K. From a consideration of the stress condition around a crack, a formula σ_FP=σ_F0+P⁄K_σ was proposed to represent the influence of hydrostatic pressure on the brittle fracture stress at low temperatures, where σ_F0 and σ_FP are the fracture stresses at atmospheric pressure and under high pressure, P is the pressure in positive sign and K_σ is the stress concentration factor at the crack. At higher temperatures, K_σ was replaced by Neuber’s plastic stress concentration factor K_σ^*.

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The melt spinning of Hastelloy-X filament was carried out to produce the heat-resistant alloy filaments. The spinning was achieved from a melt at a temperature of 1630 K with winding speeds ranging from 0.95 to 3.97 m/s. A metastable phase of fct with a=3.60×10⁻¹⁰ m, c=3.51×10⁻¹⁰ m was observed in the filament produced by the process.
Tensile strength of the filament at high temperature in the air was measured and compared with that of the stainless-steel IN 856 filament. The strength of the Hastelloy-X filament decreased to 50 percent by heating at 1023 K, while IN 856 filament was softened to the same percent at 873 K.
The Hastelloy-X filament annealed at 973 K for 3.6×10⁵ s in the air had a high strength of 650 MPa, whereas IN 856 filament had a strength of 120 MPa. However the Hastelloy-X filament treated at more hard heating condition, such as at 973 K for more than 1×10⁶ s, had a lower strength than that of a usual Hastelloy-X alloy.

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The isothermal oxidation behavior of Ni–20Cr alloys with 0.7 mass% dispersion of various oxides, Y₂O₃, La₂O₃, Al₂O₃, TiO₂, SiO₂ and Cr₂O₃ was studied in air at 1373 and 1473 K.
The dispersion of La₂O₃ and Y₂O₃, especially La₂O₃, excellently reduced the oxidation rate, whereas the effect of Al₂O₃ and TiO₂ dispersion on the reduction in the oxidation rate was slight. In contrast, the dispersion of SiO₂ and Cr₂O₃ significantly increased the oxidation rate of the Ni–20Cr alloy. There was a tendency that the oxidation of the alloys with various dispersed oxides except La₂O₃ decreased with increasing negative value of standard free energy formation of the dispersed oxides. The spallation of the scale was also remarkably depending on the type of the dispersoids. The dispersion of La₂O₃ excellently suppressed the spallation of the scale, whereas the dispersion of SiO₂ enhanced the spallation of the scale. Comparison of the ratio given by R_sp=mass of the spalled scale/mass gain for the alloys with various dispersoids suggested that the spalling behavior would be very complex. The incorporation of Ni and the dispersed elements throughout the entire thickness of the Cr₂O₃ scale was detected by IMA . There was a general tendency that the alloys, whose scale formed during the early stage of oxidation had lower Ni content, showed the lower oxidation rate for the following oxidation process. The accumulation of dispersoids at the scale-alloy interface was observed not in the alloys with La₂O₃ and Y₂O₃ which excellently reduced the oxidation rate, but in the alloy with SiO₂ which increased the oxidation rate and the spallation of the scale.

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A method for evaluation of the amount of grain boundary segregation during quenching of dilute alloys was developed on the basis of McLean’s theory. The method was applied to the corrections to the results of AES analysis of grain boundary segregation of phosphorus in the austenite range of a NiCr steel, and a considerable amounnt of phosphorus segregation was suggested to occur during the quenching from the austenite range. Investigations were made on the grain boundary segregation of oxygen, carbon and sulphur during the quenchings of Fe–O, Fe–C and Fe–S alloys. It was suggested that the segregation of carbon cannot be avoided in any conventional quenchings due to its large diffusivity. The segregation of sulphur could also be large in the quenchings from temperatures above 925 K.

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The effect of Si content on the oxidation behavior of 80Ni–20Cr alloys has been studied in the cyclic oxidation in an air stream at 1373 K . The addition of 1% and 5%Si to the alloy lowered the mass gain in oxidation, whereas the amount of spalling of oxide scale was increased with the addition of Si. The structure of oxide layers observed by microphotography, X-ray diffraction and electron probe microanalysis (EPMA) were different with the Si content of alloys. The oxide layer of the alloy with 1%Si consists of multi-layers, that is Ni oxide, Cr₂O₃ and SiO₂ as the external oxide layer. The oxide layer remaining on the alloy with 5%Si, however, was made of a single oxide layer of Cr₂O₃ containing small amounts of Si and Ni. In spite of the fact that the amount of Si in this alloy is larger than that of the alloy with 1%Si, the SiO₂ oxide layer was not observed at the oxide-alloy interface. It was found by EPMA that the concentration of Si in the oxidized 5%Si alloy substrate was increased in the vicinity of the surface, although Si in the 1%Si alloy was depleted.
From the above results the internal oxidation of Si is assumed in the near-surface region of the 5%Si alloy. The internal oxidation of the 5%Si alloy was confirmed by an increase in hardness in the near-surface region.
The difference in oxidation behavior between the 1%Si and 5%Si alloys can be understood under the assumption that the oxide layer formed of the 5%Si alloy contained much larger amounts of Ni and Si than that on the 1%Si alloy, and that this oxide layer tends to crack more easily, thus being less protective for the penetration of oxygen.

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Diffusion behavior of composition variations in supersaturated solid solutions was studied by computer simulation using a Fourier transform of the diffusion equation. The composition variations are always amplified by diffusion of atoms leading to the completion of decomposition, unless the initial composition variations are so small. The decomposition process is spinodal-like in high solute alloys but nucleation-growth-like in low solute alloys. In addition to the linear term developed by Cahn, following two non-linear terms in the diffusion equation play important roles on phase-decomposition: One is the term which works effectively in low solute alloys and amplifies locally the composition variations. The other, which works at a later stage of aging in all alloys, squares the composition variations and causes the growth of nuclei.

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Partition of nitrogen between cementite and austenite was investigated by analyzing nitrogen in nearly eutectic iron-carbon alloys and the cementites extracted from them. Nitrogen was more concentrated in cementite than in austenite and the concentration reduced with increasing temperature. Partition of nitrogen between austenite and liquid iron was examined from the measurement of the solubilities of nitrogen in these phases. The result showed that when primary austenite crystallized, nitrogen was rejected from the austenite to liquid iron at temperatures higher than 1320°C(1593 K). The partition behaviour was reversed at temperatures lower than 1320°C.

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