In the case of a 35Ni-15Cr type iron-base superalloy, in which phases such as γ′-Ni_3(Al, Ti), M_3B_2, TiC, Y-Ti_2SC, β-NiAl, α-Ni_2AlTi, η-Ni_3Ti, σ and Laves, may be present, total amount of aluminium and titanium and the ratio (Ti/Al) in the alloy exerted marked influences upon these phases. It is found that the variation of Al+Ti contents may change the weight fraction, the size and the chemical composition of γ′-phase and γ-γ′ mismatch, as well as the microstructure of the alloy after prolonged exposure at 800℃ for 500 hrs and at 700℃ for 5000 hrs. The ratio Ti/Al, however, affected the γ-γ′ mismatch and the chemical compositions of γ′-phase, but not the weight fraction and size of γ′-phase. It was observed that either σ or Laves phase was present after prolonged exposure at 800℃ and 700℃ if Al+Ti content of the alloy exceeded 5 or 4% respectively. The tensile properties at room temperature and at 650℃, the stress-rupture properties at 750℃, the tensile properties after prolonged exposure at 700℃ all showed a change of the mechanical properties of the alloy commensurate with the microstructutre aforementioned.

With the aid of etching by Fry's reagent and microhardness measurements, the crack-tip stress and strain have been investigated. The results obtained may be summarized as follows:The crack-tip stress increases simultaneously with the angle of bend of the specimen in accord with the relationJ=G+[(β/3~(1/2)+1/2(σ_(YY))_A)]δ_p derived by us under the linear hardening law:■=β+γ■until the critical point is reached:J_c=G_c+(β/3~(1/2)+1/2σ_F)δ_(p,c) demonstrating that at the critical point(σ_(YY))_A=σ_F

Unhealed porosities and free surface of dendrites with crystalline steps were occasionally observed in aluminium alloy forgings. It was found that the dendrites grow preferentially along <100> directions and the crystalline steps belong mainly to {100} and {110} planes.In the neighbourhood of the unhealed porosities the alloy matrix appeared to be embrittled and in certain cases cleavage fracture was observed.

Dark seams along the rolling direction in certain cases could be observed by means of stereo-microscopic examination of flakes and under higher magnifications in a SEM. These seams were identified as unhealed porosities with crystalline steps and microholes on their inner free surface. The unhealed porosities might be a possible source of flake formation.

An attempt has been made to provide a theoretical basis for the large sized tube milling by planetary skew rolling. Relevant factors such as the motion scheme between roller and tube, the rolling forces applied, the mode of plastic de-formation, the determination of milling pressure, the moment of rolling force, etc. have been calculated with a view to establishing a suitable design.

The very severe attack of the dolomite lining of oxygen-blown steel-making converters by high P_2O_5 containing slags has been considered on phase relations. In steel-making practice, no difference was observed between slags of high and of low P_2O_5 content in their attack upon MgO in dolomite linings, but upon CaO in the same linings was more severe and the higher the P_2O_5 content of the slag, the greater the attack. Reasons for these are as follows:1. At 1600℃ the slag of high P_2O_5 content is a homogeneous liquid or a heterogeneous liquid of high reactivity with CaO, whereas the slag of low P_2O_5 content is a heterogeneous liquid of low reactivity with CaO.2. At 1600℃ the slag of high P_2O_5 content sometimes appears to be a twophase liquid, which attacks CaO severey, whereas the slag of low P_2O_5 content is always an one-phase liquid.3. with slags of high P_2O_5 content, the greater the amount of SiO_2 present, the higher will be its saturation for CaO, thus rendering the attack on CaO more severe. This is not the case, however, with slags of low P_2O_5 content.The above problem may be remedied by introducing more CaO in slag.

An investigation has been carried out on the effect of σ-phase on the mechanical properties of a Ni-Cr-Co based superalloy. Specimens treated to different amount of σ-phase were compared with the same alloy without such phase. It was found that specimens containing σ-phase up to 0.7% (by volume)showed little deterioration in properties, whereas in the case of those with σ-phase amounted to 2—4%, the room temperature tensile strength, impact toughness, endurance, creep and fracture toughness of the alloy were very markedly lowered. Moreover, cracks along the interfaces between the σ-phase grains and the matrix were often observed. Tensile properties at high temperatures, however, seems to be little affected by such phase. It would appear that σ-phase, being hard and brittle at room temperature, becomes deformable at elevated temperatures.

The recrystallization texture of cold-rolled low-carbon steel sheets containing copper up to 0.355% has been studied by means of X-ray pole density measurement, plastic strain ratio measurement and metallographic etching-pit technique. It is shown that the {111} texture component, which is beneficial to the deep-drawing ability, appears to be enhanced with increasing copper content, especially when the copper content exceeds the limit of solubility. Fine precipitates of ε-Cu phase around dislocation in specimens containing 0.355% Cu have been observed by transmission electron microscopy. The presence of such precipitates may be regarded as the cause of the enhancement of the {111} texture component.

Two transformation matrixes appropriated to describe the rotation of the crystallographic coordinate systems are proposed. The transformation matrixes for components of vector rotated about an arbitrary axis by any angle in crystal real space or reciprocal space are derived.

A computer program has been given for calculating the fundamental data of reciprocal lattice planes, with special attention paid to the problem of systematic extinctions for phase analysis by electron diffraction methods. Satisfactory results have been obtained in the cases of diamond, spinel as well as hexagonal closepacked structures.

The hot shortness mechanism in the temperature range 1050—1250℃ of mild steels, containing 0.1—0.4％ Cu, 0.1—0.4％ As, 0.01—0.03％ Sn, has been investigated by means of hot bend tests, optical microscopy, scanning electron microscopy and electron probe. The deleterious effects due to surface enrichment of As and Cu and the oxidation at austenite grain boundaries appear to be the main cause of hot shortness of the material.