Sub-Boundaries in Aluminium Single Crystals

Single crystals of aluminium 99.97 per cent pure were made by the Bridgman method under various conditions, and the Laue spots were precisely studied with specimens which, on being etched, showed no macroscopic inhomogeneity. It was found that some spots were frequently splitted, whereas those diffracted from certain lattice planes were of the usual form, and that these special planes were {113} or planes lying close to them. From these results it was concluded that the splitting of Laue spots was due to a small angle interface of a bicrystal grown along the maximum temperature gradient, and that this boundary could be formed by the relative rotation of the crystals around [112] about one degree. Such boundary was explained by the mechanism of polygon wall in the the theory of dislocation

Elastic After-Effect

The elastic after-effect was examined with metal wires at various temperatures, and the results were explained by the theory of recovery based on the dislocation model. The formation of polygon boundary or sub-structure in the course of after-effect was briefly discussed

Scratch Hardness. II : X-Ray Investigation of Structural Change

The structural change due to scratching or indenting aluminium and silver was studied by X-ray analysis, and it was seen that it was a reasonable interpretation that the scratch hardness of a metal is related to the annealed state, which is contrary to Tammann\u27s view

X-Ray Study of Cold-Worked Metal Single Crystals

The change in the reflected intensity of X-ray due to the deformation of metal single crystals of aluminium and zinc was examined with microphotometer by using Cu-K_α radiation. In aluminium single crystals, a large change in the relative intensity of {111}-reflections was observed with an increase of the deformation, and almost saturated at a few per cent elongation. The increasing rate of the relative intensity reflected from the active slip plane was larger than that from the latent slip planes. Similar results were obtained with zinc single crystals. The increase in the integrated intensity was explained as caused by the reduction in the extinction due to the fragmentation of crystallite blocks, from which it was concluded that the distortion after slip deformation was larger in the active slip plane than in the latent slip planes. In other words, the strain-hardening is larger in the active slip plane than in the latent slip planes. Further, the recovery of the relative intensities was examined, and it was seen that in aluminium crystal it was incomplete even after long-time annealing at high temperature, whereas in zinc crystal it was almost perfect at short-time annealing

Scratch Hardness. I : Relation to Cold-Working

The scratch hardness was examined with polycrystals and single crystals of several metals. The law similar to the Meyer\u27s in the indentation hardness held good between the load and scratch width. The change in scratch width with cold-working was very small, which was explained as being due to the heat evolved during scratching. Consequently, the scratch hardness, contrary to Tammann\u27s interpretation, be related rather to annealed state than to severely hardened state of a metal

Study of Cold-Working by Microfocussing X-Ray. I : Fine Structure of Laue Spot

By giving cold-working and annealing successively to aluminium single crystals made from the melt, the changes in Laue spots were observed by the ordinary and microfocussing X-rays. It was found that with the repetition of working and annealing the fine structure of the Laue spots from the operative slip plane grew complicated, depending on the temperature of annealing. In the case of low temperature annealing, the lamellar structure of the spot remained stable, while in the case of high temperature annealing it changed into an irregular, complicated structure incapable of being resolved with the present apparatus

On the Mechanism of Cold Brittleness in Metals

The results of the present investigation may by summarised as follows : (1) Charpy impact tests were carried out with various forms of notch for Flodin iron, 0.3 and 0.7 per cent carbon steels, zinc and aluminium at temperatures ranging from that of liquid nitrogen up to about 200°. (2) For the purpose of confirming the results, tensile tests were also carried out at low temperatures under various stretching speeds. (3) It is confirmed that the transition temperature from a ductile to a brittle failure is not inherent to a metal as hitherto accepted but is greatly influenced by experimental conditions (4) Considering the time required for slipping one atomic distance caused by the movement of a dislocation at various temperatures, the cold brittleness was interpreted as the phenomenon which appears when the breaking is taken place at the given temperature within this critical time. (5) Some suggestions for the prevention of cold brittleness are remarked. In conclusion the author expresses his cordial thanks to Dr. K. Honda, under whose kind direction the present investigation was carried out, and also to Messrs. S. Yamamura, S. Hongo and H. Yamagata for their enthusiastic help during the course of the work

On the Mechanism of Cold Brittleness in Metals

The results of the present investigation may by summarised as follows : (1) Charpy impact tests were carried out with various forms of notch for Flodin iron, 0.3 and 0.7 per cent carbon steels, zinc and aluminium at temperatures ranging from that of liquid nitrogen up to about 200°. (2) For the purpose of confirming the results, tensile tests were also carried out at low temperatures under various stretching speeds. (3) It is confirmed that the transition temperature from a ductile to a brittle failure is not inherent to a metal as hitherto accepted but is greatly influenced by experimental conditions (4) Considering the time required for slipping one atomic distance caused by the movement of a dislocation at various temperatures, the cold brittleness was interpreted as the phenomenon which appears when the breaking is taken place at the given temperature within this critical time. (5) Some suggestions for the prevention of cold brittleness are remarked. In conclusion the author expresses his cordial thanks to Dr. K. Honda, under whose kind direction the present investigation was carried out, and also to Messrs. S. Yamamura, S. Hongo and H. Yamagata for their enthusiastic help during the course of the work

On the Effect of the Difference in Heat Treatments on the Yielding of a Carbon Steel

The present research may be summarized as follows : (1) Heat treatments, in one case austempering and in other case quenching and tempering, had been done on 0.9 per cent carbon steel, so that a troostitic structure with the same hardness might result. (2) With these specimens, tensile tests and impact tests were carried out at room temperature. (3) Load-elongation diagrams of test-pieces subjected to quenching and tempering clearly show the phenomenon of yielding while those for austempered one were all smooth. (4) The interpretation for the phenomenon of yielding already proposed by one of the authors was ascertained. (5) Austempered specimens show superior mechanical properties as generally known. In conclusion the authors express their cordial thanks to Mr. S. Oba, the ex-Director of Yonezawa Technical College, for his enthusiastic encouragement and to Dr. K. Honda, the ex-President of the Tohoku University, for his kind guidance