Light figures produced by the three principal crystallographic planes {0001}, {11_??_0} and {10_??_0} of zinc single crystals, etched for different time-intervals with various acids or alkalis, were observed, and the suitability of those figures for the determination of crystal orientation by the method of light figure were examined. The experimental results obtained are summerized in Table 1. Distinct light figures were observed by a short-time etching with hydrochloric acid of any concentration, with dilute sulphuric acid, or with boiliug saturated aqueous solution of sodium hydroxide or of potassium hydroxide. Of distinct figures produced by etching with hydrochloric acid or with dilute sulphuric acid, figures on {0001} planes are suitable for determining an angle which the geometrical axis of a specimen crystal makes with the hexagonal axis <0001>, while figures on {11_??_0} and (10_??_0) planes are not suitable for determining angles between the geometrical axis of the specimen crystal and the digonal axes of the first kind <11_??_0>. For the perfect determination of crystal orientation, light figures obtained by etching with boiling saturated aqueous solution of sodium hydrxide or of potassium hydroxide are suitable; figures produced by etching with the latter alkaline reagent are more suitable because of a shortness of etching time (about 20 minutes). It was also found that geometrical forms of light figures of zinc single crystals generally change with etching conditions, though their symmetry characteristics are naturally invariable.

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In the first report it was stated that the metastable intermediate transforma ion process wheh lakes place when the β-phase of Cu-Al system is supercooled represants β→β₁→β', while it inversely represents when the β' structure is heated. The conclusion was derived from the phenomena which took place when the specimens were cooled not very rapidly, or when they were heated. This is related to the phenomena taking place in the hea_??_ing process of quenched alloys and is to refer to the quenching process. The investigations were performed by differential thermal analysis, measurement of the change of electric specific resistance, differential dilatoiiietry on heating, measurement of the hardness of tempered alloys, and X-ray .analysis. It was noted that the change represented by β→β₁→β' takes place on quenching, and the inverse change β'→β₁→β occurs on reheating quenched alloys, similar to one on cooling and heating slowly. The quen hed β' crystal of hypoeutectoid alloys is strained. When the β' of this kind is heated at low tem perature, the strain disappears, being accompanied with heat evolution, decrease of electric specific resistance, and contraction of the volume.

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This report is related to the phenomena taking place in the heating process of quenched hypereutectoid alloys containing over 13.1% Al, the quenching-process of these alloys, and the tempering effect upon hardness. On quenching hypereutectoid alloys, which contain over 13.1% Al, the acciular structure having crystal structure, a little different from that of β' appears. It is called γ'. The transformation process of these alloys on quenching represents β→β₁→nγ'.The transformation β₁→γ' is reversible, namely the change γ'→β₁→β takes place on beating γ similarly to β'. The hardness of quenched hypoeutectoid alloys increases a little when they are tempered at low temperature. The tempering effect of this kind is most remarkable at about 350°.

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The Experiments was performed by methods described in the sec nd report, 2 to 6% Mn was added. The tempering process of β-alloys containing Mn are essentially not different from those of the binary alloys. It was noticable.that the accicular structure obtained on quenching may change to another one harving a different interatomic structure on reheating in low temperature, when it is cooled gradually. The tempering effect on the hardness of hypoeutectoid alloys increases with the amount of Mn added. The hardness of hypoeutectoid allays is the greatest when it is temperd at about 350°

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The residual stress restored in 29.8 and 30% Ni-Fe alloys transformed from γ to α by dipping them in various baths below 0°, and the amount of the transformed α by X ray were measured. Hardness was also measured. The results show that (1) The stress vs. Δα (depth from the surface of the specimen) curve has its minimum point as shown in Figs. 1 and 2, (2) hardness increases as the amount of the transformation increases, (3) the residual stress vs. amount of transformation has a maximum point at nearly 30% of the transformation. The change of the dimensions was also observed.

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Results obtained are shown in Figs. 4 & 5. There are many fields of phase and phases as α, α+ε, ε, α+ε+γ, ε+γ, γ+σ and α+γ+σ in the iron cornner of the system. The fields of α, α+ε and ε phases were mostly determined by measuring the thermal expansion, γ+σ by the experiment of microstructure and α+ε+γ, σ+γ and γ by both methods. The fields of γ+σ phases at higher Cr content and α+γ+σ phases were conbined to assume. It is known that hardness and specific gravity same to distinguish the field of σε phase from ther fields.

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In this report the effects both of mechanical and of electrolytic polishings on the structure of rolled zinc was examined by means of, xrays. The samples used were electrolytic zinc (E) and mixed zinc (M) which consists of electrolytic and refined zinc mixed in an equal proportion. They were rolled to a thickness of 0.3mm. These samples were polished either by emery paper or by electrolytic means, and then examined by transmitting x-rays. The following results were obtained by studying the diffraction patterns.
(1) By the electrolytic polishing the deformation structure does not change at low current density, but it recrystallises due to heating at high current density.
(2) By the mechanieal polishing the reerystallization structure is formed from fine crystals by mechanical destruction and the diffraction patterns become continuous rings. But when the sample contains a deformation structure prior to the polishing treatment, the diffraction patterns obtained for the polished one are made of continuous rings.

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Recently, micro-hardness testing is being employed in the research of metals. The authors described, in the previous report, a handy micro-hardness tester tentatively made by us In this report some experiments by the tester are given. The results obtaind are as follows:-
(1) This handy micro-hardness tester is easily constructed and easy to handle, and the measuring time is nearly the same as obtained by Vickers-hardness testing.
(2) Since it is possible to measure local hardness of metals with low load, it is applied to the hardness of each structure of metal and can also be used in the research of abnormal and unknown structure etc.
(3) The accuracy of this tester is ± (1_??_2%).
(4) Since load is changeable at will, it is possible to measure local hardness by cha nging the load according to circumstances in compliance with its structure size. The effect of hardness number by changing of load, in the range of this experimental lood, was not recongnized.
(5) When there are two or more kinds of structures in the sample, a rigorous hardness number is obtained.

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Fatig e tests were made on 12 kinds of variously finished surfaces, worked out on the Si-Mn-Cr steel with a tensile strength of 100kg/mm² The surface treated by sand blast was strongest for repeated load. The surface, polished by emery-paper or cloth longi_??_udinally, was next in rank, having a strength corresponding to 94% of the former. The surface, worked by lathe or grinding machine was the weakest, its strength corresponding to only 83% of the first. The polished surface, on which Vieker's hardness was inspected or numerals were stamped, has a fatigue streng h as high as that worked by the lathe or grinding machine. The suriaee on which numerals were wri_??_en by eleetric pencil had irregular strength and lacked reliability. The fatigue strength of the holed surface decreased to below 45% of the non-holed bar, by the notch effect of the hole, and could be raised no more even by polishing of its surface.

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The correlation between the diameter of a hole drilled perpendicular to the axis of a bar and its fatigue limit under repeated bending or torsion was inves igated experimentally for Ni-Cr steel especially the fatigue limit under rcpcated torsion and small hole diameter, which experiment has not been conducted was cleared. It was cleared that the quantitative recovery of fatigue limit is due to compression of the edge of the hole by steel ball, the fatigue limit increased straightly with the pressure of the ball, and by Ni-Cr steel with 12mm rod dianTeter, 15mm hole diameter, and 5.5mm ball diameter, the stress concentration factor attained almost unity at 2.500kgs_??_2.700kgs of ball pressure.

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The anthor picking up five different k'n Is of high speel steel, studie I the effect of heating temperature, bot bath tomperature and. holding time upon the tempering hardness of isothermal transfermattion treatment by hardness, dilatometer and microstructure, and then discussed theoratically the machanism of transformation at 300° of isothermal transfermattion diagram. It was aseertained. from this invcstigation that hot bath temperature from 100° to 600° in 90min, of holding time, except 300° showed hardly n_??_ effeet on the cutting durability. More_??_ver, the effeet of holding time in isothermal transfermattion treatment was alse testede.

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The authors, taking samples of two kinds of carbon steel containing 1% carbon obtained from “Mass” magnetic sand and iron scrap only, examined the physical properties due to heat treatment as time piece spring.
The proportional limit, elastic limit and yielding point for equal tensile strenrth of those steels which are quenchel in water or oil and temoered are higher than those which are austemperel. The impact value of steel obtained from Miss'' m_??_gnetic s_??_nd is higher than that of the steel made by iron scrap only.
Furthermora, the author, c_??_rried out a series of exper ments with thin plates of 0.4mm by cold rolling and studied the physical properties brought about by different, heat treatments, and also tested their work hardening owing to cold rolling and then softening by an nealing.
The steel being subjected to cold rolling after heat treatment increases its' hardness and tensile strength, but the toughness is greatly decreased.

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