Feathery Crystals Research Articles

アルミニウム溶接金属の機械的性質に及ぼす凝固組織の影響 Ｉ

Fatigue test was performed on a base metal and weld metals of 5052-O aluminum alloy having each solidification structure of columnar crystals, feathery crystals and equixaed dendrites. Investigations have been made on the relation between the weld solidification structures and fatigue characteristics.The fatigue strengths of the weld metals were less than the strength of the base metal. In the weld metals the strength of equixaed dendrites was the highest. In the base metal, columnar crystals and equiaxed dendrites, anisotropy of the fatigue strength was not observed. In feathery crystals, however, the anisotropy was observed. The crack propagation rates in the weld metals were less than the rate in the base metal. In the weld metals the rate was the lowest in equiaxed dendrites and the highest in columnar crystals. In the feathery crystals the rate was almost the same as that in columnar crystals when the growth direction of feathery crystals was parallel to the direction of propagation of fatigue cracks. When the growth direction of feathery crystals was normal to the direction of propagation of fatigue cracks, however, the rate decreased to that in equiaxed dendrites. Besides, it was made clear from the obser-vation of the feature of fatigue crack propagation that the cracks propagated very easily along twin planes of feathery crystals.

全羽毛状晶からなる６０６３合金半連続鋳塊の鋳造条件

Studies were made on the effects of casting conditions, the float position and the mold design on the formation of feathery crystals in 6063 alloy DC ingots by using a laboratory casting machine.The results obtained are as follows.(1) The formation of the feathery crystals become easier with decreasing the distance from the float to the bottom of the mold.(2) A mold with the thermal insulating material in the upper part of its cavity is very effective in making billets having complete feathery clystals.(3) The formation of feathery crystals becomes easier with increasing the casting rate.(4) The formation of the feathery crystals becomes easier with a rise of the casting temperature.

Morphology of quench crystals in submarine basalts

Submarine basalts from the mid-Atlantic ridge, Red Sea rift, and Joides site 105 in the western Atlantic have been studied in ultra thin, doubly polished thin sections. Most of the samples are pillow lava fragments containing a variety of skeletal crystal growth forms that can be related to three major textural zones in the pillows. Olivine appears as diffuse, lattice-like growths near quenched pillow margins, as elongated chainlike or hollow lanternlike forms within a partly crystallized variolitic zone, and as larger lantern shaped crystals within the holocrystalline pillow centers. Plagioclase forms acicular hollow prisms elongated parallel to a in the variolitic zone. In cross section, these crystals often show sector zoning developed on the 001 and 010 faces. Each sector is also progressively zoned outward from a more calcic to a more sodic composition. In holocrystalline pillow cores, plagioclase forms more nearly equidimensional solid crystals with no trace of sector zoning. Pyroxene is rarely well crystallized and is typically found as feathery crystals intimately intergrown with plagioclase in the groundmass. Spinel and magnetite are ubiquitous in the samples examined, although the glassy pillow rims usually contain spinel but not magnetite. Within the variolitic zone and holocrystalline pillow interiors, magnetite appears both as skeletal crystals and as overgrowths on spinel. Sulphides (mainly pyrite) are especially abundant in the Red Sea lavas. Phenocrysts of olivine and plagioclase and subhedral and euhedral groundmass olivine and plagioclase show no evidence of growth by filling in of hollow or lattice-like crystals similar to those of the outer pillow zones, It is suggested that development of these skeletal forms is restricted to supercooled, highly viscous magma in which relatively rapid growth is combined with low rates of diffusion. Slower growth or more rapid diffusion rates or both at crystallization temperatures maintained close to the liquidus appear to promote more even growth rates and compositional homogeneity on all crystal faces; this possibility accounts for the more nearly equidimensional form and lack of sector zoning in phenocrysts and microphenocrysts. Petrographic observations support the division of sea floor basalts into ‘Olivine tholeiites’ and ‘plagioclase tholeiites’ which has been suggested by other workers. The only large pyroxene crystals observed in the samples examined appear to be xenocrysts, and pyroxene is not a prominent quench (liquidus) phase in this or other samples studied.

Mercurous nitrate as a histochemical reagent for calcium phosphate in bone and pathological calcification and for calcium oxalate.

An aqueous solution of mercurous nitrate reacts with bone and tissue calcified sites with the formation of brown to black amorphous masses and feathery crystals, the last resembling the crystals formed from the action of an aqueous solution of mercurous nitrate on calcium orthophosphate. Calcium oxalate reacts with this mercurous nitrate solution to form brown to black deposits on the surface of the oxalate particles; this suggests an adsorption phenomenon. The brown deposits are blackened by ammonium hydroxide, gold chloride, and many sulphur-containing compounds.

Studies on structure and hot extrusion process of aluminum and 6063 alloy cast billet due to grid-mark method

This paper describes one of a series of studies on the deformation process in hot extrusion. The previous paper described that the extrudability could be explained with respect to the deformation resistance and the macrostructural flow. This paper describes that the grid-mark method was applied to the extrusion of commercially pure aluminum and 6063 alloy billets at 500°C, and the experimentally obtained deformation characteristics based on flow line were examined in terms of velocity components. Extrusion was carried out at a speed of 7mm/sec. through three die semi-angles of 45, 60, and 90° and with a extrusion ratio of 9: 1; and billet structures were converted into two different kinds of feathery and granular crystals.(1) Comparison of flow patterns between the two billet structures under the same extrusion conditions showed little difference in deformation patterns of inner shearing zone, and the deformation zone of feathery crystals extended toward the front of billet further than that of granular crystals. The high velocity distribution observed in the feathery crystal billet seemed to be attributed to the fact that the feathery crystals, having preferential orientation, showed high workability in the direction of crystal growth as described in the previous paper.(2)When the velocity components were measured for three die angles in hot extrusions, the axial velocity was larger with the increase of die angle. Whereas, the extrusion pressure was lower with the increase of the angle on the contrary to the fact in the previous paper. These facts resulted from the geometrically constrained plastic flow, and it was found that the friction behavior in hot extrusion through 90° die was smaller than that in cold extrusion.

The impregnation of bone and patholigic calcification by metal salts and their recognition by unoxidized hematoxylin.

Of 225 metal compounds tested, salts of 34 metals can enter the calcium carbonate-phosphate-protein complex of bone and calcified tissue. The soluble salts of silver and mercury (I) form black deposits by direct reaction; mercury forms black feathery or acicular crystals as well. The other metals are easily detected by the formation of colored compounds when dilute unoxidized hematoxylin is applied. Nine metals combine with the protein moiety, as their presence is still observed by color changes with hematoxylin after decalcification of the tissues with acids or sequestrene prior to metal impregnation. Because of similarity of color produced by similar metal salts, there seems to be some resemblance between the protein of the keratohyalin granules of the skin and the protein of bone and pathologic calcification.

Effects of alloying components and conditions of solidification on the formation of feathery crystals in aluminum alloys

The effects of alloying elements, their concentrations, and conditions of solidification on the formation of feathery crystals were investigated on 10 kinds of binary aluminum alloys uni-directionally solidified in insulating (Isolite) mold. The possibility of formation of feathery crystals was explained with respect to the rate of solidification (R) and temperature gradient in liquid phase in front of the solid-liquid interface (Gl).The following results were obtained.(1) The feathery crystals were formed in the following 6 kinds of binary alloys:Al-Fe (0.72-2.05%), Al-Sn (3.94-9.76%), Al-Cu (10.47-14.99%), Al-Mg (5.06-10.10%), Al-Ni (1.02-3.75%), and Al-Ti (0.08-0.13%).On the contrary, the crystals were not found in the following 4 kinds of alloys.Al-Si (1.0-10.0%), Al-Mn (0.5-4.0%), Al-Cr (1.0-4.0%), and Al-Zn (1.0-10.0%).(2) The feathery crystals in the above 6 kinds of alloys were not formed in the range of low concentration, but were more easily formed in higher concentration.(3) The feathery crystals in 5 kinds of alloys were more easily formed with the increase in solidification rate (R), temperature gradient (Gl), and the ratio of Gl/R1/2.(4) As the results of (2) and (3) described above, it was found that Gl/R1/2 should be increased with the decrease in concentration of alloying elements for the formation of feathery crystals in the Al-Fe alloys.Furthermore, the mechanism for the formation of feathery crystals was proposed as follows; the formation of twin crystals would be favorable to eliminate the instability due to constitutional supercooling. It was also assumed that the effects of alloying elements on the formation of feathery crystals would depend on distribution and diffusion coefficients of elements in molten state.

Observation of structures feathery of crystals formed during uni-directional solidification of Al-7.08% Mg, Al-0.68% and 1.5% Fe alloys

The feathery crystals of Al-Mg (7.08%) and Al-Fe (0.68 & 1.5%) alloys were formed during upward unidirectional solidification in insulating (Isolite) mold with chill plate at the bottom. The crystals formed were studied by various methods such as macroscopic and microscopic observations, etching pit method for estimating crystal orientation, microscopic observations and surface inspection testings on decanted interface. The following conclusions were drawn.(1) The feathery grains consisted of thin lamination layer of crystals having twin plane of (111), and its growth direction was presumed to be <112>(2) It seemed that as a single feathery crystal began to grow, numerous lamellae of feathery crystals were successively formed in almost parallel direction, which showed laminated structure.(3) As the results of microscopic observations and surface inspection testings on structure of decanted solidliquid interfaces, it was concluded that feathery grains grew prior to dendrites.(4) An excess of iron segregation was recognized at a position, which was assumed to be an original source of feathery crystals in Al-Fe (0.68 & 1.5%) alloys. The segregation would be due to the local accumulation of rejected solute in Al-1.5%Fe alloy, while Al-0.68% Fe alloy caused banded segregation.(5) By the observations of several cross-sections, 3-dimensional growth behavior of feathery crystals was explained.

Deformation resistance and plastic flow of aluminum alloy billets for extrusion

Resistance to compressive deformation of 6063 alloy billets was determined by experiments with a cam plastometer. The effects of heat treatment and macro-structure on the resistance to deformation were examined for strain rates of 1.6-31/sec. at between room temperature and 500°C. The following conclusions were drawn.(1) The relationship between resistance to deformation and reduction ratio in all the specimens was expressed by exponential function curves.(2) Deformation resistance in cold working was saturated by high strain rate. However, in specimens, which had been solution heat-treated and fully aged, the resistance also tended to be saturated by some strain rates.(3) The resistance to deformation tended to decrease with the rise of working temperature. For example, the stress for the compression of specimens at 500°C was 4-6kg/mm2, which was expressed by strain rates of 1.6-31/sec. and almost independent of the effects of heat treatment.(4) The relation between strain rate sensitivity (N) and relative temperature coefficient (Th) was expressed by straight or broken lines, which was evaluated to be the effects of heat treatment.(5) Resistance to deformation of billets consisting of feathery crystals was gradually approximate to that consisting of granular crystals with the rise of working temperature. However, the former billets showed nonuniform flow, which suggests unsolved problems related to shearing deformation of materials.

XXVII. On a new compound of chlorine and carbon

M. Julin, of Abo, in Finland, is proprietor of a manufactory in which nitric acid is prepared, by distilling calcined sulphate of iron with crude nitre in iron retorts, and collecting the products in receivers connected by glass tubes, in the manner of Woulfe's apparatus. In this process he observed, that when a peculiar kind of calcined vitriol, obtained from the waters of the mine of Fahlun, and containing a small portion of pyrites, known in Sweden by the name of calcined aquafortis vitriol No. 3, was used, the first tube was lined with sulphur, and the second with fine white feathery crystals. These were in very small quantity, amounting only to a few grains from each distillation; but M. Julin, by degrees, collected a portion of it, and, having brought it to this country, inserted a short account of its properties in the Annals of Philosophy, Vol. i. p. 216, to which a few observations were added by ourselves. The following are the properties of this substance, as described by M. Julin. It is white; consists of small soft adhesive fibres; sinks slowly in water; is insoluble in it whether hot or cold; is tasteless; has a peculiar smell, somewhat resembling spermaceti; is not acted on by sulphuric, muriatic, or nitric acid, except that the latter by boiling on it gives traces of sulphuric acid ; boiled with caustic potash, has a small portion of sulphur dissolved from it; dissolves in hot oil of turpentine, but most of it crystallizes in needles from the solution on cooling ; dissolves in boiling alcohol of .816, but by far the greater part crystallizes on cooling; burns in the flame of a lamp with a greenish blue flame, giving a slight smell of chlorine gas ; when heated, melting, boiling and subliming at a temperature between 350° and 400°, and subliming slowly without melting at a heat of about 250°, forming long needles. Potassium burned with a vivid flame in its vapour in an open tube, and carbon was deposited; a solution made of the residuum, and saturated with nitric acid, gave a copious precipitate with nitrate of silver. M. Julin then remarks, that the small quantity he possessed, with want of leisure, prevented him from making any farther experiments on it; and concludes, by comparing it with the chlorides of carbon that have lately been formed.