Showing papers on "Quenching published in 1982"

Electron-hole-pair quenching of excited states near a metal

Abstract: We present a calculation of the nonradiative damping of a dipole outside a metal surface. The calculation uses a realistic surface potential for the metal conduction electrons in contrast to most earlier studies. A simple experiment is suggested to test the theoretical predictions.

Fe‐B glasses formed by picosecond pulsed laser quenching

Abstract: Using picosecond pulsed laser irradiation, Fe‐B alloys have been melted and quenched into glasses, with a B content as low as 5 at. %, which is significantly less than the minimum 12‐at. % B content required for glass formation by other liquid quenching techniques. Compositionally modulated films with wavelengths on the order of 20 A were used as starting materials to ensure homogeneity of the melt after irradiation.

The effect of quenching on the solidification structure and transformation behavior of stainless steel welds

Abstract: Weld solidification structure of three different types of stainless steel,i.e., 310 austenitic, 309 and 304 semiaustenitic, and 430 ferritic, was investigated. Welds of each material were made without any quenching, with water quenching, and with liquid-tin quenching during welding. The weld micro-structure obtained was explained with the help of the pseudobinary phase diagrams for Fe-Cr-Ni and Fe-Cr-C systems. It was found that, due to the postsolidification 5 → γ phase transformation in 309 and 304 stainless steels and the rapid homogenization of microsegregation in 430 stainless steel, their weld solidification structure could not be observed unless quenched from the solidification range with liquid tin. Moreover, the formation of acicular austenite, and hence, martensite, at the grain boundaries of 430 stainless steel welds was eliminated completely when quenched with liquid tin. The weld solidification structure of 310 stainless steel, on the other hand, was essentially unaffected by quenching. Based upon the observations made, the weld microstructure of these stainless steels was summarized. The effect of cooling rate on the formation of primary austenite in 309 stainless steel welds was discussed. Finally, a simple method for determining the relationship between the secondary dendrite arm spacing and the solidification time, based on welding speeds and weld pool configurations, was suggested.

Influence of cooling rate on the microstructure and retained austenite in an intercritically annealed vanadium containing HSLA steel

Abstract: The influence of cooling rate from the intercritical αγ region on the microstructure of a vanadium bearing HSLA steel was investigated by transmission electron microscopy. Oil quenching produced an essentially ferrite-martensite dual phase structure with ∼4 vol pct of fine particle and thin film retained austenite. In contrast, the slower air cooling resulted in a larger amount (∼10 vol pct) of retained austenite in addition to the ferrite and martensite phases. A major portion of the retained austenite in the air cooled specimen was of the blocky morphology (1 to 6 μm , with the remainder eing the submicron variety, similar to that of the oil quenched specimen. In conformance with the terminology of earlier studies, “retained” ferrite and “transformed” ferrite were observed in the air cooled steel while oil quenching completely suppressed the transformed ferrite. Retained ferrite, the cleaner of the two in terms of precipitate content, is the high temperature ferrite that coexists with the austenite at the intercritical temperature and which is retained on cooling. The transformed ferrite, on the other hand, forms from the decomposition of the austenite and contains banded carbonitrides (row precipitation) much like the initial microstructure of the HSLA steel.

Differences in magnetic properties between amorphous and crystalline alloys

Abstract: The magnetic properties of the following intermetallic compounds were determined: HFCo2, HfCo3, Hf6Co23, HfCo7, TaCo2, TaCo3, NbCo2, and NbCo3. Several amorphous alloys of the type Y1−xCox (in the concentration range x=0.30 to x=0.55) were prepared by melt spinning. Their magnetic properties have been compared with those of vapor‐quenched alloys studied previously. The concentration dependence of the magnetic moments was studied in the following vapor‐quenched amorphous alloys: Mg1−xNix, Hf1−xCox, and Nb1−xCox. In various binary systems the magnetic properties of crystalline and amorphous materials have been compared and their differences are explained in terms of a local environment model.

Method of making wrought high tension steel having superior low temperature toughness

Abstract: OF THE DISCLOSURE Due to increasing demands for steel to be used for construction such as buildings, pressure vessels, pipe lines or the like, various kinds of high tension steels, particularly steels suitable for welding have increasingly been developed. Heretofore, proposed methods of making such high tension steel have relied on so-called cold rolling and/or rolling followed by quenching and tempering, however, these conventional steels have suffered from drawbacks such as a tempering step indispensable after quenching, softening of welded zone and lack of uniformity in the metal structure in the direction of plate thickness. A compositional feature of the new method resides in addition of minor amounts of Ti and B along with Nb as contributing to grain refining or precipitation hardening elements in addition to limited amounts of other ingredients such as C, Si, Mn, S, Al and N. Further addition of at least one of V, Ni, Cu, Cr, Mo, Ca and REM also acts to improve the properties of the steel. The steel prepared to have the aforesaid composition is subjected to controlled heating, subse-quent rolling under prescribed rolling reduction ratio, temperature for terminating rolling and to a specified cooling rate. The steel plate thus processed has a structure having fine bainite grains alone or a duplex grain

Electron Transfer in the Quenching of Triplet States of Zinc Phthalocyanine and Methylene Blue by the Use of Fe(III), Co(III), and Organic Oxidants

Abstract: The mechanism of the quenching of the triplet state of zinc phthalocyanine (ZnPc) and Methylene Blue (MB+) by low-spin complexes of Fe(III) and Co(III) and aromatic oxidants was studied. The quenchers studied included FeIII(CN)63−, FeIII(CN)4(2,2-bipyridyl)−, FeIII(CN)2(2,2-bipyridyl)+, ferrocenium ion, CoIII(2,2′:6′-2″-terpyridyl)3+, CoIII(1,10-phenanthroline)3+, dimethylviologen, 1,4-benzoquinone, and 2,4,7-trinitro-9-fluorenone (TNF). The rate constants of the quenching of 3ZnPc varied from a diffusion-controlled one to 6×105 dm3 mol−1 s−1 in the mixed solvent of dimethylacetamide (DMA) and water (7:3 by volume). The metal complexes quenched 3MB+ and the triplet state of protonated MB+ with a rate constant of more than 2×106 dm3 mol−1 s−1 in an aqueous solution with 0.5 mol dm−3 of MgCl2. The fractions of electron transfer yielding ZnPc\underset.+ in the quenching process (F1) were high except for TNF and the iron(III) compounds. The F1 fractions were also obtained in the quenching of 3MB+ and the trip...

Phase relations and superconductivity in the binary Re-Si system

Abstract: The phase diagram of the Re-Si system was reinvestigated by means of high temperature methods of analysis We found several modifications to the existing diagram An extended rhenium solid solution (up to 10 at% Si) was established with a rapid quenching technique Within this terminal solid solution, the superconducting transition temperature increased from 17 to 52 K The phase corresponding to the “Re 5 Si 3 ” compound was homogeneous at 33 at% Si The peritectically formed equiatomic compound decomposed eutectoidally at 1650 °C and was superconducting at 15 K The compound ReSi 2 was found to be off stoichiometric, occurring at the composition ReSi 18

Quench- and deformation-induced structures in two austenitic stainless steels

Abstract: Composite electron-diffraction patterns have been computed and used to facilitate the interpretation of experimentally determined patterns obtained from the structures and phases observed by transmission electron microscopy in two quenched and/or deformed unstabilized austenitic stainless steels. The results of these studies, together with data obtained from magnetic measurements and X-ray diffraction analyses, have demonstrated that deformation twins, stacking-fault bundles (or faulted ɛ-martensite) and α′-martensite are produced in the austenite matrix of an AISI Type 301 (18Cr–8Ni) steel after quenching and/or cold rolling, whereas only deformation twins are formed during the cold rolling of an AISI Type 316 (17Cr–13·5Ni–2·4Mo) steel. The results and observations have enabled some of the uncertainties in the literature regarding the formation of the ɛ- and α′-martensites and their orientation relationships with the parent austenite to be clarified.

Crystallization characteristics of an amorphous Nb81Si19 alloy under high pressure and formation of the A15 phase

Abstract: Amorphous Nb-19 at% Si alloy, prepared by rapid quenching from the molten state, was annealed while being subjected to a pressure of 10 GPA. X-ray diffraction investigations on the alloy specimens quenched to ambient conditions have shown that pressure greatly alters the crystallization characteristics and the cubic A15 (Nb3Si)-phase forms in preference to the tetragonal Nb3Si-phase at temperatures in the range from 710° C to 800° C. Up to 680° C, the component atoms do not show any tendency towards ordering upon crystallization and the body-centred tetragonal solid solution forms; while, at 830° C, niobium atoms diffuse to form the body-centred cubic Nb precipitates. Superconducting properties have been measured for the single-phase A15 structure with the lattice parametera=0.5155 nm with the results that the transition temperature,TC, is 3.4 K and the temperature coefficient of the upper critical field,HC2, is 1.2 MA m−1 K−1 (15 kOe K−1).

A15 Nb3(AlGe) superconductors prepared by transformation from liquid quenched body‐centered cubic phase

Abstract: A supersaturated body‐centered cubic (bcc) solid solution of Nb3(Al1−xGex) up to x = 0.3 has been prepared by the liquid quenching on a hot Cu substrate. The quenched materials are then transformed to the A15 structure by annealing above 800 °C. Following the transformation, the critical temperature rises above 18 °K. The A15 phase converted from the bcc phase has an extremely small grain size of a few hundred angstroms, resulting in a high critical current density Jc in high magnetic fields. Jc of 3.5×105 A/cm2 at 4.2 °K and 16 T has been achieved in the Nb3(Al0.8Ge0.2) sample annealed at 850 °C for 7 h.

Formation of Aluminosilicate Glasses Containing Rare‐Earth Oxides

Abstract: Formation of aluminosilicate glasses containing oxides of rare-earth elements, e.g. Sc, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, and Yb, was studied by melting at 1550°C and air quenching. The upper limit of the amount of rare-earth oxide which can be incorporated into the aluminosilicate glasses decreases according to the lanthanide contraction.

Infrared quenching of photoconductivity and the study of gap states in hydrogenated amorphous silicon alloys

Abstract: Infrared quenching of photoconductivity has been investigated for plasma‐deposited a‐Si:H alloys. The temperature and spectral dependences of the quenching are consistent with a two‐level model of competing recombination centers. The infrared quenching spectrum shows that this effect occurs for photons having energies in the range 0.4 eV

Containerless undercooling and solidification of bulk metastable Nb3Ge alloys

Abstract: Experiments using containerless undercooling and low-gravity solidification of Nb(1-x)Ge(x) alloys for x=0.13-0.27 have been carried out in a 32-m drop-tube apparatus to study the feasibility of forming metastable Nb3Ge in bulk form. It is found that bulk samples (2-3 mm diam) of Nb-Ge alloys with 18-22% Ge can be undercooled by large amounts (300-500 K) and solidified in a containerless environment. Subsequent quenching of the solidified samples in oil helps preserve the metastable A-15 phase by removing the latent heat of fusion and quickly cooling the samples to a stable temperature below 1000 C. Even at an undercooling of less than 100 K, the superconducting transition temperature of the material is enhanced over the cast material by about 1 K.

A One-Dimensional Time-Dependent Model for Flame Initiation, Propagation and Quenching

Abstract: : This report describes a one-dimensional, time-dependent, Lagrangian numerical model developed to study the initiation, propagation and quenching of laminar flames A number of new approaches and algorithms as well as input parameters used in the model are discussed Calculations of initiation and minimum ignition energies in hydrogen-oxygen-nitrogen mixtures are presented along with calculations of the burning velocity of hydrogen in air

Structural recovery of quenched and annealed glasses

Abstract: A continuous approach to the multiordering parameter equations for glass transition phenomena is presented which leads to the unification of two successful phenomenological models. The nature of distribution functions, the temperature‐structural dependence of relaxation times, the experimental rate and the state of nonequilibrium during quenching, annealing, and heating are the essential parameters. The effect of distribution function of relaxation times on the enthalpy and heat capacity of glasses, and the sensitivity and convergence of the numerical calculation, are discussed. The theoretical calculation is then compared with the calorimetric measurements of polystyrene.

Process for producing fiber-reinforced metal composite material

Abstract: The invention provides a process for producing a fiber-reinforced metal composite material which involves mixing inorganic fibers with an aluminum alloy at a temperature at or above the melting point of the alloy. A composite material of improved physical properties is then produced by either of the two following alternative procedures. In a first procedure the composite is removed from the mold at a temperature that is not higher than the solid phase line of the alloy (i.e., the temperature at which a liquid phase appears in the alloy). The composite is then heated to a temperature above the solid phase line and the elevated temperature is held for a definite period of time (heat treat-ment). In a second procedure the composite is quenched to a temperature of 200°C or lower from a temperature above the solid phase line but below the melting temperature. This quenching is done quickly before allowing the composite to cool to a temperature that is not higher than the solid phase line.

Mossbauer surface study of a nitrogen implanted medium carbon steel

Abstract: The effect of nitrogen implantation on C40 medium-carbon steel is investigated by means of Mossbauer electron backscattering spectroscopy. Samples were implanted at various doses, after quenching from the austenitizing temperature and after quenching plus tempering, in order to detect the influence of the structure previous to the implantation. A different sequence of surface compound formation is observed in the two considered cases.

Electrical and thermal properties of highly quenched amorphous V2O5 thin films

Abstract: Amorphous thin films of V2O5 have been prepared by vapour deposition in high vacuum (∼ 10−6 torr). In order to study the role of quenching, various temperatures, ranging from −196 to 260° C, have been selected for the substrate. Differential thermal analysis. X-ray diffraction and conductivity measurements clearly divide the material into two sets, depending on the efficiency of the quenching. Whereas the least-quenched samples resemble those previously obtained by splat-cooling, the better quenched are only barely stable and, as a consequence, exhibit unique features, such as the occurrence of a glassy transition and the highest crystallization temperature ever found for V2O5.

Defects in Amorphous Metals.

Abstract: : Amorphous metals is a general term that refers to a class of solid metallic materials whose diffraction pattern shows no sharp reflections. When they are formed continuously from a melt by rapid quenching (usually around 1,000,000 K/s -1) they can be called metallic glasses. They can also be prepared by vapor, sputter, or electro-deposition, or even by ion-bombardment. Where the same metallic alloy has been prepared in amorphous form both by rapid quenching and by one of the other deposition techniques, the structure and many of the properties turn out to be rather insensitive to the method preparation.

Method of inductively heat treating a thin-walled workpiece to control distortion

Abstract: In a preferred embodiment a surface layer of a thin-walled, hollow, cylindrical steel body is hardened while controlling thermal distortion by first heating with an inductor and quenching in one direction over the surface and then repeating the process in the reverse direction.