Showing papers on "Quenching published in 1976"

The drawing behavior of linear polyethylene. I. Rate of drawing as a function of polymer molecular weight and initial thermal treatment

Abstract: The drawing behavior of a series of linear polyethylene homopolymers with weight-average molecular weight (Mw) ranging from 67,800 to ∼3,500,000 and variable distribution (Mw/Mn = 5.1−20.9) has been studied. Sheets were prepared by two distinct routes: either by quenching the molten polymer into cold water or by slow cooling below the crystallization temperature (∼120°C) followed by quenching into cold water. When the samples (2 cm long) were drawn in air at 75°C using a crosshead speed of 10 cm/min it was found that for low Mw polymers the initial thermal treatment has a dramatic effect on the rate at which the local deformation proceeds in the necked region. At high Mw such effects are negligible. An important result was that comparatively high draw ratios (λ > 17) and correspondingly high Young's moduli could be obtained for a polymer with Mw as high as 312,000. It is shown how some of the structural features of the initial materials (mainly studied by optical microscopy, small-angle x-ray scattering and low-frequency laser Raman spectroscopy) can be interpreted in terms of the molecular weight and molecular weight distribution of the polymers. Although crystallization and morphology can be important at low Mw, it suggested that the concept of a molecular network which embraces both crystalline and noncrystalline material is more helpful in understanding the drawing behavior over the whole range of molecular weights.

Microstructure and Toughness of High-Strength Aluminum Alloys

Abstract: The toughness of wrought, high-strength aluminum alloys is related to the amount, type, and morphology of coarse (larger than about 1 μm) constituent particles, intermediate size (about 0.02 to 0.5 μm) dispersoids, and fine (down to about 0.001 μm) precipitates. High toughness can be attained by minimizing the size and volume fraction of constituent particles, increasing the interdispersoid distance, refining the intragranular precipitate in 2XXX alloys, and controlling the intergranular precipitate in 7XXX alloys. For highest toughness in 7XXX alloy products where low residual stress is desired, rapid quenching followed by the minimum amount of cold work required for mechanical stress relief is recommended.

Quenching of high quality gold single crystals

Abstract: An improved quenching technique is described that allows compact and delicate samples to be quenched with high quenching rates otherwise only achieved with the Joule heating method. High quality gold single crystals 1 mm in diameter with dislocation densities lower than 2000/cm2 have been quenched from temperatures between 700° and 950°C using this technique. It was found that vacancy losses during the quench were negligible in these crystals. The formation energy of vacancies in gold was found to be (0-97±0-03) eV. Polycrystalline gold wires 1 mm in diameter have been quenched from temperatures between 730° and 1000°C in the same way as the single crystals. A comparison with the results on single crystals shows that the main type of sinks for vacancies in polycrystalline Au during a quench are dislocations. A theory by Seidman and Balluffi describes these losses quantitatively. The specific resistivity attributable to vacancies was determined to be (1·69±0·20)μΩ cm/at.-%.

Relation between coercive force and microstructure of sintered SmCo5 permanent magnets

Abstract: The coercive force of a sintered SmCo5 permanent magnet is found to depend reproducibly on the temperature of heat treatment. In order to find out the origin of this, the mechanism of the demagnetization was studied by magnetic‐domain observation, using the polar Kerr effect. It appears that the highest coercive forces which are obtained by heat treating at 850–950 °C and quenching are due to difficult nucleation of reverse domains and strong pinning of domain walls by the grain boundaries. After quenching from higher temperature (∼1100 °C) the coercive force decreases owing to weaker pinning of the domain walls. The drop of the coercive force which is found to occur upon heating at lower temperature (∼700 °C) comes from an easy nucleation of reverse domains. Indirect evidence is presented which supports the assumption that this easy reverse‐domain nucleation occurs on Sm2Co17 precipitates. The Sm2Co17 precipitation is governed by the Co‐rich SmCo5 phase boundary and its metastable extension below the eutectoid temperature of SmCo5. The state of the grain boundary which may be responsible for the strong pinning is discussed.

The gas-phase emission spectrum of carbon disulfide excited by an N2 laser - magnetic quenching effect.

Abstract: The time-resolved emission spectrum and its temperature dependence were observed with gaseous CS2 excited by an N2 laser. The spectrum was found to consist of three band systems, one of them being demonstrated to be emission from the 1A2 state. The collision-free lifetimes and the collisional quenching constants were determined for the three band systems. The emission from the 1A2 state was found to be quenched by a magnetic field because of the enhancement of an intramolecular energy-transfer process. This is the first observation of the magnetic quenching of emission from an excited singlet state.

Phase identification in titanium‐rich Ti‐Fe system by Mössbauer spectroscopy

Abstract: Various phases of the titantium rich part of the Ti‐Fe binary system were obtained by thermal treatments and were identified by Mossbauer spectroscopy and x‐ray diffraction. Room‐temperature Mossbauer parameters were derived for the following phases: αm, α, ϑ, ω, β, and TiFe. The range of concentrations for which an athermal ω phase appears upon quenching was found to be 2.7⩽CFe⩽5 wt%. The athermal ω phase disappears during aging at 285 °C for 15 h, when the alloy contains CFe⩽4.0 wt%. Martensite αm was found to form when Fe concentrations were ⩽2.7 wt.%. After quenching from the β field, the β phase retains when the Fe content of the alloy is ⩾2.7 wt.%. The ϑ phase forms during aging at temperatures above 280 °C, for alloys with a Fe content ⩽2.7 wt.%. Room‐temperature Mossbauer parameters are given to enable phases to be indentified and analyzed by means of Mossbauer spectroscopy.

Effect of Quenching and Tempering on Diffusion of Hydrogen in Carbon Steel

Abstract: The effect of quenching and tempering structure of various carbon steels on the diffusivity and solubility of hydrogen were studied at room temperature by using an electrochemical permeation technique. The minimum diffusion coefficient is obtained when the steels are in the as-quenched state; i.e, in a martensitic structure the diffusion coefficient increases with increasing tempering temperature. On the other hand, the solubility of hydrogen isa maximum for the quenched martensitic structure and decreases with increasing tempering temperature. An increase in carbon content reduces the diffusivity but increases the solubility of hydrogen. The variations in diffusivity and solubility can be explained in terms of hydrogen trapping process involving lattice imperfections such as dislocations, lattice vacancies and subgrain boundaries, etc, produced by martensitic transformation. (Received January 27, 1976)

The formation and crystallization of an amorphous phase in an iron-carbon alloy

Abstract: Splat-cooled foils of a carburised high purity Fe-C alloy have been examined by transmission electron microscopy. The crystalline phases that arose with an Fe¯4.3 wt % C amorphous phase on quenching and those that nucleated from the amorphous phase on heating were identified. The former was the HCP solid solutione-phase whereas the latter, termed MS-I and MS-II, developed via two independent reactions yielding single phase ferrite grains and generally ferrite plus cementite grains, respectively. These observations have been interpreted in terms of the relative dispositions of transformation curves of the various metastable crystallization products.

Non-crystallinity of ion-irradiated metals

Abstract: THE preparation of various metals and metallic alloys in a non-crystalline state using splat cooling, vapour quenching or electrochemical deposition techniques has been reported by many authors. A distinguishing characteristic of such amorphous films is a severe modification of the structure factor from that of the crystalline state. Although usually formed only at low temperatures the non-crystalline state may in some cases be metastable to above room temperature, this being particularly true for alloys near the eutectic. We examine here evidence for metastable non-crystalline alloys resulting from ion irradiation.

Process of case hardening martensitic stainless steels

Abstract: A process for case hardening martensitic stainless steels comprising the steps of forming non-explosive and neutral or weakly reducing atmosphere consisting essentially of 975% to 95% by volume of nitrogen gas, 05% to 15% by volume of carbon monoxide and 2% to 35% by volume of hydrogen gas The carbon monoxide and hydrogen gases are produced by heat decomposition of an organic solvent mixed with the nitrogen gas The martensitic stainless steel is heated in this atmosphere at a solution heat treatment temperature in the range 900° C to 1100° C for a period required to cause nitriding of a surface thereof to a predetermined depth The steel is then quenched at a temperature within the range of 150° C to room temperature, the quenching gas being selected from the group consisting of nitrogen gas and the resulting gaseous atmosphere As a result of this process, resistance against planar pressure by loads and the strength of the martensitic stainless steel are increased The stainless steel thus treated has bright surfaces and high corrosion resistance

Thermal‐Shock Resistance and Fracture‐Strength Behavior of Two Tool Carbides

Abstract: The thermal-stress resistance and fracture-strength behavior of TiC and WC after severe thermal shocking were investigated. The damage-resistance parameter, (XIc/δf)2, for both carbides was determined over a wide range of loading rates and temperatures. The fracture-strength behavior of these two carbides in the quenching temperature range of 25° to 800°C follows Has-selman's model for an instantaneous strength loss at a critical quenching temperature. When WC was shocked at temperatures > 800°C, it exhibited higher retained strengths because of its higher (KIc/δf)2 values at these temperatures. The effects of specimen size and repeated thermal shocks on retained strength and critical quenching temperature for these carbides were also investigated.

Metal powder production by direct reduction in an arc heater

Abstract: A process for the production of metal powder from an ore by direct reduction in an arc heater characterized by the steps of introducing a finely divided ore into an arc heated plasma gas to effect reduction of the ore to small liquid droplets of elemental metal in a reducing atmosphere and quenching the metal droplets to form solid metal powder, the metal having a melting point of not more than the temperature of the chemical reduction reaction, such metal being iron, chromium, vanadium, manganese, cobalt or nickel.

The Structure and Crystallization of Amorphous Se

Abstract: The far-infrared transmission spectrum of amorphous selenium has been measured for different temperatures of quenching. The spectrum shows that the weight fraction of Se8-ring decreases and that of the polymeric chain increases if the temperature just before quenching, Tbq, increases above the melting point of 217°C. The thermal crystallization process of selenium samples with different values of Tbq has been studied by differential scanning calorimetery (DSC), The result may be explained by a phenomenological model that the crystallization of amorphous selenium develops from nuclei with the Maxwellian velocity of the crystallization front with the activation energy, E=0.85 eV for Tbq<620°C.

Production of improved metal alloy filaments

Abstract: Metal alloy filaments having improved surface characteristics and enhanced mechanical properties are extracted from a source of molten metal alloy using a quenching wheel in a partial vacuum.

Method of tempering in a fluidized quenching medium

Abstract: Heated articles may be rapidly and uniformly quenched in a fluidized bed of a dispersion of water and hydrophobic colloidal silica.

Redetermination of cross sections for formation of metastable He+(2s) ions in fast collisions using an improved calibration procedure

Abstract: A photoionization chamber has been used to determine the absolute intensity of 304 AA radiation emitted during electric-field quenching of fast He+(2s) metastable ions. The measurements have been used to redetermine with greatly improved accuracy cross sections previously measured in this laboratory for formation of He+(2s) metastable ions by (a) one-electron capture in the passage of 10-60 keV 3He2+ ions through H, H2, He, Ar, Kr, K, N2 and O2 and (b) direct excitation of 6-30 keV 3He+ ions in passage through He, Ar, Kr, H2, N2 and O2. The measurements show that, while relative cross sections for the different target gases remain unchanged, previously estimated absolute values should be increased by a factor of 2.2. Cross sections revised in this way are believed to be accurate to within 15% for H2 and 20% for the other target gases.

Electron Transfer Reactions Induced by Excited State Quenching

Abstract: Electron transfer quenching of excited states can lead to separated redox products for which back electron transfer can be highly favored. Application of flash photolysis leads to a relaxation technique in which a system at equilibrium is perturbed by separate excitation-quenching steps. The rates of several electron transfer reactions have been studied using the technique based on redox quenching of the CT excited state Ru(bpy)2+−3. Quenching and back electron transfer has also been observed for a series of excited states including examples of CT(Ru(phen)2+3, etc), π - π * (Pd(OEP)), and f-f(Eu(phen)3+3) states. In recent work, even non-emitting excited states have been shown to be quenched by electron transfer which suggests that the technique may have broad applicability. In properly designed systems containing more than one redox reagent, the quenching and back electron transfer steps can be separated and reactions have been studied which are driven photocatalytically by excited states like Ru(bpy)2+−3. A modification of the technique has been used to estimate the self-exchange rate for the Ru(bpy)3+/2+3 couple and to measure rates of electron transfer for a series of systems where the rates measured do not involve a Ru-couple.

Process for the controlled cooling of ferrous metal

Abstract: PROCESS FOR THE CONTROLLED COOLING OF FERROUS METAL ABSTRACT OF THE DISCLOSURE Austenitized ferrous metal. such as carbon steel, is quenched by means of an aqueous solution or a salt of poly-acrylic acid which develops an extremely stable and uniform water vapor envelope surrounding the steel. Rate of cooling is controlled by (1) the molecular weight of the salt, (2) con-centration of the salt in the solution, (3) solution temperature, and (4) the degree of agitation of the quenchant solution. In the case of carbon steel, by proper selection of the above variables, the austenitic structure of the hot steel may be directly transformed into non-martensitic structures of improved ductility, machinability and cold working properties, such as fine striped pearlite, without the necessity of further heat treatments, such as tempering, following quenching. The quenching solution may also be used to quench parts formed of alloy steel to obtain a martensitic structure without unwanted cracking and distortion. Non-ferrous metals may also be quenched using the polyacrylate quenching solution.

Metastable Phases Produced by Rapid Quenching from the Vapor and the Liquid

Abstract: Though some metastable phases are obtained readily, eg, common inorganic oxide glasses or some phases present in many varieties of steels, the phases of interest here are those which can be obtained only through the use of high effective quenching rates from the vapor or liquid phase This includes many thin-film phases obtained by evaporation or sputtering and not-so-thin film phases obtained by rapid cooling from the melt and by electrodeposition from a liquid electrolyte In the case of evaporation or sputtering of a metal, the substrate is exposed to a gaseous ambient containing metal as well as nonmetal atoms, whereas in the case of rapid quenching from the melt and electrodeposition, the ambient of the substrate is made up of a crystallographically uncorrelated assembly of atoms in the liquid phase or in solution

Heating and quenching steel parts such as Belleville springs - using quenching press contg. dies which clamp spring

Abstract: Heat treatment of the steel workpiece involves (a) heating to the austenising temp. in a molten salt bath; (b) laying the hot piece between the cheeks of a die or quenching jig and closing the die so it forms a cavity matching the desired final shape of the piece; (c) feeding coolant into the cavity to quench the clamped piece; (d) opening the die to remove the piece. The molten salt is pref. nitrate-nitrite and the coolant oil at 51.8 degrees C. The claims include a quenching press contg a die and gripper tongs which transfer the piece from the salt bath to the quenching press. Used for hardening parts such as coupling discs or Belleville springs without distortion or cracking, by using a quenching press and forced hot oil cooling.

Influence of heat-treatment and solute content on repeated precipitation at dislocations in Al-Cu alloys

Abstract: The influence of heat-treating parameters and Cu content on repeated precipitation of theθ′ phase which occurs at climbing dislocations during quenching dilute Al-Cu alloys has been studied by transmission electron microscopy. In Al-3.85 wt % Cu the process occurs during quenching from all temperatures within the solid solution range to all temperatures in the range from room temperature to at least 300° C. It also occurs over a wide range of quench rates. Depending on the quench rate, it can occur at a variety of dislocation geometries, including climb sources, glide dislocations which climb off their slip planes, and collapsed vacancy loops. Quenching directly to the ageing temperature establishes the distribution of almost the entire volume fraction ofθ′ by repeated precipitation during the quench. This process does not occur in alloys with Cu content below 1.5 ± 0.5 wt %.