Showing papers on "Quenching published in 1980"

Quenching and recovery investigations of vacancies in tungsten

Abstract: Resistivity and transmission-electron-microscopy investigations have been carried out on high-purity quenched tungsten These have yielded values for the monovacancy formation and migration enthalpies of HIV F=3·67±0·2 eV and HIVM=1·78 ± 01 eV respectively, Direct observations of voids formed by vacancy precipitation during quenching and subsequent annealing have led to the conclusion that the equilibrium vacancy concentration at the melting point is Cv(Tm=3695 K) ≃ 1 × 10−4 Using this value, the vacancy resistivity and formation entropy, pIV=6·3 × 10−4 Ω cm and SIV F=2·3k respectively, were deduced The results are discussed in relation to self-diffusion in tungsten and difficulties encountered in earlier work on quenched tungsten

Ultra-drawing of high molecular weight polyethylene cast from solution

Abstract: The morphology and structure of gels produced by quenching semidilute solutions of high molecular weight polyethylene\((\bar M_w = 1.5 - 3.5 \cdot 10^6 )\) in decalin is discussed. The drawing behavior of the dried gel films at room temperature and at 130 °C and the structural features of films drawn to ratios as high as 130 were examined with various microscopic techniques and wide-angle X-ray scattering.

Structure-property relations and the design of Fe-4Cr-C base structural steels for high strength and toughness

Abstract: Some design guidelines for improving strength-toughness combinations in medium car-bon structural steels are critically reviewed. From this, quaternary alloy development based on Fe/Cr/C steels with Mn or Ni additions for improved properties is described. Transmission electron microscopy and X-ray analysis reveal increasing amounts of retained austenite in these alloys with Mn content up to 2 wt pct and Ni additions at 5 wt pct after quenching from 1100°C. A corresponding improvement in toughness properties is also found. Grain refining results in a further increase in the amount of retained austenite. In addition, the excellent combinations of strength and toughness in these quaternary alloys are attributed to the production of dislocated lath martensite from a homogeneous austenite phase free from undissolved alloy carbides. The question of thermal instability of retained austenite following tempering is considered in detail and it is shown that the decomposition of retained austenite is closely related to the ease of nucleation and growth of cementite. Thus, graphitizing alloying elements such as Ni are beneficial in postponing the decomposition of retained austenite.

High tensile steel and process for producing the same

Abstract: A high tensile steel which has a satisfactory yield strength of 60 kg/mm2 or more and excellent resistances to sulfide corrosive cracking and corrosion, and which comprises, as indispensable components, 0.05 to 0.50 wt % of C, 0.1 to 1.0 wt % of Si, 0.1 to 2.0 wt % of Mn, 0.05 to 1.50 wt % of Co and the balance consisting of Fe, is produced by hot- or cold-rolling it, rapidly heating the rolled steel to austenitize it, quenching the austenitized steel and, finally, tempering the quenched steel at a temperature not higher than the Ac1 point of the steel.

The effect of heat treatment on microstructure and cryogenic fracture properties in 5Ni and 9Ni steel

Abstract: Heat treatments were utilized in 5Ni and 9Ni steel which resulted in the development of tempered microstructures which contained either no measurable retained austenite (<0.5 pct) or approximately 4 to 5 pct retained austenite as determined by X-ray diffraction. Microstructural observations coupled with the results of tensile testing indicated that the formation of retained austenite correlated with a decrease in carbon content of the matrix. Relative values ofKIC at 77 K were estimated from slow bend precracked Charpy data using both the COD and equivalent energy measurements. In addition, Charpy impact properties at 77 K were determined. In the 9Ni alloy, optimum fracture toughness was achieved in specimens which contained retained austenite. This was attributed to changes in yield and work hardening behavior which accompanied the microstructural changes. In the 5Ni alloy, fracture toughness equivalent to that observed in the 9Ni alloy was developed in grain refined and tempered microstructures containing <0.5 pct retained austenite. A decrease in fracture toughness was observed in grain refined 5Ni specimens containing 3.8 pct retained austenite due to the premature onset of unstable cracking. This was attributed to the transformation of retained austenite to brittle martensite during deformation. It was concluded that the formation of thermally stable retained austenite is beneficial to the fracture toughness of Ni steels at 77 K as a result of austenite gettering carbon from the matrix during tempering. However, it was also concluded that the mechanical stability of the retained austenite is critical in achieving a favorable enhancement of cryogenic fracture toughness properties.

Prediction of Hardenability Effects from Isothermal Transformation Kinetics

Abstract: The relationship between the size of material, fraction of martensite and austenite grain size is considered for a certain eutectoid steel under a certain cooling condition. It is assumed that the isothermal pearlite transformation can be expressed as X =1 -exp {-k(T) (tn/dm )} for the whole transformation temperature range and that the transformation is additive over the whole transformation range. The cooling rate is determined as a function of section size (which is commonly found in actual quenching). With the application of the obtained relation, the Jominy curve, DI vs DI,X (the diameter of the bar with X pct martensite at the center after an ideal quenching) and the effect of austenite grain size on the DI and Jominy distance are shown to be predictable.

Quenching of laser‐excited O2(b 1Σ+g) by CO2, H2O, and I2

Abstract: The total quenching rates of O2(b 1Σ+g) by CO2, H2O, and I2 have been determined to be (4.53±0.29)×10−13 cm3 molec−1 sec−1, (6.71±0.53)×10−12 cm3 molec−1 sec−1, and (2.04±0.28)×10−11 cm3 molec−1 sec−1, respectively. A pulsed, Raman‐shifted dye laser was used to excite a single rotational line of O2(1Σ, v′=0), while subsequent 1Σ→3Σ fluorescence was monitored by a photon counting technique to determine the deactivation rate as a function of the partial pressure of quenching gas. Rate constants for deactivation of O2(1Σ) by CO2 and H2O were found to be consistent with those measured elsewhere, whereas I2 was found to quench O2(1Σ) an order of magnitude more slowly than reported in the literature. The lower total quenching constant for I2 suggests that the reaction O2(1Σ)+I2→O2(3Σ) +2I might not be responsible for dissociation of I2 in the chemical oxygen‐iodine laser.

The relationship between microstructure and age hardening response in the metastable beta titanium alloy Ti- 11.5 Mo-6 Zr-4.5 Sn (beta III)

Abstract: The influence of heat treatment and oxygen content on the aging response and micro-structure of the metastable Β-phase titanium alloy Ti-11.5Mo-6Zr-4.5Sn (Beta III) has been studied using light and electron metallography and hardness measurements. Increasing the oxygen from 0.17 to 0.28 wt pet was shown to suppress Ω-phase formation and accelerate a-phase formation. Changing the solution treatment from above to below the Β-transus was shown to significantly increase the rate of α-phase formation at residual dislocations and subboundaries present in the warm worked material. Direct aging has been shown to greatly retard the rate of Ω-phase formation by comparison to quenching and aging. Duplex aging first at a temperature in the Ω-phase formation range and then at a temperature in the a-phase formation range results in a very fine dispersion of α-phase particles and a very high hardness. It is suggested that this α-phase forms by aninsitu Ω → α transformation. In quenched samples small amounts (10 pct) of cold work were shown to accelerate the formation of Ω-phase during subsequent aging as shown by both electron microscopy and by hardness measurements. Finally, some remarks are included to indicate the application of our observations to the commercial heat treatment of Β-III.

Dimensional changes in heat treating aluminum alloys

Abstract: Basic equations are presented for computing volumetric and linear dimensional changes in aluminum alloys resulting from the solution/precipitation reactions associated with heat treatment. Changes observed in experimental high purity alloys and commercial compositions based on the same systems are shown to be consistent with the calculations. Larger changes are observed in alloys based on binary Al-Cu, Al-Si and Al-Mg systems than for those based on ternary systems such as Al-Cu-Mg or Al-Si-Mg, in which offsetting effects of the multiple solutes and formation of different precipitates occur. Stresses from high-cooling-rate quenching cause anisotropic dimensional changes attributable to plastic deformation, and such changes are shown to be additive with repeated quenching. Indications of directional effects from precipitation in certain wrought products require further investigation for verification or disproval. Effects of composition and heat treated temper on subsequent dimensional instability are discussed briefly.

Metastable phases in laser‐irradiated Pt‐Si and Pd‐Si thin films

Abstract: Amorphous phases of Pt‐Si and Pd‐Si covering a wide range of compositions are produced by laser‐induced melting and quenching of vapor‐deposited thin films. It is concluded that with the present cooling rates all compositions except those close to the congruently melting phases and the pure elements lead to amorphous films. Thermal decomposition of the Si‐rich amorphous films reveals the formations of at least two metastable crystalline phases in the case of Pt‐Si, and a low‐temperature nucleation of the equilibrium PdSi phase in the case of Pd‐Si.

Solids quench boiler

Abstract: Apparatus for quenching and cooling the reactor effluent in a thermal regenerative cracking (TRC) system. The quench apparatus includes a section for introducing relatively cool particulate solids into a hot effluent stream to effect initial quenching and a section to further cool the composite of quenched effluent and solids.

Determination of surface heat-transfer coefficients during quenching of steel plates

Abstract: The experimentally determined relationships between temperature and time in quenched steel plates have been used in conjunction with an explicit finite-difference technique to determine the effect of surface temperature on the magnitude of the surface heat-transfer coefficient in water, polymer, and oil quenchants In the case of the water quenchant the results obtained were very sensitive to the degree of oxidation of the specimen surface; this effect was associated with the degree of stability of the vapour blanket produced during the early stages of quenching The polymer quenchant did not possess a clear advantage over water except where the concentration of the latter was as high as 25% In comparison, the values of the surface heat-transfer coefficients obtainedfrom the oil quenchant were very low; this was associated with a relatively short nucleate boiling stage

Analysis of Effect of Heat‐Transfer Variables on Thermal Stress Resistance of Brittle Ceramics Measured by Quenching Experiments

Abstract: Heat-transfer theory was used to analyze the variables which control the thermal stress fracture of brittle ceramic specimens subjected to rapid cooling by quenching into fluid media. Expressions were derived for the maximum quenching temperature difference to which circular solid cylindrical specimens can be subjected in terms of the pertinent properties of the material and fluid media. Appropriate thermal stress resistance parameters were derived. The specimen density was introduced as an additional property which controls thermal stress resistance. Recommendations were made for procedures to be followed in conducting quenching experiments.

Non-Equilibrium Segregation in Metals and Alloys

Abstract: The phenomenon of non-equilibrium segregation of solute and impurity atoms at interfaces in quenched materials is defined and the driving force and kinetics of the segregation are shown to differ significantly from those of reversible equilibrium segregation. Large point defect supersaturations are produced during quenching, irradiation and sintering, and both enrichment and depletion of solute atoms at interfaces, associated with the flow of point defects to sinks, have been observed. Some of the quantitative and qualitative experimental data on non-equilibrium segregation are described and the current understanding of the mechanisms and kinetics are summarized. Finally, some of the practical implications of non-equilibrium segregation, in terms of the effects on the deformation, fracture and mechanical properties, corrosion behaviour and structural stabilities of quenched and irradiated metals and alloys, are outlined and possible methods of inhibiting segregation are suggested.

Preparation of glassy metals

Abstract: Metallic liquids usually crystallize when subjected to the same cooling treatments that are employed to produce familiar nonmetallic glasses. By drastic quenching methods such as vapor condensation, electro­ deposition, chemical deposition, and rapid liquid quenching, however, a noncrystalline structure can be retained for many metals and alloys. A number of amorphous alloys were prepared by vapor quenching or electrodeposition in the 1950s, while the first glassy metal obtained by quenching from a melt was reported by Klement, Willens & Duwez in 1960 (1). Since the publication of their paper on glassy Au-Si alloys, many original articles on the structure, electrical and magnetic properties, and thermodynamic characterization of noncrystalline metals have appeared (2-4). Since the development of continuous fabrication of uniform glassy ribbons (5) and the subsequent discovery of technically interesting pro­ perties such as high strength (6-9), soft magnetic behavior (10-12), and excellent corrosion resistance (1 3), glassy metals have drawn further attention from the materials science community and are currently the focus of intense technological and fundamental studies. Glassy metals may be regarded as liquids whose structure has been "frozen." They are isotropic in the range � 20 A, and thus constitute ideal materials for low temperature transport and critical behavior studies as well as the study of electrons in the noncrystalline state. During recent years, new efforts directed toward basic understanding of the physical properties of glassy metals, as well as further exploration of technically important mechanical, magnetic, and chemical properties and glass­ forming systems, have been made. Extensive collections of papers on glassy metals may be found in the Proceedings oJthe Second International

Method and apparatus for forge-shaping sheet members

Abstract: A method and apparatus for forge-shaping sheet-shaped members having upper and lower dies for pressing and forge-shaping a sheet-shaped material heated to a quenching temperature or an imperfectly quenching temperature set from a required hardness. The apparatus also includes cooling ducts for quenching the forge-shape material. The material is continuously quenched as it is kept pressed.

Method and apparatus for the wet quenching of coke

Abstract: A method and apparatus for the wet quenching of coke is disclosed wherein hot coke is sprayed from above with quenching water, the steam generated by the heat of the coke is condensed by a spray of condensation water from the top of the quenching tower, and the hot condensate-water mixture is collected at the bottom of the quenching tower and recirculating to the top of the tower where it is sprayed between quenching operations to be cooled by a counterflowing stream of air. The cooled condensate-water mixture is suitable for reuse as the condensation spray water.

Photoluminescence in sputtered amorphous silicon-hydrogen alloys

Abstract: Results of photoluminescence (PL) experiments performed on amorphous silicon-hydrogen alloys prepared by sputtering in a plasma containing hydrogen are presented. A single, featureless peak centred near 1.3 eV and of 0.3 eV f.w.h.m. is observed upon excitation with 2.4 eV light in alloys of hydrogen concentration cH≥5 at.% held at temperatures below 200 K. The PL quantum efficiency and peak energy are increasing functions of ch. A high-temperature decrease in PL is observed, and electric fields of 105 V/cm are found to be sufficient to quench the PL. It is contended that the original argument in the literature concerning the necessity for Stokes shifts of the order of 0.5 eV is wrongly based. From the present data we conclude that radiative recombination in our films may best be viewed in the framework of a rigid-band model with only small perturbations caused by distortional effects of the host matrix. The high-temperature thermal quenching of the PL is analysed in terms of two quenching mechani...

Quenching and recovery experiments on molybdenum

Abstract: Quenching experiments in superfluid helium have been performed on high-purity wire specimens obtained from a Mo single crystal with a residual resistance ratio of 40 000. Quenching from various tem...

Ignition and flame quenching of quiescent dust clouds of solid fuels

Abstract: Experiments have been carried out to study the influence of particle size, dust concentration, pressure, mass transfer number and oxygen/nitrogen ratio on quenching distance and minimum ignition energy of dust clouds of solid fuels. The solids chosen were aluminium, magnesium, titanium and carbon. Ignition was accomplished by using sparks whose energy and duration could be varied independently. A separate series of tests was also conducted to ascertain optimum spark duration. The results of these tests show that particle size has a strong influence on the minimum ignition energy, the quenching distance and the optimum spark duration. To a lesser extent pressure, dust concentration, mass transfer number and oxygen/nitrogen ratio also affect ignition and quenching of dust clouds. A detailed comparison of results for the dust clouds and the liquid mists studied previously shows a strong similarity between the two. It appears that both solid and liquid fuels may be treated as members of a single family. Thus it is found that the formulae for quenching distance and minimum ignition energy derived previously for liquid fuel mists also satisfactorily predict the experimental results obtained for dust clouds of metals and carbon. Further, a typical calculation shows that for aluminium, for example, the critical particle Sauter mean diameter below which the formulae become invalid is around 6 μm.

Coarsening kinetics during solidification of Ni-Al-Ta dendritic monocrystals

Abstract: Several dendritic monocrystals of nickel-rich Ni-Al-Ta alloys were directionally solidified at about 0.25 m/h−1 under a gradient of 8 × 10−3 K/m−1. The solid-liquid interface was fossilized at a given moment by rapidly quenching the remaining liquid. In some specimens crystal pulling was interrupted for various lengths of time prior to quenching. The quenched solid-liquid interfaces were used for a convenient and rapid evaluation of: 1) isothermal coarsening kinetics of the dendritic solid at a temperature between the liquidus and the eutectic temperatures and; 2) dendrite coarsening kinetics during solidification. It was found that extension to the ternary Ni-Al-Ta system of a model previously developed for binary systems predicted isothermal dendrite coarsening kinetics in close agreement with experimental results. Agreement for coarsening kinetics during solidification was less good. An increase in tantalum or aluminum contents slowed down coarsening, yielding finer microstructures. At equal atomic percental increase in concentration, the effect of tantalum was more significant than that of aluminum.

Apparatus for producing selective particle sized oxide

Abstract: A plasma method and apparatus produce oxide particles having average diameters determined by adjustment of process conditions. Feed material is fed into a dual chamber reaction zone in which a plasma environment is established to cause the feed material to be vaporized. Subsequently, effluent containing the vaporized feed from the reaction zone is passed into a quenching zone where it is subjected to a quenching medium, the volume, velocity and direction of which are adjustable to determine output particle size characteristics. Feed material may be an oxide per se or one which forms an oxide in situ through reduction and/or oxidation.