Showing papers on "Annealing (metallurgy) published in 1968"

Hardness and low-temperature deformation of silica glass.

Abstract: Vickers diamond pyramid hardness measurements have been made on silica glass with varying thermal history using loads up to 1000 g. Hardness was independent of load and source. From interference photographs and subsequent anneal of the indentations at temperatures belowT g, it was concluded that indentation leads primarily to densification of a volume of glass in the vicinity of the indenter. A portion of the densification which is recoverable at relatively low temperatures is attributed to molecular entanglement of the glassy network due to high pressure and shear. The other portion which is not recoverable belowT g represents an approach to the final equilibrium density of the glass. Hardness of silica glass as determined by this method is thus defined as a resistance of the material to densification.

Characteristics of thermal annealing of radiation damage in MOSFET's.

Abstract: Thermal annealing characteristics of electron radiation damage in p-channel MOSFET, noting time and temperature dependence and activation energy

Polymerization of aromatic nuclei. XIII. X-ray analysis and properties of poly(p-phenylene) pellets

Abstract: X-ray diffraction experiments with poly(p-phenylene) pellets demonstrated an increase in crystallinity with increase in molding temperature or annealing temperature. The increase in crystallinity may be attributed to annealing effects and loss of chlorine under severe conditions. Lattice constants for the crystalline polymer are presented, and the crystallographic data are compared with those of the lower oligomers. Poly(p-phenylene) was investigated also in relation to oxidative thermal stability, chemical and solvent resistance, and the effect of temperature and variation in molding conditions on fracture strength. The decrease in strength at elevated temperatures appears to be related to the increase in crystallinity.

The Annealing of Voids in Quenched Aluminium and a Determination of the Surface Energy

Abstract: Octahedral voids up to 500 A in diameter have been produced in thin foils of spectroscopically pure aluminium by quenching. Transmission electron microscopy has been used to investigate the thermal stability of these voids and it is observed that they anneal out rapidly in the range 150–200°C. The kinetics of the annealing is in good agreement with that expected from a diffusion-controlled rate process, and a value for the surface energy γs = 1140 ± 200 ergs/cm2 has been obtained.

Accelerated Spheroidization of Pearlite

Abstract: A study has been made of the spheroidization of pearlite in eutectoid steel at 700° C under conditions of lengthy annealing, cold working at room temperature followed by annealing, hot torsion, and hot fatigue. The results show that hot torsion accelerates spheroidization by a factor of ∼ 104 compared with annealing but that acceleration by a factor of ∼ 100 is obtained both with cold work followed by annealing and with hot fatigue. It is suggested that the acceleration results from enhanced diffusion of iron in the ferrite due to the introduction of large-angle sub-boundaries by dynamic recovery.

Thermal Recovery of Explosive Shock-loaded Stainless Steel

Abstract: The annealing response of shock-loaded type 304 stainless steel was studied in the pressure range of 120–1200 kbars, and compared with the response of stainless steel cold-rolled 5 and 45%. The annealing kinetics of shock-loaded stainless steel are characterized by a prominent recovery and grain growth stage, with little perceptible recrystallization in the classical sense. The results indicated a pronounoed structural difference between the shock-loaded and cold-rolled materials, as observed by transmission electron microscopy. The structure of stainless steel shock-loaded to 750 and 1200 kbars is observed to be strongly influenced by the transient shock heating effect, and a dislocation cell-type substructure is observed to occur predominantly in (100) grains. The hardness produced over the pressure range 120–1200 kbars by explosive shock-loading is shown to occur by a transition from dense dislocation arraya to twin-faults, and finally to what may be dense point defect concentrations at very h...

Variations of the Unit‐Cell Dimensions of Polyethylene: Effect of Crystallization Conditions, Annealing, and Deformation

Abstract: It is shown that the orthorhombic unit cell dimensions of a given polyethylene are not unique, but depend on the physical history of a sample. For polymer crystallized from a ¾% p‐xylene solution, the values of a and b measured at 23°C by powder camera technique vary up to 0.8% for crystallization temperatures of 50°, 70°, and 90°C, annealing temperatures from 50° to 127°C, and deformation. The as‐crystallized values of a and b as well as the effects of annealing and deformation are smaller the thicker the crystals. For ``undeformed'' crystals the changes correlate with the reciprocal of crystal thickness but for deformed crystals the changes occur before the thickness increases (even below the crystallization temperature). The dimensions undergo the greatest change within the first 2 min of annealing and change very little with time thereafter. The only exception observed is a slow decrease of b with time of annealing at 100°C. Crystals grown from other solvents exhibit very nearly identical effects, and...

The effect of dispersed phases upon the annealing behaviour of plastically deformed copper crystals

Abstract: An electron microscopic investigation is described of the effect of high temperature annealing on deformed copper single crystals containing dispersed second phases of either cobalt or silica. Sections of selected orientation cut from the deformed crystals were annealed at 700°C. It was found that specimens deformed into Stage I recovered to the low dislocation densities present before deformation, whereas the crystals deformed to Stage II recovered to form structures consisting of sheets of dislocation networks on the primary slip planes. Several of the basic networks were analysed, and their formation and distribution are discussed in terms of a modification of the deformation structures. Annealing at temperatures at which the cobalt precipitate redissolved resulted in little further structural change. The ability of these crystals to resist recrystallization is ascribed to the stability of the recovered structures and the absence of suitable recrystallization nuclei, arising from the increased...

Preparation and Properties of Noncrystalline Silicon Carbide Films

Abstract: Noncrystalline silicon carbide films have been formed by physical sputtering of a hexagonal single crystal of silicon carbide. Electron‐microscopy and electron‐diffraction studies indicate that the films undergo a transition to polycrystalline cubic silicon carbide (β‐SiC) in the temperature interval 850°–900°C. The noncrystalline films were p type and exhibited an irreversible diminution of conductivity by about two orders of magnitude when annealed in the range 200°–600°C. Isothermal annealing in this temperature range produced a decrease in conductivity approximately proportional to the logarithm of annealing time. This kinetic behavior is consistent with the occurrence of thermally activated processes having a distribution of activation energies. An approximate activation energy range for annealing was determined as 0.4–2.3 eV. The irreversible change in conductivity of the noncrystalline films is interpreted as arising from the annealing of structural defects having acceptor‐like properties. Since a ...

Effect of Oxygen on “Stage III” Annealing in Neutron-Irradiated Niobium

Abstract: The effect of oxygen on “Stage III” annealing in neutron-irradiated niobium has been investigated by means of internal-friction and electrical-resistivity techniques. The oxygen Snoek peak decreased during isothermal annealing at 150°C and the kinetics of this process was similar to that of the electrical-resistivity decrease at the same temperature. Oxygen-free samples exhibited no annealing effects in Stage III. It was concluded that Stage III is caused by the migration of oxygen to radiation-produced defects.

Dominant Surface Electronic Properties of SiO2‐Passivated Ge Surfaces as a Function of Various Annealing Treatments

Abstract: The metal‐oxide‐semiconductor (MOS), capacitance vs applied voltage (C‐V) measurement technique was used to investigate SiO2‐passivated Ge surfaces as a function of high‐temperature annealing treatments in H2, O2, N2, and H2O. Capacitance measurements were made at high frequencies (100 MHz) and/or reduced temperatures (145°, 77°K) to eliminate the capacitive contribution of fast surface states to the ac signal. Since the surface states did equilibrate with the superimposed applied dc voltage, is was possible to determine surface‐state type, energy, and densityfrom voltage shifts in the C‐V traces. Hydrogen annealing at 600°C or above introduces a high density (>1013/cm2) of fast acceptor states. These states are located at the center of the Ge energy gap. In addition, hydrogen annealing at 700°–800°C introduces acceptors close to the valence band or fixed negative charge. Most of these hydrogen‐induced states are removed by annealing in oxygen or water vapor at 230°–440°C. At the same time the oxygen or w...

Influence of temperature on phosphorus ion behavior during silicon bombardment

Abstract: Silicon samples have been bombarded with 20-keV phosphorus ions along the easy channeling direction. Annealing temperatures and activation energies of the defects created during irradiation have be...

Oxidation-vacancy production in aluminium alloys

Abstract: The climb of prismatic dislocation loops in dilute aluminium alloys has been investigated as a function of alloying addition by isothermal annealing of thin foils. It was observed that the loops annealed out by shrinking in all the alloys investigated except for aluminium-magnesium where loop growth occurred. It is proposed that the vacancy supersaturation necessary for the observed growth is due to the production of vacancies in the surface regions of the foil as magnesium atoms become absorbed by a growing surface oxide film. This model has been critically examined by investigating the rate of growth as a function of annealing time, annealing temperature and the oxygen pressure of the annealing environment. The results confirm this model of vacancy production and show that in the alloys containing 0·65% magnesium, diffusion of magnesium to the surface regions is the rate-controlling process whereas in the more concentrated alloys (3·3% and 6·6% Mg) surface oxidation is rate controlling.

Electrical Studies of Neutron‐Irradiated p‐Type Silicon: Defect Structure and Annealing

Abstract: Defects produced in float‐zone and crucible‐grown p‐type silicon by neutron irradiation at 76°K were investigated, using electrical conductivity and Hall‐effect measurements. The behavior of the neutron‐produced defects is independent of the crystal growth, and exhibits an illumination dependence similar to that previously observed in n‐type silicon and attributed to the presence of defect clusters. The neutron‐produced changes in the electrical properties of p‐type silicon at 76°K are therefore ascribed to defect clusters. The annealing loss of the light‐sensitive defects occurs in diffuse stages between 150° and 550°K. The largest stage is observed between 150° and 240°K. A major fraction of the hole‐mobility annealing parallels the annealing for the light‐sensitive defects, and suggests that the mobility change caused by defect clusters is significantly larger than that caused by isolated defects formed from cluster dissociation. The most apparent crystal‐growth‐dependent annealing is observed between ...

Kinetics of Annealing of Permalloy Films with Increasing Concentrations of Sulfur

Abstract: Zero‐magnetostrictive films have been annealed isothermally at 60°, 75°, and 90°C in a hard‐axis saturating field. The films contained up to 6 wt% of sulfur. The time dependence of the change in anisotropy indicated the presence of simultaneous processes affecting a portion of the total anisotropy. The average relaxation time was independent of sulfur content at a given temperature, but the fraction of the anisotropy involved was directly dependent on the sulfur concentration in the film and independent of temperature. The kinetic equation which described the results was (lnP/lnP∞) = 1−exp[−(t/τ)1/2]. This general form may be derived from the conventional pair reorientational model by making τ = f(t) to take into account the removal, during the annealing in the transverse field, of the effect of the active centers introduced by the sulfur. An activation energy of 0.74 eV was found for the processes affected by the sulfur. Stabilization, i.e., annealing in an easy‐axis field at 150°C, made the annealing ki...

Grain-Boundary Hardening in Iron and Iron Alloys

Abstract: Hardening at the grain boundaries in irons of various purities, and in certain iron-base alloys, has been investigated by means of a microhardness technique. The difference between the grain-boundary and grain-interior hardness values (∆H) increased as the load applied to the indenter was decreased. Zero values of ∆H were found for loads > ∼ 14 g. Factors affecting the grain-boundary hardening were studied: (a) Additions of tungsten or molybdenum reduced the grain-boundary hardness to that of the grain interior at ∼ 0.5 at.-% solute; manganese additions did not affect ∆H (b) Quenching from 900°C eliminated the hardening effect in all the materials investigated. Annealing to equilibrium at temperatures between 300 and ∼ 750°C caused a return of the hardening, the magnitude of which was independent of the annealing temperature. (c) A kinetic study of the rate of recovery of the hardening effect, following quenching from 900°C, showed that it occurs very rapidly. The conditions required for the obser...

Electrical Properties of Neutron-Irradiated Silicon at 76°K: Hall Effect and Electrical Conductivtty

Abstract: Defects produced in p-type silicon by neutron irradiation have been investigated using electrical conductivity and Hall effect measurements at 76°K. Samples from crucible-grown (1, 10, and 50 ohm-cm) and float-zone (10 ohm-cm) boron-doped silicon were irradiated at 76°K with nearly fission spectrum neutrons and annealed isochronally between 76° and 700°K. The electrical properties of neutron-irradiated p-type silicon exhibit an illumination dependence similar to that observed previously in n-type silicon and attributed to the presence of defect clusters. Therefore, neutron-produced changes in the electrical properties of p-type silicon also are attributed to defect clusters. The sensitivity to illumination was observed for all resistivities and for both crucible and float-zone p-type silicon. The illumination-induced conductivity decays slowly with time at 76°K and influences the thermally produced changes in the electrical properties upon annealing for temperatures up to 150°K. Neutron-produced changes in the electrical properties measured after annealing to 150° K are found to be qualitatively consistent with an insulating void model for cluster-space-charge regions. The best modeling of the experimentally observed changes is for the 50 ohm-cm (large void volume) silicon. The annealing loss of the light sensitive defects occurs in diffuse stages between 150° and 550°K with the largest stage between 150° and 240°K. A major fraction of the hole mobility annealing parallels that for the light sensitive defects and suggests that the mobility change is caused primarily by defect clusters.