Showing papers on "Alloy published in 1983"

Strengthening mechanisms in Inconel 718 superalloy

Abstract: The yielding behaviour of underaged Inconel alloy 718, which is precipitation hardened by coherent ordered bct γ″ and ordered fcc γ′ phases, has been studied. It was found that the yielding of the ...

Influence of silicon additions on the oxidation resistance of a stainless steel

Abstract: Oxidation tests in a CO2-based atmosphere at 1123 K have been conducted on a series of 20Cr-25Ni stainless steels containing a dispersion of TiN particles and with silicon contents ranging from 0.05 to 2.35 wt.%. In all cases, a chromia surface film whose thickness increased parabolically with time was formed. The parabolic rate constant was a minimum at an intermediate alloy silicon content when an interlayer of silica was formed between the outer oxide and the metal. The significance of this duplex structure on the processes determining the oxidation rate and the extent of oxide spalling is discussed. An additional feature of the attack was the formation of subsurface voidage whose depth again increased parabolically with time. The appropriate rate constant also showed a minimum at an intermediate silicon level and the relationships between this form of attack and the development of the surface oxides are highlighted.

Fine grained metal composition

Abstract: A fine grained metal composition suitable for forming in a partially solid, partially liquid condition. The composition is prepared by producing a solid metal composition having an essentially directional grain structure and heating the directional grain composition to a temperature above the solidus and below the liquidus to produce a partially solid, partially liquid mixture containing at least 0.05 volume fraction liquid. The composition, prior to heating, has a strain level introduced such that upon heating, the mixture comprises uniform discrete spheroidal particles contained within a lower melting matrix. The heated alloy is then solidified while in a partially solid, partially liquid condition, the solidified composition having a uniform, fine grained microstructure.

Formation of an amorphous Rh‐Si alloy by interfacial reaction between amorphous Si and crystalline Rh thin films

Abstract: Interfacial reaction in bilayers of amorphous Si and crystalline Rh thin films has been studied by transmission electron diffraction and microscopy. In a bilayer of ∼190‐A amorphous Si and ∼60‐A polycrystalline Rh films, we have observed the formation of an amorphous Rh‐Si alloy film upon thermal annealing at 300 °C. The amorphous alloy film crystallizes into the RhSi phase at 400 °C. On the other hand, no amorphous alloy formation was observed upon annealing a bilayer of ∼150‐A amorphous Si and ∼100‐A polycrystalline Rh films; instead, they react at 300 °C to form Rh2Si, followed by the formation of RhSi or a mixture of RhSi and Rh5Si3 around 400 °C.

Corrosion Behavior of SiC / Al Metal Matrix Composites

Abstract: The effect of the phase on the corrosion behavior of metal matrix composites has been studied in , both in the presence and absence of dissolved oxygen. Anodic polarization behavior has been determined, and pitting potentials have been measured for three composite systems: 2024, 6061, and 5456. General corrosion behavior and the effects of anodizing on the corrosion resistance of the composites have been studied by a‐c impedance techniques. The results show that pitting susceptibility is about the same for the composites and their corresponding alloys, except for Al 2024. In this system, the composite is less resistant to pit initiation than the corresponding wrought aluminum alloy. General corrosion is more significantly affected by the presence of oxygen than by the phase. In the absence of oxygen, corrosion resistance is improved for both the alloys and composites. In addition, the corrosion resistance of the composites can be improved by anodizing.

Wear-Resistant Cobalt-Base Alloys

Abstract: Cobalt-base alloys have enjoyed extensive use in wear-related engineering applications for well over 50 years because of their inherent high-strength, corrosion resistance, and ability to retain hardness at elevated temperatures. Microstructurally, wear-resistant cobalt-base alloys consist of hard particles (Cr7C3) dispersed in cobalt-rich (Co > 50%) solid solution matrix alloys (generally Co-Cr-W/Mo). Recent investigations in the Cabot Corporation Technology Laboratories have shown that the adhesive and cavitation-erosion wear characteristics of these alloys are determined by the composition of the matrix alloy and are influenced to a large extent by a strain-induce fee → hep allotropie transformation in the matrix alloy. Further, it has been shown that the cobalt content in the matrix alloy can be decreased to approximately 30% without significantly degrading relevant wear or corrosion properties. Toughness and abrasive wear resistance, on the other hand, are determined primarily by carbide volume fraction and morphology. Large, hypereutectic carbides are generally preferred for good abrasive wear resistance but are detrimental to toughness considerations. The tribological measurements and microstructural correlations associated with these Cabot investigations are summarized and discussed in this paper.

Surface Enrichment of Nitrogen during Passivation of a Highly Resistant Stainless Steel

Abstract: Nitrogen, probably in an uncharged form, is enriched on the metal side of the metal film interface after passivation of the number 30 alloy. Molybdenum is probably present in the oxide film, but is depleted compared with the bulk alloy and shows no obvious association with nitrogen. The improvement of passivity by alloying with nitrogen probably results from segregation of nitrogen to the metal surface during preferential dissolution of metal atoms, rather than from its incorporation into an oxide film.

Precipitation reactions during the heat treatment of ferritic steels

Abstract: The precipitation reactions in two ferritic steels, 9Cr-1Mo-V-Nb and 12Cr-1Mo-V-W, were studied. Analytical electron microscopy, optical microscopy, electrolytic extractions, and hardness measurements were used to determine the types, amounts, and effects of precipitates formed as a function of the heat treatment. The effect of variations in the austenitizing treatment was ascertained. In addition to variations in the austenitizing time and temperature, different cooling rates after austenitization were also used. Air cooling after austenitization (normalization) resulted in little precipitation in both alloys. Precipitation in the 12Cr-1Mo-V-W alloy after furnace cooling was found in all cases examined. Under certain conditions precipitation was also found after furnace cooling the 9Cr-1Mo-V-Nb alloy. However, when compared to the amount of precipitate in the fully tempered state, the 9Cr-1Mo-V-Nb showed a much greater variation in the degree of precipitation following furnace cooling. In addition, the matrix microstructure of the 9Cr-1Mo-V-Nb alloy was very sensitive to cooling rate. The precipitation reactions during tempering after a normalizing treatment were followed as a function of tempering treatment. Tempering temperatures were varied from 400 to 780 °C. The carbide precipitation was essentially complete after one hour at 650 °C for both alloys. Analytical microscopy was used to identify the precipitates. In the 9Cr-1Mo-V-Nb alloy, a combination of chromium-rich M23C6 and vanadium-niobium-rich MC carbides was found. The carbides in the 12Cr-1Mo-V-W alloy were identified as chromium-rich M23C6 and vanadium-rich MC. The results give an indication of the sensitivity of these alloys to heat treatment variations.

Hydrogen separation using coated titanium alloys

Abstract: This invention relates to the separation of hydrogen from other fluids by contacting said fluids with a titanium alloy comprising about 13% by weight vanadium, about 11% by weight chromium, about 3% by weight aluminum, balance titanium, stabilized in the body centered cubic crystalline form, said alloy having at least one clean surface coated with a metal oralloy based on a member of the class consisting of palladium, nickel, cobalt, iron, vanadium, niobium or tantalum, and allowing hydrogen to permeate the coated alloy at a temperature between about 100° C. and about 500° C.

High-temperature Behavior of a Pd-Ag Alloy for Porcelain

Abstract: The mechanism of formation of nodular material on the surface of a Pd-Ag-based alloy for porcelain during pre-porcelainization heat treatment was investigated using scanning electron microscopy, x-ray diffraction, quantitative metallography, and Auger electron spectroscopy. The nodules were found to form by a Nabarro-Herring creep mechanism driven by the internal oxidation of tin and indium. Implications of this process with regard to porcelain bonding and discoloration are discussed.

Aluminum 6XXX alloy products of high strength and toughness having stable response to high temperature artificial aging treatments and method for producing

Abstract: Improved aluminum alloy products are fabricated from an improved alloy broadly containing 0.4 to 1.2% silicon, 0.5 to 1.3% magnesium, 0.6 to 1.1% copper and 0.1 to 1% manganese. The alloy is treated at very high temperatures, approaching the solidus or initial melting temperature, to provide the improved performance. Thereafter, the alloy is shaped as by rolling, extruding, forging and other known aluminum wrought product-producing operations. In the solution heat treated, quenched and artificially aged temper products so produced exhibit very high strength in comparison with 6XXX aluminum alloys, together with very high toughness and impact and dent resistance along with substantial corrosion resistance properties. In addition, the artificial aging response of the improved products enables use of high temperature, low cost aging treatments without risk of overshooting or undershooting the required or desired properties.

Mechanical properties of ductile Fe-Ni-Zr and Fe-Ni-Zr (Nb or Ta) amorphous alloys containing fine crystalline particles

Abstract: Melt-quenched Fe60–80Ni10–30Zr10 and Fe70Ni20Zr10−x(Nb or Ta) x (x≲2 at %) alloy ribbons with the duplex structure consisting of amorphous and bcc phases were found to exhibit hardness and tensile strengths higher than those of the totally amorphous alloys. The volume fraction of the bcc phase was intentionally allowed to alter in the range 0% to 60% by changing the composition and sample thickness. The bcc phase has an average particle size of 75 nm for the Fe-Ni-Zr alloys and 50 nm for the Fe-Ni-Zr-Nb alloys, and the lattice parameter is much larger than that of pure α-Fe because of the dissolution of large amounts of zirconium, niobium and/or tantalum. The hardness and tensile strength of the duplex alloys increase with amount of bcc phase and reach about 880 DPN and 2580 MPa, which are higher by about 20% to 30% than those of the amorphous single state, at an appropriate volume fraction of bcc phase. As the volume fraction of the bcc phase increases further, the duplex alloys become brittle and the tensile strength decreases significantly. The enhancement of strength was considered to be due to the suppression of shear slip caused by fine bcc particles dispersed uniformly in the amorphous matrix. It was thus demonstrated that an optimum control of melt-quenched structure results in the formation of ductile Fe-based amorphous alloys containing fine crystalline particles.

Life properties of TiMn alloy hydrides and their hydrogen purification effect

Abstract: The effects of pressure-induced absorption-desorption cycling on the degradation properties and the hydrogen purification ability of TiMn alloy hydrides were studied. The lines in the characteristic X-ray diffraction pattern were much broader and weaker in the cycled alloys but the C14 hexagonal structure was maintained and no second phase was observed. The hydrogen capacity was reduced by 30% for TiMn binary alloy and by 20% for TiMn multicomponent alloys after about 10 000 cycles in contrast with the marked reduction observed for LaNi5. In some cases slight recovery could be produced by heating at 500 °C for 1 h in a vacuum after cycling. Gas chromatography measurements on hydrogen released from TiMn1.5 hydride showed that the hydrogen purity was better than 99.9999% (except for an H2O impurity) after a purge release of only a few per cent of hydrogen when the purity of the commercial grade hydrogen absorbed by the hydride was 99.99%. It can be concluded from the results of these measurements that hydrogen purification using TiMn alloy is related to two factors. The removal of N2, CO and CO2 proceeds by surface poisoning (i.e. oxidation, physisorption or chemisorption), whereas the removal of CH4, O2, H2O and Ar is controlled by surface poisoning and concentration. The hydrogen purification effect of TiMn alloy hydrides showed little degradation even after a large number of absorption-desorption cycles.

Microstructural origin of the skeletal ferrite morphology of austenitic stainless steel welds

Abstract: Scanning transmission electron microscopy (STEM) was conducted on welds exhibiting a variety of skeletal, or vermicular ferrite morphologies in addition to one lathy ferrite morphology. These ferrite morphologies result from primary ferrite solidification followed by a solid state transformation upon cooling. During cooling, a large fraction of the ferrite transforms to austenite leaving a variety of ferrite morphologies. Comparison of composition profiles and alloy partitioning showed both the skeletal and lathy ferrite structures result from a diffusion controlled solid state transformation. However, the overall measured composition profiles of the weld structure are a result of partitioning during both solidification and the subsequent solid state transformation.

Austenitic Steels at Low Temperatures

Abstract: The Properties of Austenitic Stainless Steel at Cryogenic Temperatures- Development of Cryogenic Structural Materials for Tokamak Reactor- Martensitic Transformations in Fe-Cr-Ni Stainless Steels- The Influence of Martensitic Transformation on Strength and Plasticity of Fe-Cr-Ni Alloy Single Crystals- Austenitic-Steel Elastic Constants- Temperature Dependence of Flow Strength of Selected Austenitic Stainless Steels- Cryogenic Properties of Austenitic Stainless Steels for Superconducting Magnet- Factors Influencing the Low-Temperature Dependence of Yielding in AISI 316 Stainless Steels- Toughness and Fatigue Properties of Austenitic Steels at Cryogenic Temperature and Their Application in Complex Structures- Automated Near-Threshold Fatigue Crack Growth Rate Testing of JBK-75 Stainless Steel at Cryogenic Temperatures- Effects of Magnetic Field on Tensile Behavior at 4 K of Alloys 304 and 310- Effects of Magnetic Fields on Martensite Transformations and Mechanical Properties of Steels at Low Temperatures- Effect of EB-Weld and Cold-Rolling on Low Temperature Strength and Toughness of Austenitic Stainless Steels- The Effect of c-Ferrite upon the Low Temperature Mechanical Properties of Centrifugally Cast Stainless Steels- The Mechanical Properties of Stainless Steel Castings at 4 K- Heat Treatments to Desensitize and Remove Delta Ferrite from a 21Cr-6Ni-9Mn Stainless Steel Intended for the Fabrication of Aerofoil Models for Cryogenic Wind Tunnels- Preliminary Study on Structural Material Selection for Large Superconducting Magnets- Low Temperature Mechanical and Physical Properties of Age-Hardened Fe-Ni-Cr-Mn Alloys- Automated Near-Threshold Fatigue Crack Growth Rate Testing of JBK-75 Stainless Steel at Cryogenic Temperatures- Low Temperature Properties of High-Manganese-Molybdenum Austenitic Iron Alloys- Structure and Mechanical Properties of High-Alloy Manganese-Aluminum Steels for Cryogenic Applications- Fracture Properties of a 25Mn Austenitic Steel and Its Welds at 4 K- The Weldability of 25 Mn Steel- Instrumented Charpy Impact Tests at Low Temperatures for Several Steels- Temperatures for Several Steels- GRI's Research Program on Crack Initiation and Arrest Properties of 9% Nickel Steels Used in LNG Storage Vessels- Indexes- List of Contributors- Alloy Index

Superalloy article repair method and alloy powder mixture

Abstract: A powder alloy mixture for use in a method of repairing high temperature superalloy articles includes a first, higher temperature alloy powder in the range of about 35-65 weight percent of the mixture. The first alloy powder is based on at least one element selected from Ni and Co and is characterized as having good strength and environmental resistance along with the substantial absence of melting point depressant elements selected from Si and B in amounts greater than about 1% Si and 0.5% B. The second alloy powder is of a lower melting temperature alloy of Ni--Cr--Si--B--Co and is characterized by the substantial absence of C.

Flash annealing of amorphous alloys

Abstract: A new method to improve the magnetic properties of amorphous alloys by fast annealing is introduced. The zero-magnetostrictive Fe 4.7 Co 70.3 Si 15 B 10 amorphous alloy was flash-annealed by the resistive heating of short (of the order of a second) electric current pulse flowing through the sample. The heating/cooling rate was of the order of 104-105K/min. This enables the sample to be annealed at much higher temperatures (estimated 800°C) without causing crystallization, compared to the conventional annealing methods. The maximum permeability of a zeromagnetostrictive alloy obtained by this method is higher than those obtained by the conventional annealing, with the additional benefit of smaller disaccomodation effect.

Formation and crystallization of Al-Fe-Si amorphous alloys

Abstract: Rapid solidification experiments of Al-based Al-Fe-Si ternary alloys have been performed both by the gun and single roller methods. Glass forming tendency is found to be largest near theβ-phase (Al9Fe2Si2) composition, where the amorphous state is obtained both by the gun and single roller methods. Crystallization behaviour of amorphous AlFe13.0Si17.4 alloy, nearβ-phase composition, followed the course of (i) the appearance of fineα-Al particles and (ii) the transformation of the matrix intoβ-phase. The ratio of crystallization temperature and the melting point,T x/T m, for AlFe13.0Si217.4 amorphous alloy is smaller than 0.5 indicating the difficulty of glass formation of these alloys.

Solid state SiC/Ni alloy reaction

Abstract: The solid state reaction between silicon carbide and a model superalloy consisting of 70 at. pct Ni, 20 at. pct Cr, and 10 at. pct Al was studied between 700 °C and 1150 °C for times ranging from “0” hours to 330 hours. Reaction couples consisting of SiC/Ni, SiC/Cr, and SiC/NiCr were also studied. The reactions were carried out in air with the materials, in the shape of discs, maintained in contact under a pressure of 7 MPa. A reaction was detected with SiC and the model alloy at all temperatures studied, and the reaction was diffusion controlled with an activation energy of 184 kJ/mole. In the ceramic the reaction was dominated by the diffusion of Ni into the ceramic forming a banded structure consisting of alternating layers of δ-Ni2Si and a two phase mixture of graphite and δ. On the metal side, the reaction was very dependent on the presence of alloying elements, with pure Ni reacting to the greatest extent, followed by the binary NiCr alloy, and finally by NiCrAl. The growth and presence of the phases detected in these reactions is consistent with phase equilibria concepts.

Wear-resistant stainless steel

Abstract: A high chromium stainless steel especially suited for use as wear (galling) resisting components, for example, valve parts. A typical alloy generally contains chromium, nickel, silicon, carbon, an effective cobalt content and the balance iron plus normal impurities. The alloy may be produced in the form of castings, P/M products, hardfacing and welding materials and wrought mill products.

Sweep through process for making polycrystalline compacts

Abstract: The high pressure/high temperature catalyst sweep through process for making diamond and cubic boron nitride compacts has been improved by adding an intermediate metal or metal alloy. The added metal (whether alone or contained in an alloy) has a melting point below that of the catalyst (e.g. cobalt), is miscible with the catalyst, and preferably sweeps through the mass of abrasive crystals first. This modification has reduced flaw formation in such compacts.

Fatigue of stainless steel in hydrogen

Abstract: The fatigue crack growth rates of two austenitic stainless steel alloys, AISI 301 and 302, were compared in air, argon, and hydrogen environments at atmospheric pressure and room temperature. Under the stresses at the crack tip the austenite in type 301 steel transformed martensitically to a’ to a greater extent than in type 302 steel. The steels were also tested in the cold worked condition under hydrogen or argon. Hydrogen was found to have a deleterious effect on both steels, but the effect was stronger in the unstable than in the stable alloy. Cold work decreased fatigue crack growth rates in argon and hydrogen, but the decrease was less marked in hydrogen than in argon. Metallographic, fractographic, and microhardness surveys in the vicinity of the fatigue crack were used to try to understand the reasons for the observed fatigue behavior.

Dispersion strengthened metal composites

Abstract: There is provided a substantially fully dense powdered metal composite comprising a highly conductive metal or metal alloy matrix having dispersed therein discrete microparticles of a refractory metal oxide and discrete macroparticles of a mechanical or physical property-conferring additive material. The respective components undergo minimal alloying or interdispersion because sintering is not utilized in forming the composite. These composites are characterized by high thermal or electrical conductivity and a desired property (controlled thermal expansion, high strength, wear and arc erosion resistance, or magnetic) attributable to the composite forming material, like refractory metal, alloy, or compound. The composites are useful in forming lead frames for integrated circuit chips, electric lamp lead wires, electrical contact members, and discrete component leads.