Showing papers on "Alloy published in 1987"

The mechanism of silicon modification in aluminum-silicon alloys: Impurity induced twinning

Abstract: Modification of silicon by sodium in aluminum silicon eutectic alloy has been examined in detail by optical, SEM, and TEM methods. The aluminum phase is not significantly affected but the silicon becomes very heavily twinned. Modification by quenching does not involve an increase in twin density. Consideration of the atomic positions which attend the formation of growth twins on {111} planes suggests that adsorbed impurity atoms of suitable size, on the solid-liquid interface, could be responsible for changing the {111} stacking sequence, so promoting ‘impurity induced twinning’; the optimum hard sphere radius ratio would be ≈ 1.65. It is proposed that this condition could be the first and principal requirement for a modifying agent to be effective in this system. It is shown further, that other reputed modifiers do also induce a higher twin density. Variations in the efficiency of individual elements to promote such an effect are discussed in terms of other relevant factors which include melting points and vapor pressures, the free energies of formation of compounds — notably of oxides, and the forms of alloy phase diagrams.

The Electrical Resistivity of Metals and Alloys

Abstract: 1. Basic concepts 2. Atomic configuration of an alloy 3. The structure of magnetic materials 4. Electrons in simple metals and alloys 5. Electrical resistivity of simple metals and alloys 6. Non-simple, non-magnetic metals and alloys 7. Magnetic and nearly magnetic alloys 8. Other phenomena Appendices References Index.

Alloy Phase Diagrams

Abstract: With the presentation of a theory of liquid alloys, we have now assembled all the necessary tools for the ab initio construction of an alloy phase diagram.

Atlas of stress-strain curves

Abstract: Contains over 600 stress-strain curves for ferrous and nonferrous alloys. Curves show monotonic versus cyclic behaviour, effect of strain rate, alloying elements, product forms, deformation mode, grain size, work hardening, temperature, and much, much more. Information is provided on carbon, structural, alloy, HSLA, high-strength heat-resisting, maraging, tool, stainless steels, superalloys, cast irons, aluminum, beryllium, copper, magnesium, nickel, refractory alloys, titanium, zinc, zirconium, miscellaneous alloys, pure metals, and nonmetallic materials. Each curve is titled by standard industrial designations (AISA, CDA, AA, etc.) and thoroughly referenced to the original source to facilitate further research.

The magnetic and structural properties of R-Ti-Fe ternary compounds

Abstract: The magnetic and structural properties of RTiFe ternary alloy system were investigated. It was found that the alloy includes a new compound having the ratio of R to Ti to Fe of 1:1:10 and tetragonal structure. The SmTiFe 10 compound has a high saturation magnetization and magnetic anisotropy. It was also found that the same compound takes place in Sm-Ti-Co system.

Mechanisms of Pearlite Spheroidization

Abstract: A study of the mechanisms of pearlite spheroidization under static annealing conditions was carried out in two materials — AISI 1080 steel and pure Fe-C alloy. By electrolytically etching away the ferrite matrix, the morphology of the cementite phase was directly investigatedvia SEM and TEM techniques. It was clearly observed that the initiation and development of spheroidization are associated with morphological faults such as terminations, holes, and fissures in the cementite plates. During spheroidization the recession of terminations and the expansion of holes and fissures led to the break-up of large cementite plates into small segments. The migration of these faults is anisotropic. The preferred orientations, [010] and [210] directions in the (001) cementite plane, were determined by TEM analysis. This anisotropic morphological change is attributed to the anisotropy of the α/Fe3C interfacial energy. All the experimental evidence strongly supports the idea that the fault migration theory is the main mechanism governing spheroidization.

The effect of aluminum on the work hardening and wear resistance of hadfield manganese steel

Abstract: A study has been made of the work-hardening and wear resistance of aluminum-modified Hadfield manganese steels ranging in composition from 1.00 to 1.75 Pct carbon and from 0.0 to 4.0 Pct aluminum. Aluminum additions reduced carbon activity and diffusivity in austenites of Hadfield’s composition, increasing the metastable solubility of carbon in Hadfield steel. Aluminum additions inhibited mechanical twinning and, by inference, increased the stacking fault energy of austenite. Increasing carbon in solution in austenite expanded the temperature range over which dynamic strain aging and rapid work hardening occurred. Simultaneous aluminum additions and increased carbon content increased the work-hardening rate and high-stress abrasion resistance of Hadfield steel, but there was an optimum aluminum content beyond which both declined. Maximum work-hardening rate was exhibited by an alloy containing nominally 1.75 Pct C, 13.5 Pct Mn, and 1.3 Pct Al. Improved high-stress abrasion resistance was also found in an alloy containing nominally 1.00 Pct C, 13.5 Pct Mn, and 4.0 Pct Al.

The crystallography and morphology of the S'-phase precipitate in an Al(CuMg) alloy

Abstract: The aluminium alloy considered in this paper has a Cu/Mg ratio of 1·94 with 1·53 wt% Cu and 0·79 wt% Mg. It has been observed that on ageing at 190°C, S' precipitates form and grow as rods parallel to M cubic matrix directions with a slight tendency to cluster in groups on {110}M f.c.c. matrix planes. These groups of precipitates did not however coalesce to form laths on the {110}M or {210}M planes as has been reported in alloys with similar Cu/Mg ratios. The accepted orientation relationship has been confirmed and used to simulate a detailed and complete S'-phase diffraction pattern and morphological structure which agrees with electron microscope observations. It is suggested that lath formation is dependent upon the (Cu + Mg) concentration, which is low enough in this alloy to prevent it. Based on S'-phase lattice-parameter measurements, it is suggested that the S' precipitates are only a slightly strained version of the Al2CuMg-S phase and need not be distinguished from it.

Determination of the glass-forming concentration range in binary alloys from a semiempirical theory: Application to Zr-based alloys

Abstract: A semiempirical theory is presented to calculate free-energy diagrams of glass-forming alloys. The theory is based on the enthalpy of formation of the solid solution expressed as a sum of two contributions: (a) a chemical contribution due to electronic redistribution in forming the alloy, and (b) an elastic contribution arising from the difference in size between solute and solvent atoms. The enthalpy of formation of the amorphous phase has only the chemical contribution. The theory is used to successfully describe the glass-forming concentration range of some Zr-based alloys, which have been experimentally analyzed by several distinct techniques.

Adherent Al2O3 scales formed on undoped NiCrAl alloys

Abstract: Changes in the spalling behavior of Al2O3 scales formed on an undoped NiCrAl alloy are described. Two samples of Ni-15Cr-13Al (wt pct), one a control and the other sanded, were subjected to 25 oxidation cycles. It is observed that adherent scales formed on the sanded sample; however, the control sample had speckled, spalled scales. The data reveal that the adherent scales are caused by repeated removal of surface layers after each oxidation cycle. It is determined that interfacial segregation of sulfur influences spallation and sulfur removal increases bonding. The effect of moisture on scale adhesions is investigated.

Preparation of superconducting oxides and oxide-metal composites

Abstract: A method of preparing a superconducting oxide by combining the metallic elements of the oxide to form an alloy, followed by oxidation of the alloy to form the oxide. Superconducting oxide-metal composites are prepared in which a noble metal phase intimately mixed with the oxide phase results in improved mechanical properties. The superconducting oxides and oxide-metal composites are provided in a variety of useful forms.

Thermal conductivity of Inconel 718 and 304 stainless steel

Abstract: The results of thermal conductivity measurements on Inconel 718 and 304 stainless steel by the comparative and flash diffusivity techniques are reported for the temperature range 0–700°C For 304 stainless steel, excellent agreement with published data is found for the specific heat, thermal diffusivity, and thermal conductivity In the case of Inconel 718, the measurements show that the conductivity depends critically on the sample thermal history and the metallurgical condition of the alloy Measurements on a solution-treated sample indicated a conductivity function close to that reported previously, while precipitated samples showed a higher conductivity, similar to the conductivityvs-temperature function used for reduction of comparative thermal conductivity data with Inconel 718 references These results indicate that Inconel 718 is not a suitable reference for high-accuracy comparative thermal conductivity measurements unless its thermal history and associated conductivity function are known

High-energy heavy-ion irradiations of Fe85B15 amorphous alloy: evidence for electronic energy loss effect

Abstract: Amorphous metallic Fe85B15 alloy has been irradiated at low temperature with Ar, Kr and Xe ions of initial energies of 1.8, 2.7 and 3.0 GeV, respectively. Electrical resistance was measured in situ on samples piled up along the beam direction. It is shown that above a given electronic stopping power threshold the electronic losses play a crucial role in radiation-induced damage.

Tribological properties of Al alloy particle composites

Abstract: In recent years, a variety of particle dispersed aluminum alloy composites have been synthesized. The tribological properties of these materials include sliding wear, friction, seizure resistance and abrasive wear (of composites containing solid lubricant as well as hard ceramic particles). The potential high-performance applications of Al-alloy-graphite composites include pistons for internal combustion engines and bearings. For such applications, the low stress abrasive wear rates of composites, containing high volume fractions (0.20–0.35), are comparable to that of heat treated 1045 steel.

The hydriding properties of a mechanical alloy with composition Mg-25%Fe

Abstract: A method of mechanical alloying was used to produce an Mg-25%Fe composite hydrogen storage material. The presence of a pure metallic iron surface in contact with the magnesium leads to the promotion of the dissociative adsorption of hydrogen and the hydrogenation of Mg-25%Fe begins at the maximum rate even in the first cycle of hydriding. The activation of the mechanical alloy is completed by the third cycle of hydriding. The process of formation of Mg2FeHx is also studied.

Fracture toughness of two experimental high-strength bainitic low-alloy steels containing silicon

Abstract: The fracture toughness of two experimental silicon-containing steels in the bainitic condition has been measured and related to the microstructural state of the steels. The optimum bainitic microstructure for high strength and high toughness combinations consists of bainitic ferrite and thin interwoven laths of retained austenite instead of cementite, this condition being achieved through the silicon addition to the steels. The thin films of retained austenite are thermally and mechanically stable and act to reduce the effective fracture grain size and also possibly help to blunt propagating microcracks; blockier volumes of retained austenite are unstable and hence not beneficial to toughness. The two experimental steels achieved strength and toughness values equal to, or better than, some commercial steels in the martensitic condition.MST/528

The formation and thermal stability of amorphous Ni-Nb alloy powder synthesized by mechanical alloying

Abstract: NixNb1−x alloys were synthesized from pure crystalline Ni and Nb powder by mechanical alloying under a controlled atmosphere. The mechanically alloyed powders were amorphous in the range 0.20

Mechanical behavior of aluminum-lithium alloys at cryogenic temperatures

Abstract: The cryogenic mechanical properties of aluminum-lithium alloys are of interest because these alloys are attractive candidate materials for cryogenic tankage. Previous work indicates that the strength-toughness relationship for alloy 2090-T81 (Al-2.7Cu-2.2Li-0.12Zr by weight) improves significantly as temperature decreases. The subject of this investigation is the mechanism of this improvement. Deformation behavior was studied since the fracture morphology did not change with temperature. Tensile failures in 2090-T81 and -T4 occur at plastic instability. In contrast, in the binary aluminum-lithium alloy studied here they occur well before plastic instability. For all three materials, the strain hardening rate in the longitudinal direction increases as temperature decreases. This increase is associated with an improvement in tensile elongation at low temperatures. In alloy 2090-T4, these results correlate with a decrease in planar slip at low temperatures. The improved toughness at low temperatures is believed to be due to increased stable deformation prior to fracture.

Diamond-coated tungsten carbide-base sintered hard alloy material for insert of a cutting tool

Abstract: A diamond-coated tungsten carbide-base sintered hard alloy material for inserts of cutting tools, which has greatly improved bond strength or degree of bonding of the diamond coating layer to the matrix and therefore is capable of exhibiting excellent cutting performance over a long period of time. The sintered hard alloy material comprises: (1) a matrix of a sintered hard alloy consisting essentially of 1-4 percent by weight cobalt, and the balance of tungsten carbide and inevitable impurities, the tungsten carbide having a coarse grain structure having an average grain size of 2-10 microns; and (2) a diamond coating layer formed over surfaces of the matrix by forming an etching layer over the matrix surfaces and then forming the diamond coating layer over the matrix surfaces via the etching layer by a low pressure vapor-phase synthesization method. If required, the matrix may further contain CO1-CO8 (ISO) free carbon.