Structure and mechanical properties of alloys Ti-2.2% Al-2.2% V-2.2% Mo-2.5% Fe and Ti-2.2% Al-5% Fe equivalent to alloy VT16

Comparative studies of the structure and properties of alloys Ti-2.2% Al-5% Fe and Ti-2.2% Al-2.2% V-2.2% Mo-2.5% Fe in annealed, quenched, and aged conditions are performed. The strength level of the alloys corresponds to that of VT16. The possibility of replacing alloy VT16 by alloy Ti-2.2% Al-2.2% V-2.2% Mo-2.5% Fe is estimated. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 10–13, June, 2006.     

Effect of Compaction Pressure on Mechanical Properties of Powder Steel 0.06% C – 22% Cr – 13% Ni – 5% Mn – 2% Mo Obtained by Mechanical Alloying Followed by Annealing

Metal Science and Heat Treatment - The mechanical properties of a powder steel containing 0.06% C, 22% Cr, 13% Ni, 5% Mn and 2% Mo (UNS S20910) and manufactured by mechanical alloying with...     

Determination of the Parameters of Precipitates in Aged Mg – 8% Zn – 4% Al – 0.2% Cr – 0.5% Bi Alloy

Metal Science and Heat Treatment - The structure of precipitates in alloy Mg – 8% Zn – 4% Al – 0.2% Cr – 0.5% Bi aged at 70 and 160°C for up to 1200 h is studied by...     

Cyclic oxidation behavior of Ni3Al-7.8% Cr-1.3% Zr-0.8% Mo-0.025% B between 900 and 1100°C

A Ni₃Al-based alloy, the composition of which was Ni-16.0% Al-7.8% Cr-1.3% Zr-0.8% Mo-0.025%B, was cyclically oxidized in the temperature range of 900 to 1100°C in air for up to 500 hr. The alloy displayed good cyclic oxidation resistance up to 1000°C, with little scale spallation. It, however, lost cyclic oxidation resistance during oxidation at 1100°C after about 200 hr, displaying large weight losses due to serious scale spallation. NiO, α-Al₂O₃, NiAl₂O₄ and ZrO₂ were formed. The oxide scales consisted primarily of an outer Ni-rich layer which was prone to spallation, and (Al, Cr, Zr, Mo, Ni)-containing internal oxides which were adherent due mainly to the formation of (Al₂O₃, ZrO₂)-containing oxides that keyed the oxide scale to the matrix alloy.     

Effect of Scandium Content on the Structure and Properties of Alloy Al – 4.5% Zn – 4.5% Mg – 1% Cu – 0.12% Zr

Metal Science and Heat Treatment - The effect of scandium content on the structure and properties of alloy Al – 4.5% Zn – 4.5% Mg – 1% Cu – 0.12% Zr is determined. The...     

High-temperature oxidation of Fe-16.7% Mn-2.1% Ni-6.6% Si alloy in SO2

The oxidation of an austenitic Fe-16.7% Mn-2.1% Ni-6.6% Si (by weight) alloy in SO₂ in the temperature range 600–900°C is described. The corrosion products formed on this alloy in this environment below 800°C consist only of oxides, rather than a mixture of oxides and sulfides as is observed for unalloyed Fe or Mn. The kinetics of oxidation of the alloy in SO₂ in this temperature range are similar to those in O₂. It is proposed that these characteristics result from the presence of a thin silicate layer near the scale-metal interface that alters the gradient of oxygen potential within the scale.     

Choice of heat treatment mode for increasing the hardness of Cu-9% Al-6% Ni-5% Fe alloy

Several modes of heat treatment are tested with the aim of raising the hardness of Cu-9% Al-6%Ni-5%Fe aluminum bronze used for fabricating axial piston pumps of launching systems. A high hardness ensuring resistance to abrasion wear is one of the main requirements on the material.     

In situ ESTM and ESTS studies of the nanostructure and energetic properties of Fe-20% Cr-40% Ni and Fe-20% Cr-70% Ni alloy surfaces

Fe-20% Cr-40% Ni and Fe-20% Cr-70% Ni alloys are studied in air and in 0.01 N HCl and 0.1 N H₂SO₄ solutions at the controlled potentials of the specimen and needle using in situ techniques of electrochemical scanning tunneling microscopy (ESTM) and electrochemical scanning tunneling spectroscopy (ESTS). The changes in the potential of Fe-20% Cr-40% Ni alloy specimen fall in ranges of −0.3 to 1.1 V and 0–0.3 V (N.H.E.) in 0.01 N HCl and 0.1 N H₂SO₄, respectively, and the changes in the potential of Fe-20% Cr-70% Ni specimen, in ranges of 0.09–0.94 V and −0.1 to 0.5 V in 0.01 N HCl and 0.1 N H₂SO₄, respectively. Local spectral dependences of the tunnel current on the tunnel voltage are obtained and processed and the coefficients that characterize the local electrophysical properties of the surfaces are calculated on their basis. It is found that, in the studied acid solutions at the controlled potential, the surfaces are more energetically homogeneous than in air, where a substantially larger dispersion of the properties is observed. It is concluded that the energetic characteristics of separate surface sites of these alloys are determined on the atomic scale by the mutual effects of the neighboring atoms involved in its composition, i.e., by the matrix effect, which was discovered previously in the case of Kh18N10T stainless steel [1].     

The oxidation properties of U-16.6 at.% Nb-5.6 at.% Zr and U-21 at.% Nb

The fundamental oxidation characteristics of two U-base alloys, U-16.6 at.% Nb-5.6 at.% Zr and U-21at.% Nb, in the temperature range 500–1000° C in oxygen at 0.05 Torr are described. Both alloys undergo large dimensional changes during oxidation at temperatures above 650° C due to stresses generated in the oxide during oxidation. Oxidation rate curves for both alloys were determined at 100° C intervals between 500 and 1000° C; the activation energy for the process is shown to be small. The morphology of the oxide scale formed on the two alloys is complex and is described in detail. Stresses estimated at 10⁶ psi are shown to develop in oxidizing specimens, and a mechanism for the generation of these stresses is proposed.Research sponsored by the U.S. Atomic Energy Commission under contract with the Union Carbide Corporation.     

Effect of Heat Treatment on Microstructure and Mechanical Properties of Alloy Mg – 10% Gd – 3% Y – 0.6% Zr

Metal Science and Heat Treatment - The microstructure, mechanical properties and fracture behavior of magnesium alloy Mg – 10% Gd – 3% Y – 0.6% Zr is studied in cast condition and...     

Cube texture of recrystallization in three-layer ribbon substrates composed of nickel alloys Ni-4.8 at % W/Ni-11 at % Cr/Ni-4.8 at % W

The processes of the formation of recrystallization texture in the three-layer composite Ni-4.8 at % W/Ni-11 at % Cr/Ni-4.8 at % W ribbon, which was subjected to cold rolling with degrees of deformation of 98.4–99.3% and subsequent high-temperature annealing, are studied. The composite ribbon was found to be suitable for use as a substrate in manufacturing second-generation high-temperature ribbon superconductors. The estimation of magnetic properties showed that the specific magnetization of annealed composite ribbon at operating temperatures of high-temperature superconductors is lower than that of the Ni-5 at % W ribbon, which is currently widely used in practice.     

Evaluation of four high velocity thermal spray guns using WC-10% Co-4% Cr cermets

Four high velocity thermal spray guns were evaluated in the production of 10% Co-4% Cr tungsten carbide (WC) cermets. Three high velocity oxygen fuel guns (JP-5000, JP-5000ST, and Diamond Jet [DJ]-2700) and one plasma gun (Axial III) were used to spray the same angular, agglomerated, and crushed WC-10Co-4Cr powder. The DPV-2000 was used to monitor the in-flight velocity and temperature of the WC cermet-sprayed particles. From those values, spray conditions were selected to produce coatings that were evaluated in terms of porosity, hardness, and deposition efficiency. Results show that the plasma Axial III provides the highest particle temperature, between 2000 °C and 2600 °C, depending on the spray conditions. The JP-5000 imparts the highest velocity to the particles, between 550 and 700 m/s, depending on the spray conditions. The ST version of the JP-5000 provides the same velocity as the standard version but with lower particle temperature. The DJ-2700 sprays particles with temperature and velocity between those of the JP-5000 and the Axial III. Minimum porosity values of 2.1%, 3.7%, and 5.3%, respectively, were obtained for the JP-5000, the DJ-2700, and the Axial III guns. The porosity and carbide degradation are found to depend mostly on the particle velocity and temperature, respectively. The values for the Vickers microhardness number (200g) ranged from 950 to 1250. Measurements of the deposition efficiency indicated a variation between 10% and 80%, depending on the spray conditions and the gun used.     

Mechanical properties of injection molded Fe-6% Ni-0.4% C steels with varying Mo contents of 0.5 to 2%

In our previous studies, sintered and heat-treated alloy steels (Fe−6Ni−0.5Mo−0.4C (mass%)) produced by a MIM process showed excellent mechanical properties of 2000 MPa tensile strength and 5% elongation. This was attributed to the solid solution strengthening and the mezzo-heterogenous microstruture, which consisted of martensite or retained austenite (Ni and Mo rich phases) surrounded by a network of tempered martensite. This study has been performed to clarify the effect of Mo on the mezzo-heterogeneous microstructure and the mechanical properties of MIM processed and sintered alloy steels (Fe−6Ni−0.4C) with varying Mo content (0.5–2 mass%). The tensile properties of the heat-treated steels with added 2 mass% Mo were lower than those of the steels with added 0.5 mass% Mo. The reduction in the tensile properties, particularly the appearance of large pores formed at the original location of Mo power through the transient liquid phase formation and the low hardness of the matrix, was due to the low sintered density. By using mechanically milled fine Ni and Mo powders, the heat-treated steel (Fe−6Ni−2Mo−0.4C) showed excellent properties, including tensile strength of 1800 MPa and ductility of 2.2% elongation. This article is based on a presentation made in the symposium “The 3rd KIM-JIM Joint Symposium on Advanced Powder Materials”, held at Korea University, Seoul, Korea, October 26–27, 2001 under auspices of The Korean Institute of Metals and Materials and The Japan Institute of Metals.     

Effect of boron addition on the microstructure and mechanical properties of 6.5% V-5% W high speed steel

The effect of adding 0.04% additional boron to 6.5% V-5% W high speed steel was investigated. The microstructure characterization, phase identification, and carbide identification of the materials were performed using SEM/EDS and XRD. The cell size and carbide volume fraction were examined using image analysis software. The boron distribution was observed by PTA Boron Tracking. The addition of 0.04% more boron to a HSS alloy exerted a cell refining effect on the sample. The cell refinement of dendritic structures in the alloy containing boron may be attributed to the constitutional supercooling effect associated with the fairly small distribution coefficient for boron in iron. The addition of boron increases the bending strength of the material by more than 10%, as well as increasing its hardness.     

Effect of Adding Lanthanum to Al – 5% Ti – 1% B Master Alloy on the Efficiency of Grain Refinement in Aluminum and Al – 7% Si Alloy

Metal Science and Heat Treatment - An Al – 5% Ti – 1% B master alloy with a lanthanum addition is prepared by improved technology employing halides. The effect of adding lanthanum to...     

Effect of scandium on the structure and properties of alloy Al-5.5% Zn-2.0% Mg

Commercial weldable aluminum alloys additionally containing scandium have recently been developed in Russia: thermally nonhardening alloys based on the system Al-Mg (01570, 01523, 01515), and thermally hardening alloys based on the systems-Al-Zn-Mg (01970, 01975) and Al-Mg-Li (01421, 01423). Compared with other weldable aluminum alloys these materials exhibit improved operating properties. This is achieved as a result of a small addition of scandium which displays a high modifying effect and it promotes retention of an unrecrystallized structure for alloys. Results are presented in this article for a study of the effect of scandium content on the structure and properties of pressed strips and cold-rolled sheets of alloy Al-5.5% Zn-2.0% Mg.All-Union Institute of Light Alloys. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 25–29, July, 1994.     

Formation of metastable phases in a Ni-9.6 wt % Al-6.7 wt % Fe-1 wt % Cr intermetallic alloy

Structural changes and the formation of metastable phase states in an Ni₃Al-based intermetallic alloy after short-term 5-h annealing at a temperature of 1000°C and upon subsequent multiple deformation of the crystal by compression to 38% at room temperature have been analyzed using transmission electron microscopy and neutron diffraction.     

Influence of Minor Alloying Elements on the High Temperature Oxidation Behaviour of a 20 % Cr-25 % Ni-Nb steel

The influence of minor alloying additions of yttrium, silicon and manganese on the oxidation behaviour of a 20% Cr -25% Ni-Nb steel is considered for an environment of carbon dioxide at 800–1100°C. Emphasis is given to the fact that accurate assessments of the effects, based upon comparisons of the behaviour of different steels, frequently require variables such as metallurgical condition and surface finish to be controlled as closely as composition. In particular large grain size is associated with poor oxidation resistance. Yttrium at the level of 0.1–1.3% increases the adherence of the oxide scale over the whole temperature range considered, but only enhances oxidation resistance at 1000–1100°C. It also results in intergranular oxidation at the higher temperatures. Manganese at a concentration of 0.5–1.0% might exert an adverse influence during the early stages of oxidation but has no effect over the long term (i.e. 1000–6000 h). Silicon is considered beneficial at temperatures up to at least 850°C, with there being an optimum concentration in the region of 0.6–0.7%. By a process of deduction it is concluded that the oxidation resistance of the basis steel and its derivatives results primarily from the protection afforded by a thin layer of oxide at the oxide/metal interface. The outer scale affords little or no protection.     

Kinetics of Fe-30% Ni-12.5% Co invar alloy during high temperature oxidation

The oxidation behavior of Fe-30% Ni-12.5%Co Invar alloy possessing low thermal expansion-high strength has been studied by exposing it in temperature ranges of 1000–1200 in an air atmosphere. The formed oxide scale consisted of two layers, an outer layer and an inner layer, and the oxidation mechanism showed uniform growth for all oxidation conditions. The growth rate of the scale had a parabolic relationship with oxidation time, and the estimated activation energy for the growth of the whole oxide layer was approximately 19.84 kcal/mol. The outer scale consisted of five oxide layers, whose outermost scale consisted of major phase CoFe₂O₄ containing a particulate Fe₂O₃ phase. The oxide scale of Fe-30 Ni-12.5% Co had different compositions and phases from the Fe-30%Ni alloy investigated in previous studies. Especaally, when the alloy was exposed for a longer oxidation time and at a higher temperature, the volume fraction ratio of CoFe₂O₄ to Fe₂O₃ was found to increase     

Solidification behaviour of Al-7 %Si-Mg casting alloys

The effects of Mg content and cooling rate on the solidification behaviour of Al-7% Si-Mg(mass fraction)casting alloys have been investigated using differential scanning calorimetry, differential thermal analysis and microscopy. The Mg contents were selected as respectively 0.00%, 0.35% and 0. 70% (mass fraction). DTA curves of Al-7%Si-0.55%Mg(mass fraction) alloy at various cooling rates were accomplished and the alloy melt was cast in different cooling rates. The results indicate that increasing Mg content can lower the liquidus and binary Al-Si eutectic transformation temperatures. Large Fe-rich π-phases (AlsFeMg3Si6) are found in the 0.70% Mg alloys together with some small β-phases (Al5FeSi) ; in contrast, only β-phases are observed in the 0.35% Mg alloys. The test results of the Al-7%Si-0.55% Mg alloys identify that the liquidus and binary Al-Si eutectic transformation temperatures decrease, and the quantity of ternary Al-Si-Mg2 Si eutectic phase decreases as the cooling rate increases.