Annealing Of Alloy Research Articles

Structural evolution of Fe33Zr67 and Fe90Zr10 metallic glasses

We report on the structural evolution of melt-spun Fe33Zr67 and Fe90Zr10 glasses. These glasses are subjected to isothermal annealing over a wide temperature range, varying from the onset of crystallization up to near the melting point, for 20–300min. Over 733–1223K, the phase evolution sequence of the Fe33Zr67 glass follows: fcc FeZr2→fcc FeZr2+bct FeZr2→bct FeZr2. In contrast, annealing of the Fe90Zr10 glass over 903–1173K leads to a mixture of α-Fe, Fe3Zr and Fe2Zr phases. Some Fe2Zr crystals are not developed perfectly, showing a special twin lamellar structure. The annealing temperature and alloy composition dependence of grain size in the present Fe–Zr system is discussed.

Deformation morphology underneath the Vickers indent in a Zr-based bulk metallic glass

Hardness and plastic deformation during Vickers indentation in as-cast, annealed, and fully crystallized Zr 57Cu 27Al 11Ni 5 bulk metallic glass was examined. Subsurface deformation morphology under the indenter tip was studied at various loads and for different annealing time. Appreciable plastic deformation, through shear banding, occurs in the as-cast and annealed alloys. Two different types of shear bands are observed. Their occurrence depends upon the amount of annealing and hence on the extent of crystallization. The fully crystallized alloy exhibits extensive cracking. Trends in the deformation zone size with load are consistent with the expanding cavity model, while the shear band morphology, particularly for the as-cast sample, attests the qualitative applicability of the slip line field theory.

Deformation morphology underneath the Vickers indent in a Zr-based bulk metallic glass

Hardness and plastic deformation during Vickers indentation in as-cast, annealed, and fully crystallized Zr 57 Cu 27 Al 11 Ni 5 bulk metallic glass was examined. Subsurface deformation morphology under the indenter tip was studied at various loads and for different annealing time. Appreciable plastic deformation, through shear banding, occurs in the as-cast and annealed alloys. Two different types of shear bands are observed. Their occurrence depends upon the amount of annealing and hence on the extent of crystallization. The fully crystallized alloy exhibits extensive cracking. Trends in the deformation zone size with load are consistent with the expanding cavity model, while the shear band morphology, particularly for the as-cast sample, attests the qualitative applicability of the slip line field theory.

Experimental study of L1 2 phase precipitation in the Pb–0.08wt%Ca–2.0wt%Sn alloy by resistivity and SANS measurements

This work deals with the precipitation of the hardening phase during the ageing of a Pb–0.08wt%Ca–2.0wt%Sn alloy. The resistivity measurements revealed the presence of a single step for the precipitation mechanism. The precipitation kinetics were also followed by SANS technique: it appeared that annealing temperature and alloy tin content are preponderant factors.

Formation of a new F.C.C. τ2 phase in rapidly quenched Al55Cu35V10 alloy

AbstractX‐ray diffraction and transmission electron microscopy experiments were carried out to study the structure of rapidly solidified as‐cast and annealed Al55Cu35V10 alloy. The as‐cast Al55Cu35V10 alloy shows the presence of a new f.c.c. τ2 phase (a=0.58nm) along with a b.c.c. (a = 0.89 nm) phase which after subsequent annealing transforms into single f.c.c. phase (a = 0.58 nm). In this paper, it is also reported that these phases are crystalline approximants to an icosahedral phase on the basis of e/a (valence electron per atom) constant line. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Nonlinear composition dependence of x-ray photoelectron spectroscopy and Auger electron spectroscopy features in plasma-deposited zirconium silicate alloy thin films

The local bonding of Zr, Si, and O atoms in plasma-deposited, and post-deposition annealed Zr silicate pseudobinary alloys [(ZrO2)x(SiO2)1−x] was studied by x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Systematic decreases in XPS binding energies, and increases in AES kinetic energies with alloy composition x are consistent with an empirical chemical bonding model based on electronegativity equalization; however, there are significant departures from the predicted linear composition dependencies of that model. Deviations from linearity in the XPS compositional dependencies are correlated with dipolar network atom fields as determined from ab initio calculations. The nonlinearities in the x dependence of ZrMVV and OKVV AES spectral features are determined primarily by oxygen–atom coordination dependent shifts in valence band offset energies. The energy spread in the compositional dependence of binding energies (∼1.85 eV) for the XPS Zr 3d5/2 and Si 2p features combined with x-ray absorption spectroscopy data indicates that the conduction band offset energies between the Si substrate and Zr silicate dielectrics are alloy composition independent. Changes in O 1s XPS features in alloys with x∼0.3 to 0.6 as function of annealing temperature are consistent with a previously identified chemical phase separation that occurs after 60 s anneals at 900 °C in a nonoxidizing ambient, Ar.

Influence of Material Anisotropy and Friction on Ring Deformation

The influence of material anisotropy and friction on ring deformation has been examined in relation to the distribution of normal pressure and frictional shear stress, deformed ring shapes, and estimated errors in the coefficient of friction. Based on the flow rule associated with von Mises’ and Hill’s yield criteria, the analyses have been carried out with the finite element method (FEM) for three cases, namely, (1) an anisotropic ring oriented 90 deg to the axis of rotational symmetrical anisotropy under uniform coefficient of friction; (2) an isotropic ring under frictional anisotropy condition; and (3) an anisotropic ring oriented 0 deg to the axis of rotational symmetrical anisotropy under uniform coefficient of friction. In the first two cases, the results show that the influence of anisotropy on ring deformation is quite similar to that obtained by changing the frictional condition. Therefore, in the third case, if the anisotropic behavior is mistakenly attributed to friction, the possible estimated error for the coefficient of friction can be as high as 80 percent for a pronounced anisotropic material. Deformed ring shapes have been verified in experiments using the extruded annealed aluminum alloy AA6082 (Al-Si1Mg0.9Mn0.1).

Effect of Laser and Thermal Annealing on Optical and Structural Properties of Amorphous Metal Alloys

The results of ellipsometric measurements of rough and annealed amorphous alloys of 3d-transition metals (Fe, Ni, and Co) with metalloids are presented. Composition of alloys, directions of steady-state bonds between their compounds, and frequencies of the Auger electron transitions are determined by the methods of Auger spectroscopy and from the Raman spectra. Frequencies of metal-metalloid oscillations are determined and strains arising in nanoregions of the crystalline phase are obtained. Different characters of thermal and laser actions on the optical properties of alloys are established, and changes in the optical properties caused by these actions are compared.

On the System Silicon–Ytterbium: Constitution, Crystal Chemistry, and Physical Properties

Phase equilibria in the silicon-rich part of the system Si–Yb (>60 at.% Si) have been established from DTA, LOM, EMPA, and X-ray diffraction experiments on arc-melted and annealed bulk alloys as well as on single crystals grown from pure gallium or indium metal used as a flux solvent. Phase relations are characterized by the existence of a defect disilicide showing polymorphism. Yb3Si5, the low-temperature modification with Th3Pd5 type, is a line compound at 62.5 at.% Si, stable below 947±7°C. Above this temperature Yb3Si5 transforms into the YbSi2−x (defect AlB2-derivative type) corresponding to a peritectoid equilibrium at 947±7°C: YbSi2−x+YbSi⇔Yb3Si5. YbSi2−x exhibits a small homogeneity region from ∼62.5 at.% to ∼63.5 at.% Si and melts incongruently at 1408±9°C at ∼63 at.% Si. On cooling it decomposes according to a eutectoid reaction at 763±7°C: YbSi2−x⇔Yb3Si5+(Si). The silicon-rich part of the diagram is characterized by a eutectic equilibrium at 1135+7°C and ∼81 at.% Si: L⇔YbSi2−x+(Si). From magnetic susceptibility and electrical resistivity measurements, performed on single-crystalline specimens, Yb3Si5 was found to be an intermediate valent system.

Icosahedral quasicrystal in annealed ZnMgSc alloys

A new icosahedral quasicrystal has been found in Zn 85-x Mg x Sc 15 ( x = 3,4,5) alloys annealed at 922K for 5-100h. Electron diffraction and powder X-ray diffraction experiments indicate that this quasicrystal has a primitive icosahedral quasilattice (P type) and a six-dimensional lattice parameter a 6D =0.7115nm. The stoichiometric composition of the icosahedral quasicrystal was estimated to be close to Zn 80 Mg 5 Sc 15, since the icosahedral quasicrystal coexists in the x = 5 samples with small amounts of a MgZn 2 -type Laves phase and a Zn 17 Sc 3 -type cubic phase with lattice parameter a =1.3854nm. The latter is interpreted to be a 1/1-type approximant crystal of the icosahedral quasicrystal. The atomic cluster included in the Zn 17 Sc 3 -type cubic phase indicates a structural similarity between the Zn-Mg-Sc quasicrystal and the Cd-Yb (and Cd-Ca) icosahedral quasicrystals recently reported.

Structural and magnetic studies of CoCu granular alloy obtained by ion implantation of Co into a Cu matrix

CoCu granular alloys have been prepared at room temperature using ion implantation of Co + ions into Cu host at 160 keV. The Cu layer has been deposited on silicon substrate by DC sputtering at room temperature. The as-implanted and annealed CoCu alloys at different temperatures have been characterized by X-ray diffraction, Rutherford back scattering (RBS) for the structural properties, resistivity and magnetization measurements for the magneto-transport properties. Magnetization measurements show a classical superparamagnetic behavior as expected for granular alloy. The observation of the giant magnetoresistance (GMR) at 300°C annealing temperature indicates the beginning of Co phase decomposition. The decrease of the GMR at high annealing temperature is due to the atomic Co and Cu diffusion into Si substrate as supported by X-ray and RBS analysis.

Microstructure and mechanical properties of Inconel 625 superalloy

The service-exposed (∼60 000 h/873 K) Alloy 625 ammonia cracker tubes showed higher strength and lower ductility compared to the virgin material in the solution annealed state. Precipitation of intermetallic γ″ and Ni 2(Cr,Mo) phases and the inter and intragranular carbides were found to be responsible for higher strength of the service-exposed alloy. Subjecting the service-exposed alloy to thermal aging treatments subsequently at 923 K and 1123 K (above the service temperature of the exposed alloy) led to the dissolution of the intermetallic phases that in turn increased the ductility of the alloy. Post-service aging of the alloy at 923 K for short durations resulted in the dissolution of the Ni 2(Cr,Mo)-phase. The dissolution of the Ni 2(Cr,Mo)-phase exhibited significant influence upon yield strength (YS) but negligible effect on ductility. Prolonged aging of the alloy for 500 h at 923 K resulted in the precipitation of intermetallic δ-phase. Post-service aging of the alloy at 1123 K promoted the dissolution of both Ni 2(Cr,Mo) and γ″ formed during service. Longer duration aging at the same temperature led to the precipitation of the δ-phase with an associated increase in strength and loss in ductility. Re-solution annealing of the service-exposed alloy at 1423 K caused the dissolution of the strengthening phases. When the re-solution annealed alloy was subjected to prolonged exposure at 923 K, the yield stress was found to increase rapidly with aging time with attendent loss in ductility due to the precipitation of γ″.

Effects of AB 5-type hydrogen storage alloy prepared by different techniques on the properties of MH/Ni batteries

The effects of hydrogen storage alloy prepared by different preparation techniques with composition Mm(NiCoMnAl) 5 on the properties of MH/Ni batteries have been investigated. Compared with as-cast alloy, as-quenched and as-quenched+annealed alloy could produce advantages to the battery in high rate dischargeability, internal pressure, cycle lifetime and internal resistance at beginning of cycles. Unfortunately, the rapidly quenched alloy slowed down the initial activation rate of the battery voltage, but after annealing, the rate would improve slightly. The influence of the alloy from different preparation techniques on the capacity and voltage of batteries is slight. The annealing would mainly improve the high rate dischargeability and depress the internal pressure contrasted with the as-quenched alloy. The differences can be ascribed to the change of phase and microstructure caused by different preparation techniques.

Effects of B addition on giant magnetoresistance in Co-Cu granularribbons

Effects of B addition on the structure and magnetoresistance ofas-quenched and annealed Co-Cu granular alloys have been studied. Theformation of the Co2B phase reduces the number of small magneticparticles, which are the centres for spin-dependent scattering. Themagnetoresistance of Co-Cu-B granular ribbons decreases with increasingB content.

Effects of annealing treatment on phase structures, hydrogen absorption–desorption characteristics and electrochemical properties of a V 3TiNi 0.56Hf 0.24Mn 0.15Cr 0.1 alloy

The effects of annealing treatment on the phase structures, hydrogen absorption–desorption characteristics and electrochemical properties of the V 3TiNi 0.56Hf 0.24Mn 0.15Cr 0.1 alloy have been studied. It is found that both the as-cast and annealed alloys consist of a main phase with b.c.c. structure and a C14-type secondary phase with hexagonal structure. With increasing annealing temperature, the lattice parameters of two phases decrease and the volume fraction of the main phase increases slightly. The present results indicate that annealing treatment decreases the maximum hydrogen desorption capacity, which could be attributed to a decrease in stability of alloy hydride due to the decrease in cell volume of the alloy phases. Furthermore, increasing annealing temperature decreases the high rate capability and deteriorates the durability of the alloy electrode in the alkaline electrolyte during charging–discharging cycles, which would be associated with the change in composition of the secondary phase and the grain growth of the main phase.

Annealing dependence of giant magnetoresistance in CuFeNi alloys

Giant magnetoresistance (GMR) in granular CuFeNi alloys is comparable in magnitude to that observed in CuCo. Here we study magnetization M and GMR (0<H<70 kOe; 4.2 K<T<300 K) in metal-spun and annealed Cu80Fe20−xNix (x=0, 2.5, 5, 10, and 15) as a function of annealing temperature Tan<500 °C, using a superconducting quantum interference device (SQUID) magnetometer. A wide variety of granular structures characterized by different average values of the particle sizes is obtained for different Fe/Ni ratios and annealing conditions. For Cu80Fe10Ni10, neither M nor GMR exhibit static hysteresis for T>50 K. At this temperature, the largest GMR value (19%) was obtained for a sample annealed at 400 °C for 2 h. In Cu80Fe5Ni15, on the other hand, the microstructure and magnetic properties of the alloy are much more sensitive to annealing. The magnetoresistence is strongly dependent upon both the annealing and the measuring temperatures. For Fe-rich Cu80Fe20−xNix, the magnetic properties other alloys show a weak dependence upon annealing temperature. Magnetization curves for both as-cast and annealed alloys indicate many large particles which saturate at low magnetic fields. GMR versus alloy composition is presented for two annealing temperatures.

Structural Characterization of Y2Pd14B5

Y2Pd14B5 is the major phase in as-cast and annealed multiphase alloys with nominal compositions near YPd5B3C0.3. Its crystal structure determined the first time here by single crystal X-ray diffraction is body-centered tetragonal (space group I41/amd). Transmission electron microscopy (TEM) reveals that in as-cast specimens the tetragonal phase has a modulated structure and is oriented intergrown with a face-centered cubic phase of similar composition, namely YPd7B2. According to Rietveld analyses of the multiphase system the structure of this phase can be well-described by space group Fm m. Annealing the sample for 150 hrs at 973 K results in a coarsening and enrichment of the tetragonal phase as well as a disappearance of the modulations allowing a detailed structure analysis by single crystal diffractometry.

The Magnetic Properties and the Barkhausen Noise of the Hydrogenated Fe-V-B Amorphous Alloy

As a consequence of the annealing process, the study of structural changes which can be followed by measuring structure sensitive magnetic properties as the stress induced anisotropy, the coercive force, the demagnetizing factor, and the Barkhausen noise parameters of the as-cast and annealed Fe80V5Β15 amorphous alloys was performed. The structural changes were connected with the temperature range where the Fe 80 V5 Β15 amorphous alloy was characterized by the soft magnetic properties. PACS numbers: 61.43.Dq, 75.50.Kj, 75.60.Ej

The Magnetic Properties and the Barkhausen Noise of the Annealed Fe-V-B Amorphous Alloy

As a consequence of the annealing process, the study of structural changes which can be followed by measuring structure sensitive magnetic properties as the stress induced anisotropy, the coercive force, the demagnetizing factor, and the Barkhausen noise parameters of the as-cast and annealed Fe80V5Β15 amorphous alloys was performed. The structural changes were connected with the temperature range where the Fe 80 V5 Β15 amorphous alloy was characterized by the soft magnetic properties. PACS numbers: 61.43.Dq, 75.50.Kj, 75.60.Ej

The effect of annealing on the discharge characteristics of ZrV0.7Mn0.5Ni1.2 alloy

Abstract In order to improve the discharge performance of the ZrV 0.7 Mn 0.5 Ni 1.2 alloy electrode, the alloy was annealed at 1000°C for 12 h. It is shown that total hydrogen storage capacity is unchanged, but the plateau pressure is increased in the lower hydrogen concentration range of the P–C–T curve after annealing. The annealed alloy has a higher rate capability and higher discharge capacity than the as-cast one. In order to analyze the above phenomena, the reaction surface area and surface reaction kinetics were examined by BET and EIS analyses, respectively. The measurement of the fully activated electrode surface area by BET analysis shows that there is little difference between as-cast and annealed alloy. The higher rate capability is due to the decrease of charge transfer resistance for the hydrogenation reaction in KOH electrolyte after annealing. It is well known that the Ni component plays a role in improving the electrocatalytic activity of the alloy electrode. The microstructures of the as-cast and annealed alloys were investigated by SEM and EDS analyses. The second phase (Zr–Ni phase) is widely distributed in the as-cast alloy, but this second phase disappears after annealing, resulting in homogenizing of the alloy and increasing Ni content in the matrix. The annealed alloy has a higher exchange current density than any single phase of the as-cast alloy. Consequently, it is concluded that the improved rate capability of the annealed alloy is due to increased Ni content in the matrix resulting from the disappearance of the secondary phase.