Microstructure and mechanical behavior of nanostructured composite Cu60Fe40 alloy

In this study, bulk nanostructured composite Cu₆₀Fe₄₀ alloy is prepared by a combustion synthesis technique. The prepared Cu₆₀Fe₄₀ alloy consists of Cu(Fe) solid solution and Fe(Cu) solid solution phases. The large-scaled compositional segregation in the Cu-rich and Fe-rich phases is not observed, respectively. A few micron-sized dendrite (Fe(Cu) solid solution) is embedded into the nanostructured matrix (Cu(Fe) solid solution). The grain size of the matrix is in the range 50–300?nm. The yield and fracture strength of the Cu₆₀Fe₄₀ alloy are 540 and 1050?MPa, respectively, and the fracture strain obtained from the compression test is about 20.9%. The Cu₆₀Fe₄₀ alloy displays notable work hardening in the compressive deformation.     

Formation of Cu precipitates and vacancy clusters in neutron-irradiated Fe–Cu alloys

Two Fe–Cu binary model alloys, Fe–0.3Cu and Fe–0.6Cu, were irradiated with fission neutrons at doses ranging from 4?×?10^?6 to 0.16 dpa (displacements per atom) at ～573 K to investigate the formation of Cu precipitates and microstructural evolution. The Cu content only affected the formation of Cu precipitates and microvoids at low doses. In Fe–0.3Cu, the formation of microvoids and Cu precipitates initiated at doses of 1.2?×?10^?4 and 4?×?10^?5 dpa, respectively. On the other hand, the formation of microvoids started at a dose of 4?×?10^?4 dpa in Fe–0.6Cu, and Cu precipitates were formed even after irradiation to 4?×?10^?6 dpa. On further irradiation, the difference in the formation of Cu precipitates and microvoids was small. Microvoids grew with increasing irradiation dose up to 3?×?10^?3 dpa in both alloys. Prominent aggregation of Cu atoms occurred upon irradiation from 3?×?10^?3 to 1.6?×?10^?2 dpa and the microvoids shrank. The Cu precipitates no longer grew, and microvoids nucleated and grew in the matrix above a dose of 1.6?×?10^?2 dpa in both alloys. The present studies clearly reveal the relationships between the formation and growth of Cu precipitates and microvoids with irradiation dose.     

Effect of Sb on coarsening of Fe particles in a Cu-Fe alloy

The influence of Sb on the coarsening behaviour of spherical α-Fe and γ-Fe particles in a Cu?Fe alloy has been investigated. The size of thparticles was determined by transmission electron microscopy and the Fe concentration in the Cu matrix by electric resistivity measurements. Adding Sb decreases the coarsening rate of the Fe particles, primarily via a reduction in the volume diffusivity of Fe in Cu. The pre-exponential factor and activation energy for volume diffusion are increased by the addition of Sb atoms in the matrix. The Sb addition changes the incoherent α-Fe?Cu interface energy by segregation of Sb at the incoherent interfaces but not the coherent γ-Fe?Cu interface energy.     

Local order description of an icosahedral Al–Cu–Fe quasicrystal

Abstract

A rapidly solidified Al₆₅Cu₂₀Fe₁₅ icosahedral alloy has been studied by extended X-ray absorption he structure above the Cu and Fe K absorption edges. The local order has been determined around Cu and Fe atoms and compared with results obtained previously in other icosahedral alloys     

Friction and wear behaviour of Inconel 718 alloy fabricated by selective laser melting after heat treatments

ABSTRACT

The effect of heat treatments (solution and double aging) on friction and wear behaviour of Inconel 718 (IN718) alloy fabricated by selective laser melting (SLM) were studied. After heat treatment of solution and double aging, the friction and wear of the alloy have been improved. The worn surfaces of heat-treated IN718 alloy became smoother, and micro-ploughing became shallower. After solid solution hearting, a portion of the Laves phase ((Ni, Fe, Co)₂(Nb, Ti, Mo)) dissolves into the matrix, after which the γ″ phase (Ni₃Nb) andthe equilibrium phase of the δ phase (Ni₃Nb) precipitates during double ageing. After solution and double aging, nano-scale γ′ (Ni₃(Al, Ti)) and γ″ phases distribute homogeneously in the matrix, which improves the material hardness and wear resistance of the SLMed IN718 alloy.     

Observation of phase separation in magnetron sputter-deposited Al–Cu thin films

The microstructures of Al–1.8 to 92.5?at.% Cu thin films prepared by radiofrequency (13.56?MHz) cathodic magnetron sputtering have been investigated by X-ray diffraction (XRD) and transmission electronic microscopy (TEM). A phase separation occurs in films of nominal Al–66.64?at.% Cu composition, consisting of a fcc Al solid solution phase, a fcc Cu solid solution phase and an unexpected sc Cu₃Al ordered phase with a Cu₃Au structure and a lattice parameter of about 0.36?nm.     

Effect of metastable Cr(Mo)s/Cr(Mo)a powders on mechanical alloying the immiscible Cu–Mo–Cr system

Metastable-state alloy powders are usually synthesised by milling and occur as products of mechanical alloying (MA), but they are rarely used as starting materials for other MA processes. In this work, metastable-state alloy powders, including supersaturated solid-solution Cr(Mo)s and amorphous Cr(Mo)a were prepared in advance. Then, the Cr(Mo)s/Cr(Mo)a powder mixture was mechanically alloyed with elemental Cu to form Cu–Mo–Cr alloy. The effects of the metastable-state powder Cr(Mo)s/Cr(Mo)a on MA of the immiscible Cu–Mo–Cr system were evaluated. Phases and microstructures of the milled powders were analysed by XRD and TEM, respectively. The results show that amorphous Cu-60wt.%Cr(Mo) and supersaturated solid-solution Cu-20wt.%Cr(Mo) alloy powders can be synthesised by MA. It is concluded that MA of the Cu–Mo–Cr ternary alloy system is significantly promoted when elemental Cu powder is milled with metastable-state alloy powder Cr(Mo)s/Cr(Mo)a. Furthermore, the promoting effect of amorphous Cr(Mo)a on MA the Cu–Mo–Cr alloy system is much greater than that of supersaturated solid-solution Cr(Mo)s, during the milling process.     

Surface tension measurement of undercooled liquid Ni-based multicomponent alloys

The surface tensions of liquid ternary Ni–5%Cu–5%Fe, quaternary Ni–5%Cu–5%Fe–5%Sn and quinary Ni–5%Cu–5%Fe–5%Sn–5%Ge alloys were determined as a function of temperature by the electromagnetic levitation oscillating drop method. The maximum undercoolings obtained in the experiments are 272 (0.15T _L), 349 (0.21T _L) and 363?K (0.22T _L), respectively. For all the three alloys, the surface tension decreases linearly with the rise of temperature. The surface tension values are 1.799, 1.546 and 1.357?N/m at their liquidus temperatures of 1719, 1644 and 1641?K. Their temperature coefficients are ?4.972?×?10^–4, ?5.057?×?10^?4 and ?5.385?×?10^?4?N/m/K. It is revealed that Sn and Ge are much more efficient than Cu and Fe in reducing the surface tension of Ni-based alloys. The addition of Sn can significantly enlarge the maximum undercooling at the same experimental condition. The viscosity of the three undercooled liquid alloys was also derived from the surface tension data.     

Influence of Cd and Ge on the kinetics of Guinier–Preston zone formation in Cu–Be alloys

The influence of Cd and Ge on the kinetics of Guinier–Preston zone formation has been studied for Cu–2?wt%?Be–0.3?wt%?Cd and Cu–2?wt% Be–0.3wt%?Ge solid solutions. The relative volume fractions of these Guinier–Preston (GP) zones are determined for different times of ageing at 473?K by a method based on microhardness measurements. Cd atoms in Cu–Be–Cd accelerate GP zone formation. This is due to the supersaturation of Cd atoms in Cu and their strong binding energy with vacancies. In contrast, the Ge atoms do not influence GP zone formation in Cu–Be–Ge. The binding energies between the two solute atoms and a vacancy, and the concentration of the quenched-in vacancies bound to the solute atoms, are calculated using the Hasiguti formula and the Kimura equation.     

Ni-based fully amorphous metallic coating with high corrosion resistance

A Ni₅₃Nb₂₀Ti₁₀Zr₈Co₆Cu₃ fully amorphous metallic coating has been deposited by means of kinetic metallization (KM) using gas atomized powders. As the thickness of the amorphous metallic coating is increased to 400?µm, it attains the excellent corrosion resistance of the amorphous alloy, as indicated by the extremely low passive current density and wide passive region in 1?kmol/m³ HCl aqueous solution. The corrosion rate is as low as 10^–3?mm/year in the extremely corrosive environment of 6?kmol/m³ HCl aqueous solution.     

Strain rate response of a Ni–Ti shape memory alloy after hydrogen charging

In this work, we investigate the susceptibility of Ni–Ti superelastic wires to the strain rates during tensile testing after hydrogen charging. Cathodic hydrogen charging is performed at a current density of 10?A/m² during 2–12?h in 0.9% NaCl solution and aged for 24?h at room temperature. Specimens underwent one cycle of loading-unloading reaching a stress value of 700 MPa. During loading, strain rates from 10^?6 to 5?×?10^?2?^?s^?1 have been achieved. After 8?h of hydrogen charging, an embrittlement has been detected in the tensile strain rate range of 10^?6 to 10^?4?s^?1. In contrast, no embrittlement has been detected for strain rates of 10^?3?s^?1 and higher. However, after 12?h of hydrogen charging and 24?h of annealing at room temperature, the embrittlement occurs in the beginning of the austenite-martensite transformation for all the studied strain rate values. These results show that for a range of critical amounts of diffused hydrogen, the embrittlement of the Ni–Ti superelastic alloy strongly depends on the strain rate during the tensile test. Moreover, it has been shown that this embrittlement occurs for low values of strain rates rather than the higher ones. This behaviour is attributed to the interaction between the diffused hydrogen and growth of the martensitic domain.     

Iron in solution with aluminum matrix after non-equilibrium processing: an atom probe tomography study

In this paper, we report on the influence of rapid solidification and severe plastic deformation on the solid solubility of Fe in Al. Atom probe tomography, for the first time, was performed on fine (3–4 μm diameter) and coarse (~100 μm) as-atomised Al-5 at.% Fe powder and cryomilled Al-5 at.% Fe powder. The atomised powders exhibited negligible Fe in solution with Al, whereas the cryomilled powder contained ~2 at.% Fe in solution. Moreover, our results suggest that severe plastic deformation is preferable to atomisation/rapid solidification for increasing the non-equilibrium solid solubility of Fe in Al.     

Tensile properties of precracked tempered martensitic steel specimens tested at ultralow strain rates in high-pressure hydrogen atmosphere

Tensile tests were performed on precracked Cr–Mo martensitic steel (C: 0.38, Si: 0.22, Mn: 0.84, P: 0.024, S: 0.021, Ni: 0.08, Cr: 1.11, Mo: 0.15, Cu: 0.12, Fe: bal. (wt%)) specimens at various strain rates (ranging from 6.5 × 10^?8 s^?1 to 1.0 × 10^?4 s^?1) in high-pressure (95 MPa) hydrogen and helium atmospheres. Irrespective of the strain rate, the tensile strength in the helium atmosphere was 1400 MPa. In the hydrogen atmosphere, the tensile strength decreased to less than 600 MPa at a strain rate of 2.0 × 10^?5 s^?1. However, the tensile strength increased to 900 MPa when the strain rate was decreased to 6.5 × 10^?8 s^?1. This recovery of the tensile strength was because of the decrease in the local stress in the vicinity of the precrack because of hydrogen.     

Rapid dendritic growth within an undercooled Ni–Cu–Fe–Sn–Ge quinary alloy

A liquid quinary alloy with composition Ni–5%Cu–5%Fe–5%Sn–5%Ge has been prepared from a containerless state by undercooling. Dendritic growth of α-Ni phase took place with a velocity of 28 m s^?1 at the maximum degree of undercooling, which was as high as 405 K (0.24T _L). All of the four solute elements Cu, Fe, Sn and Ge exhibited a significant solute trapping effect during the rapid dendrite growth. Segregation-less solidification is consequently realized when the degree of undercooling is sufficiently large. The lattice constant of α-Ni solid solution phase is found to increase with the amount of multicomponent solute trapping.     

Studies of interaction between He and elements with mass number 140 in Fe by time-differential perturbed-angular-correlation measurements

Room-temperature time-differential perturbed-angular-correlation (TDPAC) spectra of ¹⁴⁰Ce arising through ¹⁴⁰Ba-¹⁴⁰La from ¹⁴⁰Cs in He-doped Fe, unannealed and annealed in vacuum at various temperatures, were obtained in order to examine whether Ce (or rather, La and Ba) and He form complexes having a definite geometrical structure in Fe, as suggested by first-principles density-functional theory calculations. No clear signal of such complexes was observed in the TDPAC spectra. However, the TDPAC spectra indicate that Ce and He form complexes having a variety of geometrical structures. Comparison with reported TDPAC results on ¹¹¹Cd arising from ¹¹¹In in He-doped stainless steel shows that the parent atoms (La and Ba) of ¹⁴⁰Ce trap He atoms more efficiently than In atoms do, indicating stronger bonding of He to the former atoms, while different from the present case, ¹¹¹Cd (In)–He complexes form a unique geometrical structure.     

Composition and magnetic character of nanometre-size Cu precipitates in reactor pressure vessel steels: Implications for nuclear power plant lifetime extension

The sensitivity of positrons to nanometre-size Cu precipitates in Fe alloys has enabled us to apply a novel spin-polarized element-specific method to probe the composition and magnetic character of the precipitates responsible for reactor pressure vessel (RPV) steel embrittlement. The results clearly show that the precipitates are non-magnetic and place an upper limit of about 10at% on their Fe content. The practical implication of this result is that the Cu precipitate contribution to RPV steel embrittlement saturates is not expected to contribute further during lifetime extension. Our study demonstrates that polarized positrons can be used as a powerful probe of the magnetic character of nanoscale materials, even those embedded in a strongly magnetic host.     

Intermetallic compound identification and Kirkendall void formation in eutectic SnIn/Cu solder joint during solid-state aging

Microstructural investigations were performed on the interfacial reactions between eutectic SnIn solder and Cu substrate during reflowing at 433?K and solid-state aging at 373?K. Cu₂(In,Sn) was identified as the only intermetallic compound (IMC) at the interface, which consists of two sublayers with different morphology, a fine-grained sublayer at the Cu side and a coarse-grained sublayer at the solder side. During solid-state aging, voids were found between these two Cu₂(In,Sn) sublayers but not at the substrate interface, which is also attributed to the Kirkendall effect considering the different diffusion fluxes of Sn or In and Cu atoms in different sublayers.     

Illness representations predict adherence in adolescents and young adults with type 1 diabetes

Objective: Most adolescents and young adults (AYAs) with type 1 diabetes struggle with diabetes self-management and exhibit suboptimal glycemic control. This study examined two models of association between illness representations, a modifiable predictor of suboptimal outcomes, and adherence and glycemic control in AYAs with type 1 diabetes.

Design and main outcome measures: Ninety-nine AYAs (ages 15–20?years) completed measures of illness representations and adherence at two visits. Blood glucose monitoring frequency and haemoglobin A1c were obtained via chart review. Relationships were examined using structural equation modelling.

Results: Illness representations accounted for a significant proportion of the variance in blood glucose monitoring frequency (ΔR^2?=?.23, p?<?.01) and adherence to emergency precautions at Time 1 (ΔR^2?=?.07, p?=?.03). Illness representations also accounted for significant variance in blood glucose monitoring frequency (ΔR^2?=?.08, p?=?.01), adherence to recommendations for insulin and food (ΔR²?=?.08, p?=?.02) and exercise (ΔR^2?=?.10, p?<?.01), and adherence to emergency precautions (ΔR^2?=?.16, p?<?.01) at Time 2.

Conclusion: Illness representations are salient predictors of adherence in this population. Interventions targeting adherence promotion and glycemic control in AYAs with type 1 diabetes may be enhanced by efforts to modify illness representations.     

Interplay of diffusion and phase transformations in microstructural evolution of the interaction zone between U–9 wt.% Mo and Zr–1 wt.% Nb alloys

Metallurgical interaction between U–9?wt.% Mo metallic fuel alloy and Zr–1?wt.% Nb clad material has been assessed. Interdiffusion of constituent elements across their interface, together with the phase reactions occurring at high temperature and during subsequent cooling, resulted in development of a layered interaction zone where coexistence of a bcc solid solution phase with varying compositions, along with α-U, α-Zr and Mo₂Zr phases could be noticed.