Cr Alloy Research Articles

A novel class of ATF fuels with large grain size, enhanced thermophysical properties and oxidation resistance

Two strategies have been extensively employed to develop advanced accident tolerant fuels (ATF): improving thermal conductivity and producing large grain sized pellets. However, there are few reports on the simultaneous utilization of both strategies. In this work, we fabricated Mo–Cr alloy reinforced UO2 (UMC) composite pellet with both high thermal conductivity and large grain size by a simple in-situ alloying method for the first time. The average grain size of UO2 increased from 6 μm to 113 μm. Thermal conductivity of the UMC pellet (with 2 vol% Mo) at 1200 °C increased by 36.46% compared with pure UO2. The increase rate of thermal conductivity per 1 vol% dopant reached about 18%. The Mo–Cr alloy formed continuous micro-cell layer around UO2 particles. Such continuous micro-cell Mo–Cr alloy layer and increase of UO2 grain size both helped improve the thermal conductivity of UMC composite pellets. Thermal expansion coefficient of the UMC under the operating temperature decreased by 11.90% compared with pure UO2. The oxidation resistance of the UMC pellet under high temperature steam was also improved. This work provides a new strategy towards fabricating ATF with both high thermal conductivity and large grain size.

Effect of Radiation Dose on the Deformation Behavior of the Single-Crystal Fe–10Ni–20Cr Alloy

Effect of Radiation Dose on the Deformation Behavior of the Single-Crystal Fe–10Ni–20Cr Alloy

Heterogeneous Catalyst Coating for Boosting the Activity and Chromium Tolerance of Cathodes for Solid Oxide Fuel Cells

AbstractA challenge hindering the development of durable solid oxide fuel cells (SOFCs) is the significant performance degradation of cathodes owing to poisoning by volatile Cr originating from the Fe─Cr alloy interconnect. Herein, a heterogeneous catalyst coating, composed of Ba1−xCe0.8Gd0.2O3–δ and BaCO3, remarkably improves the oxygen adsorption, dissociation capability, and Cr resistance of a La0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF) cathode is demonstrated. The coherent heterointerface interactions formed between the catalyst coating and LSCF result in varied levels of surface strain and electrostatic interactions, significantly suppressing Sr surface segregation on LSCF. A single cell with the catalyst coating‐decorated LSCF (CC‐LSCF) achieves a peak power density of 1.73 W cm−2 at 750 °C, with no noticeable performance degradation for 100 h. The CC‐LSCF cathode also exhibits outstanding durability under accelerated Cr poisoning conditions, compared with the tremendous degradation rate of 0.42% h−1 for the bare LSCF cathode. The enhanced Cr resistance is attributed to synergy induced by the stabilization of the lattice Sr cations by heterointerface interactions and the remarkable structural stability of the catalyst coating under Cr poisoning conditions. The novel heterointerface engineering strategy in this study provides insight into the design and development of active and Cr‐tolerant cathodes.

Effects of different Cr contents on microstructure, mechanical and electrical properties of Cu-Zr-Cr alloy

Cu-0.3Zr-0.05Cr and Cu-0.3Zr-0.15Cr alloys were prepared by vacuum melting method, and solution treatment was carried out at 900 °C. In order to explore the best heat treatment process, the alloy was aged with different parameters. Through performance test and microstructure analysis, the following conclusions were drawn. After hot forging, 60% cold rolling, and 450 °C 120 min aging treatment, Cu-0.3Zr-0.15Cr alloy exhibited favorable performance with 180 HV hardness, 467 MPa tensile strength, 84.4% IACS electrical conductivity, and 12.1% elongation. The Cu-0.3Zr-Cr alloys showed a considerable increase in texture content and maximum texture strength as the Cr concentration rose. The primary mechanism for strengthening alloys is precipitation strengthening. During the aging treatment, Cr and Cu5Zr phases are precipitated in the alloy. The Cr phase formed a semi-coherent interface with the Cu matrix, which allowed the alloy to retain its good flexibility. The dispersed precipitates greatly increased the strength and electrical conductivity of the alloy, resulting in outstanding overall performance.

A review on machining Ti–5Al–5V–5Mo–3Cr alloy using defined geometry tools

A review on machining Ti–5Al–5V–5Mo–3Cr alloy using defined geometry tools

Mechanically Durable and Fluorine‐Free Ni–Cr Alloy‐Based Highly Hard Superhydrophobic Coating on Al Alloy

Superhydrophobic coatings, known for their water‐repelling properties, play an important role in corrosion resistance and self‐cleaning applications. This study addresses the pressing need for eco‐friendly and durable fabrication methods for metal surfaces, particularly Al alloys, recognized for their inherent low mechanical properties. The innovative electroplating technique successfully fabricates superhydrophobic coatings on Al alloy surfaces, incorporating a high‐hardness Ni–Cr alloys layer and a low‐surface‐energy stearic acid layer. The resulting coatings exhibit outstanding mechanical durability, corrosion resistance, and self‐cleaning capabilities. With a water contact angle of 165° and a corrosion protection efficiency of 98.6%, these coatings offer a substantial improvement over traditional methods. Moreover, the Leeb hardness of the coated alloy experiences an impressive 83% increase compared to pristine Al alloy. This universally applicable approach opens avenues for developing mechanically robust superhydrophobic coatings on various metallic substrates, with broad implications for engineering applications.

Enhanced high-temperature mechanical properties of the Cu–1.16Ni–0.36Cr alloy owing to interactions between metastable precipitates and dislocations

Herein, an alloy Cu–1.16Ni–0.36Cr with outstanding high-temperature mechanical properties was obtained, and the underlying mechanism was discussed. The properties were compared with those of commercial Cu–Fe–P alloys. The alloy exhibited a high-temperature softening temperature of 674.7 °C. Tensile tests conducted at high temperatures revealed that at 700 °C, the alloy maintained a tensile strength of 131.3 MPa, whereas Cu–Fe–P alloys only exhibited a tensile strength of 58.7 MPa. Microstructural analysis revealed the formation of nanoscale Ni3Cr7 precipitates near fractures at high temperatures, with the average size being approximately 10 nm. These nanoscale precipitates hindered the coarsening of Cr particles and dislocation slips, forming dislocation rings and substantially enhancing the high-temperature mechanical properties of the alloy. Furthermore, the nanoscale precipitates considerably impeded the growth and expansion of recrystallized grains. After a high-temperature treatment at 700 °C, a portion of the microstructure in the alloy remained stretched, with the small-angle grain boundaries being high (68.2%) and the recrystallization degree being only 50.4%.

Co-evolution of point defects and Cr-rich nano-phase in binary Fe-20 at.% Cr alloy: A comprehensive investigation using positron annihilation spectroscopy and atom probe tomography

The role of point defects in temporal evolution of Cr-rich α′-phase separation in Fe-20 at.% Cr alloy is elucidated by intercepting the long term (upto 1000 h at 773 K) aging at regular intervals and probing by a combination of atom probe tomography (APT) and positron annihilation spectroscopy (PAS). Since the Cr concentration of nano-scale α′-phase in Fe-20 at.% Cr alloy increases continually on aging, the point defects play active role throughout the aging duration. The near-atomic resolution of APT and self-seeking ability of positrons towards point defects make this analysis possible. The difference of positron affinities between Fe and Cr enables identification of the Cr-rich nano-phases that are specifically associated with defects; they would otherwise be indiscernible in the absence of defect. Thus, the temporal evolution of Cr-rich nano-phase along with the associated point defects can be fully characterized at each stage of aging using APT and PAS, respectively. The combined APT-PAS study shows that Cr-rich α′-precipitation is preceded by vacancy-Cr complex that act as nucleation site for Cr-clusters, which in turn, cause an early rise in micro-hardness due to cluster hardening. Interestingly, this is accompanied by redistribution of the quenched-in vacancies and their trapping in Cr-clusters. Our results depict that the vacancies present in the core of the α′-precipitates migrate towards the precipitates’ interface during the course of aging and eventually get recovered resulting in virtually defect-free precipitates. This study chronicles the way the point defects shape the process of α′-phase separation throughout the entire length of aging.

Effect of Cr Segregation on Mechanical Behavior and Deformation Mechanism of Ni─Co─Cr Alloy

AbstractNi─Co alloys have attracted extensive attention from materials researchers in recent years because of their excellent properties. The effect of solute segregation on the properties of the alloy is studied by molecular dynamics simulation. The results show that the yield strength increases from 2.8 to 3.5 GPa when the solute atom Cr is introduced into the grain boundary. Under the action of stress, the disorder of segregation grain boundary is enhanced, which hinders the growth of grain, produces less layer fault structure, and the peak number of HCP (Hexagonal Close Packed) atom decreases from 50 000 to 37 000. The introduction of solute atoms provides a strong support for the grain boundary and has a similar skeleton structure, which improves the deformation resistance of the lattice. In addition, the improved grain boundary stability leads to the difficulty of nucleation of the dislocation, because the obstruction of the grain boundary makes it difficult to activate the dislocation source in the adjacent grain, and the maximum reduction of the perfect dislocation is 74%. In general, the microscopic mechanism of solute segregation strengthening is discussed from dislocation, phase structure, and energy, which provides guidance for plastic deformation of solid‐solution alloys.

Effect of Cr addition on the microstructure evolution, precipitation behavior and properties of Cu–Ag alloy

This investigation systematically explores the impact of minor Cr additions on the microstructural evolution, precipitation kinetics, mechanical properties, and electrical properties of Cu–Ag alloys, with a specific focus on Cu–6 %Ag-(0.4 %Cr). The alloys underwent casting through a vacuum induction furnace, followed by meticulous treatments involving solution heat and aging at varied temperatures and durations. Results indicate a significant improvement in the mechanical properties of Cu–Ag alloy upon Cr addition, with only a slight reduction in electrical conductivity. As per differential scanning calorimetry (DSC) measurements, the activation energy for continuous precipitation in the Cu–Ag–Cr ternary alloy is slightly higher than that in Cu–Ag. However, Cu–Ag–Cr lacks peaks corresponding to the discontinuous phase. Microstructural analysis unveils that Cr incorporation suppresses the discontinuous precipitation of Ag, fostering continuous precipitation during aging. Moreover, both micro-sized and nano-sized Cr particles were detected in the Cu–Ag–Cr alloy, contributing to the formation of finely spaced continuous Ag precipitates and fine Cr precipitates. This intricate microstructure imparts higher hardness and strength to the alloy compared to Cu–Ag. Specifically, following aging treatment at 450 °C for 2 h, the Cu–6 %Ag-0.4 %Cr alloy exhibited a remarkable increase of 76.1 % in hardness, 43.6 % in strength, and a moderate decrease of 15.8 % in conductivity.

Microstructure and properties of Mn–Si–Cr alloy steel modified by quenching and partitioning

Abstract This study investigates the influence of modification on the microstructure and properties of Mn–Si–Cr alloy steel. The results indicate that the as-cast microstructure of Mn–Si–Cr alloy steel is composed of black acicular bainitic ferrite lath and white retained austenite. The microstructure of the alloy steel changes to martensite, austenite, and carbide after quenching and partitioning treatment. After rare-earth magnesium modification and compound modification, the as-cast microstructure of Mn–Si–Cr steel becomes more refined and displays a more regular arrangement. Furthermore, the martensite and austenite grains in the modified samples show refinement, and the arrangement of martensite is more systematic. Additionally, the amount of austenite decreases, and the amount of carbides increases after quenching and partitioning heat treatment. In comparison with the unmodified samples, the modified samples show negligible changes in hardness. However, the impact toughness of modified quenched and partitioned steel increases by 20 %. Moreover, the wear resistance of compound modified quenched and partitioned steel is 38 % higher than that of the unmodified sample. The compound modified sample steel exhibits excellent wear resistance and comprehensive mechanical properties.

Effect of Cr content on the microstructure and mechanical properties of Ti–Cr alloys manufactured by laser directed energy deposition

Titanium (Ti) and titanium alloys have been increasingly used in fixed and removable prostheses and aerospace bearing materials because of its excellent biocompatibility, corrosion resistance and mechanical properties. Cr element is often added to titanium alloys as a solid solution strengthening element. However, the content of Cr was restricted in the commercial titanium alloy to avoid β-flecks and deterioration of mechanical performance because of the strong segregation of Cr. A series of homogeneous Ti-xCr (x = 6, 8.5, 10, 13.4, 15 wt%) binary alloys near the eutectoid point were manufactured by laser directed energy deposition. The phase composition and morphology, mechanical properties and deformation mechanism were investigated. It was demonstrated that the eutectoid reaction of additive manufacturing Ti–Cr alloy has been suppressed. Hypoeutectoid Ti-xCr alloys (x = 6, 8.5, 10 wt%) obtained microstructures consisting of α and β phase. The Ti-xCr alloy with eutectoid compositions (x = 13.4 wt%) obtained a microstructure mainly composed of ω and β phase. And hypereutectoid Ti-xCr alloy (x = 15 wt%) exhibited a fully β microstructure. For α+β type Ti–Cr alloys, and the average width of α lath decreased from 868 nm to 157 nm with Cr content increased from 6 wt% to 10 wt%. Correspondingly, the α+β type Ti–10Cr alloy presented a good combination of strength (an ultimate tensile strength of 1042 MPa) and ductility (an elongation of 7.1 %). Then, a high density of ω phase was found in the Ti-13.4Cr alloy with eutectoid compositions, which leads to its brittleness. Due to the solid solution of high concentration of Cr, β-type Ti–15Cr alloy obtained a high ultimate tensile strength of 941 MPa. Furthermore, stress-induced ω phase and {112}<111> twinning formed during the deformation, which helps to accommodate stress concentration, thereby the β-type Ti–15Cr alloy can maintain high ductility (20.3 %).

Evaluation of hydrogen embrittlement in ODS-Cu, Cu–Cr–Zr, and Cu–Cr alloys using slow strain rate technique test

Precipitation-hardened Cu–Cr–Zr alloy is proposed as a heat sink material for various components of the ITER owing to its high strength, high conductivity, and superior resistance against neutron irradiation. Oxide-dispersion-strengthened copper (ODS-Cu) was selected as the candidate material. Hydrogen embrittlement of Cu–Cr–Zr, Cu–Cr, and ODS-Cu (GlidCop® CuAl60) alloys was evaluated using the slow strain rate technique (SSRT) in 0.1 M sodium sulfate (Na2SO4) solutions under cathodic hydrogen charging or after D2 gas exposure. Thermal desorption spectroscopy (TDS) measurements were performed to estimate the differences in the hydrogen-trapping sites using hydrogen charging methods. According to the TDS results, the quantity of hydrogen retained in ODS-Cu exceeded that in the other alloys by an order of magnitude because of hydrogen trapping at the grain boundaries and the particle/matrix interface. Cu–Cr–Zr alloys tend to trap more hydrogen than Cu–Cr alloys because of the addition of Zr. As a result of the SSRT, no hydrogen embrittlement was observed in any alloy, regardless of the hydrogen charging method. All alloys exhibited excellent hydrogen embrittlement resistance under the conditions adopted in this study.

Epitaxial growth of magnetron sputtered NiAl on Ge mediated by native GeOx

In this work, the growth of a magnetron sputtered NiAl film on Ge was investigated. Two growth parameters were varied: the deposition temperature and the presence of native GeOx. An epitaxial layer was obtained at a deposition temperature of 400 ∘C and without removal of the native GeOx prior to deposition. At this growth condition, Ni and Al diffused into the Ge forming an epitaxial germanide. This germanide is most likely the τ 3 phase of the Ni–Al–Ge ternary system. The growth of the τ 3 phase is enabled by the GeOx acting as a diffusion barrier for Al. The native GeOx was found to be amorphous and to contain holes through which the NiAl can directly contact the τ 3 germanide and grow epitaxially. These holes are likely formed by thermal degradation when the substrate is heated for deposition. The electrical resistivity for epitaxial NiAl was found to be 13 .cm at a thickness of 30 nm which was the lowest value of the tested conditions. Epitaxial NiAl can be used as a seed layer to grow other layers epitaxially in a CMOS-compatible process, e.g. Fe(Co), Cr, MgO, and Heusler alloys.

Zn–Cr pulse coatings for corrosion protection

ABSTRACT The influence of the Zn–Cr electrodeposition bath composition, cathode current density under direct current conditions, and the average pulse current density and the current density under pulse plating current conditions on the content of chromium in the obtained Zn–Cr coatings, the current efficiency and their corrosion properties were investigated. The obtained Zn–Cr coatings contained from about 0.01 wt-% to about 10 wt-%. The corrosion resistance largely depended on the chromium content of the coating, but also on the morphology and surface development. The best corrosion resistance was achieved for Zn–Cr alloy coatings obtained under impulse current conditions for average current densities 3 and 4 A dm−2, while cathodic peak current densities were 30 and 40 A dm−2.

Quick and Green Procedure for the Quantification of Chromium in an Anionic Surfactant System

This study aims to establish a facile, user-friendly, accurate, and repeatable spectrophotometric detection method for Cr(III) ions in trace quantities. The method utilises reagent 1-nitroso-2-naphthol (NNPh) in a sodium dodecyl sulphate (SDS) 1.0 % micellar solution, replacing the old, time-consuming, and expensive solvent extraction method that employs hazardous solvents such as carbon tetrachloride and chloroform. SDS surfactant is used to solubilise indissoluble chelates, making the proposed technique easy, rapid, and environmentally friendly. The established method exhibits an improved linear calibration range, sensitivity, limit of detection, and selectivity compared to earlier spectrophotometric methods employing different complexing agents. The stoichiometric ratio between Cr and NNP was observed to be 1 : 3. The molar absorption coefficient (&amp;lt;i&amp;gt;ε&amp;lt;/i&amp;gt;) was determined to be 2.05 ∙ 104 l mol&amp;lt;sup&amp;gt;–1&amp;lt;/sup&amp;gt; cm&amp;lt;sup&amp;gt;–1&amp;lt;/sup&amp;gt; at &amp;lt;i&amp;gt;λ&amp;lt;/i&amp;gt;&amp;lt;sub&amp;gt;max&amp;lt;/sub&amp;gt; 579 nm. The limits of detection for Cr(III) was measured as 3.49 ng l&amp;lt;sup&amp;gt;–1&amp;lt;/sup&amp;gt;. A calibration linear curve was achieved in the concentration range of 0.5–5.0 μg ml&amp;lt;sup&amp;gt;–1&amp;lt;/sup&amp;gt;. Results obtained showed good comparison with the results obtained by atomic absorption spectrometry. The developed method has been adapted for the analysis of Cr(III) in various alloys, pharmaceutical, environmental, and biological samples.

Initial oxidation of Fe–Cr alloys at different temperatures and atmospheric conditions: A ReaxFF molecular dynamics approach

Initial oxidation of Fe–Cr alloys at different temperatures and atmospheric conditions: A ReaxFF molecular dynamics approach

Effects of Cr-addition on ageing response of an Al–Si–Mg die cast alloy

Chromium (Cr) is rarely added to Al–Si die cast alloys as it has a strong tendency to induce the formation of coarse-sized sludge particles. In the present study, high pressure die-cast samples made of Al-7wt.%Si–Cr–Mg alloys with varied Fe contents (0.11 wt%, 0.26 wt% and 0.32 wt%) were tensile tested under as-cast and T5 heat-treated conditions, in comparison to those made of Al-7wt.% Si–Mn–Mg alloy with a constant Fe content (0.11 wt%). The results demonstrated that under the as-cast condition, the Al–Si–Cr alloys with higher Fe contents can achieve comparable tensile properties as the Al–Si–Mn alloy with strictly controlled Fe level. However, after a T5 heat treatment (205 °C for 60 min), the increment in yield strength is less for the Al–Si–Cr alloys in relative to the Al–Si–Mn alloy, regardless of Fe contents. Scanning electron and scanning transmission electron microscopic characterizations were conducted on the as-cast and heat-treated microstructures, aiming to understand the undermined ageing response caused by Cr addition.

Fe–Ni–Cr alloy matrix composite reinforced by superhard in-situ TiB2 produced through casting

ABSTRACT Fe–7.2Ni–16.2Cr–7Ti–3B (wt-%) composition was melted and cast into strips producing an in-situ TiB2 reinforcement within a stainless-steel matrix. The composite was characterised for microstructure and nanoindentation hardness. The microstructure consisted of in-situ formed particles of TiB2 and fine eutectic of austenite–borides. Superhigh nanoindentation hardness of 47.2 GPa was measured on TiB2 particles with 590.2 GPa elastic modulus while these values for the matrix were 6.95 and 277 GPa respectively.

ZTA/high Ni–Cr alloy steel composites prepared by liquid phase sintering

The interfacial bonding, wear resistance, corrosion resistance and high temperature oxidation resistance of ZTA/high Ni–Cr alloy steel composites prepared by liquid phase sintering were investigated. The results showed that the ZTA particles bonded well with high Ni–Cr alloy steel matrix and produced transition new phases, including (Al, Cr)2O3, Al60Mn11Ni4, Mn2SiO4, MnCr2O4, (Mn, Fe)2SiO4 and MnSiO3. With the addition of ZTA particles, the wear resistance of the composites was reduced substantially. When the ZTA content is 40 vol%, the wear resistance is two times of the matrix, which is better than that of the Cr16 material. The small content of ZTA particles added can enhance the corrosion resistance of the composites. When ZTA was in small amounts, there was passivation of the samples and the corrosion resistance increased. When the content of ZTA reaches 30 vol%, the passivation phenomenon disappears. The corrosion resistance of the composites is much higher than that of the Cr16 material. The composites have good resistance to high temperature oxidation at temperatures below 700 °C. Industrial testing of plate hammers was carried out on a corrosive slag machine at a high temperature of 700 °C. The results show that the ZTA/high Ni–Cr alloy steel composite has twice the service life of the Cr26 material.