Zr Alloy Research Articles

Improving the Mechanical Properties and Intergranular Corrosion Resistance of Al-9.2Mg-0.8Mn-0.2Zr Alloy by Sn Addition

Improving the Mechanical Properties and Intergranular Corrosion Resistance of Al-9.2Mg-0.8Mn-0.2Zr Alloy by Sn Addition

Construction of Dynamic Recrystallization Critical Strain Model, Kinetic Model, and Hot Workability of Mg–8Gd–4Sm–1Zn–0.5Zr Alloy

Construction of Dynamic Recrystallization Critical Strain Model, Kinetic Model, and Hot Workability of Mg–8Gd–4Sm–1Zn–0.5Zr Alloy

Bimodal grain structure, phase transformation, and mechanical properties of a Mg-Gd-Y-Zn-Zr alloy during hot extrusion

In this study, we investigated the evolution of grain structures and second phases of a Mg-9.5Gd-4Y–2Zn-0.3Zr alloy during two-stage deformation that took place in the metal during hot extrusion, as well as their effects on its mechanical properties. We found that the alloy exhibited a bimodal grain structure consisting of equiaxed dynamic recrystallized (DRXed) grains and elongated unDRXed grains. As the extrusion process progressed, DRX occurred on a large scale, resulting in an increase in the proportion of DRXed grains from 17.8% to 93.2%, and a reduction in average grain size from 80.3 μm to 9.41 μm. The grain orientation also underwent a transition from a single orientation of an extrusion direction (ED) parallel to <0001> (i.e. ED//<0001>) to mixed orientations of ED//<01–10> and ED//<0001>. The primary mechanism of dynamic recrystallization (DRX) during extrusion involved particle-stimulated nucleation (PSN) accompanied by both continuous and discontinuous DRX. The Mg-9.5Gd-4Y–2Zn-0.3Zr alloy mainly contained intergranular 18R-long period stacking order (LPSO) phases and intragranular 14H-LPSO. As the extrusion process progressed, 18R-LPSO changed from blocky to lamellar to accommodate deformation, and β-Mg5(Gd,Y) phase particles dynamically precipitated along DRXed grain boundaries. The 14H-LPSO phase was found to be primarily distributed within coarse unDRXed grains. As deformation via extrusion progressed, the quantity of 14H-LPSO gradually decreased. Ultimately, with the gradual dissolution of Mg5(Gd,Y), 14H-LPSO reprecipitated within the recrystallized grain boundaries. As the extrusion process progressed, both the yield strength (YS) and elongation (EL) increased from 132.6 MPa to 287.6 MPa and from 10.8% to 15.5%, respectively. This was mainly attributed to the significant reduction in grain size and second phase size.

Microstructure and Properties of Cu – Cr – Zr Alloys After Plastic Deformation and Aging

Microstructure and Properties of Cu – Cr – Zr Alloys After Plastic Deformation and Aging

Empowering Tri-Functional Palladium's Catalytic Activity and Durability in Electrocatalytic Formic Acid Oxidation Reaction via Innovative Self-Caging and Alloying Strategies.

Direct formic acid fuel cells (DFAFCs) stand out for portable electronic devices owing to their ease of handling, abundant fuel availability, and high theoretical open circuit potential. However, the practical application of DFAFCs is hindered by the unsatisfactory performance of electrocatalysts for the sluggish anodic formic acid oxidation reaction (FAOR). Palladium (Pd) based nanomaterials have shown promise for FAOR due to their highly selective reaction mechanism, but maintaining high electrocatalytic durability remains challenging. In this study, a novel Pd-based electrocatalyst (UiO-Pd-E) is reported with exceptional durability and activity for FAOR, which can be attributed to the Pd nanoparticles encapsulated within a carbon framework where concurrent chemical alloying of Pd and Zr occurs. Further, the UiO-Pd-E demonstrates noteworthy multifunctionality in various electrochemical reactions including electrocatalytic ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR) in addition to the FAOR, highlighting its practical potentials.

Effects of coolant pH on crud deposition behavior on fuel cladding tube under subcooled nucleate boiling condition in high temperature pressurized water

The effects of coolant pH on the crud deposition behavior on the Zr alloy and the FeCrAl fuel cladding tubes under subcooled nucleate boiling condition were investigated. With the increase of coolant pH, the coverage rate and thickness of crud on the surfaces of both the Zr alloy and the FeCrAl fuel cladding tubes showed a decreasing trend. The solubility of crud compositions was reduced due to the increase of coolant pH, which resulted in the inhibition of the crud deposition process caused by SNB condition. Consequently, the elevated coolant pH value reduced the amount of crud on the surface of the fuel cladding tube.

Refined Microstructure and Enhanced Anticorrosion Properties of Mg–4Y–3Nd–0.5Zr Alloy Fabricated by Laser Surface Remelting

Refined Microstructure and Enhanced Anticorrosion Properties of Mg–4Y–3Nd–0.5Zr Alloy Fabricated by Laser Surface Remelting

Formation of Structural-Phase State and Elastic and Durometric Properties of Biocompatible Cold-Rolled Titanium Ti–Nb–Zr-Based Alloys during Aging

The methods of scanning electron microscopy, X-ray diffraction analysis, and microindentation are used to study the effect of alloying with zirconium (within 3 to 6 at %) and complex Zr + Sn and Zr + Sn + Ta additions on the evolution of the structure, phase composition, and properties (effective modulus of elasticity, hardness, and wear-resistance parameters) of quenched biocompatible β-titanium (at %) Ti–6% Nb–% Zr, Ti–6% Nb–% Zr, Ti–6% Nb–% Zr, Ti–6% Nb–% Zr–% Sn, and Ti–6% Nb–% Zr–% Sn–0.7Ta alloys during aging (at 400°C for 4, 16, and 64 h) after multipass cold rolling with a total degree of strain of 85%. As compared to the quenching, the cold rolling of the studied Ti–b–r alloys is shown to suppress the occurrence of the β → ω transformation in the course of aging and to favor the acceleration of the decomposition of β solid solution with the formation of nonequilibrium αl phase in the course of aging. The increase in the zirconium content from 3 to 6 at % in the cold-rolled ternary Ti–6% Nb –х% Zr alloys and introduction of complex Zr + Sn and Zr + Sn + Ta additions to the Ti–6% Nb alloy instead of only zirconium addition hinder the decomposition processes of the β phase during aging; this impacts the intensity of variations of the effective modulus of elasticity and microhardness. The aging of the cold-rolled alloys under study was found to allows us to obtain the higher values of the parameters H/Er and (Н is the hardness and Er is the resolved modulus of elasticity) associated with the wear resistance as compared to those for the widely used medical Ti–Al–V alloy. The compositions of the alloys and conditions of their treatment are determined, which allow us to obtain the combination of the highest-level properties.

Hot deformation behavior and microstructural evolutions of a Mg-Gd-Y-Zn-Zr alloy prepared by hot extrusion

The hot deformation behavior of extruded Mg-9.5Gd-4Y-2Zn-0.5Zr alloy was studied through hot compression tests conducted at deformation temperatures of 350–500 °C and strain rates of 0.001–1 s−1. Under most deformation conditions, the flow stress first reached a maximum before decreasing to a stable value, demonstrating characteristics of dynamic recrystallization (DRX). The constitutive equation of the alloy was established as ε.=1.03*1011sinh0.01287*σp2.422exp(−171150/RT) through calculations and derivation. The influences of the deformation temperature and strain rate on the microstructure and DRX of the alloy during the hot compression process were investigated using electron backscatter diffraction. It was found that at temperatures between 350 °C and 450 °C, the alloy texture exhibited multiple {0001} peak rings distributed around the normal axis of the compression direction. When the strain rate was 0.001 s−1, the average equivalent grain diameter significantly increased from 3.3 μm to 22.4 μm with the rise in deformation temperature, whereas when the deformation temperature was 450 °C, the volume fraction of DRX grains noticeably decreased from 87.6 % to 13.2 % with the increasing strain rate. Further research revealed that due to the restriction of strain rate on grain boundary migration, discontinuous dynamic recrystallization and continuous dynamic recrystallization were the predominant DRX mechanisms at low and high strain rates, respectively.

Recrystallization of amorphous AlNbCr coatings irradiated with chromium ions

Applying an AlNbCr layer on the surface of Zr alloys significantly enhances the alloy resistance to oxidation and high-temperature corrosion. However, the effects of irradiation on AlNbCr coating remain largely unexplored. This work investigates the microstructural evolution of Cr ion-irradiated AlNbCr coatings under varying temperatures, utilizing bright-field transmission electron microscopy (TEM) observations and electron diffraction pattern analyses. With increasing Cr ion irradiation dose, the coatings gradually transitioned from an initial amorphous to a crystalline state. The onset of crystallization occurred earlier at higher temperatures, indicating that the crystallization process was significantly influenced by temperature. Moreover, the dynamic crystallization process of the crystalline structure was also analyzed, as well as the different irradiation responses at the Near-Interface Area (NIA) and Far-Interface Area (FIA). These findings provide new insights for understanding and optimizing the performance of AlNbCr coatings in high-irradiation environments.

Influence of direct aging treatment on microstructure and mechanical properties of Al-4Cu-2Mg-0.3Sc-0.7Zr alloy processed by selective laser melting

This work investigates the microstructure and mechanical properties of select laser melting (SLM) fabricated Al-4Cu-2Mg-0.3Sc-0.7Zr alloys after direct aging treatment. In the as-fabricated alloy, typical duplex grain microstructure, primary Al3(Sc, Zr) precipitates and CuMg co-segregation are observed. After aging treatment at 203 °C for 2.5 h, it was found that two types of S (Al2CuMg) precipitates with {100}Al and {120}Al growth direction. The superlattice lattice confirmed the presence of the secondary Al3(Sc, Zr) precipitates with L12 structure after aging at 225 °C to 496 °C. The disappearance of CuMg segregation and the coarser scale Al3(Sc, Zr) particles lead to the poor Zener-pinning effect and abnormal growth of fine grains at 496 °C aged. The fine secondary Al3(Sc, Zr) precipitates enhanced mechanical properties greatly, the yield strength achieved 435.5 MPa (increased about 18 %) with the elongation of 10.5 % after aging at 440 °C.

La drives the remarkable strength enhancement of the Cu-Cr-Zr alloy through traditional thermo-mechanical treatment

The Cu-1Cr-0.1Zr alloy with different La addition (0 %, 0.07 % and 0.14 wt%) was processed using industry suitable two-step cold rolling and aging treatment to achieve superior strength and electrical conductivity. The role of La addition on the microstructure evolution and comprehensive properties of the Cu-1Cr-0.1Zr alloy is investigated during the second rolling and subsequent aging stages. During pre-aging process, the presence of La in the Cu-1Cr-0.1Zr-0.07La alloy led to formation of smaller precipitate sizes compared to La-free Cu-1Cr-0.1Zr alloy. This facilitates a stronger cut interaction between dislocations and precipitates during secondary rolling process, which promotes the redissolution of precipitates into Cu matrix and thus results in a larger decline of 44.72 % ICAS for the electrical conductivity of Cu-1Cr-0.1Zr-0.07La alloy. After post-aging treatment, precipitates are newly formed with increased number and refined size of Cr precipitates with maintaining a coherent relationship with the matrix. Besides, the addition of La promotes Cr-rich phase precipitation and dislocation accumulation. Resultantly, remarkable increase in tensile strength by 11 % with the addition of 0.07wt%La. While, the 0.14La added alloy exhibits comprehensive properties of tensile strength 600 MPa and electrical conductivity 80.08 %IACS after aging at 440 °C for 180 min. The increase in strength was primarily attributed to precipitation strengthening and dislocation strengthening. This work provides new kinds of Cu-1Cr-0.1Zr alloy and industrial suitable thermo-mechanical treatment for fabricating high performance cooper alloy sheets.

Effect of trace silver addition on microstructure and properties of Cu-0.45Cr-0.1Zr alloy

Cu-0.45Cr-0.1Zr-(0.3Ag) were produced and subjected to multistage thermo-mechanical treatment. The microstructure evolution and properties of the alloys during aging were investigated in detail and the effect of trace Ag on comprehensive properties of Cu-Cr-Zr alloy was discussed by kinetic and strength calculations. The results showed that Cu-0.45Cr-0.1Zr-0.3Ag alloy had a higher strength than Cu-0.45Cr-0.1Zr alloy while maintaining a high electrical conductivity. After multistage thermo-mechanical treatment, the tensile strength, yield strength and electrical conductivity of Cu-0.45Cr-0.1Zr-0.3Ag alloy reached 611MPa, 601MPa and 78.7 %IACS, respectively. The addition of Ag had little influence on the precipitation process of Cu-Cr-Zr alloy during aging: Cr particles transitioned from GP zones to face-centered cubic (fcc) structure and finally stabilized in body-centered cubic (bcc) structure, however, the composition of Zr precipitates changed after Ag doping. Most of Zr atoms segregated at grain boundaries in the form of Cu4AgZr in Cu-0.45Cr-0.1Zr-0.3Ag alloy instead of Cu5Zr in Cu-0.45Cr-0.1Zr alloy. The calculation results showed that the addition of Ag refined the size of Cr particle, increased the density of dislocations, enhanced the effect of dislocation strengthening.

Revealing the substantial impact of trace Mg addition on the microstructural configuration of a cast Al-Li-Cu-Zr alloy under various conditions

In this study, the impact of 0.2 wt% Mg addition on the microstructural configuration of a cast Al-2.5Li-2.5Cu-0.15Zr alloy under different heat treatment conditions was investigated using multiscale characterization. Results indicate that in the as-cast state, trace Mg forms the low-melting-point Al2CuMg eutectic phases and promotes grain refinement. In the natural aging state, trace Mg promotes the precipitation of fine Guinier-Preston (GP) zones independent of pre-existing δ′-Al3Li phases. In the artificial aging state, trace Mg mainly leads to the inducing of GP zones, suppression of θ′-Al2Cu phases, and promotion of T1-Al2CuLi phases. δ′ phases with slight diameter reduction and minimal S′-Al2CuMg phases with two variants are also observed. Atomic-level analysis of the two newly formed composite precipitates indicates that L12 structure phases on both sides of the GP zone have an anti-phase relationship. This study is expected to provide theoretical insights into the microstructural origins underlying the beneficial effects of Mg microalloying in cast Al-Li-Cu alloys.

Study on tensile behavior at various temperatures of the Mg-7Gd-5Y-1Nd-2Zn-0.5Zr alloy

Mg-rare earth (RE)-Zn alloys with long-period stacking ordered (LPSO) structure show excellent room temperature, elevated temperature mechanical properties. In this work, microstructure and mechanical properties of Mg-7Gd-5Y-1Nd-2Zn-0.5Zr (wt%) alloy after tensile deformation at various temperatures (room temperature (RT), 250 °C and 300 °C) were investigated. The pre-precipitated alloy exhibited tensile yield strength (TYS) of 149 MPa at room temperature, while it maintained relatively high TYS at 250 °C (154 MPa) and 300 ℃ (123 MPa). The microstructural characterizations revealed that such outstanding heat resistance is mainly attributed to the blocky LPSO structure near the grain boundary; basal plate-like precipitates, twins and kink bands inside the grain. The blocky LPSO structure exhibits a coherent boundary with one α-Mg grain, while being incoherent with other α-Mg grains or the LPSO structure. Cracks primarily occured along the incoherent interface. Basal plate-like precipitates formed during elevated temperature tensile deformation included GP zones, γ', metastable LPSO building blocks, and fine 14H-LPSO structure. A probable γ-precipitation sequence is supersaturated solid solution → GP zones (ABAB-type) → single LPSO building block (γ')→ various metastable LPSO building block clusters→ 14H-LPSO (γ). The deformation modes (sliding, twinning, kinking, grain boundary sliding, etc) modified with the tensile temperature increase. <c+a> dislocations were observed at elevated temperatures. As the temperature of tensile test increases, twins become less. Grain boundary sliding occurs at elevated temperatures.

Study on the fretting wear performance of oxide layer and Cr coating on zirconium alloy in high-temperature water

Grid-to-rod fretting wear is an important factor causing the fuel failure in nuclear power plants. Accident tolerant fuel (ATF) Cr coating and oxide ceramic coating have been developed to improve the fretting wear performance. In this research, two different oxide layers and Cr coating were prepared on zirconium (Zr) alloy, and the fretting wear performance were studied. The morphology, microstructure, tribo-corrosion reaction, and wear characteristics were analyzed. The oxide layer formed at high-temperature pressurized water (HTPW) has the lowest wear rate of 0.11×103 μm3/Nm due to the high hardness and compact structure, which leads to the corresponding friction pairs presenting the highest wear rate of 8.42×103 μm3/Nm. The wear depth of oxide layer formed at HTPW is about 5 times lower than that of as-received Zr alloy, and it is also less than the thickness of oxide layer. The oxide layer formed at HTPW after fretting has a larger thickness than the initial state because the plastic deformation layer caused by shear stress can quickly oxidize to zirconia in high-temperature water, and the wear rate of oxide layer is lower than the formation rate of oxide layer. The wear mechanism of two different oxide layers is delamination and abrasive wear, and that of Cr coating is abrasive wear and fatigue wear.

Healing the high-temperature-retrogression-caused wide precipitation-free zones in Al-Zn-Mg-Cu alloy via strain-aging induced precipitates

Retrogression and re-aging (RRA) treatments have been demonstrated to effectively increase the corrosion resistance of high-strength Al-Zn-Mg-Cu alloys. However, RRA-treated Al-Zn-Mg-Cu alloys still suffer from poor ductility and intergranular corrosion because the wide precipitation-free zones (PFZs) caused by high-temperature retrogression treatment cannot be eliminated during the following re-aging process. Herein, inspired by the fact that retrogression dissolves part of the existing precipitates to obtain supersaturation in the matrix and dislocations as heterogeneous nucleation sites for precipitation are more prone to accumulate into the soft PFZs, a strategy of introducing pre-deformation after retrogression to trigger the secondary precipitation in the retrogression-caused PFZs during the subsequent re-aging is developed to heal this inherent weakness. Furthermore, the dislocations aggregation around the precipitated phases within grains accelerate the transformation of their morphology from platelet-like to circle-like after re-aging. In particular, the precipitates in the dislocation-dense band structures become coarser than those in the out-of-band regions. The synergy of the secondary precipitation at retrogression-caused PFZs and the circle-like and band-distributed precipitates within grains weakens the strength and electrochemical difference between the grain interior and the grain boundary. Compared with the traditional RRA treatment, this innovative technique further enhances the corrosion resistance and ductility of the fully recrystallized Al-8.99Zn-2.12Mg-1.98Cu-0.092Hf-0.12Zr alloy without sacrificing strength. This finding offers practical and straightforward implications for overcoming the current limitation in RRA-treated Al-Zn-Mg-Cu alloys and has the potential to expand to other aging-hardening alloys.

Influence of doping elements X (X= Hf, Zr, Y, Re, Pd, Ir) on the structural stability and tension property of α-Al2O3/PtAl2-S interfaces

Pt-Al coatings are promising materials for protective materials for turbine blades in new-generation aero-engines. Therefore, it is worth noting that the interface stability and tension property between Pt-Al and the oxide layer, prolonging coating service time. However, systematic studies of doping elements effects on interface adhesion of α-Al2O3/PtAl2 with and without impurity S are still lacking. In this paper, the site preference of the six elements (Hf, Zr, Y, Re, Pd, and Ir) in the PtAl2 alloy, effects of doping elements on the interface adhesion and tension properties of the α-Al2O3/PtAl2-S interface are further explored, performing the first-principles calculation method. Considering comprehensively, Y doping has an excellent enhancement effect on the static interface adhesion and dynamic tensile strength, regardless of whether impurity element S exists in the α-Al2O3/PtAl2 interface. This study will provide necessary theoretical guidance for the composition design of Pt-Al coating and the research of new metal protective coating materials.

Effects of cerium micro-alloying on microstructural evolution and dispersion strengthening in Al-Yb-Er-Zr alloy

This study investigates the impact of trace cerium (Ce) addition on the precipitation behavior of Al-0.03Yb-0.03Er-0.06Zr (at%) alloys, with a focus on the formation of eutectic phases and nanoscale dispersoids. Ce, known for its low solubility in Al, preferentially segregates at grain boundaries, leading to the formation of Ce-rich eutectic phases and significant grain refinement. Isochronal annealing experiments revealed a double-peak hardening pattern. The first peak, associated with Al3RE (RE= Yb, Er, Ce) precipitates, demonstrated minimal sensitivity to Ce addition. The second peak, related to core-shell L12-Al3(RE, Zr) precipitates, exhibited a notable increase in hardness in the Ce-added alloy. Isothermal annealing at 450 °C and 475 °C further demonstrated that Ce accelerates the annealing-hardening response and increases the number density of Al3(RE, Zr) dispersoids at elevated temperatures. This enhancement may be attributed to Ce serving as an effective inoculant element and significantly reducing the stacking fault energy, which facilitates easier nucleation of these particles.

Molecular dynamics study on the deformation mechanism of Cu–Zr/Al laminated composites

In this paper, molecular dynamics simulation was used to investigate the micromechanical behavior of the Cu–Zr/Al composite interface after rapid solidification. The effects of different Zr contents and different strain rates on the tensile strength of the Cu–Zr/Al composite interface were investigated. The results show that the tensile strength of the composite plate increased and then decreased with the increase of Zr content, and the tensile strength is the highest when the Zr content is 0.33 wt%. It was found that the plastic deformation process of the composite model at different strain rates is similar, which is divided into three stages: the expansion of stacking faults in the Cu–Zr/Al solid solution, the expansion of stacking faults successively in the Al and Cu–Zr alloy layers, and the spreading of cross - stacking faults. But the greater the strain rate is, the slower the stacking faults fracture is. So the composite model with different strain rates had different fracture modes during the tensile fracture process. When the strain rate is 0.01 ps−1 and 0.001 ps−1, it is a ductile fracture, while when the strain rate is 0.0001 ps−1, it is a brittle fracture.