La Alloy Research Articles

Unraveling the new role of La on arc erosion behavior of C/Cu-based electrical contacts

Copper/carbon (C/Cu) electrical contact materials are widely used in low-voltage appliances due to their exceptional conductivity and anti-ablation properties. However, the oxidation of Cu during operation and the suboptimal wettability at the C/Cu interface negatively impact its arc-resistant performance. This study explores the potential for enhancing the arc-resistant characteristics of C/Cu electrical contact materials through the alloying of La in Cu. The findings indicate that La alloying in Cu significantly decreases the contact resistance (from 50 mΩ to 2.2 mΩ) and mass loss (by 50%) of C/Cu electrical contact materials.

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.

Enhanced hydrogen kinetics of Mg–Ni–La alloys via slight Y element additive

Alloying represents an effective approach for addressing challenges related to over stable thermodynamics and slow kinetics in magnesium alloys. The incorporation of Y dopant served to enhance the quantity of grain boundaries and phase boundaries, thereby addressing the issue of high dehydrogenation temperature observed in Mg85–Ni10–La5, which can be decreased to 273.3 °C after the addition of 0.5 wt% Y additive. In addition, the initial hydrogenation rate of Mg85–Ni10–La4.5-Y0.5 reached up to 3.42 wt% H2 at 260 °C and the apparent activation energy for dehydriding was decreased from 115.31 to 86.05 kJ/mol. Theoretical calculations suggested that the hydrogen adsorption energy of Mg85–Ni10–La4.5-Y0.5 was dramatically lower than that of Mg85–Ni10–La5, improving hydrogenation properties. The consistency between theoretical calculations and experimental outcomes provided a valuable reference for the selection of suitable magnesium-based hydrogen storage materials.

Effects of nano-micron TiB2-Al2Y particles on the microstructural evolution and mechanical properties of extruded Mg-9Y-0.6La composites

In this study, the nano-micron TiB2-Al2Y/Mg-9Y-0.6La composites were prepared by introducing nano-TiB2 and micron-Al2Y particles into Mg-9Y-0.6La alloys via the addition of nano-TiB2/Al master alloy. The introduction of nano-micron TiB2-Al2Y particles refined the α-Mg grains, weakened the basal texture, and promoted the dynamic recrystallization of the composites. The yield strength and tensile strength of the 4.31 wt% TiB2-Al2Y/Mg-9Y-0.6La composite were increased by 69 MPa and 65 MPa, respectively, compared with the Mg-9Y-0.6La alloy. The main strengthening mechanisms of the composites were fine grain strengthening, Orowan strengthening, and coefficient of thermal expansion strengthening caused by the TiB2-Al2Y particles.

Effect of pre-recovery solid solution treatment on microstructure and comprehensive properties of Al-11.0Zn-3.0Mg-1.0Cu-0.2Zr-0.16Ti-0.15Er-0.15La alloy

ABSTRACT In this paper, the microstructure and comprehensive properties of Al-11.0Zn-3.0Mg-1.0Cu-0.2Zr-0.16Ti-0.15Er-0.15La aluminium alloy with two solid solution regimes of G1 and G2 were investigated. The microstructure of the alloy was characterised using an optical microscope (OM) and a scanning electron microscope (SEM). The phases were analysed using an X-ray diffraction (XRD). The grains were measured using an electron backscatter diffraction (EBSD). The hardness and tensile properties of the alloy were investigated using a Vickers hardness tester and a tensile testing machine, respectively. The results showed that the best property of the alloys was obtained after pre-recovery solid solution treatment of G2. The grain size of the alloy was significantly refined, and the tensile strength and elongation at break of the alloy after G2 solid solution treatment were increased by 10.4% and 6.9% compared to those of G1, respectively. The G2 alloy possessed good resistance to intergranular corrosion, exfoliation corrosion and electrochemical corrosion. The maximum corrosion depth of its intergranular corrosion was decreased by 34.7% and the grade of exfoliation corrosion was PB. The electrochemical corrosion current density and corrosion potential of G2 alloy were 5.421 × 10−5A/cm2 and −0.978 V, respectively.

Modificated microstructure and enhanced mechanical properties of Cu-Sn-P alloy with rare earth La addition

Rare earths are often added to copper alloys as trace alloying elements to modify the structure and improve related properties. In this study, the Cu-7.8Sn-0.16 P and Cu-7.8Sn-0.16 P-0.15La alloy strips were fabricated through full-chain process of vacuum casting, cold rolling, intermediate annealing, cold rolling and low temperature annealing process. Then, the distinctive microstructure features and mechanical properties of Cu-7.8Sn-0.16 P and Cu-7.8Sn-0.16 P-0.15La alloys were comprehensively analyzed in special view of rare earth affected phase types and property evolution. The results indicate that the addition 0.15 wt% La has effectively refined the dendrite segregation and dispersed the microporosity. Specifically, La combines with P and form a stable and dispersed micron sized LaP2 intermetallic compound, which replaces the low melting point (α+δ+Cu3P) ternary phase in the La-free alloy. Furthermore, a new nanoscale La(Cu2P)2 precipitated phase is characterized in the Cu-7.8Sn-0.16 P-0.15La alloy during low-temperature annealing process. As well, the tensile strength of Cu-7.8Sn-0.16 P-0.15La strips display notable increase to 915 MPa from 834 MPa of Cu-7.8Sn-0.16 P after low-temperature annealing. Such increase in tensile strength is attributed to the formation of La-containing phase of varied sizes in the Cu-7.8Sn-0.16 P-0.15La alloy, where the nano scale La(Cu2P)2 precipitated phase makes the most significant contribution.

Processing of high-strength thermal-resistant Al-2.2% cerium-1.3% lanthanum alloy rods with high electric conductivity by High Pressure Torsion Extrusion

A novel severe plastic deformation (SPD) process of High Pressure Torsion Extrusion (HPTE) was applied to the rods of the Al-2.2 wt.% Ce-1.3 wt.% La (Al–3.5RE) alloy. The microstructure, microhardness, the mechanical strength, thermal stability, and electrical conductivity of the alloy after HPTE and subsequent annealing have been investigated. It was demonstrated that HPTE processing can simultaneously increase yield strength from 127 to 225 MPa and electrical conductivity from 54.7% IACS to 55.7% IACS in this alloy. Such a remarkable combination of properties was achieved thanks to significant refinement of microstructure constituents: grain size of Al matrix was reduced down to 0.9 µm and initially continuous network of Al11RE3 phase was broken to micrometer- and nanometer-sized particles. Furthermore, the yield strength of the HPTE-processed Al–3.5 RE alloy remains stable at 230 °C for 1 h due to micrometer- and nanometer-sized particles that pin the grain boundaries. Therefore, HPTE processing of Al–RE alloys has a high application potential in the electric power industry.Graphical abstract

Effects of quenching temperature on the structure, segregation, and properties of the AM4.5Kd + 0.2 wt.% La alloy after artificial aging

The identification of structural components in the AM4.5Kd + 0.2 wt.% La alloy, subjected to quenching at different temperatures (535–605 °C) and artificial aging at 155 °C for 4 h, was conducted through electron microscopy and XRD. An increase in the quenching temperature from 535 to 605 °C promotes the enlargement of structural components, including the α-solid solution, various aluminides, and eutectics. We observed that the base metal is not homogeneous in its chemical composition, consisting of two types of solid solutions: α1 and α2. The Cu and Mn solubility in the α2-solid solution is higher than in the α1-solid solution. As the quenching temperature increases to tq = 605 °C, the copper content in the α1-solid solution decreases. In contrast, the copper content in the α2-solid solution follows a curve with two maxima at 545 °С (4.5 at.%) and 585 °С (8.7 at.%). The Mn content in the α1-solid solution decreases sharply to the 545 °С quenching temperature and remains relatively constant up to tq = 605 °С (0.2 at.%). The Mn content in the α2-solid solution follows a curve with its maximum at tq = 545 °С (4.3 at.% Mn). Subsequent temperature rise results in a sharp drop in Mn content from 1.0 at.% at t = 565 °С to 0.3 at.% at 605 °С. Hence, the max solubility of Cu and Mn in the α2-solid solution occurs at 545 °C. At 585 °С, only an elevated Cu content (~8.7 at.%) was observed. Aluminides of alloying elements with different stoichiometries crystallize at different quenching temperatures, with complex AlxTiyLazCuvCdw and AlxCuyMnzCdv alloyed aluminides being most commonly found. ncreasing the quenching temperature to 535–545 °С results in higher hardness of the AM4.5Kd + 0.2 wt.% of La alloy, reaching 98–104 HB, with subsequent decrease to 60 HB as the quenching temperature reaches 605 °С. The hardness of the unhardened alloy is 60 HB. The optimal quenching temperature for the AM4.5Kd + 0.2 wt.% of La alloy is in the range of 535–545 °С. This temperature corresponds to the highest hardness of the alloy and the microhardness of the aluminide.

Improved Discharge Performance of AZ72-0.05La Alloy Anode via Refining Mg17Al12 Phase

The morphology of phases in magnesium alloys is vitally important for their performance. It is found that improved discharge performance is achieved in AZ72-0.05La alloy via a refining Mg17Al12 phase by means of hot rolling. Before rolling, as-cast AZ72-0.05La alloy has a relatively coarse and strip-like Mg17Al12 phase. After rolling, the Mg17Al12 phase becomes much finer, showing a granulated shape. Due to the refinement of the Mg17Al12 phase, the discharge voltage and energy density of an Mg-air battery with as-rolled AZ72-0.05La alloy as the anode increases by 6% and 3% under a discharge current density of 20 mA·cm−2 in a 3.5% NaCl solution, respectively. The corrosion rate of the as-rolled AZ72-0.05La alloy is slightly larger than the as-cast AZ72-0.05La alloy, but still much lower than as-cast AZ72 alloy. The as-rolled AZ72-0.05La alloy possesses a discharge voltage of 0.74 V and an energy density of 918 mWh·g−1 under a discharge current density of 20 mA·cm−2, and a relatively low corrosion rate of 0.51 mg·cm−2·h−1, demonstrating good overall discharge performance. This work provides a method for improving the discharge performance of Mg-air batteries.

Inhibition of precipitation structure transformation and enhancement of hardness by trace La addition in Cu-1Cr-0.1Zr alloy sheets

Cu-1Cr-0.1Zr and Cu-1Cr-0.1Zr-0.07La alloy sheets were prepared by the following process: vacuum casting– homogenization treatment– hot forging– solid solution treatment– cold rolling– aging treatment. The effect of trace La on the aging behavior and mechanical properties of Cu-1Cr-0.1Zr alloy was investigated. Compared to the Cu-1Cr-0.1Zr (0La) alloy, the Cu-1Cr-0.1Zr-0.07La (0.07La) alloy exhibited a significant increase in hardness and a slight decrease in electrical conductivity due to larger number of finer and coherent f.c.c Cr-rich precipitates. It was found that trace La can affects the evolution of precipitation phases. The thermodynamics calculation indicates that with La addition, the Cr-rich precipitates were much more inclined to nucleate with f.c.c structure, and the precipitation growth kinetics results indicate that the addition of La can reduce the activation energy of precipitation, promote the precipitation of f.c.c Cr phase and form Cr-poor zones, making it more difficult to form bcc nuclei. Thus, the transformation of nanoscale Cr-rich precipitates from f.c.c structure to bcc structure was inhibited due to trace La addition, causing higher hardness with appropriate conductivity.

Improved toughness and oxidation resistance of Nb[sbnd]Si based ultra-high temperature alloys by in-situ generated La2O3 phase

The effects of in-situ rare earth oxide phase La2O3 on the microstructure and properties of NbSi based ultrahigh temperature alloys were investigated. The NbSi based alloys were doped with varying amounts of La (0.05, 0.1, 0.2, 0.4 and 0.8 at.%). The La2O3 phase forms in situ during the melting process. The fracture toughness is greatly improved by the La2O3 phase, and the KQ value of the 0.4La alloy is 27.1% higher than that of the base alloy. The improvement of fracture toughness is due to these three aspects: first, the high-melting-point La2O3 phase (TmLa2O3= 2588 K) precipitates first and effectively refines the microstructure. As a result, the frequency of secondary cracking and crack bridging increases. Second, the formation of the La2O3 phase significantly reduces the issue of oxygen contamination. Third, the high-hardness La2O3 phase separates during the fracture process, reducing the constraints on the deformation of NbSi based alloys. Additionally, La2O3 has the lowest Gibbs free energy among all possible formed oxides. During the oxidation process, the continuous oxidation behavior of the La2O3 phase reduces the degree of oxidation inside the alloy. Therefore, the oxidation resistance is significantly improved.

Inhibition of Ti-rich precipitates and improvement of the irradiation resistance in V-4Cr-4Ti by adding La element

Four kinds of V-4Cr-4Ti-xLa (nominal composition x = 0, 0.1, 0.5, 1.0 wt.%) alloys with different La contents were prepared by vacuum arc melting. Three of them (x = 0, 0.1, 1.0 wt.%) were selected for single He+ (2000 appm for peak concentration) irradiation and sequential He+/V2+ (10 dpa for peak damage) irradiation at 550 °C. The results showed that the addition of La element could refine the grains by forming the second phase La2O3 particles. Moreover, the addition of La element reduced the sum of impurity elements concentration in the alloy, which inhibited the formation of Ti-rich precipitates and affected the vacancy concentration, thus affecting the evolution of He bubbles under different irradiation types. In addition, the V-4Cr-4Ti-1.0La alloy had a lower irradiation hardening after sequential He+/V2+ irradiation, which might be related to the removal of impurity elements. This work provided a reference for the performance optimization of vanadium alloy for fusion reactors.

Prolonging cycling life of AB3-type superlattice alloys by adjusting hydrogen absorption/desorption behaviors of [A2B4] and [AB5] subunits

AB3-type La-Mg-Ni-based hydrogen storage alloys are known for their high electrochemical hydrogen storage capacity. However, their practical application has been hindered by fast capacity degradation. Herein, we managed to improve their cycle life by synchronizing the hydrogen absorption/desorption behaviors of [A2B4] and [AB5] subunits based on a series of AB3-type single-phase La0.60R0.12Mg0.28Ni3 (R = La, Pr, Nd, Gd) superlattice alloys. This is achieved by the preferable occupation of Pr, Nd and Gd in [A2B4] subunits rather than [AB5] subunits compared to La, which decreases the volume difference between [A2B4] and [AB5], significantly reducing the mismatch between [A2B4] and [AB5] during hydrogen absorption/desorption. Resultantly, the microstrain of the R = Gd alloy is only half that of the R = La alloy, leading to enhanced anti-pulverization and anti-oxidation/corrosion resistance, as well as an improved cycle stability. The S100 of the R = Gd alloy is more than 15 % higher than the R = La alloy. Moreover, the plateau pressure is adjusted to a proper level, enabling an increase in the high-rate dischargeability (HRD1500) from 53.6 % (R = La) to 66.4 % (R = Gd). This work provides impressive insights into developing high-performance superlattice hydrogen storage alloys.

Study of the process of preparing amorphous Fe–W(La) alloy plating by induced co-deposition

To obtain high-performance Fe–W alloy plating instead of environmentally hazardous chromium plating, the effects of the cathode material, electrolyte pH, temperature, current density, plating time and rotational speed on the cathode current efficiency and alloy plating are investigated in this paper. The results show that the pH and current density of the plating solution greatly influence the morphology and current efficiency of the cathode. The current efficiency of the cathode can reach 63.56%, and the tungsten content can reach 55% at pH = 8, 60 °C, 12 A/dm2, 100 r/min, 75 min, 0.1 mol/l of Fe2+ and 0.2 mol/l of W6+. After XRD analysis, the plating is found to consist of the Fe7W6 amorphous phase. In addition, La is added to the Fe–W alloy under optimal conditions. By analyzing the polarization curve, the potential of the Fe–W(La) alloy is positively shifted by 0.039 V compared with the Fe–W alloy, which has good corrosion resistance.

Mechanical properties, corrosion and degradation behaviors, and in vitro cytocompatibility of a biodegradable Zn-5La alloy for bone-implant applications.

Zinc (Zn) and its alloys are used in bone-fixation devices as biodegradable bone-implant materials due to their good biosafety, biological function, biodegradability, and formability. Unfortunately, the clinical application of pure Zn is hindered by its insufficient mechanical properties and slow degradation rate. In this study, a Zn-5 wt.% lanthanum (Zn-5La) alloy with enhanced mechanical properties, suitable degradation rate, and cytocompatibility was developed through La alloying and hot extrusion. The hot-extruded (HE) Zn-5La alloy showed ultimate tensile strength of 286.3MPa, tensile yield strength of 139.7MPa, elongation of 35.7%, compressive yield strength of 262.7MPa, and microhardness of 109.7 HV. The corrosion resistance of the HE Zn-5La in Hanks' and Dulbecco's modified Eagle medium (DMEM) solutions gradually increased with prolonged immersion time. Further, the HE Zn-5La exhibited an electrochemical corrosion rate of 36.7μm/y in Hanks' solution and 11.4μm/y in DMEM solution, and a degradation rate of 49.5μm/y in Hanks' solution and 30.3μm/y in DMEM solution, after 30 d of immersion. The corrosion resistance of both HE Zn and Zn-5La in DMEM solution was higher than in Hanks' solution. The 25% concentration extract of the HE Zn-5La showed a cell viability of 106.5%, indicating no cytotoxicity toward MG-63 cells. We recommend the HE Zn-5La alloy as a promising candidate material for biodegradable bone-implant applications. STATEMENT OF SIGNIFICANCE: This work reports the mechanical properties, corrosion and degradation behaviors, in vitro cytocompatibility and antibacterial ability of biodegradable Zn-5La alloy for bone-implant applications. Our findings demonstrate that the hot-extruded (HE) Zn-5La alloy showed an ultimate tensile strength of 286.3MPa, a yield strength of 139.7MPa, an elongation of 35.7%, compressive yield strength of 262.7MPa, and microhardness of 109.7 HV. HE Zn-5La exhibited appropriate degradation rates in Hanks' and DMEM solutions. Furthermore, the HE Zn-5La alloy showed good cytocompatibility toward MG-63 and MC3T3-E1 cells and greater antibacterial ability against S. aureus.

Comparative study for microstructure and hydrogen storage capabilities of Mg95Zn2R3 (R[dbnd]Y, La) alloys

For the sake of enhancing the hydrogen storage kinetics of Mg-based alloys, the functions of Y and La on microstructure evolution and de/hydrogenation behavior of Mg–Zn alloy are examined and discussed. The thermodynamic calculations reveal that the kind of rare-earth element affect solidification paths of the alloys. La introduction enables the eutectoid transformation. The hydrogenation kinetics of Mg95Zn2Y3 and Mg95Zn2La3 is dominated by hydrogen diffusion. The fine α-Mg grains and alternating structured eutectoid phase in Mg95Zn2La3 provide abundant phase boundary for hydrogen diffusion. Besides, the residual Mg content in hydrogenated Mg95Zn2La3 is far lower than that in Mg95Zn2Y3, which is ascribed to the weakened effect of nucleation-growth-impingement caused by growing MgH2. The hydrogen desorption kinetics of Mg95Zn2Y3 and Mg95Zn2La3 is determined by the nucleation and growth of Mg/MgH2. The fine La8H18.4 nanophases and Mg grains provide plenty of nucleation sites for Mg on MgH2. Additionally, La8H18.4 nanophase exhibits more positive role than YH2/YH3 phase in promoting hydrogen desorption.

Effect of Cu Addition on Properties of an Al-La Alloy

The effect of copper content on the microstructure and properties of an aluminum copper alloy containing lanthanum was studied by adding 0.5 wt% lanthanum and different contents of copper to the 2A12 alloy. We used a universal testing machine, Brinell hardness tester, and friction and wear testing machine to test the mechanical properties of the alloy. The microstructure and phase composition of the alloy were analyzed using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The results show that, after adding La and Cu, the alloy grain is refined, and the fracture mode changes from dissociation fracture to quasi dissociation fracture. A new phase containing La accumulates at the grain boundary. If the amount of Cu added is too large, the tendency for hot cracking increases, which can easily lead to the formation of voids or even cracks. The tensile strength and hardness of the cast alloy significantly increase with the increase in Cu addition. In the range of adding 2 wt% to 5 wt% Cu, the tensile strength and hardness of the cast alloy increases by approximately 12% and 17.84%, respectively, compared with the original alloy. With the increase in Cu addition, the elongation of the alloy first increases and then decreases, reaching its maximum value when Cu addition is 3 wt%. Adding Cu is beneficial for improving the wear resistance of the alloy. When the addition of Cu is 3 wt%, the alloy has the best wear resistance and minimum wear amount. This is due to the enrichment of La and Cu at the grain boundaries, forming new La phases or other phases with higher hardness, which changes the properties of the alloy. It shows that the content of Cu in the 2A12 alloy can be increased to 7-8% with the increasing of additional rare-earth elements, and a new Al-Cu (7 wt% to 8 wt%)-Mg (1.2 wt% to 1.8 wt%)-Mn (0.3 wt% to 0.9 wt%)-La (0.5 wt%) alloy, in which tensile strength, hardness, and elongation of the alloy are increased by 8.1%, 16%, and 79.1%, respectively, can be formed. In addition, the wear resistance of Al-La alloys also improves significantly with the addition of copper content. The coefficient of friction is reduced by 68% compared with no copper addition.

Effect of Rare Earth Elements (Y, La) on Microstructural Characterization and Corrosion Behavior of Ternary Mg-Y-La Alloys.

In this study, the microstructural properties and corrosion behavior of RE elements (Y, La) added to magnesium in varying minors after casting and homogenization heat treatment were investigated. Three-phase structures, such as α-Mg, lamellae-like phases, and network-shaped eutectic compounds, were seen in the microstructure results. The dendrite-like phases were evenly distributed from the eutectic compounds to the interior of the α-Mg grains, while the eutectic compounds (α-Mg + Mg) RE (La/Y)) were distributed at the grain boundaries. According to the corrosion results, the typical hydroxide formation for lanthanum content caused the formation of crater structures in the material, and with the increase in lanthanum content, these crater structures increased both in depth and in density. In addition, the corrosion products formed by Y2O3 and Y(OH)3 in the Mg-3.21Y-3.15 La alloy increased the thickness of the corrosion film and formed a barrier that protects the material against corrosion. The thinness of the protective barrier against corrosion in the Mg-4.71 Y-3.98 La alloy is due to the increased lanthanum and yttrium ratios. In addition, the corrosion resistance of both Mg-3.21Y-3.15 La and Mg-4.71 Y-3.98 La alloys decreases after homogenization. This negative effect on corrosion is due to the coaxial distribution of oxide/hydroxide layers formed by yttrium and lanthanum after homogenization.

Interfacial properties and fracture behavior of β"/Mg interface in Mg–La alloy: A first-principles study

A deeper investigation into the characteristics of the β"/Mg interface represents a promising strategy for improving the ductility and strength of Mg–La alloys. This study systematically investigates the interface adhesion, stability, electronic structure, and tensile fracture behavior of three β"/Mg interfaces with different orientations through the first-principles method. The results indicate that the Mg1-T4-β"(1‾ 010) interface has the strongest binding capacity, and the atomic arrangement at the interface is consistent with the observation results from previous studies using HAADF-STEM. The PDOS and CDD analysis reveal differences in the atomic orbital hybridization, resulting in the formation of Mg–Mg homometallic bonds and Mg–La heterometallic bonds, contributing to the interface strength. The three interfaces exhibit varying mechanical properties with different strengths and strains, influenced by orientation and arrangement of atoms. The fractures occur near the La atom at the interface when the strain reaches a certain level due to insufficient bonding strength between Mg and La. The ductility of the β" precipitate is critical to the interface's ability to undergo plastic deformation. These findings offer new insights into the precipitate interface of Mg–La alloy and could guide the optimization of its properties for various applications.

Hydrogen absorption/desorption cycling performance of Mg-based alloys with in-situ formed Mg2Ni and LaH (x = 2, 3) nanocrystallines

Aiming to elucidate the hydrogen absorption/desorption cycling properties of Mg-based alloys with in-situ formed Mg2Ni and LaHx (x = 2, 3) nanocrystallines, the hydrogen storage cycle stability, hydriding/dehydriding cycling kinetics and thermodynamic stability of the experimental alloys have been investigated in detail. The results show that the Mg–Ni–La alloys exhibit improved hydrogen storage cycling properties and can remain storage hydrogen above 5.5 wt% after 200 cycles. With the increase of cycling numbers, the dehydrogenation rates of the experimental samples increase firstly and then gradually decrease, and eventually maintain relative stable state. Microstructure observation reveals that powders sintering and hydrogen decrepitation both exist during hydrogen absorption/desorption cycles due to repeated volume expansion and contraction. Meanwhile, the in-situ formed LaHx (x = 2, 3) and Mg2Ni nanocrystallines stabilize the microstructures of the particles and hinder the powders sintering. After 200 cycles, the average particle size of the experimental samples decreases and the specific surface area apparently increases, which leads to the decomposition temperatures of MgH2 and Mg2NiH4 slightly shift to lower temperatures. Moreover, Mg2Ni and LaHx (x = 2, 3) have been proven to be stable catalysts during long-term cycling, which can still uniformly distribute within the powders after 200 cycles.