As-cast Alloy Research Articles

Mechanical properties of surface-modified magnesium alloy AZ61 with nanoparticles of aluminum oxide and titanium dioxide by friction stir processing

The present work investigates the mechanical properties of surface-modified magnesium alloy AZ61 reinforced with Al2O3 and TiO2 nanoparticles by using the friction stir processing (FSP) technique. Surface-modified AZ61 alloys were fabricated by the addition of dufferent amount of Al2O3 and TiO2 nanoparticles (5, 10, and 15 vol.%). The developed surface composites were studied regarding microstructure, revealing a uniform dispersion of the added nanoparticles, which resulted in improved mechanical properties of the obtained composites by FSP. The ultimate tensile strength, impact strength, and microhardness improved by 20, 45, and 67 % by reinforcing the alloy with nanoTiO2 particles when compared to the as-cast alloy. The results of this study indicate that the reinforced AZ61 Mg alloy can be a potential material for applications in automobile sectors due to its high strength and lightweight components.

Using the Cluster-Plus-Glue-Atom model to design the composition of low Young’s modulus β-Ti alloys for orthopaedic applications

The design and development of metastable β-type Ti alloys with low Young’s moduli (E) requires the use of multiple β-phase stabilising alloying elements. The most commonly used alloy development design strategies do not provide accurate composition design. Moreover, the process of developing alloys is still based on empirical exploration, which is costly and time consuming. In this study, the cluster-plus-glue-atom (CPGA) model was employed in the composition design and interpretation of low-E, β-type Ti based alloys. Microstructure, phase analysis, Young’s modulus (mechanical testing and nano-indentation testing) of the as-cast alloys were investigated. The results demonstrated that the CPGA model was effective in formulating compositions which were able to simultaneously achieve high β-phase stability and low-E as exemplified by the [(Mo0.4Sn0.6) (Ti)14] (Nb)1 alloy which obtained a Young’s modulus of 59 GPa.

Homogenization heat treatment influence on microstructure evolution and mechanical properties of as-cast Al–Li–Cu–Mg–Zr alloy for lightweight aerospace application

Al–Li–Cu–Mg–Zr alloys are widely used in the aerospace industry for different applications and make an excellent concurrent to high-performance composites. This family of alloys has remarkable properties like low density, high elastic modulus, high strength and specific stiffness, fracture toughness, fatigue crack growth resistance, and improved corrosion resistance.The present work aims to investigate a family of Al–Li alloys by employing suitable characterization techniques such as computer-aided cooling curve analysis and thermal dilatometry to characterize the as-cast alloy. The characterization temperatures of the alloy were obtained and the phase transformation temperatures were concluded as thermal expansion inflection points as well. Furthermore, the homogenization heat treatment effect of the alloy is examined through optical microscopy (OM), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Vickers microhardness testing to determine the optimum heat treatment time. The results reveal the formation of δ′, δ and β’ precipitates in the alloy after different hours of homogenization heat treatment. Notably, our investigation identifies the optimum heat treatment time for the alloy as 26h at 515 °C, resulting in reduced hardness and barely any chemical segregation. These findings contribute to the characterization of as-cast Al–Li alloys and the understanding of microstructure evolution and mechanical properties during homogenization heat treatment that offer a valuable insight for enhancing their performance in aerospace applications.

The influence of cooling rate on the structure and mechanical properties of Al4CoCrCuFeNi multicomponent alloy

The present study focused on examining the composition, structure, and mechanical properties of an Al4CoCrCuFeNi multicomponent high-entropy alloy. Two states of the alloy, namely as-cast and melt-quenched, were investigated. The composition of the alloy was determined based on established criteria found in literature, which consider factors such as entropy, enthalpy of mixing, valence electron concentration, and atomic size difference of the components. To synthesize the alloy films, a splat-quenching technique was employed, where the films were rapidly cooled from the molten state. The estimated cooling rate of the films was approximately 106 K/s, calculated based on the film thickness. X-ray diffraction analysis was conducted on both the as-cast and melt-quenched Al4CoCrCuFeNi alloy samples, revealing that they exhibited an ordered B2 phase in their structure. The microhardness measurementswere carried out to evaluate the mechanical properties of the alloy. The as-cast alloy displayed a microhardness of 6500 MPa, while the melt-quenched film exhibited a significantly higher microhardness, reaching 9400 MPa.

Enhancing the mechanical properties of Mg–Al alloy by introducing Al2Y nanoparticles via rapid-cooling solidification and optimized heat treatments

Coarse grain and poor thermal stability of Mg17Al12 are usually present in the as-cast Mg–Al alloys, which are detrimental to the mechanical properties. In this work, the microstructure evolution, and mechanical properties of as-cast AZ31-1Y alloy with different cooling rates (4.0–29.9 °C/s) were systematically investigated by thermal analysis and microstructure characterization. The results show that the addition of Y to AZ31 alloy results in the formation of primary Al2Y and eutectic Al2Y, while suppressing the formation of β-Mg17Al12. The AZ31-1Y alloy with a cooling rate of 29.9 °C/s exhibits the finest grain, with a grain refinement efficiency 40.9 % higher than that of AZ31 alloy with a cooling rate of 4.0 °C/s. After heat treatment, the acicular eutectic Al2Y is modified into a granular shape and numerous nano-sized Al2Y precipitates are observed within the α-Mg matrix. The addition of Y can effectively improve the mechanical properties of AZ31 alloy under high cooling rates, but the mechanical properties deteriorate at slower cooling rates due to stress concentration caused by the agglomeration of large-sized Al2Y particles. The optimal mechanical properties of the AZ31-1Y alloy are achieved at a cooling rate of 29.9 °C/s combined with subsequent heat treatment, and its YS, UTS, and EL reached up to 69 MPa, 293 MPa, and 14.5 %, respectively. Moreover, the related strengthening mechanisms are quantified. It is believed that this work can provide guidance for controlling the microstructure and optimizing the mechanical properties of as-cast Mg–Al alloys.

The effect of friction stir-back extrusion speed on Al-Cu-Mg-Li alloy microstructure and corrosion behaviour

ABSTRACT In this study, the effect of extrusion speed on the microstructure and corrosion behaviour of a friction stir-back extruded Al-Cu-Mg alloy containing 0.5 wt.% Li was investigated. Results show that friction stir-back extrusion on an as-cast aluminum alloy with a dendritic microstructure forming finely equiaxed recrystallized grains. With decreasing extrusion speed from 80 to 40 mm/min, the average grain size increases from 6.0 ± 1.2–9.8 ± 3.2 µm. After friction stir-back extrusion, the morphology of the Cu-Mg-rich precipitates has completely changed, and the fine precipitates (0.25-0.42 µm) with a uniform distribution have formed in the microstructure of the extruded wires. With the reduction of the extrusion speed from 80 to 40 mm/min, the accumulated strain in the extruded wires increases from 0.006-0.011. Compared to as-cast alloy, friction stir-back extrusion results in at least 23, 37, and 22% increases in yield strength, tensile strength, and elongation. The minimum corrosion current (1.32 × 10−4 A.cm−2) and corrosion rate (0.003 mm/year) were achieved in the wire extruded at a rotational speed of 800 rpm and an extrusion speed of 60 mm/min.

On phase stability and phase relations of topologically close packed phases in binary Cr-Os system over the temperature range of 900–1300 ℃

Osmium (Os) addition has been found to be beneficial in enhancing the creep resistance and microstructure stability of nickel-based single-crystal superalloys. The phase stability and phase relationship of topologically closely packed (TCP) phases in a binary Cr-Os system is thus essential for developing a better understanding of the constitutional effects of Os in multicomponent nickel-based single-crystal superalloys, but are still not fully understood in the literature. In this paper, a series of Cr-Os alloys were prepared, and the phase constituents and the microstructure of both as-cast and annealed alloys over a temperature range of 900–1300 ℃ were analyzed using the X-ray diffraction (XRD) and electron probe microanalysis (EPMA) techniques. The experimental results show that (Cr) solution, (Os) solution and Cr2Os phases are formed during solidification. After long-term annealing at 900–1300 ℃, the phase constituents and the microstructure of the alloys display obvious changes. Based on the measured data, the phase stability and phase equilibria of TCP between 900 and 1300 ℃ in the binary Cr-Os system are accordingly updated. The stability results for the two TCP phases in the binary Cr-Os system demonstrate that the Cr3Os phase exists stably, while the Cr2Os phase decomposes into Cr3Os and (Os) at 900–1300 ℃.

Effect of microstructure and temperature on the bulk and small-scale deformation behavior of 2nd and 3rd generation advanced intermetallic TiAl alloys

Advanced intermetallic TiAl alloys have attracted considerable attention as a high-temperature structural material in aerospace and automobile sectors owing to their low density, elevated temperature strength, superior creep, and oxidation resistance. The present study is focused on assessing the effect of alloy composition, heat treatment and microstructural variation on the bulk and small-scale deformation behavior of commercial grade 2nd generation and newly developed 3rd generation TiAl alloys at 25 °C (298 K), 300 °C (573 K), and 500 °C (773 K). Twinning is noted to be the dominant deformation mechanism irrespective of the temperature. The highest yield strength and hardness are noted for the as-cast 3rd generation TiAl alloy owing to the finer microstructure and compositional variation. Heat treatment however modifies the TiAl microstructure significantly resulting to unique bilamellar-biglobular (BLBG) microstructure, devoid of the brittle β0 phase. Consequently, nano twins- and micro twins-induced enhanced deformability is noted for such microstructure, as compared to the as-cast counterparts. Interestingly, an anomalous increase in strength with an increase in temperature is observed for the studied alloys owing to the presence of high-density twins and Kear-Wilsdorf locks. Most importantly, a temperature dependant hardness anomaly is noted in the TiAl alloys that opens new avenues for further research in nanoscale deformation. This piece of research potentially strengthens the understanding of the role of constituent phases and temperature in the deformation behavior of complex TiAl alloys. Twin-induced deformation mechanism noted for the novel BLBG microstructure, can also be valid for different generations of TiAl alloys to achieve enhanced deformability that paves the way for the development of next-generation material.

Stoichiometry and annealing condition on hydrogen capacity of TiCr2-x AB2 alloys

This study presents the effect of stoichiometry and annealing condition on Ti–Cr AB2-type hydrogen storage alloys. Prior to annealing the majority phase of the as-cast alloys was the C14 Laves phase, with separate Ti and Cr phases. Annealing treatment (1273 K/14 d) led to a transition from C14 to C15 Laves phase structure. Both C14 (as-cast) and C15 (annealed) cell size increased with Ti content, up to a ratio (Cr/Ti) of 1.6, due to B-site Ti substitution in the lattice up to a limit. Pressure composition isotherm (PCI) measurements demonstrated alloys containing a greater Ti content had a better maximum hydrogen storage capacity (1.5 vs. 1.03 wt%) and lower plateau pressure (9.4 vs. 15.8 bar) at 253 K. Annealing resulted in a lower storage capacity (1.05 vs. 1.49 wt%), greater plateau pressure (ca. 30 bar) and flatter plateau slope (25 % reduction in plateau slope). Reduction in hydrogen storage capacity of annealed alloys could be due to diffusion of residual Cr in the alloy into the C15 Laves phase during the annealing process, thereby changing the local composition as confirmed through X-ray diffraction (XRD).

Changes in effective grain delineation criteria induced by strong texturing of Zn-0.15Mg alloys after friction stir processing

Friction stir processing (FSP) was employed to enhance the mechanical properties of Zn-0.15Mg biodegradable alloys. The FSPed Zn-0.15Mg alloys exhibited a higher ultimate tensile strength of 164.1 MPa than the as-cast alloy. Nevertheless, the mechanical properties of these alloys deviated from the traditional fine-grain strengthening. When assessing the mechanical properties of FSPed-Zn-0.15Mg alloys, it is crucial to evaluate the cleavage fracture unit or effective grain size thoroughly. The determination of the misorientation tolerance angle for the effective grain size (EGS) yielded a value of 25°. A comprehensive analysis was conducted to examine the impact of microstructure properties on the EGS with particular emphasis on texture.

Expansion of chromatic color range and improvement of mechanical properties on Cu–Ge supersaturated solid solution alloys

The Cu–Ge solid solution alloys have a limited color range and relatively low strength due to its limitation of Ge solubility for a solid solution α-Cu phase at room temperature. To extend chromatic color range and to improve mechanical properties of Cu–Ge solid solution alloys, the Cu–Ge alloys with relatively higher Ge content than solubility limit on equilibrium state were fabricated by induction casting. The as-cast Cu–Ge alloys with 7–10 at.%Ge exhibited dual-phase structure composed of α-Cu and ζ-Cu17Ge3 phases with dendritic structure. By annealing at 700 °C for various times and followed quenching processing, the alloys successfully transformed into the supersaturated α-Cu single-phase structure. To confirm the color difference between the supersaturated single α-phase alloys with a high Ge content and the as-cast single α-phase alloys with low Ge content, the reflectivity analysis, CIE L*a*b* color space system, and color difference indicator were used. As a result, it was confirmed that there was a distinct color difference between supersaturated single α-phase alloys and as-cast single α-phase alloys, and the reflectivity and color difference of the alloys significantly depended on Ge content. Moreover, the Vickers hardness of as-cast and solution treated single α-phase alloys highly improved with an increase of Ge content. The influence of Ge content on phase formation, chromaticity and mechanical properties of solid solution Cu–Ge alloys was systematically discussed.

Achieving strength-ductility synergy in a novel Al-Mg-Zn-Cu-Si lightweight multi-component alloy via eutectic structure refinement

The development of lightweight multi-component alloys (MCAs) with good strength plasticity synergy faces a significant challenge, owing to the enormous number of potential component combinations, serious microstructure defects caused by poor castability, and the inefficiency of conventional empirical trial-and-error approaches. To surmount this challenge, we proposed an alloy design method, using the CALPHAD-based high-throughput calculation (HTC) to quickly identify compositions in Al(100−w-x-y-z)MgwZnxCuySiz MCAs over high-dimensional composition space that can make α-Al and Mg2Si nucleate at the same time. Then successfully low-cost prepared large-sized MCA ingots with less segregation and porosity, and good performance according to the HTC screening results, and the calculated nucleation temperatures were in high agreement with the experimental values, with an error ranging within 0.5%. The granular eutectic Mg2Si phase exhibited exceptional uniformity and dispersion within the microstructure of the Al77Mg8Zn5Cu6Si4 alloy, with an average size of 1.8 µm. Consequently, the as-cast Al77Mg8Zn5Cu6Si4 alloy displayed superior strength plasticity synergy at room temperature (RT), with the ultimate compressive strength reaching 706 MPa and the strain reaching 14.2%. This work demonstrates that the CALPHAD-based HTC approach provides an effective strategy for accelerating the design of lightweight MCAs with large-size and excellent mechanical properties.

Effect of thermomechanical processing on microstructure evolution and mechanical properties of metastable β Ti–5Al–5V–5Mo–3Cr alloy

Two distinct thermomechanical processing (TMP) schedules are applied to as-cast Ti-5553 alloy pancakes, to optimize its microstructure and mechanical performance. While TMP-I involves 40 % thickness reduction via forging, TMP-II employs rolling with 20 % thickness reduction. Typical bimodal microstructures with nearly similar sizes, distributions, and morphologies for the primary αp grains and colonies of secondary αs and β are noted to generate for both TMP-I and TMP-II. Certainly, rolling for only half the extent of that used for forging, appears ideal and economical for obtaining the targeted microstructure. Interestingly, similar and improved localized hardness values with respect to as-cast alloy, are obtained for bimodal microstructure, generated through both the TMP schedules. However, indentation size effect is noted to be nominally lower for the rolled alloy, thereby proving its suitability for large-scale application. Global behavior assessed through tensile tests also shows that bimodal microstructures obtained through forging or rolling leads to higher strengths, toughness and ductility, as compared to as-cast counterparts. This is primarily owing to non-uniform strain distribution in the as-cast alloy, resulting to crack initiation and failure, as revealed through digital image correlation-based study. Overall, TMP employing rolling with reduced deformation in particular appears beneficial for the mechanical property improvement of the alloy.

Degradable Zn–5Ce alloys with high strength, suitable degradability, good cytocompatibility, and osteogenic differentiation fabricated via hot-rolling, hot-extrusion, and high-pressure torsion for potential load-bearing bone-implant application

Zinc (Zn)-based alloys are considered the next-generation biodegradable material for promising bone-implant devices due to their good degradability, formability, and functionality. Nevertheless, the as-cast Zn alloys showed a low strength-toughness, making it challenging to meet the mechanical properties requirements for high-load-bearing bone implants due to their hexagonal close-packed structure, coarse grain size, and less sliding system. Herein, we have developed biodegradable Zn–5Ce alloys by cerium (Ce) alloying followed by hot-rolling, hot-extrusion, and high-pressure torsion (HPT), respectively, for potential bone-implant application. Mechanical testing revealed that the HPT sample exhibited the best mechanical performance matching among the Zn–5Ce samples with a high ultimate tensile strength of ∼345 MPa, yield strength of ∼230 MPa, a moderate elongation of ∼11.4%, and macro-hardness of ∼96.6 HB. Electrochemical corrosion and static immersion testing revealed that the HPT sample showed the highest electrochemical corrosion rate of ∼416 μm/y and degradation rate of ∼43.8 μm/y in Hanks' solution among the Zn–5Ce samples, which is suitable for degradation rate requirements for bone-implant application. Bio-tribological testing revealed that the HPT sample showed high bio-tribological properties matching in Hanks’ solution with the lowest friction coefficients of ∼0.530 and moderate wear loss of ∼2.2 mg. Cytocompatibility and osteogenic differentiation assessment revealed that the diluted extract of the HPT sample showed the highest cytocompatibility towards 3T3 and MG-63 cells and osteogenic differentiation performance towards 3T3 cells among the most diluted extracts. Accordingly, the HPT Zn–5Ce sample is expected to be used for high-load-bearing degradable bone-implant devices, including bone fixation and guided bone regeneration systems.

Microstructural effects on the ambient temperature indentation creep behavior of metastable β Ti-5Al-5V-5Mo-3Cr alloy

Ti-5553 alloy is considered as a potential candidate for heavy structural components such as landing gears in aerospace industries, that operate particularly at room temperature. For achieving the targeted performance, microstructural modification and corresponding improvement in mechanical properties, particularly room temperature creep behavior of Ti-5553 alloy is of significant concern. In this regard, an optimized thermomechanical processing (TMP) schedule is employed to tailor the microstructure of as-cast Ti-5553 alloy. Typical bimodal microstructure containing both α and β phases is noted to evolve upon TMPing, as compared to its as-cast counterpart, having sole β phase. The size and volume fraction of αp are noted to be 0.85 ± 0.39 µm and 11.7 ± 0.5%, respectively. Such pronounced variation in the microstructural features is expected to alter the localized mechanical properties significantly. To assess that, room temperature small-scale creep behavior of as-cast and TMPed Ti-5553 alloys is investigated using nanoindentation technique. The effect of maximum load on different creep parameters are analyzed and correlated with the corresponding microstructures. It is noted that at any particular applied load level, creep deformation of TMPed Ti-5553 alloy is ∼ 20–64% lower than that for the as-cast one. This is reflected in significant reduction in the minimum creep strain rate from 10−4 s−1 for as-cast to 10−5 s−1 for TMPed Ti-5553 alloy. Dislocation creep mechanism is found to be active for both the alloys since creep exponent for both the as-cast and TMPed Ti-5553 alloys exceed the value of 2. Discontinuous semi-circular micro-shear bands are noted to form around the indents for the as-cast Ti5553 alloy. The kernel average misorientation map for this alloy reveals a lower degree of misorientation and a more homogeneous distribution of plastic strain. In contrary, the TMPed Ti-5553 alloy exhibits higher misorientation around the indent impression, thereby indicating towards the restriction of dislocation movement against α/β laths and hence positively influencing the creep behavior. Overall, the study highlights the important role of TMP in enhancing the creep resistance of Ti-5553 alloy for industrial applications.

Excellent elastocaloric and mechanical performance in Mn-doped Co–V-Ga as-cast polycrystalline alloy with simple preparation

With the rapid development of solid-state refrigeration technology, elastocaloric materials face higher requirements, such as a higher elastocaloric effect (eCE), better mechanical properties, and simpler and faster large-scale preparation. In this work, we propose a composition design strategy for Mn-doped Co–V-Ga shape memory alloys, which can enhance both the eCE and the mechanical properties. We combine first-principles calculations and experiments to demonstrate this strategy. Our results reveal that the lattice distortion caused by the difference in atomic radii produces a solid-solution-strengthening effect within the alloy, impeding dislocation motion and significantly improving the mechanical properties. Through composition optimization, the low-cost Co51.7V31.3Ga14.75Mn2.25 as-cast polycrystalline alloy exhibits a large adiabatic temperature change (ΔTad) of −11.2 K at room temperature, while its maximum compressive strength and strain can reach up to 1859 MPa and 26% at room temperature, respectively. Importantly, the alloy exhibits excellent cycle stability, and its ΔTad does not decay after 100 loading and unloading cycles, indicating that it has the potential for practical application. Further comparison with the annealed sample shows that the secondary defects deteriorate the ΔTad of the alloy. Our research provides an effective strategy for the simple, rapid and large-scale production of as-cast eCE alloys.

Influence of alloying elements and composition on microstructure and mechanical properties of Cu-Si, Cu-Ag, Cu-Ti, and Cu-Zr alloys

This study aims to quantitatively compare the effects of alloying elements on the microstructures and mechanical properties of Cu–Si, Cu–Ag, Cu–Ti, and Cu–Zr binary alloys over an alloying content range up to 2 wt%. The alloys were produced using vacuum arc melting, followed by homogenization and cold-rolling into plates. Subsequently, the annealing response of the cold-rolled plates was examined over a temperature range of 200–700 °C. The as-cast alloys show distinct microstructural features attributable to the alloying elements. Following the homogenization and cold-rolling processes, substantial microstructural transformations were observed. The analysis of mechanical properties revealed that solid solution hardening played a dominant role in increasing strength in Cu–Si alloys. Cu–Ag alloys displayed a minor increase in strength with alloying content, implying the influence of Cu–Ag precipitates on strength. Conversely, Cu–Ti and Cu–Zr alloys demonstrated remarkable strength improvements due to the presence of intermetallic precipitates and grain size reduction. While all other alloys displayed an inverse relationship between strength and elongation with increasing alloying content, the Cu-Si alloys exhibited a simultaneous enhancement of both strength and elongation. This effect can be attributed to the twinning-induced plasticity, brought about by the reduction of stacking fault energy in Cu through the addition of Si.

Study on the Microstructure and Properties of Mg-Gd-Ni-Y Alloy Containing LPSO Phase

The long-period stacking ordered (LPSO) structure, functioning as a strengthening phase in magnesium alloys, plays a pivotal role in compensating for inherent performance limitations. In this study, an as-cast Mg-Gd-Ni-Y alloy, including the LPSO phase, was initially obtained through an ingot metallurgy process. Subsequently, the alloy underwent distinct thermal treatments: annealing at 500 °C for 10 h, and extrusion using an extrusion ratio of 10 at a speed of 5 mm/s. Comparative analysis of the microstructure and corrosion characteristics was performed across these three alloy states. Comprising primarily of α-Mg, LPSO phase, and eutectic structures (ES), the alloy exhibited distinctive microstructural features. Immersion experiments conducted in a 3.5% NaCl solution revealed that the as-cast alloy displayed the highest dissolution rate at various temperatures, from room temperature, to 50 °C, and 70 °C. Following annealing, a reduction in the second phase content within the alloy significantly contributed to the observed decrease in its dissolution rate. Extrusion processes resulted in a denser network structure within the microarchitecture, to some extent impeding the spread of corrosion to some extent. By emloying scanning Kelvin probe force microscopy (SKPFM) and micro-electrochemical testing, it was discerned that predominantly the electrochemical system involving α-Mg and the second phases predominantly dictated the heightened dissolution rate of the alloy. This study presents valuable insights into understanding the dissolution mechanisms and potential strategies for controlling the dissolution performance of magnesium alloys containing the LPSO phase.

Effect of number of ECAP passes on structure and mechanical properties of Al–Ca–Mn–Fe alloy

The effect of number of equal-channel angular pressing (ECAP) passes on the structure and mechanical properties of the as-cast 4% Ca–1.3% Fe–0.8% Mn–0.1% Zr–0.1% Sc Al alloy is studied. ECAP was carried out at room temperature, through BC path using an angle between the channels of 110°. The number of ECAP passes was N = 2, 3, and 4. The as-cast alloy consisted of the solid solution dendrites (Al) and the [(Al) + Al10CaFe2 + Al4Ca] eutectic, as well as of a small fraction of the Al6(Fe, Mn) particles. As a result of ECAP, the dendrites are elongated approximately at an angle of 30° relative to the direction of ECAP. After two passes of ECAP, the dislocation density increased, but with an increase in the number of passes, the dislocation density slightly decreased as a result of the rearrangement of the dislocation structure; besides calcium segregated from the eutectic. After ECAP, a significant hardening of the alloy was observed. The highest strength observed after two passes (the ultimate tensile strength of the as-cast alloy was 130 MPa, and after the second pass it was 305 MPa), and the lowest one was after four passes (the ultimate strength was 219 MPa). The relative elongation of the ECAP-processed samples did not depend on the number of passes and it was about 1%.

Evolution of Mechanical Properties of Pb–Sb–Sn–As–Se Grid Alloys for Lead-Acid Batteries During Natural Aging

This study is devoted to the investigation of mechanical properties of a series of low-antimony Pb–Sb–Sn–As–Se grid alloys for lead-acid batteries in as-cast condition and after natural aging during storage. Mechanical properties were characterized by ultimate tensile strength, yield strength, elongation, and Young's modulus determined at room temperature using TIRAtest 2300 and P-0.5 universal testing machines. For most investigated as-cast alloys, an increase in ultimate tensile strength is accompanied by an increase in elongation. Within the temperature range between 70 ºС and 150 ºС, higher heating temperature of a casing mold does not markedly affect average elongation but causes the slight decrease (by ~4 %) in average ultimate tensile strength. When aged during storage for 30–33 days, the Pb–Sb–Sn–As–Se grid alloys, attain higher values of ultimate tensile strength, yield strength, and Young's modulus but lower values of elongation. This is due to precipitation of second-phase particles from lead-based solid solution oversaturated by antimony, arsenic, and selenium. The most noticeable effect of strengthening is observed during first five days of natural aging.