As-cast Alloy Research Articles

Impact of the Plastic Deformation Microstructure on the Corrosive Resistance of Metallic Materials – The State of the Art and the Effect of Microstructure Refinement on the Example of the 2000 Series Aluminum Alloy

The article discusses the role of the microstructure formed through plastic deformation in the corrosion resistance of metallic materials. Additionally, a review of the existing knowledge in this area is conducted. In particular, the role of the refinement of intermetallic phases is emphasized. For that purpose, investigations of as-cast aluminum alloy, as well as after plastic deformation, from the 2000 series have been performed. Metallographic tests of the examined materials have been carried out, and electrochemical tests as well as SEM examinations of the surface after the corrosion tests have been conducted. It has been documented that the presence of large precipitates existing at distances typical of as-cast alloys favours intensive corrosion. In turn, a significant amount of fine-dispersive precipitates at the initial stage of corrosion can work as a barrier counteracting the corrosion processes.

Achieving ultrahigh strength and ductility in biodegradable Zn-xCu alloys via hot-rolling and tailoring Cu concentration

In this present paper, a biodegradable Zn-xCu alloys with an ultrahigh strength and ductility can be achieved via hot-rolling and tailoring Cu concentration, and the role of Cu concentration on the microstructure and texture evolution in the Zn-xCu alloys during hot-rolling were investigated by XRD, EBSD and TEM analysis. The results show that the microstructure of as-cast Zn-xCu alloys consisted of large sized CuZn5 phase and Zn matrix grains before hot-rolling, and numerous submicron CuZn5 phase can dynamically precipitate during hot-rolling of Zn-xCu alloys. The existence of CuZn5 phase can result in the particle stimulated nucleation of recrystallization (PSN), and then result in the formation of fine recrystallized grains. Moreover, three texture components including 0001<112¯0>, 101¯1<1¯012> and 112¯0<0001> textures can form in the Zn-xCu alloys after hot-rolling. With boosting Cu concentration, the intensity of 112¯0<0001> texture gradually reduced, while the intensity of 0001<112¯0> and 101¯1<1¯012> texture components firstly raised with the augment of Cu concentration, and then reduced. For the Zn-xCu alloys with 8 wt%Cu concentration, a combination of high yield strength, ultimate tensile strength and elongation (269.7 MPa, 322.9 MPa and 26.3 %) can be achieved, which can meet the high-performance demands of biodegradable metal vascular stents.

The influence of heat treatment on the high temperature tensile properties of a near-α as-cast titanium alloy

The influence of heat treatment on the high temperature tensile properties of a near-α as-cast titanium alloy

Synergistic effects of boron carbide and eggshell particles on mechanical and tribological properties of ultrasonic-assisted stir cast aluminium alloy based composites

Aluminium matrix composites are in high demand for their lightweight nature and favourable properties, yet issues like high thermal expansion, low microhardness or high cost often challenge them. To address these limitations, the integration of sustainable, cost-effective reinforcing agents that can enhance hardness and wear resistance can be explored, as this can broaden the application scope of these composites across various industries. The present study fabricates aluminium matrix composites with aluminium alloy (AA6063-T6) as a matrix and different wt.% (0%, 2% and 4%) of micro-sized eggshell (ES) and boron carbide (B4C) particles as reinforcements through ultrasonic-assisted stir-casting. Analysis of microstructure, mechanical and tribological properties of the fabricated composites are done and compared to those of the as-cast base alloy. Results from optical and scanning electron microscopy (SEM), together with energy-dispersive X-ray spectroscopy (EDS) analysis, revealed the uniform distribution of reinforcements in all three composites. X-ray diffraction (XRD) indicated the formation of several compounds in each composite. Among all, the as-cast base alloy exhibited the lowest porosity at 0.48%. The AA6063-T6/B4C composite demonstrated the highest hardness, with an increase of 46.08%, while the AA6063-T6/ES/B4C composite achieved the highest tensile strength, showing a 62.28% improvement compared to the as-cast base alloy. As the load increased from 20N to 60N, the wear rate of the reinforced composites rises while the coefficient of friction decreased, with the AA6063-T6/B4C composite showing the highest wear resistance.

Effects of Hot Extrusion on the Microstructure and Wear Properties of A380-Yb Alloy

A380-Yb (Ytterbium) alloy was prepared by the ultrasonic melting casting method, and effects of hot extrusion on the microstructure and wear properties of the alloy were studied. The results indicate that the addition of rare earth Yb can refine the microstructure of the matrix alloy. After hot extrusion (extrusion ratio of 22.56) of the as-cast A380-Yb alloy, the secondary phase in its microstructure was further refined and the distribution became more uniform. EBSD (electron backscatter diffraction) organizational analysis shows that the average GND (geometrically necessary dislocation) density of extruded rare earth aluminum alloy is significantly increased, by 16.5 times that of the cast matrix alloy. In addition, there are a large number of grains parallel to the &lt;111&gt; orientation and &lt;001&gt; orientation in the extrusion direction. The alloy undergoes dynamic recrystallization during hot extrusion, and the proportion of small-angle grain boundaries is significantly reduced. Under the same friction and wear conditions, the wear rate and average friction and wear coefficient of the extruded rare earth aluminum alloy are relatively small, reduced by 53.8% and 42.6%, respectively, compared to the cast matrix alloy. Its wear mechanism is mainly abrasive wear and slight plastic deformation. In addition, the study also found that under fixed other wear conditions, as the friction speed increases, the wear rate of the extruded rare earth aluminum alloy shows a trend of first decreasing and then increasing. However, with the increase in load, its wear rate gradually increases, and the change in wear morphology is consistent with the trend of wear rate. When the wear rate is high, the wear mechanism of the extruded aluminum alloy is mainly delamination wear and adhesive wear, and is sometimes accompanied by severe plastic deformation. When the wear rate is low, its wear mechanism is mainly abrasive wear.

Effects of strain rate, temperature and microstructure on mechanical properties of (CoCrNi)94Al3Ti3 medium-entropy alloy: Experiments and constitutive modeling

Mechanical properties and microstructure evolution of as-cast, solution-treated and aged (CoCrNi)94Al3Ti3 medium-entropy alloys (MEAs) are investigated under uniaxial compression at strain rates from 10−3 to 3700 s−1 within temperatures from 123 to 573 K. Compared to the single-phase solution-treated MEA, spherical nanosized particles result in an increase in the yield stress approximately by 55 % (to 586 MPa) and 73 % (to 655 MPa) for the as-cast and aged (CoCrNi)94Al3Ti3, respectively. At ambient temperature, the as-cast and aged alloys demonstrate significantly higher dynamic strain rate sensitivity. At a fixed strain rate, the yield strengths and flow stresses increase with decreasing temperature for all three alloys. The as-cast and aged alloys exhibit significantly higher yield strength primarily due to precipitation strengthening of the coherent ordered L12 precipitates. Dislocation slip dominates the plastic deformation and leads to the weak but apparent 〈110〉 texture along the loading direction, and no deformation twins are observed in all alloys. Besides, Khan-Liu constitutive models are developed and can well describe the plastic flow of three alloys over a wide range of strain rates and temperatures.

Comprehensive property combination for biomedical application achieved in a Ti35Zr35Nb15Mo5Fe5Cr5 complex concentrated alloy

A novel Ti35Zr35Nb15Mo5Fe5Cr5 complex concentrated alloy (CCA) with potential for biomedical application was developed by vacuum arc melting and its microstructural evolution, mechanical properties, corrosion and wear behavior, and cytocompatibility were systematically evaluated. The alloy has an experimentally measured density of 6.37 g/cm³, suitable to fulfill the requirement of light weight. XRD analysis revealed that the as-cast and annealed specimens contain two BCC solid solution phases and a TiCr2 type Laves phase. The average microhardness (H) and elastic modulus (E) of the as-cast CCA are 618.39 ± 9.26 HV and 97.32 ± 3.58 GPa, respectively. Moreover, the yield strength (YS) of the as-cast alloy, estimated from elastoplastic analysis of the microindentation data, is 1203.94 ± 30.28 MPa. However, the CCA annealed at 1100˚C exhibits a microhardness of 833.08 ± 7.58 HV and a YS of 1669.65 ± 24.79 MPa, with the elastoplastic stress-strain response revealing no significant loss of plasticity due to the increased hard Laves phase. Corrosion and wear tests conducted in simulated body fluid confirmed the alloy's excellent corrosion and wear resistance. Cell culture experiments with MG-63 and HEK-293 cells demonstrated superior cell viability and proliferation compared to CP-Ti and 316 L SS. Moreover, confocal fluorescence images of MG-63 cells stained with AO/EtBr, Rh-123, and DCFH-DA revealed that the present CCA exhibits good biocompatibility. Thus, a comprehensive combination of low density, compatible elastic modulus, good strength with adequate plasticity, and sufficient corrosion resistance and biocompatibility were successfully achieved, unraveling significant potential of the alloy for biomedical applications.

Effects of TiB2 particles on deformation behavior, softening mechanisms and recrystallization texture of hot-compressed Fe-TiB2 composites

Fe-TiB2 composites, also termed as high modulus steel, offer a promising solution to the challenge of achieving both lightweight and high stiffness materials. However, the presence of TiB2 particles in Fe-TiB2 composites results in poor hot-workability. Therefore, understanding the effects of TiB2 particles on the hot deformation behavior, dynamic recrystallization (DRX), and microstructural evolution of Fe-TiB2 composites is crucial for optimizing their hot-working process. In this study, we elucidated the effects of TiB2 particles on deformation behavior and dynamic softening behavior by conducting a series of isothermal compression tests on as-cast Fe-TiB2 composites and as-cast base alloys (control group) at temperatures of 800–1200 °C, strains of 0.36–1.2, and strain rates of 0.01–1 s⁻1. Using electron backscatter diffraction, we characterized the microstructures of composites and base alloys, showing that TiB2 particles induce a DRX process through particle stimulated nucleation (PSN) at low temperatures and promote continuous dynamic recrystallization (CDRX) at high temperatures. The presence of TiB2 particles have significantly affected the dislocation movement and distribution, which changes the deformation energy distribution and thus facilitates different DRX behaviors under various thermal deformation conditions. Additionally, the microstructure resulting from DRX through PSN exhibits significant texture weakening and grain refinement, presenting a promising method for fabricating ultrafine-grained Fe-TiB2 composites.

Influence of Hot Rolling on Microstructure, Corrosion and Mechanical Properties of Mg–Zn–Mn–Ca Alloy

The effect of hot rolling on the microstructure, mechanical, and corrosion properties of the magnesium alloy 96 wt% Mg–2.3 wt% Zn–0.7 wt% Ca–1 wt% Mn was studied. After heat treatment, the original plates of an as-cast alloy were rolled from a 7 mm thickness to a 0.2 mm thickness at two temperatures—300 or 400 °C. It has been established that increasing the rolling temperature from 300 to 400 °C increases the fraction of recrystallized grains in the microstructure and after rolling at 400 °C, the microstructure is fully recrystallized. The best strength–ductility balance of the alloy was obtained after rolling at 300 °C, with a high total percentage reduction of 93–97%: the yield stress, the ultimate tensile strength, and the elongation averaged at 285 MPa, 310 MPa, and 5%, respectively. The alloy after rolling, annealed at 400 °C, shows improved ductility but lower strength: the yield stress, the ultimate tensile strength, and the elongation were 200 MPa, 260 MPa, and 17%, respectively. The strong dependence of corrosion resistance on respect to rolling direction is observed, which can be reduced after heat treatment. The as-rolled alloy and the heat-treated alloy had low corrosion rates in Hanks’ solution of 0.54 and 0.19 mm/year, respectively.

Enhanced corrosion resistance of AZ31 magnesium alloys through the use of high-purity raw magnesium

Poor corrosion resistance is a critical barrier to the widespread application of magnesium alloys. Statistically, the literature reported that approximately 70 % of as-cast AZ31 magnesium alloys exhibit corrosion rates exceeding 1 mm ·y−1 in 3.5 wt.% NaCl solution, which is unacceptable for industrial use. Furthermore, there is a considerable discrepancy in the corrosion rates reported by different studies (as-cast alloys ranging from 0.4 to 215 mm ·y−1). These phenomena may be attributed to the uncontrollable content of impurity elements in commercial magnesium alloys, which fluctuate widely between batches. In the present work, we prepared as-cast AZ31 magnesium alloys with different impurity contents using two different purities of raw magnesium (Mg-99.9% and Mg-99.99%). The impact of impurity contents on the corrosion resistance of AZ31 magnesium alloys was then analyzed. The AZ31 magnesium alloy prepared with 99.99% raw magnesium showed superior corrosion resistance compared with that prepared with 99.9% raw magnesium, with a reduction in corrosion rate by approximately 98 % and a decrease in the fluctuation range of corrosion rate by 91 %. Thus, enhancing the purity of raw magnesium is an effective method to improve both the corrosion resistance and consistency of magnesium alloys.

Increasing the high-temperature mechanical properties of Mg-Gd-Y-Zn alloys by adding AlN/Al particles

The AlN particles reinforced Mg-10Gd-3Y-1Zn (GWZ) composites were prepared by mixing AlN/Al particles using ball milling followed by stirring casting method. The influence of AlN/Al particles on the microstructural evolution and high-temperature mechanical properties of GWZ alloys were revealed and discussed. With AlN/Al particles added into the as-cast alloys, the Mg3RE phase was transformed into lamellar LPSO phase, while the content of Al2RE and LPSO phase increased. Since the Al2RE and AlN were effective nucleation sites for α-Mg, the grain size of AlN/Al-GWZ composites was reduced obviously from 126.1 to 39.8 μm. After homogenization, due to the coherent lattice matching relationships between 18R-LPSO phase and Al2RE or AlN particles, the 18R-LPSO phase nucleated on the Al2RE and AlN particles. After ageing treatment, the 2AlN/Al-GWZ composite showed the optimum mechanical properties at 250 °C, with the yield strength, ultimate tensile strength and elongation of 247.1 MPa, 265.5 MPa and 4.0%, respectively. The strengthening effect was primarily originated from the AlN particles, Al2RE and LPSO phases in the 2AlN/Al-GWZ composite. Besides, the composites can achieve the enhancement of high-temperature strength without the sacrifice of plasticity due to the coordinated deformation of AlN particles as well as the refinement of grains.

Effect of rolling process on deformation structure and mechanical properties of CoCrFeNiMo0.35 high entropy alloy

In this work, CoCrFeNiMo0.35 high entropy alloy was hot-rolled at 900°C by varying different reductions (10%, 20%, 30%, 40%, 50%) and the impact of hot rolling on the structure and mechanical properties of this alloy has been investigated. It is found that the phase composition of CoCrFeNiMo0.35 high entropy alloy after hot rolling has not been changed, and it still consists of FCC phase and σ phase (Cr and Mo-rich phase), which is the same as the as-cast state alloy. Besides, the grain size becomes finer after hot rolling and is stretched to a flat shape in the rolling direction, and the grain orientation gradually changes from <001> and <101> direction to <101> direction with the increase of reduction. At the same time, as the increase of rolling reduction, the volume fraction of σ phase increases, and the yield strength (∼817.8 MPa), tensile strength (∼891.7 MPa) and hardness of the alloy are improved. The comprehensive influence of fine grain strengthening, second phase strengthening and dislocation strengthening is the main reason for this result. Besides, the fracture mode of the tensile sample changes from mixed tough-brittle fracture to brittle fracture. The research results can be used as a reference for hot rolling strengthening of CoCrFeNiMo0.35 high entropy alloy.

Effect of Gd content on microstructure and mechanical properties of Mg-xGd-Zr alloys via semicontinuous casting

Mg-Gd based alloys are an important class of high-performance Mg alloys. In this study, three Mg-Gd alloys with different gadolinium (Gd) contents: Mg-9.54Gd-0.40Zr (wt.%, G10 K), Mg-15.11Gd-0.35Zr (wt.%, G15 K) and Mg-19.67Gd-0.33Zr (wt.%, G20 K) were prepared by semicontinuous casting and subsequent solution and aging heat treatments. The role of Gd content on microstructures and mechanical properties of the Mg-Gd-Zr alloy is studied. All three as-cast alloys exhibit eutectic phases of Mg5Gd, with the amount increasing as the Gd content rises. Mg5Gd disappears after the solution heat treatment (the G10 K alloy solution-treated at 480 °C for 4 h, the G15 K alloy at 500 °C for 12 h and the G20 K alloy at 520 °C for 24 h, respectively). Aging heat treatment at 200 °C for 64 h after solution introduces numerous prismatic β′ precipitates, with a significant increase in their area number density corresponding to increased Gd content. Additionally, the morphology of the β′ precipitates exhibits distinct variations: the G10 K alloy is characterized by an enhanced aspect ratio. Consequently, the peak-aged G10 K alloy demonstrates superior strength-ductility synergy, with a yield strength (YS) of 216 ± 1 MPa, an ultimate tensile strength (UTS) of 363 ± 1 MPa, and an elongation (EL) of 8.7 ± 0.6 %. This study suggests that plasticity diminishes and precipitation strengthening is limited when the gadolinium content exceeds 15 wt.%.

Optimizing dry milling of stir-cast and heat-treated AZ80 magnesium alloy using multiple criteria optimization technique: an experimental study.

The primary aspects of this research are to evaluate surface roughness, cutting force, and material removal rate and optimize it with dry milling process parameters for heat-treated and stir-cast AZ80 magnesium alloy. Multiple methodologies are utilized in the research, which includes the Integration of design of experiments-response surface methodology for experimental design with the technique for order of preference by similarity to ideal solution for multi-criteria optimization. In order to evaluate the effect of process parameters on the response, the experimental design manipulates the depth of cut, feed rate, and cutting speed in a systematic manner. An evaluation of the machined surface's quality is conducted via surface roughness measurements. Likewise, insights into the forces exerted during milling can be obtained through continuous monitoring of cutting forces. The calculation of material removal rate is predicated on weight reduction. The interaction between the depth of cut and feed rate has a significant impact on the critical-to-quality characteristics of the alloy, which has contribution percentage greater than 25%. This finding validates that despite the heat-treated alloy having a similar composition to the as-cast alloy (where the closeness coefficient is 0.9843), the optimal process parameters of the former are not applicable to the latter. Nevertheless, the technique used to prepare the specimen has no bearing on the material removal rate, which is a process parameter-specific effect.

Regulating microstructure and mechanical properties of the as-cast Mg-4Zn-0.5Y-0.5Nd alloy by heat treatment

The Mg-4Zn-0.5Y-0.5Nd alloy was designed and fabricated by conventional casting with subsequent heat treatment to regulate the microstructure and mechanical properties. The microstructure, secondary phase, mechanical properties, and fracture behavior were analyzed to elucidate the influencing mechanism. The results reveal that the as-cast alloy is composed of equiaxed grains with large sizes and discontinuously distributed secondary phases. Moreover, the secondary phase is mainly W-Mg3Zn3Y2, which partly forms the eutectic structure. The solid solution treatment coarsens the equiaxed grains and transforms the secondary phase into near continuous distribution. The Mg41Nd5 phase appears and volume fraction of secondary phase decreases a little. The combining of solid solution and aging treatment increases grain size and volume fraction of secondary phase more or less. Furthermore, the Mg24Y5 phase appears and secondary phases have been changed into semi-continuous distribution. After heat treatment, the average grain size reaches its maximum value of 107.18 μm, and the volume fraction of secondary phase climbs up to 2.73 %. Moreover, the solid solution treatment weakens the crystallographic orientation preference along {0001} but induces diversified crystallographic orientation preference. The heat treatment increases microhardness from 57.2 HV0.1 of the as-cast state to 70.5 HV0.1 of the heat-treated state. Comparatively, the solid solution treatment decreases mechanical properties, while the solid solution and aging treatment increase strength and ductility simultaneously. Especially for the ductility, it has been improved by more than 80 %, which is beneficial to the subsequent thermalmechanical processing greatly.

Preparation and excellent mechanical properties of nanocrystalline GW103K Mg alloy by HDDR technology

Grain size of GW103K Mg alloy powder were markedly refined to about 45 nm from 20 μm by an optimized hydrogenation-disproportionation-desorption-recombination (HDDR) process. By changing temperature, hydrogen pressure and time, the optimum hydrogenation conditions are explored by orthogonal design. Then the complete dehydrogenation process was determined by using single factor control variables. Furtherly, the HDDRed powder was spark plasma sintering (SPS) sintered and hot extruded to prepare GW103K alloy bulk. XRD, OM, scanning electron microscopy (SEM), and transmission electron microscope (TEM) were used to analyze the phase transformation and microstructure evolution, based on which the grain refining mechanism during the HDDR were discussed. The optimum HDDR parameters for preparing nanocrystalline Mg alloy powders are hydriding at 550 °C under 5 MPa hydrogen pressure for 24 h and dehydriding at 550 °C for 8 h in vacuum. The nanocrystalline GW103 alloy presents a notable dimensional stability and the grain size of the alloy bulk is 43 nm after SPS and hot extrusion. As a result, the nanocrystalline GW103K specimens exhibit excellent mechanical properties compared to the coarse-grained counterparts. Especially, the nanocrystalline GW103K alloy has a tensile elongation of 21.1% which is much more than those of the as-cast and as-extrusion alloys.

Enhancing machinability in free-cutting duplex brass alloys: Isotropic blocky α phase formation via optimized hot extrusion processing

Despite the active utilization of duplex brass alloys in the electronics and automotive industries, optimizing thermomechanical treatment conditions for achieving excellent machinability remains a subject of ongoing debate. In this study, to establish a strategy to achieve enhanced machinability via industrial-scale direct hot extrusion processing, we systematically investigated the effect of hot extrusion processing conditions on microstructural evolution, mechanical properties, and machinability of duplex brass alloys. In particular, the yield strength was effectively interpreted through the extended Hall-Petch relationship, and the machinability was further elucidated through the evaluation of rotational torque during the drilling test as well as the precise analysis of segmented chips produced in the drilling test. As a result, our microstructural analysis of the as-cast Cu58Zn39Pb3 alloy revealed that the cooling process during industrial-scale casting inevitably results in the formation of the Widmanstätten structured α phase and the heterogeneous dispersion of Pb particles. In contrast, 670 ℃ extruded lower part and 730 ℃ extrudates, which were extruded in the single β region that caused complete dynamic recrystallization behavior, exhibited a uniform and isotropic blocky α structure and uniformly redistributed Pb particles, ultimately leading to superior mechanical properties and machinability. Notably, our findings suggest that achieving an isotropic blocky α structure can be attained at temperatures up to 100 ℃ below the β-transus temperature by optimizing extrusion pressure conditions. This approach offers an efficient methodology for minimizing defects caused by high-temperature extrusion, such as surface oxidation and hot shortness cracking, while simultaneously minimizing processing costs.

Nanostructured bulk HPT β Ti-42Nb alloy as biomaterial for implants obtained directly from micrometric powders

The effect of high-pressure torsion (HPT) processing on mechanical properties in a β Ti-42Nb alloy micrometric powder consolidated in a nanostructured bulk disc through severe plastic deformation for biomedical applications is investigated. XRD, SEM and TEM/ASTAR characterization are used to characterize microstructure of the original micrometric powder and the consolidated disc of β Ti-42Nb alloy after HPT. The results show that severe plastic deformation processing improves Vickers hardness of β Ti-42Nb alloy, and leads to a low modulus bulk material with E = 63 GPa after HPT, comparable with that of as-cast alloy. The obtaining of nanostructured grain size around 55 nm bulk β Ti-42Nb alloy consolidated through HPT from micrometric atomized powder opens perspectives of applications as biomedical implants.

Effects of Ca contents on microstructures and mechanical properties of friction stir processed Mg alloys

Ca alloying is beneficial for improving the uniform elongation for friction stir processed (FSPed) Mg-4Al-2Sn-xCa (0, 0.5, 1.0 and 1.5 wt.%) (AT42-xCa) alloys. Coarse CaMgSn and Al2Ca particles in as-cast AT42-xCa alloys lead to a sharp decrease in elongation. Friction stir processing (FSP) is effective in improving strength and elongation by refining grain structure along with CaMgSn and Al2Ca particles, and inducing grain orientations with high Schmid factors for basal slip. Consequently, FSPed AT42-0.5Ca alloy exhibits simultaneously enhanced ultimate tensile strength (∼224 MPa) and elongation (∼30.9%). Compared to the Ca-free alloy, 0.5 wt.% Ca alloying increases the heat input and promotes the dislocation recovery, reducing residual dislocations. Nano-sized CaMgSn precipitates in grain interiors inhibit the dynamic recovery of dislocations during tensile, facilitating the work-hardening ability. Besides, high Schmid factors facilitate basal dislocation slips. Therefore, high EL is primarily due to the dislocation-free fine grain (∼2.7 μm), refined CaMgSn particles (micron-sized particles (∼1.3 μm) and nano-sized precipitates (∼55 nm)) and high Schmid factors (∼0.446) for basal slips.

Excellent mechanical properties and giant room-temperature elastocaloric effect in spark plasma sintered Ni-Co-Mn-Ti shape memory alloy

All-d-metal Heusler-type Ni-Mn-Ti alloys have emerged as a research focus in the field of elastocaloric refrigeration due to their remarkable elastocaloric effect. However, the mechanical properties of these materials present a challenge for their engineering applications. In this work, Ni37Co13Mn33.5Ti16.5 alloys with varying particle sizes were successfully prepared under different conditions using spark plasma sintering. The influence of particle size on the microstructure, mechanical properties and the elastocaloric effect were systematically explored. The results indicate that smaller particle sizes can significantly enhance mechanical properties during the SPS process, primarily due to grain refinement and the presence of Ti-rich second phases within the grains. Notably, compressive strength and fracture strain reached as high as 2225 MPa and 33 %, respectively, marking an increase of 145.9 % and 312.5 % over the as-cast alloy. Additionally, an unprecedently adiabatic temperature variation of 31.2 K was obtained upon loading in the sintered Ni-(Co)-Mn-Ti shape memory alloys.