CuAlNi Shape Memory Alloy Research Articles

A Study of the Effect of Graphene on Fatigue Life of CuAlNi Shape Memory Alloy

A Study of the Effect of Graphene on Fatigue Life of CuAlNi Shape Memory Alloy

Experimental and theoretical results of gamma shielding features for copper based shape memory alloys

In this study, the gamma ray attenuation characteristics for CuAlNi shape memory alloys with different proportions of Sn doping was investigated. We determined the mass attenuation coefficient (μ/ρ) of CuAlNiSn alloys both experimentally and theoretically within an energy range of 59.5–1332.5 keV. The experimental measurements were made using a high purity Germanium detector (HPGe) and theoretical calculations were made using WinXCOM program. To evaluate the gamma radiation shielding abilities of the alloy samples, the obtained (μ/ρ) values were used to determine the gamma protection parameters μ, HVL, TVL, MFP, and Zeff. In addition, the radiation protection efficiency (RPE) parameter was determined using gamma ray intensities in the absence and presence of the attenuator. Further analysis of the samples was conducted using a Rigaku Miniflex 600 model computer-controlled X-ray diffractometer (CuKα & λ = 1.5405 A0). The crystallographic structure of the alloys before and after irradiation was investigated. Other analysis which include EDX analysis (to investigate the chemical content) and SEM analysis (to investigate the microstructure) were conducted. According to result outcomes, gamma ray radiation did not affect the shape memory properties of structure. Another interesting observation is that, the radiation attenuation properties increase with increasing Sn concentration. Finally, we discovered that the CuAlNiSn4 alloy (which has the highest doping rate) provides good protection especially at low energy levels.

Hysteresis gap-shrinking and structural effects of minor Al and Ti modifications on binary CuAl-based high-temperature shape memory alloys

Cu-based shape memory alloys (SMAs), except for exhibiting shape recovery, superelasticity, and high damping, are desirable because these smart materials have higher electrical and thermal conductivity and much lower prices than NiTi SMAs. However, they also have some downsides in mechanical strength and brittleness (mostly stemming from their coarse grain structure) and thermal instability. Therefore, adding some grain refining elements to these SMAs to improve their shape memory effect (SME), and thermal, structural, and mechanical properties is a widespread and simple way that significantly affects their martensitic phase transitions, structure, and mechanical properties. One of these grain-refining elements is titanium. Its thermal conductivity is lower than those of Cu and Al elements and has a low solubility in Cu-matrix. Besides the effects of small Al variations, the use of minor amounts of titanium in binary CuAl-base alloys can show impressive effects on all characteristics of these shape memory alloys, such as shape memory effect properties, martensitic transformation kinetics parameters, and microstructural features. In this research work, CuAlTi ternary high-temperature shape memory alloys (HTSMAs) with new compositions were produced by the arc melting method without a complicating use of Mn or Ni components in usual ternary CuAlMn and CuAlNi shape memory alloys. Thermal analyses of the prepared samples of the alloys were investigated by using differential scanning calorimetry (DSC) and differential thermal analysis (DTA) measurements. In contrast, x-ray diffraction (XRD) test results and optical micrographs were used for analyzing the structure of the alloy samples. The effect of different amounts of low soluble and grain refining Ti element on the binary CuAl alloy system was investigated.

A review on CuAlNi shape memory alloys: Production methods, applications and current trends

Shape Memory Alloys (SMAs) are one sort of shape memory material (SMM) that “remembers” the initial shape when subjected to stimuli like magnetic or thermomechanical changes. Cu-based SMAs in the past decade have emerged successfully as potential materials in various applications such as Sensors, actuators, and high-damping materials. Cu-Al-Ni SMAs have received attention because they are more thermally stable than other Copper-based SMAs. Cu-Al-Ni SMA is an excellent candidate with excellent SME and super-elastic behaviour in the narrow temperature range of 373–473 K. Nickel is added in the binary system of Cu-Al to lower the high transformation temperature and stabilise the austenite phase. This Paper reviews Production Methods, Applications and Current Trends of CuAlNi SMA.

Simultaneous enhancement of mechanical and functional properties by heat-treatment in CuAlNi shape memory alloys fabricated by laser powder bed fusion

Laser powder bed fusion (LPBF) is a promising manufacturing method for fabricating Cu-based shape memory alloys (SMAs), but further performance improvement is needed to ensure service stability and broaden the engineering applications. To achieve simultaneous enhancement of mechanical and functional properties of CuAlNi ternary SMAs fabricated via the LPBF process, this study conducts isochronous and isothermal quenching treatments to tailor the microstructure. The heat-treated specimens with a high quenching temperature and long soaking time exhibited high ultimate tensile strength of 696 ± 10 MPa, large ductility of 8.9 ± 0.2%, and excellent recoverable strain under 2% pre-strain with a shape recovery rate of 100%, which were considerably superior than those of as-built specimens (ultimate tensile strength of 612 ± 10 MPa, elongation of 2.6 ± 0.1%, and 1.26% recoverable strain). This is attributed to the element homogenization during heat treatment, release of residual stress, and coordinated martensite network boundary. However, no significant strain platform of martensite reorientation or detwinning was found in the tensile deformation of the as-built and heat-treated samples, due to localized strain concentration in the parent grain. The microstructural evolution under different quenching treatments and the underlying mechanisms for the improvement of mechanical and functional properties are discussed in detail. This work not only reveals the unique functional response of LPBF fabricated Cu-based SMAs, but also provides a simple and effective method to improve their performance.

Energy and morphology of martensite–twinned martensite interface in CuAlNi shape memory alloy: A phase-field study

Needle-like twins are observed experimentally within the transition layer at the martensite–twinned martensite interface. We utilize a phase-field approach to investigate this microstructure. Our goal is to simulate the morphology of the transition layer and to perform a detailed analysis to characterize its interfacial and elastic micro-strain energy. To illustrate the micromechanical framework developed for that purpose, sample computations are carried out for a CuAlNi shape memory alloy undergoing a cubic-to-orthorhombic martensitic transformation. A particular focus of the study is on size-dependent morphology through examining the impact of twin spacing. Additionally, our results reveal that certain twin volume fractions lead to the emergence of twin branching as a way to minimize the total free energy stored in the microstructure.

Deformation mechanism of Cu-Al-Ni shape memory alloys fabricated via laser powder bed fusion: Tension-compression asymmetry

Introducing the unique advantage of additive manufacturing technology into copper-based shape memory alloys (SMAs) to fabricate high-performance alloys has garnered great attention in recent years, but the intrinsic relationships between microstructure and mechanical properties need to be further clarified. In this paper, the microstructural evolution of ternary CuAlNi SMAs fabricated by laser powder bed fusion (LPBF) under the tensile-compressive loading was investigated to determine the underlying mechanism of tension-compression asymmetry, that is, excellent compressive but poor tensile properties. Multiscale characterization of the different deformation stages revealed the numerous activated deformation mechanism on the 18R martensite matrix. A twin-related transformation dominated the main plastic deformation process due to lower stacking faults energy and high-density pre-existing planer defects in the CuAlNi SMAs. Deformation twinning nucleated at prior austenite boundaries and developed into parallel and network structures inside the parent grain of different sizes. In addition, the preferred orientation in different stages, the stress-induced γ phase transformation, and the interaction between dislocations and stacking faults are discussed. These results not only provide significant insights to understand the detwinning and deformation twinning process of SMAs but also establish the essential framework of microstructure and mechanical properties of Cu-based SMAs fabricated by LPBF.

Study of the thermodynamic parameters, microstructure and mechanical properties of a CuAlNi shape memory alloy produced with recycled aluminum

In this work two CuAlNi alloys produced with recycled aluminum and with pure aluminum, respectively were made under argon atmosphere and characterized by microscopy, X-ray diffraction, differential scanning calorimetry and microhardness. Our results demonstrate that the microstructure, phase transformation temperatures, thermodynamic parameters and microhardness of the CuAlNi alloy, produced with recycled aluminum, are compatible with those presented by the CuAlNi alloy, produced with pure aluminum, making it possible to obtain alloys with CuAlNi shape memory with recycled aluminum an economical alternative with positive effects on energy savings and environmental trends.

Process-microstructure-properties of CuAlNi shape memory alloys fabricated by laser powder bed fusion

Cu -based shape memory alloys (SMAs) show great potential in the application of high temperature, but their performance improvement combining with additive manufacturing is still challenging. In this paper, nearly defect-free (99.7% relative density) CuAlNi SMAs with two types of thermal-induced martensites, 18R and 2H, were successfully fabricated by laser powder bed fusion (LPBF). The remelting printing strategy with systematic optimization framework including densification and printability analysis was used to get optimal process window. The twin-related self-accommodation structure with long period stacking order substructure was formed during additive manufacturing process. The as-build samples show excellent mechanical properties (ultimate compressive strength of 1593 ± 10 MPa and large fracture strain of 23.0% ± 0.1%) with double-yielding, and outstanding shape memory effect, with maximum recoverable strain of 3.39% and nearly 100% recovery rate under compressive strain not exceeding 6%. Furthermore, the microstructural evolution in LPBF involving remelting, martensitic transformation, and 2H martensite was discussed. This result not only builds the microstructure framework involving high reflectivity alloys and martensitic transformation but also provides insight into the applicability of LPBF process in producing Cu-based SMAs.

Photo-electrical Characterization of New CuAlNi/n-Si/Al Schottky Photodiode Fabricated by Coating Thin-Film Smart Material

Micro/nano scale thin-film shape memory alloys (SMAs) have been used in many different miniaturized systems. Using them as thin-film metal components in fabrication of Schottky photodiodes has started a few years ago. In this work, a new SMA-photodiode device with CuAlNi/n-Si/Al structure was produced by coating nano-thick CuAlNi SMA film onto n-Si wafer substrate via thermal evaporation. The photoelectrical I-V, C-V and I-t photodiode signalization tests were performed under dark and varied artifical light power intensities in room conditions. It was observed that the new device exhibited photoconductive, photovoltaic and capacitive behaviors. By using conventional I-V method, the diode parameters such as electrical ideality factor (n), Schottky barrier height (ϕb) and rectification ratio (RR) of the produced photodevice for the condition of dark environment were computed as 12.5, 0.599 eV and 1266, respectively. As good figure of merits, the photodiode’s performance parameters of responsivity (Rph), photosensivity (%PS) and spesific detectivity (D*) maxima values determined for at -5 V reverse voltage bias and under 100 mW/cm2 of light power intensity condition are as 0.030 A/W (or 30 mA/W), 18693 and 1.33×1010 Jones, respectively. The current conduction mechanism analysis revealed that the space charge limited conduction (SCLC) mechanism is the dominant current conduction mechanism. By the drawn reverse squared C-2-V plots, the values of diffusion potential (Vd), donor concentration (ND), Fermi level (EF) and also barrier height (ϕb) were determined for the SMA-photodiode. The results indicated that the new SMA-photodiode device can be useful in optoelectronic communication systems and photosensing applications.

Correction: Experimental investigation of the effects of different quaternary elements (Ti, V, Nb, Ga, and Hf) on the thermal and magnetic properties of CuAlNi shape memory alloy

Correction: Experimental investigation of the effects of different quaternary elements (Ti, V, Nb, Ga, and Hf) on the thermal and magnetic properties of CuAlNi shape memory alloy

Experimental investigation of the effects of different quaternary elements (Ti, V, Nb, Ga, and Hf) on the thermal and magnetic properties of CuAlNi shape memory alloy

Experimental investigation of the effects of different quaternary elements (Ti, V, Nb, Ga, and Hf) on the thermal and magnetic properties of CuAlNi shape memory alloy

The Effect of Heat Treatment on Damping Capacity and Mechanical Properties of CuAlNi Shape Memory Alloy

This paper discusses the effect of different heat treatment procedures on the microstructural characteristics, damping capacities, and mechanical properties of CuAlNi shape memory alloys (SMA). The investigation was performed on samples in the as-cast state and heat treated states (solution annealing at 885 °C/60′/H2O and after tempering at 300 °C/60′/H2O). The microstructure of the samples was examined by light microscopy (LM) and scanning electron microscopy (SEM) equipped with a device for energy dispersive spectrometry (EDS) analysis. Light and scanning electron microscopy showed martensitic microstructure in all investigated samples. However, the changes in microstructure due to heat treatment by the presence of two types of martensite phases (β1′ and γ1′) influenced alloy damping and mechanical properties by enhancing alloy damping characteristics. Heat treatment procedure reduced the alloys’ mechanical properties and increased hardness of the alloy. Fractographic analysis of the alloy showed a transgranular type of fracture in samples after casting. After solution annealing, two types of fracture mechanisms can be noticed, transgranular and intergranular, while in tempered samples, mostly an intergranular type of fracture exists.

Effect of Aging on Corrosion Behavior of Martensite Phase in Cu-Al-Ni Shape Memory Alloy

Polarisation methods, and Open circuit potential measurements have been utilized to evaluate the impact of heat remediation on the corrosion characteristics of CuAlNi shape memory alloy in 3.5 percent NaCl solutions. CuAlNi alloy specimens were investigated in their as-sintered condition and following a thermal remediation processing that included annealing at 900 °C for 60 min associated with water quenching, and 200-degree centigrade for 30 hrs. and rapid cooling in iced water. The enhancement in polarisation resistance and reduction in corrosion rate of heat-treated CuAlNi alloy further suggests that heat remediation has a positive effect on CuAlNi alloy corrosion resistance. After measurements of polarisation, optical microscopy, SEM/EDX, and XRD examination of specimen surfaces reveal the presence of corrosion damage on the electrode surfaces, with CuCl2, AlCl3, and Cu2Cl (OH)3 compounds as surface corrosion products..

Precipitation and martensitic transformation in polycrystalline CuAlNi shape memory alloy – Effect of short heat treatment

In this work, the influence of different heat treatments on the martensitic transformation and precipitation in polycrystalline Cu13%Al4%Ni shape memory alloys have been investigated. A CuAlNi strip were subjected to different heat treatments in order to obtain a variety of microstructures. In this way, the samples were aged at a temperature between 200 and 450 °C. Some specimens were heat-treated at 900 °C followed by ageing processes. The transformation temperatures were measured using Differential Scanning Calorimetry (DSC) method. To determine the mechanical properties, the samples were subjected to the tensile and hardness tests. Microstructural studies were performed using optical and scanning electron microscopies. According to the experimental results, increasing the ageing temperature up to 370 °C results in strength and transformation stress to increase. As the temperature rises to 350 °C, some precipitates appear in the microstructure. Once the temperature reaches 450 °C, there is no martensite in the microstructure. Accordingly, the hardness increases and the elongation decreases drastically in such a way that the alloy breaks in the elastic region. The solution treatment at 900 °C for 20 min yields the martensite to reappear in the microstructure resulting the hardness and strength to decrease and the elongation to increase. Ageing of the samples after solution treatment, increases the mechanical properties again but no precipitation takes place.

Parametric investigation on laser micro-patterned CuAlNi Shape-memory alloy (SMA) bimorph micromirror and its actuation performance

Parametric investigation on laser micro-patterned CuAlNi Shape-memory alloy (SMA) bimorph micromirror and its actuation performance

Biocompatibility of copper-based shape memory alloy

To represent biocompatibility of CuAlNi shape memory alloy manufactured by continuous casting. Test samples were cut by electro erosion into discs shape. After polishing and cleaning, samples were UV sterilized for 1h. For the indirect test, discs were incubated in DMEM for 24h at 37°C in humidified 5% CO2 atmosphere (0.2 g/ml), and supernatant was collected the next day. Human gingival cells (HGCs) were isolated by outgrowth method from gingival tissues of healthy donors. HGCs were seeded in 96 well plates, and the next day undiluted material extract was added in corresponding wells. For the assessment of mitochondrial activity of HGCs after 24 and 168h from exposure to material supernatant, medium was discarded, and medium containing 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide was added to each well and incubated. After 4h supernatant was discarded, and dimethyl sulfoxide was added to each well and optical density was measured. Cells cultured in growth medium alone were used as control. After 24h mitochondrial activity was increased in test group (HGCs exposed to material supernatant) in comparison to control group (untreated HGCs). After 168h of exposure to extracts mitochondrial activity was still higher in test group in comparison to control. T-test of paired samples showed that there was not statistically significant decrease in mitochondrial activity during time (p=0.642). Although Cu-based alloys are controversial in terms of their biocompatibility, our study justified that biocompatibility depends on the manufacturing process and surface modification but not directly from the content of Cu.

Microstructure and Thermo-Mechanical Properties after Recovering Treatments in Aged CuAlNi Shape Memory Alloys

Microstructure and Thermo-Mechanical Properties after Recovering Treatments in Aged CuAlNi Shape Memory Alloys

A Probabilistic Method for Estimating the Influence of Corrosion on the CuAlNi Shape Memory Alloy in Different Marine Environments

This paper gives an approach to the probabilistic percent corrosion depth estimation model for the CuAlNi Shape Memory Alloy (SMA) in different marine environments. Real testing was performed for validation of the theoretical model, where CuAlNi SMAs were exposed to 6 and 12 months in different seawater environments. Focus Ion Beam (FIB) analysis was used to measure the real corrosion depth on the surfaces of tested samples. A statistical approach to the investigation of the corrosion rate of CuAlNi SMA is given, where the corrosion rate is observed as a continuous random variable described by a linear corrosion model, with the assumption that corrosion starts immediately upon alloy surfaces being exposed to the influences of the marine environment. The three best-fitted two-parameter distributions for estimating the cumulative density function and the probability density function of the random variable were obtained by applying adequate statistical tests. Furthermore, using EDX analyses, we identified the chemical composition of the corroded materials, and with the help of Principal Component Analyses, we determined which corrosion environment had the most dominant influence on the corrosion process. The research results indicated that the changeable environment in the tides had a more heterogenic chemical content, which accelerated the corrosion rate.

Investigating the various properties of cold sprayed CuAlNi shape memory alloys developed by post annealing process

CuAlNi shape memory alloy (SMA) has wide scope in vibration damping applications for machine tools. A bespoke cold spray based additive manufacturing system was used to fabricate CuAlNi SMA precursor structures of two different compositions with optimized deposition parameters, which were subsequently alloyed via annealing. The two compositions of CuAlNi chosen for the study were Cu rich in wt% (Cu-82%, Al-14%, Ni-4%) and the Ni rich in wt% (Cu-12%, Al-2%, Ni-80%) shape memory alloy material. The various properties of developed samples were compared with commercially available CuAlNi structure. The properties compared include surface morphology, crystal structure, phase transformation temperature, and mechanical properties were studied with scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) compression testing respectively. The shape memory characteristics were also analyzed using dynamic mechanical analyzer (DMA). Among the two samples, Cu rich sample exhibited better SMA qualities than Ni rich sample as reported in the literature. The micro-hardness of Cu rich sample was to be 356 ± 3 VHN comparatively lower than Ni rich sample. The DSC results revealed the phase transformation hysteresis for Cu rich sample to be very low at 5 ± 3°C. The Cu rich CuAlNi SMA showed very good shape memory characteristics in the DMA results in the range of 50°C to 100°C.