Search

CuAlMn alloys are cheaper and more promising alloy types compared to NiTi alloys. In this study, based on CuAlMn shape memory alloy, thermodynamic and structural characteristics of some new alloys containing four elements were investigated in detail. In this study, five new quaternary shape memory alloys, each containing a CuAlMn base alloy and a different fourth additive element (Ga, Nb, V, Zr, and Cr), were produced. The properties of the obtained alloys were characterized using a series of analysis methods such as X-ray diffraction (XRD), optical microscopy, differential scanning calorimetry (DSC), and differential thermal analysis (DTA). The results showed the effects of different elements on the crystal structures of the alloys and how different elements could change the thermal behavior of the alloys. [ABSTRACT FROM AUTHOR]

In this work, the new quaternary CuAlTiMg high-temperature shape memory alloy (HTSMA) with an unprecedented composition and with extended solubility of Ti was produced by the arc melting method. The thermal shape memory effect characterization tests were done by performing a series of differential calorimetric (DSC and DTA) measurements. The obtained thermograms of the alloy displayed the martensitic phase transformation peaks. The forward (martensite to austenite) phase transformation was found to occur at above 350?C, which qualifies the produced alloy as an HTSMA. The microstructural XRD measurement was performed to reveal the atomic planes of martensite structures formed in the alloy, which constitute the shape memory effect property of the fabricated alloy. The alloy surface was monitored by optical microscopy image taken at room temperature, and finely dispersed Ti-rich X-phases were observed. [ABSTRACT FROM AUTHOR]

In this study, changes in mechanical properties as a result of uniaxial tensile strain applied to Cu nanowires containing different percentages of vacancy and interstitial defects were investigated by Molecular Dynamics (MD) simulation method. The Embedded Atom Method (EAM) potential function, which includes many-body interactions, was used to determine the forces acting on Cu atoms. Depending on the density of the point defects, the stress-strain curves, Young's modulus, yield stress values were determined as a result of the uniaxial tensile stress applied to the Cu model nanowire. Structural changes, dislocation formations and their spread resulting from the applied deformation were examined by common neighbour analysis method (CNA) and dislocation analysis (DXA), respectively. It was determined that hcp unit cell stacking fault defects and Shockley dislocations caused by tensile strain were effective on the mechanical properties of the model nanowire. [ABSTRACT FROM AUTHOR]

The first generation of high-entropy alloys (HEAs) has five or more equiatomic components fabricated together in the concentration of 5–35 at.%. Recently, the second generation of HEAs was identified as having non-equimolar compositions. HEAs have excellent mechanical properties and magnetic behavior that may vary with the doping of other alloying elements. In the current study, various components (Ti, Cr, Sn, V, Hf, Ga) were added to an equiatomic AlCoFeMnNi alloy, and then the microstructure, thermal and magnetic properties of the alloys were investigated. As a result, all samples showed ferromagnetic behavior, and the highest value of magnetization was found in the AlCoFeMnNi alloy (141.1 emu/g). In comparison, the lowest value (51.2 emu/g) was detected through Hf addition to the AlCoFeMnNi alloy. Therefore, the change in magnetic characteristics is due to the phase change related to different element additions. In addition, the calculated coercivity for the tested alloys was in the range of 78–325 Oe, which means that the produced alloys have semi-hard magnetic behavior. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this study, using the Molecular Dynamics (MD) simulation method, the effects of the tensie stress applied to the Fe nano wire along the direction of [100] for different temperatures and strain rates were tried to be determined. The stress-strain curve, Young’ s modulus, yield stress and plastic deformation of the model system under tensile stress were investigated. The Embedded Atom Method (EAM), which includes many body interactions, was used to determine the interactions between atoms. It was determined that temperature and strain rate had an effect on the mechanical behaviour of α-Fe nanowire. It was found that the Young’ s modulus is independent of the strain rate at low temperatures, but decreases with increasing temperature. It was also determined that the flow strain decreased with increasing temperature and decreasing strain rate. The motion of dislocations and twinning corresponding to plastic deformation and the resulting reorientation of regional crystal structures were attempted to be determined by the method of Common Neighbour Analysis (CNA). [ABSTRACT FROM AUTHOR]

In this study, the effects of temperature, number of atoms and uniaxial strain on the stress behavior of the Cu model system were investigated using molecular dynamics method. The Embedded Atom Method (GAM), which includes many body interactions, was used to determine the interactions between atoms. During the strain process, the changes of the regional atomic structures were determined by the Common Neighbor Analysis-CNA method designed by Honeycutt and Andersen. It was observed that temperature, atomic number and strain rate had an effect on the stress behavior of model Cu element, critical loading value decreased with increasing temperature and increased with increasing strain rate and atomic number. [ABSTRACT FROM AUTHOR]

In this study, the liquid Fe model system, which consists of 4000 atoms with molecular dynamic simulation method, is cooled under 0 GPa, 5 GPa, 7 GPa pressure values with 1x1012 K / s and 1x1013 K / s cooling rates, and the different unit cell atomic atomic structure formed by crystal and glass transition temperatures in the structure. clusters were tried to be determined. The Embedded Atom Method, which is based on many body interactions, was used in the calculation of interactions between atoms. It was seen that the pressure increase had an effect on the formation of crystal and amorphous structures in Fe cooled from the liquid phase and the transition temperatures to these structures. Binding energy per unit atom and the Wendt-Abraham parameter were used to determine the crystal and amorphous phase transition (Tg) temperatures. In addition, the percentage of different unit cell structures formed in the Fe model system during solidification from the liquid phase was determined using the Ackland-Jones analysis method. [ABSTRACT FROM AUTHOR]

When the phase diagram of the element Fe is examined, it is seen that it has different crystal structures at different temperatures below its melting temperature. In this study, the solid-solid phase transformations occurring at different temperatures in the Fe model system consisting of 4000 atoms were investigated using molecular dynamic simulation method. The Embedded Atom Method(EAM), which includes many body interactions, was used to calculate interactions between atoms. For the element Fe, the α, γ and δ phases formed below the melting temperature and the transformation temperatures for these phases were determined and the results were compared with the experimental values. Radial distribution function, changes in thermodynamic quantities and Ackland-Jones analysis method were used in the structural analysis of the model system. [ABSTRACT FROM AUTHOR]

In this study, physical changes occurring in the material as a result of the advanced grinding process of scale, which is obtained from KARDEMİR and which is one of the iron and steel wastes, together with carbonized almond shells, was examined. In the studies, the carbonization processes of the almond shells were carried out first, and the carbon ratio of the almond shells, which were treated at 800 ° C for 1440 minutes, was found to be 97.97% and the sulfur rate 0.014%; The calorific value of this sample was found to be 8647.6 cal / g. In the second stage of the study, the scale and carbonized product mixture was prepared with a mixture / ball ratio of 1/10, FeO / C ratio of 80/20, 70/30 and 60/40 and grinded in a high energy mill for 30 - 120 minutes. PSD and SEM-EDX images of the products obtained after grinding were taken. [ABSTRACT FROM AUTHOR]