The Magnetic Behavior and Physical Characterization of?Cu�CMn�CAl Ferromagnetic Shape Memory Alloy

In this study, Cu?CAl?CMn alloys with different weight percentages were fabricated by melting metal powders in an induction furnace under argon atmosphere and then by applying rapid solidification. Due to the changes of the alloy percentages after the casting processes, alloy rates were determined by using energy-dispersive X-ray spectroscopy results received from least three different zones. For five different samples, the alloy percentages were found as Cu?C11.96%Al?C3.21%Mn, Cu?C14.09%Al?C10.78%Mn, Cu?C13.73%Al?C13.12%Mn, Cu?C13.44%Al?C12.68%Mn and Cu?C12.14%Al?C15.67%Mn, respectively. The magnetic properties of CuAlMn alloys were investigated as a function of Mn concentration. From the measurements, two important properties were observed. One of them is the temperature-dependent behavior, which indicates that the Curie temperatures of the samples are high (they are in the range of 304?C344?°C). The other property is the saturation magnetization, which is highly dependent on the Mn concentration. Although the Mn atoms want to cluster and interact antiferromagnetically, it is observed that the saturation magnetization is increased with increasing Mn concentration in these alloys. From these observations, it is suggested that the magnetic interactions in our samples are mostly due to the Mn and Al centers.     

Effects of Annealing Temperature on Thermomechanical Properties of Cu–Al–Ni Shape Memory Alloys

The effects of the annealing temperature on structural properties and the phase transformation of a Cu–14.1Al–3.9Ni (mass %) shape memory alloy (SMA) have been investigated. The annealing process was carried out at temperatures in the range of $700\,^{\circ }{\mathrm{C}}$ 700 ° C to $850\,^{\circ }{\mathrm{C}}$ 850 ° C . The structural changes of the as-quenched and annealed samples were studied by optical microscope and X-ray diffraction measurements. The evolution of the transformation temperatures was studied by differential scanning calorimetry with different heating and cooling rates. The activation energy and thermodynamic parameters of the samples were determined. It was found that the heat treatment has an effect on the characteristic transformation temperatures and on thermodynamic parameters such as enthalpy, entropy, and activation energy. The crystallite size of the as-quenched and annealed samples were determined. Vickers hardness measurements of the as-quenched and annealed samples were also carried out. It is evaluated that the transformation parameters of a CuAlNi SMA can be controlled by heat treatment.     

Phase and Microstructure Analysis of Cu-Cr-Zr Alloys

Phases of Cu-（0.4%-2.0%） Cr-（0.05%-0.16%） Zr alloys were analyzed in both as cast and deformed state. Solute-rich clusters of Cr, which was supposed to form during aging treatment, were observed in as cast state; along with the morphology character, corresponding preferential orientation of Cr phase in as cast state was also investigated. Precipitates were observed to distribute in the matrix with a bimodal distribution, viz. coarse precipitates with dimension larger than several hundred nanometers and fine precipitates with size of 2- 10 nm. Three types of intermetallics, the common compound of Cu51Zr14, correspondingly infrequent Cu5Zr and rare Cu5Zr3, were characterized in different samples.     

Influence of Small Cr Addition on Thermal Stability and Magnetic Properties of Fe-Co-Zr-Nb-B Glassy Alloys

Fe62Cos-xCrxZr6Nb4B20 （x=0-4 at. pct） metallic glasses show high thermal stability with a maximum supercooled liquid region of about 84.8 K. The addition of 2 at. pct Cr causes the extension of the supercooled liquid region remarkably, leading to the enhancement of thermal stability and glass-forming ability. The crystallization of the Fe-based glassy alloys takes place through a single exothermic reaction, accompanying the precipitation of more than three kinds of crystallized phases such as α-Fe, Fe2Zr and ZrB2. The long-range atomic rearrangements required for the precipitation of the multiple crystalline phases seem to play an important role in the appearance of the large supercooled liquid region through the retardation of the crystallization reactions. The Fe-based alloys exhibit soft ferromagnetic properties. The saturation magnetization decreases with increasing Cr content while the saturated magnetostriction increases as a function of Cr content. There is no distinct change in the saturation magnetization and coercive force with annealing temperature below the crystallization temperature. The devitrification gives rise to a considerable enhancement in both as and He.     

Microstructure, Compression Property and Shape Memory Effect of Equiatomic TaRu High Temperature Shape Memory Alloy

The microstructure, phase transformation, compression property and strain recovery characteristics of equiatomic TaRu super high temperature shape memory alloy have been studied by optical microscope, XRD, DTA, compression tests and TEM observations. When cooling the alloy specimen from high temperature to the room temperature,β(parent phase)→β′(interphase) →β"(martensite) two-step phase transformations occur. The microstructure at room temperature show regularly arranged band morphology, with the monoclinic crystal structure. The twinning relationship between the martensite bands is determined to be (101) of Type I. Reorientation and coalescence of the martensite bands inside the variant happened during compression at room temperature. The β′→β reversible transformation contributes mainly the shape memory effect, with the maximum completely recovery strain of 2%.     

Oxidation Resistance and Magnetic Properties of SmCo7?x Si x Permanent Magnetic Alloys

The crystal structure, oxidation resistance, and magnetic properties of SmCo_7−x Si _x (x=0, 0.4, 0.6, and 0.9) permanent magnetic alloys were investigated systematically. It is found that the addition of silicon in the as-cast SmCo₇ ingot plays an important role in stabilizing TbCu₇ phase and improving inherent oxidation resistance. For the bulk nanocrystalline SmCo_7−x Si _x magnets, the oxidation resistance remarkably enhances but the corresponding Curie temperature T _c and maximum energy product (BH)_max exhibit a decreasing trend with the increase in Si content x. For the typical SmCo_6.4Si_0.6 nanocrystalline magnet, its final mass gain was about 1.71 mg/cm² after oxidation at 500 °C for 100 h, indicating the enhanced inherent oxidation resistance. Its T _c and (BH)_max were about 708 °C and 35.4 kJ/m³, respectively.     

Microstructure and Mechanical Properties of Two-phaseTiAl Alloys in Lamellar Form

In two-phase TiAl alloys, the lamellar structures are of special interest and importance since they are so common and persistent. not only under as-cast conditions but also after thermal treatment. However. the lamellar structures are still poor in ductility,although they are beneficial for toughness and high temperature strength. This article will review the recent progress made in understanding the basic mechanical properties of the γ and α2 phases which comprise the two-phase alloys in Iamellar form, and discuss how an improved balance of strength and ductillty in the lamellar form may be achieved     

Annealing Influence on the Microstructure and Magnetic Properties of Ni–Mn–In Alloys Ribbons

We report on the structure, microstructure and inverse magnetocaloric effect associated with the first-order martensitic phase transition, in Heusler Ni_50.0Mn_35.5In_14.5 alloy ribbons. We have studied the short-time vacuum annealing influence at 1048?K, 1073?K, 1098?K, and 1123?K in these properties. At room temperature, an increase in the degree of structural order for ribbons annealed up to 1098 K was observed, corresponding to cubic L2₁ austenite phase. Meanwhile, for the sample annealed at 1123?K a monoclinic 10M martensitic phase was detected. A comparison of magnetic entropy change as a function of the applied field, after using zero-field-cooling thermomagnetic and isothermal magnetization measurements, has been made for the sample annealed at 1073?K.     

Effect of Ga on Magnetic and Microstructural Properties of Nd-Fe-Co-B Alloys

1.IntroductionIn this work Ga and Co were added inthe Nd-Fe-B alloys to increase the Curietemperature and improve the temperaturedependence.The improvement of alloy per-formance and the mechanism of coercivitywith the additions of Ga and Co elementsare reported.The Curie temperature of the     

The Effects of the Thermal Treatment on the Structural and Magnetic Properties of Zn–Co Alloys Prepared by Electrochemical Deposition

In this study, the samples were electrolytic grown under identical conditions, using potentiostatic control. We have studied the structural and magnetic properties of the Zn–Co samples. The alloy composition, structure and morphology, the effects of the thermal treatment temperature and the magnetic properties were strongly dependent on the cathode potential during the electrodeposition process. Detailed XPS analysis indicates the presence of zinc oxide (ZnO) in the samples as-prepared and after thermal treatment. We have also obtained information about the evolution of the magnetic susceptibility and the curves of magnetic hysteresis subsequent during thermal treatment. The coercivities of the Zn–Co samples as-deposited and annealed at 350 °C temperature increase after annealing.     

Internal States of Temperature Hysteresis in Shape Memory Alloys

We propose a thermodynamic theory that permits us to connect the size of the temperature hysteresis loop to the interfacial energy between martensite and austenite. The free energy is a function of four variables, viz. deformation of austenite, deformation of martensite, phase fraction and temperature. A diagonal line inside the hysteresis loop in the deformation-temperaturediagram is identified as the line of unstable phase equilibrium. Upon reaching this line the phasemixture loses its (meta-)stability and the transformation from one phase to the other shouldoccur. The theoretical results are supported by experiments on NiTi and CuAINi specimens.     

Microstructure and Mechanical Properties of TiB-Containing Al–Zn Binary Alloys

The microstructure and mechanical properties of newly developed Al–35Zn cast alloys with Ti B re?ner addition were evaluated by X-ray diffractometry, optical microscopy, and scanning electron microscopy coupled with energy dispersive spectrometry. The microstructure of these alloys featured α-Al dendrites surrounded by Al–Zn(α + η) eutectic structures. After the addition of Ti B re?ner, the alloy grain sizes decreased, and its morphology abruptly changed from dendritic to equiaxed grains. Such an improved microstructure of the modi?ed alloys was accompanied by a signi?cant increase in the tensile strength and elongation percentage compared to those of the Al–Zn or Zn–Al-based alloys. The results showed that with the increase of Ti B content up to 0.05%, the morphology of α-Al dendrites and α + ηphases changed from coarse dendrite and lamellar structures into independent and ?ne ones. Based on these results, the effect of Ti B re?ner addition on the microstructure and mechanical properties of the Al–35Zn binary alloys was investigated.     

Magnetic Properties and Thermal Stability of Pr_(1-x)La_xCo_(5-y)Alloys

Pr1-xLaxCo5-y (x=0, 0.15. 0.25, 0.35,1.0, y=0.5, 0.7, 0.9, 1.0) alloys were investigated. The effect of the variation of x and y on magnetic properties and thermal stability of the alloys were studied. The magnetic properties for the Pr0.85La0.15Co4.3 and Pr0.75La0.25Co4.1 magnets are iHc=368 kA/m, Br=0.91 T, (BH)max=145.6 kJ/m3, αBr=-0.03%/℃ and iHc=568 kA/m,Br=0.8 T, (BH)max=127.2 kJ/m3,αBr,=-0.06%/℃, respectively The phase structures of as-cast alloys and magnets were investigated     

Microstructure and Thermal Conductivity of As-Cast and As-Solutionized Mg–Rare Earth Binary Alloys

The microstructure and thermal conductivity of four groups of Mg–rare earth(RE) binary alloys(Mg–Ce,Mg–Nd, Mg–Y and Mg–Gd) in as-cast and as-solutionized states were systematically studied. Thermal conductivity was measured on a Netzsch LFA457 using laser flash method at room temperature. Results indicated that for as-cast alloys, the volume fraction of second phases increased with the increase of alloying elements. After solutionizing treatment, a part or most of second phases were dissolved in α-Mg matrix, except for Mg–Ce alloys. The thermal conductivity of as-cast and as-solutionized Mg–RE alloys decreased with the increase of concentrations. The thermal conductivity of as-solutionized Mg–Nd,Mg–Y and Mg–Gd alloys was lower than that of as-cast alloys. Thermal conductivity of as-solutionized Mg–Ce alloys was higher than that of as-cast alloys, because of the elimination of lattice defects and fine dispersed particles during solutionizing treatment. Different RE elements have different influences on the thermal conductivity of Mg alloys in the following order: Ce Nd Y Gd. Ce has the minimum effect on thermal conductivity of Mg alloys, because of the very low solubility of Ce in the α-Mg matrix. The variations in the atomic radius of the solute elements with Mg atom( r), valence, configuration of extranuclear electron of the solute atoms, and the maximum solid solubility of elements in the α-Mg matrix were suggested to be the main reasons for the differences in thermal conductivity of resulting Mg–RE alloys.