Microstructures of Ti–Ni–Fe wire after severe cold-drawing and annealing

The microstructures and mechanical properties of Ti–47 at%Ni–3 at%Fe shape memory alloy wire under the condition of severe cold-drawing at room temperature and different postdeformation annealing processes were intensively investigated using transmission electron microscope(TEM),X-ray diffraction(XRD),Vickers microhardness tester and electron tensile tester.It is indicated that the structure of the alloy evolves into a predominant amorphous structure with a trace of nanocrystalline B2 phase after the cold-drawing of 76%areal reduction.Postdeformation annealing process exerted significant influence on the microstructure and mechanical properties.Crystallization occurs when the cold-drawn wire was annealed at 300℃ for 30 min.The ultimate tensile strength and ductility as well as the superelasticity of the wire are improved significantly by cold-drawing plus postdeformation annealing.     

Surface plasmon resonance and electrical properties of RF: magnetron sputtered carbon–nickel composite films at different annealing temperatures

In this work, the optical absorption spectra of carbon–nickel films annealed at different temperatures(300–1000 °C) with a special emphasis on the surface plasmon resonance(SPR) were investigated. The films were grown on quartz substrates by radio-frequency(RF)magnetron co-sputtering at room temperature with a deposition time of 600 s. The optical absorption peaks due to the SPR of Ni particle are observed in the wavelength range of 300–330 nm. With annealing temperature increasing up to 500 °C due to the increase in Ni particle size, the intensity of the SPR peaks increases, but weakens with annealing temperature increasing over 500 °C. The Ni nanoparticle size, the dielectric function of carbon matrix(ε_m) and the plasma frequency of the free electrons(ω_p) at500 °C have the maximum values of 21.63 nm, 0.471 and5.26 9 10~(15)s~(-1), respectively. The absorption peak shows a redshift trend up to 500 °C and then turn to blueshift with annealing temperature increasing over 500 °C. These observations are in a good agreement with the electrical measurements in temperature range of 15–520 K and the Maxwell–Garnett(M–G) effective medium theory(EMT).     

Evolution of the structure and mechanical properties of sheets of the Al–4.7Mg–0.32Mn–0.21Sc–0.09Zr alloy due to deformation accumulated upon rolling

The mechanical properties and microstructure of sheets of an Al–4.7Mg–0.32Mn–0.21Sc–0.09Zr alloy deformed and annealed after rolling have been investigated. The total accumulated true strain was ε_f = 3.33–5.63, and the true strain at room temperature and at 200 °C was ε_с = 0.25–2.3. The strength properties of the sheets (yield stress σ_0.2 = 495 MPa and ultimate tensile strength σ_u = 525 MPa) in the deformed state were greater than those after equal-channel angular pressing (ECAP) deformation. The mechanical properties of the deformed sheets after annealing depended on the size of subgrains inside the deformed grains bands with high-angle grain boundaries (HABs). With the increase in the annealing temperature from 150 to 300°С, the subgrain size increased from 80 to 300 nm. The relative elongation δ in the as-cast state and after annealing at 200–250°C (δ = 40–50%) was higher than that after annealing at 300–370°C (δ = 24–29%).     

Thermal Stability Study of Ultrafine Grained 304L Stainless Steel Produced by Martensitic Process

An ultrafine grain 304L stainless steel with average grain size of about 650 nm was produced by martensitic process. 10 mm as-received sheets were 80% cold rolled in the temperature of ?15 °C and then annealed at 700 °C for 300 min to obtain ultrafine grained microstructure. The results showed that the ultrafine grained 304L steel has yield strength of 720 MPa, tensile strength of about 920 MPa, and total elongation of 47% which is about twice that of coarse grain structure. The effect of annealing temperature (750-900 °C) on the grain growth kinetics was modeled by isothermal kinetics equation which resulted in the grain growth exponent (n) and activation energy for grain growth of 4.8 and 455 KJ/mol, respectively. This activation energy was also compared with those for other austenitic steels to better understanding of the nature of grain growth and atoms mobility during annealing. It was found that activation energy for grain growth is about twice higher than self-diffusion activation energy of austenite that is related to the Zener pinning effects of the second phase particles.     

Thermal stability evaluation of nanostructured Al6061 alloy produced by cryorolling

Grain growth of nanostructured Al6061 produced by cryorolling and aging process was investigated during isothermal heat treatment in 100–500 °C temperature range. Transmission electron microscopy (TEM) observations demonstrate that after cryorolling and aging at 130 °C for 30 h, the microstructure contains 61 nm grains with dispersed 50–150 nm precipitates and 0.248% lattice strain. In addition, an increase in tensile strength up to 362 MPa because of formation of fine strengthening precipitation and nano-sized grains was observed. Thermal stability investigation within 100–500 °C temperature range showed release of lattice strain, dissolution of precipitates and grain growth. According to the X-ray diffraction (XRD) analysis, Mg₂Si precipitates disappeared after annealing at temperatures higher than 300 °C. According to the results, due to the limited grain growth up to 200 °C, there would be little decrease in mechanical properties, but within 300–500 °C range, the grain growth, dissolution of strengthening precipitates and decrease in mechanical properties are remarkable. The activation energies for grain growth were calculated to be 203.3 kJ/mol for annealing at 100–200 °C and 166.34 kJ/mol for annealing at 300–500 °C. The effect of precipitation dissolution on Al lattice parameter, displacement of Al6061 (111) XRD peak and Portevin–LeChatelier (PLC) effect on stress–strain curves is also discussed.     

Bulk Ultrafine-Grained Interstitial-Free Steel Processed by Equal-Channel Angular Pressing Followed by Flash Annealing

Interstitial-free steel workpieces are deformed by equal-channel angular pressing (ECAP) for equivalent strain ε_vm = 3 and ε_vm = 21 followed by flash annealing. Microstructures are analyzed by optical microscopy, scanning electron microscopy and transmission electron microscopy. Mechanical properties are evaluated by hardness testing. Yield strength of materials is calculated from hardness values. Flash annealing (at 675 °C) of ECAPed samples for ε_vm = 3 and ε_vm = 21 results in abnormal subgrain growth and abnormal grain growth, respectively. Flash annealing at 700 °C of ECAPed (at ε_vm = 3) IF steel converts abnormally grown subgrains to grains which serve as nuclei for recrystallization and that result in bimodal grain size distribution. Bimodal grain size distribution is also produced when ECAPed IF steel for ε_vm = 21 is flash annealed at 675 °C due to abnormal grain growth or secondary recrystallization. Flash annealing of IF steel samples ECAPed for low ε_vm, in the temperature range 600-675 °C, decreases the hardness continuously with increase in the annealing temperature but it increases at high ε_vm. The former is due to annihilation of defects but the later is caused by ordering of nonequilibrium boundaries. The hardening and strengthening behaviors are similar.     

Influence of Annealing on the Properties of Explosively Welded Titanium Grade 1—AW7075 Aluminum Alloy Bimetals

Explosive welding of titanium Grade 1 to AW7075 aluminum alloy arranged in parallel setup was performed. The annealing of produced bimetals at the temperatures of 450, 500 and 550 °C for times ranging from 20 to 100 h was carried out after explosive welding. The produced bimetal was characteristic by its wavy interface typical for that bonding process. Increase in the microhardness at the interface was recorded due to work hardening. Delamination of titanium Grade 1 flyer sheet was firstly observed when annealing temperature of 500 °C for 40 h was carried out. Annealing at 550 °C also resulted in delamination of upper sheet. The intermetallic compound (IMC) layer was observed at the interface after annealing of bimetals. The higher the annealing temperature and time, the higher the thickness of continuous IMC layer. The maximum measured thickness of IMC layer averaged 13 µm. Energy dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD) analyses revealed that the interface layer is consisted of Al₁₈Ti₂Mg₃ IMC. Microhardness at the interface increased dramatically up to 439 HV0.1 after annealing of bimetal due to the presence of above-mentioned IMC.     

Formation of the Nanocrystalline Structure in an Equiatomic NiTi Shape-Memory Alloy by Thermomechanical Processing

The microstructural evolution during cold rolling followed by annealing of an equiatomic NiTi shape-memory alloy was investigated. The high purity Ni₅₀Ti₅₀ alloy was cast by a copper boat vacuum induction-melting technique. The as-cast ingots were then homogenized, hot rolled, and annealed to prepare the suitable initial microstructure. Thereafter, annealed specimens were cold rolled up to 70 % thickness reduction at room temperature. Post-deformation annealing was conducted at 400 °C for 1 h. The microstructure was characterized using scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and differential scanning calorimetry techniques. The initial microstructure was free from segregation and Ti- or Ni-rich precipitates and was composed of coarse grains with an average size of 50 μm. The cold rolling of NiTi alloy resulted in a partial amorphization and the deformation-induced grain refinement. A nanocrystalline structure with the grain size of about 20-70 nm was formed during the post-deformation annealing.     

Shape Memory Effects in TiNi-based Alloys Subjected to Electroplastic Rolling

One of the prospective methods for structure refinement is electroplastic rolling (EPR). The use of an electric current pulse during cold rolling enhances deformability (1.5-3 times for TiNi-based alloys). It was shown that EPR (e > 1) with post-deformation annealing at 450-500 °C leads to nanostructure formation with a grain size of 60-120 nm. Also, EPR leads to an increase in functional properties of TiNi-based alloys. So, the recovery coefficient was revealed as being better than the undeformed alloy (90-96% for Ti_49,2Ni_50,8 and 75-80% for Ti_50,0Ni_50,0). In the Ti_50,0Ni_50,0 subjected to EPR up to strain 3.6 and subsequent annealing at 450 °C for 1 h, the superelasticity effect is found.     

The phase diagram of the terbium–gold alloy system

The terbium-gold phase diagram has been investigated in the 0–100 at% Au field by differential thermal analysis (DTA), X-ray diffractometry (XRD), optical microscopy (LOM), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Eight intermetallic phases were found, namely: Tb₂Au orthorhombic oP12–Co₂Si, peritectic decomposition at 1000°C, TbAu, L.T. form, orthorhombic oC8–CrB type and H.T. form, cubic cP2–CsCl type, congruent melting at 1590°C, Tb₃Au₄ trigonal hR42–Pu₃Pd₄ type, peritectic decomposition at 1340°C, Tb₇Au₁₀ tetragonal tI136–Gd₇Au₁₀ type, peritectic decomposition at 1210°C, TbAu₂ tetragonal tI6–MoSi₂ type, congruent melting at 1265°C, TbAu₃ orthorhombic oP8–TiCu₃ type, congruent melting at 1215°C, Tb₁₄Au₅₁ hexagonal hP65–Gd₁₄Ag₅₁ type, peritectic decomposition at 1175°C, and TbAu₆ tetragonal tP56–SmAu₆ type, peritectic decomposition at 855°C. Four eutectic reactions were found to occur at 880°C and 20.0 at% Au, at 1195°C and 62.5 at% Au, at 1160°C and 71.0 at% Au and finally at 805°C and 89.0 at% Au. A catatectic reaction occurs in the Tb-rich region. The experimental results are discussed and compared with the general behaviour of the other R–Au systems.     

Ferroelectric properties of dysprosium-doped Bi4Ti3O12 thin films crystallized in various atmospheres

Dysprosium-doped Bi4Ti3O12 （Bi3.4Dy0.6Ti3O12, BDT） ferroelectric thin films were deposited on Pt（111）/Ti/SiO2/Si（111） substrates by chemical solution deposition （CSD） and crystallized in nitrogen, air and oxygen atmospheres, respectively. X-ray diffraction （XRD） and scanning electron microscopy （SEM） were used to identify the crystal structure, the surface and cross-section morphology of the deposited ferroelectric films. The results show that the crystallization atmosphere has significant effect on determining the crystallization and ferroelectric properties of the BDT films. The film crystallized in nitrogen at a relatively low temperature of 650 ℃, exhibits excellent crystallinity and ferroelectricity with a remanent polarization of 2Pr = 24.9 ℃/cm^2 and a coercive field of 144.5 kV/cm. While the films annealed in air and oxygen at 650 ℃ do not show good crystallinity and ferroelectricity until they are annealed at 700 ℃. The structure evolution and ferroelectric properties of BDT thin films annealed under different temperatures （600-750 ℃） were also investigated. The crystallinity of the BDT films is improved and the average grain size increases when the annealing temperature increases from 600 ℃ to 750 ℃ at an interval of 50 ℃. However, the polarization of the films is not monotonous function of the annealing temperature.     

Effects of annealing on mechanical properties and degradation behavior of biodegradable JDBM magnesium alloy wires

Mg–Nd–Zn–Zr magnesium alloy (JDBM) has been studied widely as biodegradable medical material. To process high quality JDBM wires, effects of annealing on the mechanical properties and degradation behavior after drawing were studied by microscopic observations, tensile and immersion tests. The as-extruded wires with a diameter of 3 mm could be drawn up to 9 passes without annealing until 125% cumulative drawing deformation. Complete recrystallization occurred after annealing at 325 °C for 30 min, 350 °C for 5 min or 450 °C for 3 min, respectively. Room temperature tensile tests and simulated body fluid immersion tests showed that annealing at slightly elevated temperature for short time could obtain better properties due to the finer grain size and more dispersive distribution of precipitates. For this study, annealing at 350 °C for 5 min is the best parameters which can be utilized to further fabricate fine wires.     

Effect of annealing temperature on the texture of copper wire

It has been found by textural analysis methods that, in the course of annealing with heating and cooling at a rate of 100 K/s, the textured state of an oxygen-containing copper wire of grade M00 deformed by drawing to 97% reduction changes, retaining the zonal structure. In the central zone, at a relative current radius from 0 to 0.3, the ??111?? orientation dominates to a temperature of 300°C. At the higher temperatures, the ??100?? orientation becomes dominant and remains up to 500°C. At relative current radii of 0.6?C1.0 (peripheral zone) and 0.3?C0.6 (intermediate zone), the dominant ??100?? orientation is retained to 300°C; at the higher temperatures, the dominance of the ??100?? orientation levels off. As the annealing temperature increases, the intermediate zone wedges out at the expense of growth of the central and peripheral zones. On the whole, the annealing at high temperatures (above 400°C) leads to the predominance of the ??100?? orientation; it is highly dominant for relative radii of 0?C0.5.     

On the Liquid/Solid Phase Equilibria in the Al-Rich Corner of the Al-Si-Ti Ternary System

The nature of liquid-solid phase equilibria in the Al-rich corner of the Al-Si-Ti system are determined by drawing three isothermal sections at 620, 680 and 727 °C. The solubility of Ti in Al-Si liquids is determined for four different compositions (0, 9, 13 and 18 at.%Si) at temperature below 800 °C. Combination of the two sets of experimental results leads to an attempt of liquidus projection. The primary crystallization surface of Al₃Ti is found to extend up to 9.5 at.%Si in the liquid phase at 620 °C and 11 at.%Si at 727 °C. The solubility of Ti is found to be not significantly dependent on the Si content of the liquid. From DSC measurements and deduction on microstructure, the last invariant reaction of the solidification path is found to be quasi-peritectic: ${\text{L}} + \uptau_{1} - {\text{Ti}}_{7} {\text{Al}}_{5} {\text{Si}}_{12} \Leftrightarrow {\text{Al}} + {\text{Si}} .$      

Oxidation Behavior of the CrMnFeCoNi High-Entropy Alloy

Oxidation of the Cr₂₀Mn₂₀Fe₂₀Co₂₀Ni₂₀ (at%) high-entropy alloy (HEA) was investigated at 500–900 °C in laboratory air. At 600 °C the oxide was mainly Mn₂O₃ with a thin inner Cr₂O₃ layer; at 700 and 800 °C it was mainly Mn₂O₃ with some Cr enrichment; at 900 °C it was Mn₃O₄. The oxidation rate was initially linear but became parabolic at longer times with an activation energy of 130 kJ/mol, comparable to that of Mn diffusion in Mn oxides but much lower than that for sluggish diffusion of Mn in the HEA. The diffusion of Mn through the oxide is considered to be the rate-limiting process.     

The Effect of Static Magnetic Field on Electroless Ni-P In Situ Deposition and Post-annealing

The influence of static magnetic field of 4 T on electroless Ni-P deposition process and post-annealing was investigated in this study. The results from differential scanning calorimeter have shown that the imposed high magnetic field during electroless deposition had a further beneficial effect on defects migration and annihilation after Ni-P alloys heated at around 250 °C. Furthermore, it is found that some metastable phases were presented after magnetic annealing at 300 °C (below crystallization temperature), and the hardness of magnetic-annealed Ni-P alloys was greater than that of conventionally annealed Ni-P alloys. The morphology of the Ni-P alloys was characterized by scanning electron microscope, and shows typical spherical nodular structure for the as-deposited Ni-P alloys. The boundaries of these spherical nodular crystals blurred after annealing; however, the boundaries were apparently observed after magnetic annealing at 300 °C.     

High-Temperature Electrical Insulation Behavior of Alumina Films Prepared at Room Temperature by Aerosol Deposition and Influence of Annealing Process and Powder Impurities

Alumina (Al₂O₃) is a widely used material for highly insulating films due to its very low electrical conductivity, even at high temperatures. Typically, alumina films have to be sintered far above 1200 °C, which precludes the coating of lower melting substrates. The aerosol deposition method (ADM), however, is a promising method to manufacture ceramic films at room temperature directly from the ceramic raw powder. In this work, alumina films were deposited by ADM on a three-electrode setup with guard ring and the electrical conductivity was measured between 400 and 900 °C by direct current measurements according to ASTM D257 or IEC 60093. The effects of film annealing and of zirconia impurities in the powder on the electrical conductivity were investigated. The conductivity values of the ADM films correlate well with literature data and can even be improved by annealing at 900 °C from 4.5?×?10^?12 S/cm before annealing up to 5.6?×?10^?13 S/cm after annealing (measured at 400 °C). The influence of zirconia impurities is very low as the conductivity is only slightly elevated. The ADM-processed films show a very good insulation behavior represented by an even lower electrical conductivity than conventional alumina substrates as they are commercially available for thick-film technology.     

Influence of Post-Weld Annealing on Transformation Behavior and Mechanical Properties of Laser-Welded NiTi Alloy Wires

The influence of annealing on the transformation behavior, mechanical, and functional properties of laser-welded NiTi wires was investigated. The results show that Ti₃Ni₄ precipitates occur after post-weld annealing and coarsen with increasing annealing temperature. The as-welded specimen exhibits one-step B2 → B19′ transformation, while the annealed ones show two-step B2 → R → B19′ transformation. Annealing at 400 °C for 1 h can improve the tensile strength and superelasticity of the welded joints. However, these properties decrease when annealing at 500 °C for 1 h. The change of mechanical and functional properties after annealing is attributed to the different size of Ti₃Ni₄ precipitates. Annealing to produce smaller coherent precipitates (10 nm) improves the mechanical and functional properties of the welded joints. As the Ti₃Ni₄ precipitates coarsen, the mechanical and functional properties decrease.     

Processing and microstructure control of (α2+B2+O) alloy sheet in Ti–Al–Nb system

Rolling processing and microstructure evolution during rolling and heat treatment for two typical α₂+B2+O alloys, Ti–24Al–14Nb–3V and Ti–23Al–17Nb (at%), were investigated. The experimental results showed that the alloys have good workability for rolling at temperatures both in the α₂+B2 and in α₂+B2+O fields. The thickness reduction up to 99% was obtained for the sheets rolled above 900°C in a quasi-isothermal condition without cracking. A typical duplex microstructure of the α₂+B2+O phases formed when the sheets were rolled and then solution treated at temperatures in the α₂+B2 phase field plus aging in the O+B2 field. Such duplex microstructure was proved to have good mechanical properties both in room and elevated temperatures. A microstructure of fine equiaxed α₂ and O phases distributed in B2 matrix was obtained for the sheets rolled and then solution treated at the temperatures in the α₂+B2+O phase field, which possess excellent room temperature ductility and superplasticity in temperatures of 900∼1000°C. An advanced cold rolling processing plus a proper vacuum heat-treatment used for the production of high-quality foils of Ti–24Al–14Nb–3V (at%) alloy are also reported.     

Effect of composition and temperature on the redistribution of alloying elements in Fe-Cr-Ni alloys during cold deformation

Deformation-induced redistribution of components in a steel Kh11N30 was shown to decrease up to zero as the deformation temperature increases from 0 to 300°C. The maximum Curie temperature of deformation-induced ferromagnetic clusters formed in steels Kh11N30, Kh12N30, and Kh15N38 is the same and is equal to ～160°C. The formation of 3–5-nm particles of an ordered L1₀ or L1₂-type phase whose amount is 5 to 10 vol % was found by field-ion microscopy.