Nanocrystallization in Amorphous Fe–P–V Alloys under Pulsed Irradiation

The crystallization behavior of amorphous Fe–P–V alloys under pulsed irradiation is studied. The results demonstrate that the crystallized alloys contain not only the equilibrium phases -Fe and (Fe,V)₃P but also two metastable phases, -FeV and (Fe,V)₂P, whose stability decreases with increasing annealing temperature and irradiation energy. As a result, these phases transform into equilibrium phases, increasing the mobility of atoms and particle size and reducing the degree of hardening.     

Production, Properties and Applications of Bulk Amorphous Alloys

A review is given of recent work concerned with the production method, the characteristic properties(1) Bulk amorphous system; (2) Mechanical and magnetic properties of bulkamorphous alloys; (3)application of bulk amorphous alloys.     

Effects of Thermal Annealing and Pulsed Photon Processing on the Relaxation and Crystallization of Amorphous Fe–P–Si Alloys

The crystallization behavior of amorphous Fe–P–Si alloys is found to be influenced by preliminary relaxation via thermal annealing below the crystallization temperature T _x or pulsed photon processing with energy densities in the range 1–18 J/cm². High-temperature annealing (above T _x) and pulsed photon processing reduce the particle size and microhardness of the alloys.     

Microstructure and Mechanical Properties of Rapidly Solidified Hypereutectic Al–Si and Al–Si–Fe Alloys

The microstructure and mechanical properties of rapidly solidified Al–18 wt% Si and Al–18 wt% Si–5 wt% Fe alloys were investigated by a combination of optical microscopy, scanning electron microscopy, transmission electron microscopy, x-ray diffraction, tensile testing, and wear testing. The centrifugally atomized binary alloy powder consisted of the -Al (slightly supersaturated with Si) and Si phases and the ternary alloy powder consisted of the -Al (slightly supersaturated with Si), silicon, and needle-like metastable Al–Fe–Si intermetallic phases. During extrusion the metastable -Al₄FeSi₂ phase in the as-solidified ternary alloy transformed to the equilibrium -Al₅FeSi phase. The tensile strength of both the binary and the ternary alloys decreased with a high-temperature exposure, but a significant fraction of the strength was retained up to 573 K. The specific wear gradually increased with increasing sliding speed but decreased with the addition of 5 wt% Fe to the Al–18 wt% Si alloy. The wear resistance improved with annealing due to coarsening of the silicon particles.     

Influence of Metalloid Elements on the Magnetic Properties and Anisotropy of FeNi-based Amorphous Alloys

The magnetic properties and anisotropy of amor-phous(Fe_(80)Ni_(20))_(78)Si_xB_(22-x).alloys have been investigatedsystematically.The maximum permeability,coercive forceand remanence have been determined for as-prepared andannealed samples,The results on the technical magneticproperties of this alloy system have been discussed andcompared with Masumoto's.     

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.     

Physicochemical Properties of Calcium Phosphate–Chitosan Composites and Scaffolds

This paper reports a study of the physicochemical properties of composites and scaffolds (synthesized for the first time) based on dicalcium phosphate dihydrate (DCPD, brushite), hydroxyapatite (HA), and chitosan. The crystallite size of the composites has been shown to increase with increasing chitosan concentration in the starting solution. The first technique has been proposed for the fabrication of scaffolds based on brushite, HA, and chitosan gel. The pore size in the scaffolds has been shown to increase with increasing brushite content. Raising the calcination temperature improves the stability of the scaffolds, whereas the composites persist in the form of powder independent of heat treatment. Analysis of the dissolution behavior of the synthesized composites and scaffolds in an isotonic solution indicates that, in the DCPD–chitosan system, the dissolution rate decreases with increasing chitosan concentration, whereas the HA–chitosan system exhibits opposite behavior.     

Effect of Si on the Glass Formation and Magnetic Properties of High-Iron Fe–Zr–Si Alloys

High-iron Fe–Zr–Si amorphous ribbons were fabricated through the melt-spun technique. Then, the effects of Si content on the glass-forming ability and magnetic properties of Fe_90?xZr₁₀Si_x (x =?1, 2, 3, 4, 5, 10) alloys were investigated. Results showed that the amorphous structure only formed in an alloy composition of 3 at.% Si. Moreover, α-Fe(Si) and Fe₃Zr phase appeared gradually when Si was added. Fe₈₇Zr₁₀Si₃ alloy is a unique amorphous structure in Fe_90?xZr₁₀Si_x ribbons. The peak temperatures of the two crystallization stages were 464 and 600 ^°C. The saturation magnetization (M_s) values of the alloys ranged from 91.2 to 132.3 emu/g, and all had an initial increase before decreasing and their coercivity (H_c) values increased with increased Si content. The Fe₈₇Zr₁₀Si₃ amorphous alloy exhibited a low H_c value of approximately 39.1 A/m, which shows good magnetic properties in the as-quenched state. After annealing, the M_s of the amorphous sample considerably improved, particularly reaching 165.3 emu/g at 600 ^°C.     

Influence of Overheating and Cooling Rate on the Structures and Properties of Alloys of the Fe–B System

Materials Science - It is shown that the overheating of a melt by 150°K over the liquidus curve and a cooling rate of 102?104 °K/sec favor the formation of a homogeneous finely...     

Structure and Properties of Nanostructured Vacuum-Deposited Foils of Invar Fe–(35–38 wt%)Ni Alloys

The process of electron beam vacuum deposition of the Fe–(35–38 wt%)Ni alloys at substrate temperatures Ts from 300 to700 °C were used to produce vacuum-deposited foils with the FCC structure, differing by the size of characteristic microstructural elements(grains and subgrains). It was shown that refinement of foil microstructural elements to nanoscale is accompanied by their microhardness increase up to 4–5 GPa. The change of the thermal expansion coefficient(TEC) of the nanostructured(NS) foil of the Fe–35.1Ni alloy within the temperature range from-50 to 150 °C has some deviation from that observed for cast Invar alloy of the same composition. It has been found that the main factors affecting the peculiarities of thermal expansion of the NS foil can be related to the presence of small fraction of BCCphase in them, high level of crystalline lattice microstrains and inhomogeneous magnetic order in FCCphase. It was shown that as a result of additional thermal treatment of NS foils their invar properties become similar to that observed for cast Invar alloy but mechanical properties remain on the same level.     

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.     

The role of cementite in the metal dusting of Fe–Cr and Fe–Ni–Cr Alloys

Abstract

Model Fe–25 w/o (weight percent) Cr and Fe–25 Cr–Ni alloys containing 2.5, 5, 10 and 25w/o nickel were exposed to a CO–26H₂–6H₂O (vol. pct) mixture at 680°C under thermal cycling conditions. The supersaturated carbon activity was calculated to be 2.9 (referred to graphite) and M₃C was predicted to form on Fe–25Cr and Fe–25 Cr–2.5 Ni, but not on higher nickel content alloys. Metal dusting occurred on all alloys, accompanied by internal carburisation. Transmission electron microscopy of the dusting deposit showed that much of the carbon consisted of hollow graphite nanotubes. Small, metal-rich particles were found at the carbon filament tips. These were identified as single crystal Fe₃C in the case of Fe–25 Cr, and M₃C, containing low levels of nickel, in the case of Fe–25 Cr–2.5 Ni and Fe–25 Cr–5 Ni. In contrast, the particles found at the filament tips on the higher nickel, two phase, alloys were both M₃C and austenitic Fe–Ni. Strong orientation relationships were determined between the graphite and cementite particles, however, no consistent and clear crystallographic relationship was deduced between the graphite and austenite particles. It is concluded that carbon deposition from the gas is catalysed by both Fe₃C and austenite. Subsequent carbon nanotube growth reflects the orientation relationship between Fe₃C and the graphite.     

Properties and application of Fe–6Si–14Mn–9Cr–5Ni shape memory alloy

Abstract

Three iron based shape memory alloys were studied and Fe–6Si–14Mn–9Cr–5Ni alloy showed the best shape memory effect. By thermomechanical training, the shape memory effect was improved and an absolute recovery strain of 6·2% was obtained. To promote the ε→γ transformation, which is not complete even after heating the alloy to 1000 K, the As and Af temperatures are decreased and the transformation enthalpy is increased by thermal cycling and increasing prestrain. The alloy also shows good creep and stress relaxation resistance. In addition, under a tensile force of 20 kN and a sealing test pressure of 6 MPa pipe joints made using the alloy remain effective and can satisfy the requirements for possible industrial applications.