Structural and Magnetic Properties of Fe60–xNix(ZnO)40 Nanocomposites Produced by Mechanical Milling and Coated by Thermal Spraying on a Steel Substrate

Powder Metallurgy and Metal Ceramics - This work aims to study the effect of mechanical milling of Fe, ZnO, and Ni elemental powders and thermal spraying processes on chemical composition,...     

Research on Nitrogen Solubility of Fe–Cr–Mn–V–N System Alloys in Liquid and Solid Phases

In this paper, the thermodynamic model of nitrogen solubility in vanadium nitrogen microalloyed high strength weathering steels of Fe–Cr–Mn–V–N system, according to Hillert’s model for Gibbs energy of its various phases, was established and validated. In the model, the effect of the nitrogen partial pressure on the activity coefficient and the lattice structure characteristics of the vanadium nitrogen precipitated phase were considered. It would be of guiding significance for the design and smelting of Fe–Cr–Mn–V–N system alloys. Based on the established model, the nitrogen contents in \(\delta\), \(\gamma\), \(\alpha\) phase and liquid were calculated as a function of the temperature for Fe–Cr–Mn–V–N system alloys. The results show that: first, the maximum solubility of nitrogen in the solidification process is obviously affected by the phase transition when there is a sudden change in the solubility of nitrogen at the phase transition point. The maximum nitrogen solubility of the molten steel in the delta phase region determines whether nitrogen bubbles are formed during the solidification process. The nitrogen solubility is lowest in the solid–liquid region (about 1673 K). Secondly, the increase of Cr and Mn content is beneficial to improve nitrogen solubility in liquid and solid phases. However, the increase of V content mainly affects the nitrogen solubility in the solid phase because the nitrogen in this temperature range is precipitated in the form of vanadium nitride, as the second phase plays a role in strengthening. In addition, the alloying element Mn has a significant effect on nitrogen solubility since the Mn element is the promoting element of austenitic formation. During the solidification process, the delta ferrite region gradually reduces and may disappear with increasing Mn content. Therefore, increasing the Mn content of the alloy system in the design of alloy composition, can reduce the precipitation trend of the nitrogen during the solidification process, which can effectively avoid bubble formation in high nitrogen weathering steels. Lastly, with the increase in the nitrogen partial pressure, the solubility of nitrogen increases during the liquid and solid phases.     

Chemical stability of simulated waste forms Zr_(1–x)Nd_xSiO_(4–x/2): Influence of temperature,pH and their combined effects

The chemical stability of simulated waste forms Zr_(1–x)Nd_xSiO_(4–x/2) was investigated using the static leach test(MCC-1) with lixiviants of three pH values(pH=4, 6.7 and 10) at three temperature points(40, 90 and 150 oC) for periods ranging from 1 to 42 d, and the influence of temperature, pH, as well as their combined effects were explored in detail. The results showed that all the normalized release rate of Nd firstly decreased with leaching time and closed to equilibrium after 14 d. As the temperature increased, the normalized release rate of Nd also increased, but it was no more than 3×10~(–5) g/(m~2·d). And, the normalized release rate of Nd reached the highest values(~5×10~(–5) g/(m~2·d)) when pH=4, whilst the normalized release rate of Nd remained the lowest value(~1×10~(–5) g/(m~2·d)) near neutral environment(pH=6.7).     

Cold Sintering of Fe–Ag and Fe–Cu Nanocomposites by Consolidation in the High-Pressure Gradient

Russian Journal of Non-Ferrous Metals - The results of fabricating dense Fe–Ag and Fe–Cu nanocomposites from mixtures of powders consolidated by high-pressure cold sintering and from...     

The Friction Stress of the Hall–Petch Relationship of Pure Mg and Solid Solutions of Al,Zn, and Gd

Temperature and solute concentration effects on the friction stress, σ_o, of cast (texture-free) polycrystals of pure Mg, and of Mg-Al, -Zn and -Gd binary solid solutions are discussed using phenomenological arguments. The temperature effects on the pure metal suggest that σ_o relates to the ratio between the CRSS of prism and basal slip, against early suggestions that it should only relate to the CRSS for basal slip. Solid solution softening upon prism slip accounts for the minima in σ_o at ~ 0.5 at. pct in Mg-Zn and Mg-Gd alloys. In the concentrated alloys, solute-specific hardening effects upon slip and twinning lead to diverging behaviors: in Mg-Al and Mg-Zn, σ_o remains below that of pure Mg. Strong short-range order by Gd leads to a steep monotonic increase, and to a value larger in compression than in tension due to the activation of {10-11} twinning at high concentrations. The negative σ_o of the dilute Mg-Zn alloys is an artifact created by the tension/compression asymmetry stemming from the polar character of {10-12} twinning.     

The Structure and Properties of Precipitation-Strengthened Composites Produced From a Cast Alloy in the Al–Si–Mg System

Powder Metallurgy and Metal Ceramics - The properties of precipitation-strengthened composites produced from an aluminum alloy were studied. The composites were prepared by powder and casting...     

Effects of Synthesis Temperatures on Crystal Structures and Lattice Vibration Modes of (Ba0.3Sr0.7)[(Zn1–x Mg x )1/3Nb2/3]O3 Solid Solutions

(Ba_0.3Sr_0.7)[(Zn_1?Cx Mg _x )_1/3Nb_2/3]O₃ (BSZMN, x?=?0.4, 0.6, and 0.8) solid-solution ceramics were synthesized by the conventional solid-state synthesis technique. X-ray diffraction (XRD) and vibration spectra (Raman spectroscopy and Fourier transform far-infrared reflection spectroscopy) were employed to evaluate effects of synthesis temperatures on crystal structures and lattice vibration modes of these solid solutions. The XRD results reveal that BSZMN ceramics have a phase transformation, from pseudocubic structure to hexagonal distorted perovskite structure with different Mg²⁺ concentration and different synthesis temperatures, i.e., symmetry decreases with increasing synthesis temperatures. From Raman spectra, synthesis temperatures have an obvious influence on the phonon modes, which are closely related to the 1:2 ordered structure. Variation of the phonon parameters corresponds to the ordering degree; however, the phase transformation and the second phase can influence the phonon characteristics. The results are also proved by far-infrared reflection analyses.     

The effect of Mn on the structural and magnetic behaviour of Fe–6Si–8B alloy produced by high energy ball Milling

The alloys of Fe–6Si–8B and Fe–6Si–8B–1Mn were prepared using high energy planetary ball mill. X-ray diffraction patterns of the milled samples confirmed the formation of the alloys by dissolution of Si in Fe after 30 and 24 h of milling for the Fe–6Si–8B and Fe–6Si–8B–1Mn samples respectively. The lattice parameter was found to increase continuously with milling time and the rise was steeper for the quaternary alloy. After 36 h of milling, the crystallite size for the two samples were reduced to 98 and 86 nm respectively. Mössbauer spectra suggested the formation of minor amount of α-Fe₂O₃. The value of saturation magnetization was 162 Am²/kg for Fe–6Si–8B alloy obtained after 18 h of milling. However, the value decreased with increased milling time as well as with Mn-addition. The remanance value showed similar tendency as that for saturation magnetization. In contrast, the coercivity value was found to be increasing with milling time and with Mn-addition.     

Electrochemical formation of Mg–La–Mn alloys by coreduction of Mg(II), La(III) and Mn(II) in LiCl+KCl molten salts

In the present work, cyclic voltammetry (CV), square wave voltammetry (SWV) and chronopotentiometry (CP) were used to investigate the electrochemical coreduction behaviors of La(III) and Mg(II) as well as La(III), Mg(II) and Mn(II) on Mo electrode in LiCl + KCl molten salts. CV and SWV results exhibit that the coreduction mechanism of La (III) and Mg(II) on Mo electrode is that La(III) is reduced and Mg–La intermetallic compound is formed, leading to the deposition potential of La(III) shifting to more positive one. The electrochemical signals pertaining to the formation of metallic La, Mg and Mn as well as Mg–La intermetallic compound are also observed by coreduction of La(III), Mg(II), and Mn(II) in LiCl + KCl molten salt on the inert Mo electrode. However, the electrochemical signals associated with the formation of La–Mn and Mg–Mn alloys are not observed, which means that the depolarization effect of La(III) and Mg(II) does not occur on pre-deposited Mn electrode. The Mg–La–Mn alloys were formed by co-deposition of La(III), Mg(II), and Mn(II) on Mo electrode at various concentration ratios of La(III) and Mg(II). The results of scanning electron microscopy equipped with energy dispersive spectroscopy and X-ray diffraction displays that the Mg–La–Mn alloys are comprised of La–Mg compound Mg₁₇La₂, Mg and Mn phases. The concentration ratio of La(III) and Mn(II) has few effects on the alloy composition.