Chemical and physical studies of metallic alloy-based old Indian coins with LIBS coupled with multivariate analysis

The present work aims to demonstrate the capabilities of Laser-induced Breakdown Spectroscopy(LIBS)coupled with a multivariate technique for rapid quantification and classification of old Indian coins made of various alloys.Thirteen old Indian coins in different years of circulation,(1922–1986)were selected for the study.The concentrations were determined by Calibration free LIBS(CF-LIBS)method.The concentration of cuprum(Cu)is negligible,and aluminum(Al)is maximum in the first five coins,and vice-versa in the remaining eight coins.Two different multivariate methods,Principal Component Analysis(PCA)and Soft Independent Modelling of Class Analogy(SIMCA)have been used to classify and identify the coins.PCA classified all thirteen samples into four main alloy categories.The discernment of unknown samples to their probable class membership of alloy was performed using SIMCA.The surface hardness(Brinell hardness number)is linearly correlated with the plasma temperature and LIBS intensity ratios.The sample surface of the first and fifth coin belongs to Al-alloy,having the least surface hardness,and it became harder for Cu–Ni alloy,Ni-brass alloy,and bronze alloy.The hardness of the surface is more for bronze sample twelve.It is also observed that the plasma temperature increases monotonically with the Brinell hardness number.This analysis provides valuable information on fabrication methodology and explains large diversification in the elementary composition of old coins.

Potential Application of Entangled Porous Titanium Alloy Metal Rubber in Artificial Lumbar Disc Prostheses

Entangled Porous Titanium Alloy Metal Rubber(EPTA-MR)was used as a nucleus pulposus material in the design of non-fusion intervertebral disc prosthesis for the first time.A novel artificial lumbar intervertebral disc prosthesis was designed by reconstructing the lumbar model with reverse engineering technology,and the biomechanical behavior of the prosthesis was simulated under varied working conditions.The nucleus pulposus size was determined by the actual size of human prosthesis.EPTA-MR samples with different densities were prepared by medical titanium alloy wire experimental studies were conducted on static stiffness,damping energy consumption,and fatigue life.The results indicated that the static stiffness of EPTA-MR could reach approximately 1500 N mm and its loss factor remained higher than 0.2,and the variation range was relatively small,with excellent vibration damping capacity and bearing capacity.Among them,the overall performance of EPTA-MR with a density of 2.5 g em 3 was closer to that of the physiologic intervertebral disc.A macro experiment of five million fatigue vibration tests combined with microstructure observation exhibited a wear rate of only 0.9396 g-MC with no noticeable change in the internal micro-morphology.Therefore,the EPTA-MR has a broad application prospect as the nucleus pulposus material of artificial intervertebral disc prosthesis.

Theoretical investigations of half-metallic ferromagnetism in new Half-Heusler YCrSb and YMnSb alloys using first-principle calculations

Structural,electronic,and magnetic properties of new predicted half-Heusler YCrSb and YMnSb compounds within the ordered MgAgAs Clb-type structure are investigated by employing first-principal calculations based on density functional theory.Through the calculated total energies of three possible atomic placements,we find the most stable structures regarding YCrSb and YMnSb materials,where Y,Cr(Mn),and Sb atoms occupy the(0.5,0.5,0.5),(0.25,0.25,0.25),and(0,0,0) positions,respectively.Furthermore,structural properties are explored for the non-magnetic and ferromagnetic and anti-ferromagnetic states and it is found that both materials prefer ferromagnetic states.The electronic band structure shows that YCrSb has a direct band gap of 0.78 eV while YMnSb has an indirect band gap of 0.40 eV in the majority spin channel.Our findings show that YCrSb and YMnSb materials exhibit half-metallic characteristics at their optimized lattice constants of 6.67 and 6.56 ,respectively.The half-metallicities associated with YCrSb and YMnSb are found to be robust under large in-plane strains which make them potential contenders for spintronic applications.

Magnetism of Metals, Alloys and of Clusters of Transition Metal Atoms

A condition for local moment formation in metals derived by Stoddart and March (Ann. Phys. NY 1972 64, 174) is first used to discuss the ferromagnetism of body-centred-cubic Fe. A less detailed discussion is also added on Ni and Co. This leads into a treatment of the non- linear response of such 3d ferromagnets to dilute substitutional impurities. Antiferromagnets responding to local changes in the exchange field caused by such impurities are also studied, Mn in Cr being one such system discussed. The paper concludes with a brief summary of clusters of transition metal atoms, with most attention devoted to Cr and to Mn.

Wettability of Monocrystalline Silicon Carbide by Molten Metals and Binary Metal－Silicon Alloys

The wettability of monocrystalline silicon carbide by liquid metals (Au , Ge, Ag , Sn and Cu) and binarymetal-silicon (Ag-Si and Sn-Si) alloys was investigated between their melting points and 1430℃ with the ses-sile drop method in argon with an extremely low oxygen partial pressure. For Au and Ge on SiC, the contactangles exhibited a weak temperature dependence. Under the same experimental conditions, however, complexwetting behaviours were observed for Ag , Sn and Cu on SiC , which could be attributed to the chemical reactivi-ties between the metals and the ceramic.Additional experirnents were also performed for binary Ag-Si and Sn-Si alloys on the same SiC substratesunder the same experimental conditions. The obtained coiitact angle isotherms for the two binary alloy/SiC sys-tems were discussed and interpreted by using a statistical thermedynamics mixlel.

Study on the Effect of Dental Metal Alloys on the Histamine Liberation of Blood Basophiles in Vitro

Biomaterials for restoration or replacement of diseased tissues may have any origin.The major characteristic for biomaterials is biocompatibility.All biomaterials,used in medicine (dentistry,in particular),interreact with the organism tissues.And the changes occur both in the materials and the organism tissues.It is considered that there are no "inert biomaterials." The number of allergic diseases and complications is constantly growing all over the world,taking an important place in the structure of infectious and noninfectious pathology[1].Pollen,household,epidermal,and food-borne allergens,and haptens are the most frequent sources of sensibilization.

Extending the Lifetime of Copper-beryllium Alloys as Plastic Injection High-end Needle Valve Mold Nozzle Tips Through a Heat-treatment-based Microstructure Optimization Approach

The relationship between the microstructure and the practical performance of two different copper-beryllium alloys including their lifetime has been investigated.Herein,two valves made of two different alloys with very similar compositions and the same heat treatment methods were investigated by various standard techniques including metallography,X-ray diffraction,chemical composition,microhardness,and thermal conductivity measurements.Although both alloys experienced the same heat-treatment processes,they revealed different thermal and mechanical properties due to the minor difference in their chemical composition.The alloy providing a longer lifetime (40%more) as the tip had a higher thermal conductivity of 280.3 W(m·K)^(-1) (about two times that of the other alloy).Regarding the metallography images and the measured thermal conductivity values of the alloys,the extended lifetime of the nozzle with the optimum performance is ascribed to its biphasic microstructure and the minor grain boundaries and interfacial thermal resistance.And important difference in the chemical composition was investigated in this study.

ON-LINE ELECTROLYTIC DISSOLUTION OF SOLID METAL SAMPLE AND DETERMINATION OF COPPER IN ALLOY BY AAS

On-line dissolution of solid metal sample can be carried out by electrolysis under the control of flow injection analyzer(FIA),and the dissolved sample can be transferred to atomic spectrometer for the direct analysis.The hyphenated technique of FIA on-line electrolytic dissolution of alloy and atomic absorption spectrometer(AAS)detection is developed.The research is focused on the effects of electrolyte composition and electrolysis parameters on the sample dissolving,as well as the quantitative analysis of Cu in Al alloy samples.

Self-healing Ga-based liquid metal/alloy anodes for rechargeable batteries

With the rapid development of electronics,electric vehicles,and grid energy storage stations,higher requirements have been put forward for advanced secondary batteries.Liquid metal/alloy electrodes have been considered as a promising development direction to achieve excellent electrochemical performance in metal-ion batteries,due to their specific advantages including the excellent electrode kinetics and self-healing ability against microstructural electrode damage.For conventional liquid batteries,high temperatures are needed to keep electrode liquid and ensure the high conductivity of molten salt electrolytes,which also brings the corrosion and safety issues.Ga-based metal/alloys,which can be operated at or near room temperature,are potential candidates to circumvent the above problems.In this review,the properties and advantages of Ga-based metal/alloys are summarized.Then,Ga-based liquid metal/alloys as anodes in various metal-ion batteries are reviewed in terms of their self-healing ability,battery configurations,working mechanisms,and so on.Furthermore,some views on the future development of Ga-based electrodes in batteries are provided.

Ternary alloy and metal oxides embedded in yolk–shell polyhedrons as bifunctional oxygen electrocatalyst

To improve the efficiency of oxygen electrolysis,exploiting bifunctional electrocatalysts with excellent activity and stability is extremely important due to the four-electron transfer dynamics of oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).Herein,a series of yolk-shell hollow polyhedrons(YHPs)embedded with NiCoFe ternary alloy and metal oxides,which are named YHP-x(x=1,2,3,4),were reported.By controlled etching multi-layered zeolitic imidazolate frameworks and following pyrolytic integration,YHPs are endowed with mass transfer tunnels,accessible inner active sites,and good electrical conductivity.Due to the synergetic effect of the alloy,metal oxides and the yolk-shell structure,YHP-1 exhibits excellent ORR performance with a half-wave potential of 0.79 V and YHP-2 displays superior OER performance with a low overpotential of 257 mV at 10 mA cm−2.The strategy described in this work can be extended to a number of hollow/yolk-shell electrocatalysts for water splitting and metal–air batteries.

Structure and Magnetic Properties of Fe1-xCx Solid Solution Prepared by Mechanical Alloying

Supersaturated solid solutions Fe1-xCx （0≤x≤0.9 ） of wide composition range have been prepared by mechanical alloying process. Nanocrystalline phase was formed for 0 ≤ x ≤ 0.67 and a large grain phase for 0.75 ≤ x ≤ 0.9. The large fraction of graphite volume puts off formation of nanocrystalline phase for high carbon content. In the large grain phase, magnetization follows simple magnetic dilution, and eoereivity He is mainly due to dissolution of carbon at grain boundaries. In the nanocrystalline phase the alloying effect of carbon is revealed by a distinct reduction of average magnetic moment. The increasing lattice constant with increasing carbon content is observed for x ≤ 0.5, suggesting that the high carbon concentration may enhance diffusion of carbon into the Fe lattice. It shows a discontinuity in the Hc variation with a grain size D of nanocrystalline phase. For small grain D below the critical value, Hc increases with D. For a large grain D, Hc decreases with increasing D. The solubility limit of carbon in a-Fe extended by nanocry- stalline phase formation is discussed.

Effect of multiaxial deformation on structure, mechanical properties, and corrosion resistance of a Mg-Ca alloy

This article provides a report on the effect of multiaxial deformation(MAD) on the structure, texture, mechanical characteristics, and corrosion resistance of the Mg-0.8(wt.)% Ca alloy. MAD was carried out on the alloy in the as-cast and the annealed states in multiple passes, with a stepwise decrease in the deformation temperature from 450 to 250 ℃ in 50 ℃ steps. The cumulative true strain at the end of the process was 22.5. In the case of the as-cast alloy, this resulted in a refined microstructure characterized by an average grain size of 2.7 μm and a fraction of high-angle boundaries(HABs) of 57.6%. The corresponding values for the annealed alloy were 2.1 μm and 68.2%. The predominant mechanism of structure formation was associated with discontinuous and continuous dynamic recrystallization acting in concert. MAD was also shown to lead to the formation of a rather sharp prismatic texture in the as-cast alloy, whilst in the case of the annealed one the texture was weakened. A displacement of the basal poles {00.4} from the periphery to the center of a pole figure was observed. These changes in the microstructure and texture gave rise to a significant improvement of the mechanical characteristics of the alloy. This included an increase of the ultimate tensile strength reaching 308 MPa for annealed material and 264 MPa for the as-cast one in conjunction with a twofold increase in ductility. A further important result of the MAD processing was a reduction of the rate of electrochemical corrosion, as indicated by a significant decrease in the corrosion current density in both microstructural states of the alloy studied.

Modification of Recrystalization Grain Structure of Ytria Dispersion Strengthened MA956 Alloy by Pre-deformation

The effects of cold deformation on recrystallization characteristics of a mechanically alloyed yttria dispersion strengthened alloy (Fe 20%Cr 4.5%Al 0.5%Ti 0.01%C 0.5%Y 2O 3 (wt%)) are studied. Experimental techniques employed include optical and transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and laser processing methods. In addition, a recrystallization grain growth model is presented to explain the observed reduction of recrystallized grain aspect ratio as a result of cold forging.

Formation and Mechanical Properties of Zr-Nb-Cu-Ni-Al-Lu Bulk Glassy Alloys with Superior Glass-Forming Ability

Glass-forming ability（GFA） and mechanical properties of（Zr_（0.58）Nb_（0.03）Cu_（0.16）Ni_（0.13）Al_（0.10））_（100-x）Lu_x（x= 0-3 at%） alloys have been investigated.The GFA of Zr_（58）Nb_3Cu_（16）Ni_（13）Al_（10） alloy is dramatically enhanced by adding Lu.The（Zr_（0.58）Nb_（0.03）Cu_（0.16）Ni_（0.13）Al_（0.10））_（98）Lu_2 alloy possesses the highest GFA in the studied Zr-Nb-Cu-Ni-Al-Lu alloys,with its critical diameter for glass formation reaching 20 mm by copper-mould casting method,while that of the Lu-free Zr_（58）Nb_3Cu_（16）Ni_（13）Al_（10） alloy is 7 mm.The critical diameters of（Zr_（0.58）Nb_（0.03）Cu_（0.16）Ni_（0.13）Al_（0.10））_（100-x）Lu_x（x =1 at%and 3 at%） alloys are 15 mm and 12 mm,respectively.The Lu addition to Zr_（58）Nb_3Cu_（16）Ni_（13）Al_（10） alloy induces the change of initial crystallization phases from face-centred-cubic Zr_2Ni and tetragonal Zr_2Ni phases for the Lu-free Zr_（58）Nb_3Cu_（16）Ni_（13）Al_（10） alloy to an icosahedral quasi-crystalline phase for the Lu-doped alloys,which may be the origin for the enhanced GFA of the Lu-doped alloys.The compressive fracture strength and plastic strain of the bulk glassy（Zr_（0.58）Nb_（0.03）Cu_（0.16）Ni_（0.13）Al_（0.10））_（98）Lu_2 alloy are1 610 MPa and 1.5%,respectively.

Mechanical Property and Microstructure of Oxide Dispersion Strengthened Nickel-base Superalloy MA758

The mechanical property and microstructure of a mechanically alloyed (MA) oxide dispersion strengthened (ODS) nickel base superalloy MA758 were investigated by compression testing and microscopy techniques. It was found that the yield strength of the as extruded fine grain material is significantly dependent on temperature, droping from 880 MPa at 560℃ down to 15 MPa at 1160℃. The yield strain also drops with temperature, from 0.037 at 560℃ to 0.024 at 1160℃. The second part of the current research has revealed large amount of strings of Al 2O 3 particles forming after high temperature annealing in air, aligned along the extrusion direction. Upon annealing in vacuum, such particles do not formed, though Ti/Cr nitrides and carbides are present in small quantities. This phenomenon explains the observed weak transverse mechanical property in several ODS alloys.

Microstructure Development during Extrusion of Mechanically Alloyed Powder

Sections from partially extruded bars of iron base MA956 and nickel base MA758 were studied using a combination of microscopy with heat treating method. It has been found that the mechanically alloyed powder, prior to extrusion, had a heavily deformed microstructure with hardness higher than the extrusion products, and there was no dynamic recrystallization during the mechanical alloying process. Clear evidence revealed dynamic primary recrystallization during extrusion in the nickel base alloy, but not in the steel, in accord with earlier observations of fully extruded materials. In MA758, primary recrystallization which normally happens during extrusion process can indeed be induced by simple high temperature heat treatment of the mechanically alloyed powder.

Recrystallization in Oxide Dispersion Strengthened Nickel－base Superalloy MA760

The recrystallization behavior of a mechanically alloyetl oxide dispersion strenghened Nibase superalloyMA760 (Ni-19.51 %Cr-6%Al-3. 4 1 %W-1. 19%Fe-1. 02 %Y_2O_3 (wt%)) has been investigated by using acombination of microscopy, ealorimetry and hardness measurement techniques. It has been found that recrystal-lization occurs at very high temperatures and has a very fast kinetics. Recrystallization onset temperature in-creases with increasing heating rate, while recrystallized grain size decreases. The effects of pre-anneal havebeen found to be reducing the stored energy for recrystallization and the subsequent recrystallized grain size. Toexplain all these experimental observations, a model has been proposed considering grain boundary Junction pin-ning during the initial stage of recrystallization process.