Addition Of Minor Elements Research Articles

Effects of metalloid Si on the microstructure and mechanical properties of Fe36Ni36Cr10Mo1Al17−XSiX alloys

Multi-component alloys with good mechanical properties and casting liquidity have become a hotspot in the materials field. Typically, the addition of minor metal elements plays a vital role in strengthening the mechanical properties. However, doping metalloid elements such as Si into multi-component alloys is also an effective method to enhance the mechanical properties. In the present study, the effect of Si (0 ∼ 4 at%) on the microstructure and mechanical properties was investigated within both as-cast and thermal mechanical treatment states. In as-cast state, all 4 alloys exhibited dendrites and interdendrites structure. The fine structure enhanced tensile strength for Si1 and improved ductility for Si2. Once the Si content reached 4 at%, both the strength and ductility dropped dramatically. Phase selective recrystallization and aging greatly increased the tensile strength and ductility simultaneously. The alloys with addition of Si had similar mechanical properties after thermal mechanical treatment process. Si2 after recrystallization and aging was considered a promising candidate for further application with a yield strength of 960 MPa, tensile strength of 1463 MPa and fracture strain of 20.5%. This work provided a new prospect to design multi-component alloys with nonmetallic elements, which may be applied to wear, corrosion and oxidation resistance fields.

Deterioration of silver alloy electrode caused by photocatalytic reaction for crystalline silicon solar cells

In recent years, some minor elements are added into silver paste in order to improve the Ag/Si contact properties for crystalline silicon solar cells. Nevertheless, along with the addition of minor elements, the early discoloration of silver electrode appears on solar cells. In this work, the deteriorated silver alloy electrode on crystalline silicon solar cells was analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results prove that there exists a small amount of bismuth sulfide on the surface of the deteriorated electrode compared with normal electrode. An important finding is that the photocatalytic reaction of bismuth sulfide can accelerate the early discoloration of the silver alloy electrode. Then, the effect of silver alloy electrode deterioration on the peel force of ribbon for solar cells was investigated. The results indicate that the peel strength between ribbons and solar cells is decreased sharply due to the poor solderability of the deteriorated electrode. Additionally, it is found that the deteriorated silver alloy electrode can be recovered at 450 °C annealing for 60 s in a sintering furnace. After recovery experiments, the average peel force of ribbons attached to recovered busbars is up to 85% of normal busbars. The peel force of ribbon is significantly improved. The results obtained in this paper indicate that more attention should be given to the negative effect of minor elements on the electrode, when minor elements are added into silver paste to improve its performance.

The Effects of Minor Element Addition on the Structural Heterogeneity and Mechanical Properties of ZrCuAl Bulk Metallic Glasses

The present study reveals the role of Nb and Ni minor addition on the nanomechanical properties and nanostructure of ZrCuAl bulk metallic glass (BMG). For this purpose, atomic force microscopy (AFM) was used to evaluate the viscoelastic response of the BMG surface at the nanoscale, while the nanoindentation technique was applied to show the mechanism of plastic deformation. The results indicated that minor Nb addition decreased the relaxation of enthalpy accompanied by the weakening of structural heterogeneity. On the other hand, Ni addition improved the stored energy of the material and intensified the distribution of loosely packed regions in the microstructure. Moreover, the mechanical test unveiled that Ni addition enhanced the viscoelastic response; however, it came at the expense of creep resistance. The evaluation of the magnitude of the derivative in the nanoindentation test also demonstrated that the Ni-added sample exhibited a multiple shear-band mode for plastic deformation.

Preparation and Performance of Ternesite-Ye'elimite Cement.

Ternesite–ye’elimite (TCSA) cement is a new type of environmentally advantageous binder prepared by introducing ternesite, a reactive phase, into belite calcium sulfoaluminate cement clinker. This paper reports the laboratory production of TCSA cement by the addition of minor elements to achieve the coexistence of ternesite and ye’elimite. The influence of dopants on the mineralogical composition of clinkers and the clinkering conditions for the preparation of TCSA cement clinkers were investigated by X-ray powder diffraction and scanning electron microscopy. The mechanical properties and hydration products of the cement pastes were also studied. The results indicated that the addition of CaF2, P2O5 and Na2O can promote the coexistence of ternesite and ye’elimite, and that Na2O is the most effective candidate. TCSA cement clinkers could be successfully prepared at 1150 °C for 30 min by doping 0.3% Na2O. The TCSA cement clinkers exhibited shorter setting times than the BCSA cement clinkers. The later strength of TCSA cement showed a significant increase compared with BCSA cement. The effect of Na2O was different on the strength development for TCSA and BCSA cement. The dissolution of ternesite could promote the formation of ettringite. The reactivity of belite was higher in TCSA cement due to the formation of strätlingite.

The effect of Ni on the growth morphology of primary β-phase in an In-35 wt%Sn alloy

In-35 wt%Sn alloy is a superconductive alloy and its superconductivity is highly dependent on the properties of the β-In3Sn phase. However, detail solidification behaviour with microstructure development had not been studied with minor element additions. This paper investigates the effect of minor addition of Ni on the β-phase evolution in an In-35 wt%Sn alloy during the solidification process using the in-situ real-time synchrotron radiography technique. The β-phase preferably formed a columnar dendritic structure that made a transition to a mix structure of cellular and dendrite with a unique morphology with an addition of 0.05 wt%Ni. The findings provide detailed observations of microstructure evolution, specifically β-In3Sn phase, and examine the effects of Ni addition during solidification of the In-35 wt%Sn alloy, as well as the thermal properties of the alloys by differential scanning calorimeter.

Effects of Mo/Zr addition on deuterium retention in W-Y2O3 alloys

Mo/Zr were added to further improve the mechanical properties of W-Y 2 O 3 alloys, thus improving W ductility due to the addition of Y 2 O 3 nanoparticles. Herein, the effects of minor addition of elemental Mo/Zr and Fe-ion pre-irradiation on D retention in W-Y 2 O 3 alloys were investigated. The maximal fluence of W-1 wt.%Mo-0.25 wt.%Y 2 O 3 and W-0.1 wt.%Zr-0.25 wt.%Y 2 O 3 samples irradiated with 5-keV-energy D 2 ions was 10 22 D 2 /m 2 , and Fe-ion pre-irradiation was performed at ion fluences of up to 4 × 10 18 /m 2 at the energy of 1 MeV. For both alloys, the D desorption amount increased with increasing D 2 -ion irradiation fluence, regardless of Fe-ion pre-irradiation. Compared with W-Y 2 O 3 , the overall amount of the D desorption increased for both alloys without Fe-ion pre-irradiation. However, it decreased for both alloys with Fe-ion pre-irradiation, when the D 2 -ion irradiation fluence was 10 22 D 2 /m 2 . The addition of Mo/Zr prevented the diffusion of D from the surface to the inside of the sample. Therefore, Fe-ion pre-irradiation had a negligible effect on D desorption in the Mo- or Zr-added W-Y 2 O 3 alloys. Changes in the microstructures of the W alloy owing to the addition of minor elements strongly affected the D desorption. The addition of Mo promoted the formation of dislocation loops during the D 2 -ion irradiation. In contrast, the addition of Zr refined the Y 2 O 3 particles. These defects served as D trapping sites, thereby weakening the pre-irradiation effect of Fe ions.

Uncovering the origin of enhanced strengthening in Li-added Al–Cu–Mg alloys

The addition of minor elements is effective in designing high-strength aluminum alloys by modifying precipitation, such that clarifying the strengthening origin is highly significant. Here, 0.5 wt% Li is added in an Al–Cu–Mg alloy (AA2024 alloy), where, obvious increases in strength without reducing the ductility are achieved in both the unstretched and stretched alloys, as compared to those in the counterpart Li free alloys. The enhanced strength arising from Li addition is mainly related to the modified precipitation behavior (rather than the solute strengthening due to Li elements), in terms of Guinier–Preston–Bagaryatsky (GPB) zones and S-phase; the strengthening sources in the unstretched and stretched alloys, however, are fundamentally different. Correlative characterizations reveal that, for the unstretched alloy in the peak-aging (PA) state, the Li-addition favors a high density of uniformly distributed GPB zones while suppressing the nucleation of S-phase precipitates. Whereas, for the stretched alloys in the PA state, the Li-addition, in combination with the possible strengthening due to the T1 phase, results in refined S-phase precipitates. These modified precipitates (GPB zones and S-phase) are decorated with Li enrichments, which are believed to be correlated with the proposed mechanism of the Li-Vacancy complex. Thus, elucidating the origin of strengthening in Li-added Al–Cu–Mg alloys under both unstretched and stretched conditions, is expected to provide basic insights into the strengthening mechanisms in other high-strength Al alloys when Li is added as the minor element.

Cu-Ag nanocomposites in-situ formed on the surface of CuZr-based metallic glasses as highly efficient catalysts for improving catalytic behavior and reusability towards wastewater treatment

Minor element addition will be considered to modulate the atomic structures of materials to achieve surface activation for enhancing catalytic capability. Herein, Ag minor alloying enhances the catalytic behaviors of Cu-Zr-Al MGs in degrading dye molecules due to in situ formed Cu-Ag nanocomposites as highly efficient and stable catalysts. The higher degradation efficiency and faster reaction rate for Cu46Zr44.5Al7.5Ag2 ribbons than those of Cu47.5Zr46Al6.5 ribbons are accurately achieved more than 99% efficiency and 0.32 min−1 reaction rate within 20 min after 30th run. The thermal activation energy barrier (ΔE) of 5.97 kJ mol−1 for Cu46Zr44.5Al7.5Ag2 ribbons is lower than that of 8.47 kJ mol−1 for Cu47.5Zr46Al6.5 ribbons. The enhanced capability can be attributed to the corrosion engineering and electrochemical principle, the inclusion of Ag as a cathode contributes to forming a micro-electric couple with Cu as an anode to generate a variety of active copper-based nanocomposites due to surface modification. More importantly, introducing Ag atom can promote the enrichment of Cu-Ag nanocomplexes on the surface of ribbons in order to provide stronger surface activity and faster electron transfer to further improve catalytic performance. These findings are expected to help open up new functional applications of CuZr-based MGs in environment field.

High Temperature Behavior of Al-7Si-0.4Mg Alloy with Er and Zr Additions

In recent years, many efforts have been devoted to the development of innovative Al-based casting alloys with improved high temperature strength. Research is often oriented to the investigation of the effects of minor element additions to widely diffused casting alloys. The present study focuses on Al-7Si-0.4Mg (A356) alloy with small additions of Er and Zr. Following previous scientific works on the optimization of heat treatment and on tensile strength, creep tests were carried out at 300 °C under applied stress of 30 MPa, a reference condition for creep characterization of innovative high-temperature Al alloys. The alloys containing both Er and Zr displayed a lower minimum creep strain rate and a longer time to rupture. Fractographic and microstructural analyses on crept and aged specimens were performed to understand the role played by eutectic silicon, by the coarse intermetallics and by α-Al matrix ductility. The creep behavior in tension of the three alloys has been discussed by comparing them to tension and compression creep curves available in the literature for Al-7Si-0.4Mg improved by minor elemental additions.

Nano-scale structural evolution of quaternary AlCrFeNi based high entropy alloys by the addition of specific minor elements and its effect on mechanical characteristics

The AlCrFeNi eutectic high entropy alloys have been developed by adding specific minor elements such as 1, 3, 5 at% of Mo and Ti to analyze the mechanical behavior with double phase strengthening. The X-ray diffraction results illustrate that the crystal structure includes dual phases such as B2 and BCC. Regarding on the compositional variation, the formation of eutectic structure was observed by adding minor elements. The detailed investigation of nano structural evolution of the alloy identified that the morphology of nanoscale Al-Ni-rich B2 phase and Cr-Fe-rich A2 phase have a high degree of coherence in dendritic and lamellar regions. As the result of volume fraction changes and variation in grain size on the nanoscale with the addition of minor elements, the enhancement of mechanical properties confirmed the high-temperature hardness behavior of the alloys. In this study, nanoscale features of the AlCrFeNi based HEAs and mechanical characteristics were explored in detail.

Influence of minor additions on Icosahedral Short-Range Order (ISRO) and its consequences on nucleation and solidification growth kinetics in fcc alloys

The present contribution reviews the recent progress related to the influence of Icosahedral Short-Range Order (ISRO) and icosahedral Quasicrystals (i-QC) formation on the solidification of fcc alloys through minor solute element additions. From intensive crystallographic analysis of multi-twinned regions in as-cast Al-based and Au-based fcc alloys, Kurtuldu et al. have shown recently that a so-called “iQC-mediated” nucleation mechanism occurs when a few hundred ppm of Cr and Ir, respectively, are added to the melt [1] [2]. Similarly, it appears that the growth directions of dendrites in Al-Zn:Cr is also influenced by ISRO in the liquid, thus showing an attachment kinetics effect [3]. In a recent contribution, we have shown that iQC-mediated nucleation also occurs in pink gold alloys with Ir-additions, but two additional phenomena at high solidification speed [4]: (i) a spinodal-type decomposition of the liquid, leading to the formation of twinned Cu precipitates in addition to multi-twinned Au-rich grains; (ii) a change of the microstructure of the Au-rich grains, from 〈100〉 dendrites to 〈111〉 textured cells in the columnar zone.

Influence of Minor Additions on Icosahedral Short-Range Order (ISRO) and Its Consequences on Nucleation and Solidification Growth Kinetics in fcc Alloys

The present contribution reviews the recent progress related to the influence of icosahedral short-range order (ISRO) and icosahedral quasicrystal (iQC) formation on the solidification of fcc alloys through minor solute element additions. From intensive crystallographic analysis of multi-twinned region in as-cast Al-based and Au-based fcc alloys, it has been shown recently that a so-called iQC-mediated nucleation mechanism occurs when a few hundred ppm of Cr and Ir, respectively, are added to the melt (Kurtuldu et al. in Acta Mater 61(19):7098–7108, 2013; Acta Mater 70:240–248, 2014). Similarly, it appears that the growth directions of dendrites in Al–Zn/Cr are also influenced by ISRO in the liquid, thus showing an attachment kinetics effect (Kurtuldu in Influence of trace elements on the nucleation and solidification morphologies of fcc alloys and relationship with icosahedral quasicrystal formation, 2014). Similar observations have been made recently in pink gold alloys with Ir additions, when the solidification speed is increased (Zollinger et al. in Acta Mater, 2018).

Role of atomic-scale chemical heterogeneities in improving the plasticity of Cu-Zr-Ag bulk amorphous alloys

The addition of minor elements to binary amorphous alloys often results in simultaneous improvement in plasticity and strength. This is particularly the case for alloy systems that promote atomic-scale compositional separation during quenching. Considering that plasticity and strength are two contrasting properties originating from different atomic-scale structures characterized by short-range orders (SROs), this experimental observation at first seems contradictory when viewed from an SRO perspective. We performed comparative studies on (Cu0.5Zr0.5)100-xAgx amorphous alloys using experiments and molecular dynamics (MD) simulations to elucidate how these two mutually exclusive properties can be realized at the same time. MD simulations showed that while the addition of Ag promotes the formation of stable icosahedral orders responsible for improved strength, it also encourages the formation of weak/unstable Ag-bearing polyhedra that mitigate strain localization. In this study, the mechanistic origin of the enhanced plasticity is assessed by introducing a new descriptor that can quantitatively evaluate the characteristics of Ag-bearing polyhedra in terms of their size, softness, population, and spatial uniformity.

Tailoring shear banding behaviors in high entropy bulk metallic glass by minor Sn addition: A nanoindentation study

The present work investigated systematically the glass forming ability, the mechanical properties and the shear deformation of the TiZrHfCuBe high entropy bulk metallic glass (HE-BMG) with minor Sn addition. The results revealed that the glass forming ability and the thermal stability are enhanced by minor Sn addition but within a rather limited composition range. A nanoindentation study of the mechanical response in the (TiZrHfCuBe)1-xSnx (x = 0, 1, 2 and 3 at. %) HE-BMGs showed that the structural heterogeneity caused by Sn addition resulted in higher hardness, larger number of shear bands and smaller size of shear transformation zone, ascribing to the positive enthalpy of mixing between the Sn and Cu/Be elements. A statistical analysis of the serrated flow revealed that the chemical heterogeneities promote a relatively large population of shear deformation units and lead to multiple nucleation of shear bands. The present work might has implications in establishing the link between minor element addition and structure heterogeneity, which is of critical importance for understanding of shear banding behaviors in BMGs.

Nanoporous Copper Fabricated by Dealloying Mn–Cu Precursors with Minor Nickel Element Addition and Heat Treatment Coarsening

Nanoporous copper (NPC) and nanoporous copper-nickel (NPC-Ni) can be prepared by free corrosion dealloying Mn[Formula: see text]Cu[Formula: see text]Nix ([Formula: see text], 1, 3[Formula: see text]at.% Ni) precursor alloys. Microscopic morphology characterization by scanning electron microscopy exhibited a three-dimensional bicontinuous porous structure with nanoscale ligaments and pores. NPC with a pore size of 48.7[Formula: see text]nm was obtained in 0.1[Formula: see text]M hydrochloric acid solution for 3.5[Formula: see text]h dealloyed at 25[Formula: see text]C. Under the same free corrosion dealloying condition, NPC-Ni1 and NPC-Ni3 were obtained with the pore size of 36.6[Formula: see text]nm and 28.1[Formula: see text]nm, respectively. The results indicate that minor Ni atoms addition to the precursor greatly refined the dealloyed nanoporous structure. This effect could be attributed to the lower Ni surface diffusivity than that of Cu and resulted in slow down of the diffusion and rearrangement of Cu atoms during dealloying process. Post-dealloying heat treatment at 300[Formula: see text]C, 450[Formula: see text]C and 600[Formula: see text]C made the ligaments coarsen in NPC and NPC-Ni.

Microstructure and mechanical performance of a secondary cast aluminium piston alloy with minor element additions

The effect of individual and combined minor element additions (Sr, Sb, Mn, Cr and Al-5Ti-1B grain refiner) on microstructure and mechanical performance of a secondary cast aluminium piston alloy, with 1 wt-% Fe was investigated. It was observed that addition of Cr of up to 1% was better than a 0.53%Mn addition in improving tensile strength, impact energy and percent elongation of the alloy. The high mechanical performance recorded with addition of 1%Cr alloy was attributed to the significant reduction in porosity levels compared to all other minor element additions. It also resulted in a microstructure with fine compact intermetallic compounds. Other element additions also resulted in improved mechanical properties with 0.53%Mn performing better than 0.3%Mn + 0.2%Cr. Marginal improvements in mechanical performance were recorded with addition of 0.02%Sr (or 0.05%) and 0.02%Sb individually or in combination with 0.53%Mn. This was attributed to general increase in porosity and volume fraction of intermetallics.

Effects of Minor Elements to the Liquidus Temperatures of Blast Furnace Slags

The effects of minor elements TiO, MnO, NaO, KO, CaS, and BO to the liquidus temperatures of blast furnace slags were experimentally studied. The base blast furnace slag composition in SiO-AlO-CaO-MgO system is fixed at CaO/SiO=1.1, 16 wt% AlO and 8 wt% MgO. The liquidus temperatures of the synthetic slags have been determined by high temperature equilibration, quenching and Electron Probe X-ray Microanalysis (EPMA) techniques. It was found that within the present investigated composition ranges, the additions of minor elements to the BF slags remain in melilite primary phase field. The minor element decrease the liquidus temperatures of the blast furnace slags in different extents and follows the tendency: BO > CaS > NaO > KO > TiO > MnO. The present measurements were also compared with FactSage predictions.

Controlling crystallization process and thermal stability of a binary Cu–Zr bulk metallic glass via minor element addition

In this paper, the effect of minor element addition on the initial structural evolution during crystallization in a simple binary Cu–Zr bulk metallic glass (BMG) forming liquid has been investigated by using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Despite no changes in the completely crystallized products, the remarkable opposite impacts on the supercooled liquid region (SLR) and crystallization reaction rate constant [Formula: see text] are observed as a result of minor selective additions of an affine element, i.e., Sn and an immiscible element, i.e., Nb into the Cu–Zr BMG alloy, respectively. Furthermore, it is demonstrated that the primary devitrification pathway and crystalline phases are simultaneously modified, which leads to significant changes in kinetics of atomic rearrangement and thus thermal stability of this material. Such a finding offers a promising way to control the type of primary crystalline phases of BMG-forming metallic supercooled liquids to synthesize novel BMGs or BMG matrix composites for structural or functional applications.

The effect of minor addition of insoluble elements on transformation kinetics in amorphous Al alloys

Nanocrystalline metallic materials based on partial devitrification of amorphous aluminum alloys show an attractive combination of high strength and low density. A key feature concerning the improved mechanical properties is the high number density of Al nanocrystals (1022–1023m−3) that precipitate within the amorphous precursor structure upon low temperature annealing. For Al87Y7Fe5Pb, the melt-spun ribbons consisted of an amorphous matrix with a dispersion of Pb nanoparticles (10nm diameter). HRTEM images of the Pb–Al interface revealed a good wetting behavior between the Al and the Pb nanoparticles. Isothermal annealing for Al87Y7Fe5Pb showed no transient stage even though the crystallization onset, Tx, was at a much lower temperature (247°C) compared with Al88Y7Fe5 (267°C). For Al(88−x)Y7Fe5Inx (x=0.5, 1.0, 1.5, 2.0), the DSC results indicated that Tx continuously decreased from 232°C to 220°C as the indium level increases from 0.5at.% to 2.0at.%. Under STEM, the image showed a coherent interface between Al and In particles. In the analysis of the transformation kinetics, the addition of minor elements can effectively promote additional nucleation of Al nanocrystals by providing heterogeneous nucleation sites. These developments offer new opportunities for the control of nanoscale microstructures.

Microstructural Change and Magnetic Properties of Nanocrystalline Fe-Si-B-Nb-Cu Based Alloys Containing Minor Elements

The effect of minor element additions (Ca, Al) on microstructural change and magnetic properties of Fe-Nb-Cu-Si-B alloy has been investigated, in this paper. The Fe-Si-B-Nb-Cu(-Ca-Al) alloys were prepared by arc melting in argon gas atmosphere. The alloy ribbons were fabricated by melt-spinning, and heat-treated under a nitrogen atmosphere at 520-570oC for 1 h. The soft magnetic properties of the ribbon core were analyzed using the AC B-H meter. A differential scanning calorimetry (DSC) was used to examine the crystallization behavior of the amorphous alloy ribbon. The microstructure was observed by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The addition of Ca increased the electrical resistivity to reduce the eddy current loss. And the addition of Al decreased the intrinsic magnetocrystalline anisotropy K1 resulting in the increased permeability. The reduction in the size of the α-Fe precipitates was observed in the alloys containing of Ca and Al. Based on the results, it can be concluded that the additions of Ca and Al notably improved the soft magnetic properties such as permeability, coercivity and core loss in the Fe-Nb-Cu-Si-B base nanocrystalline alloys.