Design of low-alloying and high-performance solid solution-strengthened copper alloys with element substitution for sustainable development

Solid solution-strengthened copper alloys have the advantages of a simple composition and manufacturing process,high mechanical and electrical comprehensive performances,and low cost;thus,they are widely used in high-speed rail contact wires,electronic component connectors,and other devices.Overcoming the contradiction between low alloying and high performance is an important challenge in the development of solid solution-strengthened copper alloys.Taking the typical solid solution-strengthened alloy Cu-4Zn-1Sn as the research object,we proposed using the element In to replace Zn and Sn to achieve low alloying in this work.Two new alloys,Cu-1.5Zn-1Sn-0.4In and Cu-1.5Zn-0.9Sn-0.6In,were designed and prepared.The total weight percentage content of alloying elements decreased by 43%and 41%,respectively,while the product of ultimate tensile strength(UTS)and electrical conductivity(EC)of the annealed state increased by 14%and 15%.After cold rolling with a 90%reduction,the UTS of the two new alloys reached 576 and 627MPa,respectively,the EC was 44.9%IACS and 42.0%IACS,and the product of UTS and EC(UTS×EC)was 97%and 99%higher than that of the annealed state alloy.The dislocations proliferated greatly in cold-rolled alloys,and the strengthening effects of dislocations reached 332 and 356 MPa,respectively,which is the main reason for the considerable improvement in mechanical properties.

Effect of two-step solid solution on microstructure andδphase precipitation of Inconel 718 alloy

Inconel 718 is the most popular nickel-based superalloy and is extensively used in aerospace,automotive,and energy indus-tries owing to its extraordinary thermomechanical properties.The effects of different two-step solid solution treatments on microstructure andδphase precipitation of Inconel 718 alloy were studied,and the transformation mechanism fromγ″metastable phase toδphase was clarified.The precipitates were statistically analyzed by X-ray diffractometry.The results show that theδphase content firstly increased,and then decreased with the temperature of the second-step solid solution.The changes in microstructure andδphase were studied by scanning electron microscopy and transmission electron microscopy.An intragranularδphase formed in Inconel 718 alloy at the second-[100]_(δ)[011]γ step solid solution temperature of 925℃,and its orientation relationship withγmatrix was determined as//and(010)_(δ)//(111)γ.Furthermore,the Vickers hardness of different heat treatment samples was measured,and the sample treated by second-step solid solution at 1010℃ reached the maximum hardness of HV 446.84.

Multi-solute solid solution behavior and its effect on the properties of magnesium alloys

The low-density magnesium(Mg)alloys are attractive for the application in aerospace,transportation and other weight-saving-required fields.The mechanical properties and corrosion properties of Mg alloys are the key-property issues for the wide application.It is surprising to find that the solid solution of alloying elements in theα-Mg phase can have multi-effects on the properties of Mg alloys,e.g.,solid solution strengthening,solid solution corrosion-resistance-enhancing,etc.Additionally,the alloy design theory of"solid solution strengthening and ductilizing"proposed by Pan and co-workers has attracted extensive attentions.It is promising that by selected proper multi-alloying-elements(with optimal ratio)solid solutioned in theα-Mg phase,the comprehensive properties of Mg alloys can be synergistically improved.In this work,the solid solution behavior of Mg alloys and the followed solid solution property-enhancing effects were reviewed.The mechanisms proposed recently by researchers for these solid solution property-enhancing behaviors were presented,and the related calculations and predictions were also described.It is shown the demonstrations of the fundamentals for the solid solution property-enhancing of Mg alloys,especially from the atomic inter-reaction aspects,still require elaborated characterization work and calculation work.Additionally,it could be expected that the multi-solute in Mg alloys can bring many possibilities,or,in another saying,"cocktail effects".With understanding the multi-solute interaction behavior and the corresponded solid solution property-enhancing effects,the good balanced high-performance Mg alloys can be developed.

Solid solution strengthening and damping capacity of Mg-Ga binary alloys

The mechanical behaviors and damping capacities of the binary Mg−Ga alloys with the Ga content ranging from 1 to 5 wt.%were investigated by means of optical microscope(OM),scanning electron microscope(SEM),X-ray diffraction(XRD),hardness test,tensile test and dynamic mechanical analyzer(DMA).The hardness(HV_(0.5))increases with the increase of Ga content,which can be described as HV_(0.5)=41.61+10.35c,and the solid solution strengthening effect∆σ_(s)of the alloy has a linear relationship with c^(n),where c is the molar fraction of solute atoms and n=1/2 or 2/3.Ga exhibits a stronger solid solution strengthening effect than Al,Zn or Sn due to the large atomic radius difference and the modulus mismatch between Ga and Mg atoms.The addition of Ga makes the Mg−Ga alloys have better damping capacity,and this phenomenon can be explained by the Granato−Lücke dislocation model.The lattice distortion and the modulus mismatch generated because of the addition of Ga increase the resistance to motion of the dislocation in the process of swinging or moving,and thus the better damping capacity is acquired.

Densification of Mo Alloys at 1473 K by Adding Ni-Cu Solid Solution

Mo is difficult to sinter densely at a relatively low temperature due to its high melting point. In the present paper,by adding different weight contents of Ni and Cu additives, Mo alloys have been densified at 1473 K for an hour byhot-pressing method, and the optimum contents of Cu and Ni additives have been acquired: when the contents of Niand Cu are 3 and 2 wt pct respectively, the relative density of the sample reaches the maximum value. It was foundthat when the Ni-Cu solid solution was added into Mo alloys. the achieved density is higher than the case of Ni andCu additives. The experimental results indicate that, Ni and Cu play different roles in the process of sintering, theNi-Cu solid solution has the same function as Ni and Cu additives in the course of sintering Mo alloys, It shows moreactivating sintering feature for Mo than the Ni and Cu additives.

Effects of Ni content on the cast and solid-solution microstructures of Cu-0.4wt% Be alloys

The effects of Ni content（0–2.1wt%）on the cast and solid-solution microstructures of Cu-0.4wt%Be alloys were investigated,and the corresponding mechanisms of influence were analyzed.The results show that the amount of precipitated phase increases in the cast alloys with increasing Ni content.When the Ni content is 0.45wt%or 0.98wt%,needle-like Be_（21）Ni_5 phases form in the grains and are mainly distributed in the interdendritic regions.When the Ni content is 1.5wt%or greater,a large number of needle-like precipitates form in the grains and chain-like Be_（21）Ni_5 and Be Ni precipitates form along the grain boundaries.The addition of Ni can substantially refine the cast and solid-solution microstructures of Cu-0.4wt%Be alloys.The hindering effects of both the dissolution of Ni into the matrix and the formation of Be–Ni precipitates on grain-boundary migration are mainly responsible for refining the cast and solid-solution microstructures of Cu-0.4wt%Be alloys.Higher Ni contents result in finer microstructures;however,given the precipitation characteristics of Be–Ni phases and their dissolution into the matrix during the solid-solution treatment,the upper limit of the Ni content is 1.5wt%–2.1wt%.

Effect of component substitution on the microstructure and mechanical properties of MCoCrFeNiTi_x (M = Cu, Al) solid-solution alloys

MCoCrFeNiTix （M = Cu, Al; x： molar ratio, x = 0, 0.5） alloys were prepared using the new alloy-design strategy of equal-atomic ratio and high entropy. By the component substitution orAl for Cu, the microstructure changes from the face-centered cubic solid solution of original CuCoCrFeNiTix alloys to the body-centered cubic solid solution of AlCoCrFeNiTix alloys. Compared with original CuCoCrFeNiTix alloys, AlCoCrFeNiTix alloys keep the similar good ductility and simultaneously possess a much higher compressive strength, which are even superior to most of the reported high-strength alloys like bulk metallic glasses.

Formation condition of solid solution type high-entropy alloy

Formation condition of high-entropy alloys with solid solution structure was investigated. Seventeen kinds of the high-entropy alloys with different components were prepared, the influencing factors （the comprehensive atomic radius difference δ, the mixing enthalpy AH and the mixing entropy AS） of phase composition of the alloys were calculated, and the microstructure and phase compositions of alloys were analyzed by using SEM and XRD. The result shows that only the systems with δ≤2.77 and △H≥-8.8 kJ/mol will form high entropy alloy with simple solid solution. Otherwise, intermetallic compounds will exist in the alloys. So, selection of the type of element has important effects on microstructure and properties of high entropy alloys.

Microstructure evolution of Mg-9Gd-2Er-0.4Zr alloy during solid solution treatment

Microstructure evolution of the cast Mg-9Gd-2Er-0.4Zr alloy during solid solution treatment at temperature of 460-520 ℃ for 3-12 h was investigated by using optical microscope（OM）,scanning electron microscope（SEM） and transmission electron microscope（TEM）.The results indicated that the grain size and the shape of second phase were obviously changed with time and/or temperature going on.At 460 ℃ for 3 h,the morphology of the Mg5（GdEr） phase was changed into fragmentized island morphology and the volume faction of the phase decreased.After solution solid treatment at 460 ℃ for 6 h,the Mg5（GdEr） phase was already completely dissolved,but some cuboid-shaped RE-rich phase precipitated.As the temperature increased,the morphology of the Mg5（GdEr） phase was transformed into the same morphology as that at 460 ℃ for 6 h.It was suggested that the microstructure evolution of the alloy during the solid solution treatment was concluded as follows：Mg5（GdEr） eutectic phase→Gd/Er atom diffusing into matrix→spheroidic Mg5（GdEr） phase→cuboid-shaped RE-rich phase→grain boundary immigration.

Microstructure and Properties of Cu-Cr-Zr Alloy after Rapidly Solidified Aging and Solid Solution Aging

The structure and properties of Cu-Cr-Zr alloy were studied after rapidly solidified aging and solid solution aging.At the early stage of aging （500℃ for 15 rain）, the hardness and the conductivity of the alloy rapidly solidified are 143 HV and 72% IACS, respectively. Under the same aging condition, the hardness and electrical conductivity of the alloy solid solution treated can reach 86 HV and 47% IACS, respectively. The microstructure was analyzed, and the grain size after rapid solidification is much smaller than that after solid solution treatment. By rapidly solidified aging the fine precipitates distribute inside the grains and along the grain boundary, while by solid solution aging there are large Cr particles along the grain boundary.

Effects of single and multi-stage solid solution treatments on microstructure and properties of as-extruded AA7055 helical profile

The effects of single-stage solution treatment(SST),enhanced solution treatment(EST),high-temperature pre-precipitation(HTPP)and multi-stage solution treatment(MST)on the microstructure,mechanical properties and corrosion resistance of the as-extruded 7055 aluminium alloy(AA7055)helical profile were investigated using differential scanning calorimetry(DSC),optical microscopy(OM),scanning electron microscopy(SEM),electron back-scattered diffraction(EBSD)and transmission electron microscopy(TEM).It was observed that EST and MST could promote the dissolution of the second-phase particles compared with the traditional SST,and the intergranular phases were distinctly discontinuously distributed after HTPP and MST.There was obvious difference in the main texture type and texture strength for the alloy after different solid solution treatments.HTPP could improve the corrosion resistance of the alloy by regulating the intergranular phases,but the mechanical properties were severely weakened.While the good corrosion resistance of the alloy could be obtained by MST without obvious strength loss.As a result,the MST is an ideal solid solution treatment scheme for AA7055.

Solid solution evolution during mechanical alloying in Cu–Nb–Al compounds

This work concerns the structural evolution of Cu70Nb20Al10(at%) alloy processed by mechanical alloying using a planetary ball mill in air atmosphere for different times(4 to 200 h). The morphological, structural, microstructural, and thermal behaviors of the alloy were investigated by scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and differential scanning calorimetry. X-ray diffraction patterns were examined using the Rietveld refinement technique with the help of the MAUD software. A disordered FCC-Cu(Nb,Al) solid solution was formed after 8 h of milling. The crystallite size, microstrain, and lattice parameter were determined by the Rietveld method. With increasing milling time, the crystallite size of the final product-ternary-phase FCC-Cu(Nb,Al)-is refined to the nanometer scale, reaching 12 nm after 200 h. This crystallographic structure combines good mechanical strength and good ductility. An increase in microstrain and partial oxidation were also observed with increasing milling time.

Nanometer Stripe Microstructure of Supersaturated Solid Solution in Fe-Cu Alloy

Strengthening due to precipitation of Cu in the a-Fe matrix is an important phenomenon utilized in the design of HSLA steels. In the present work, the microstructure of supersaturated solid solution in Fe-1.18%Cu binary alloy was investigated by means of high resolution electron microscopy. The results indicated that the solid solution was heterogeneous, there were lots of Cu atom clusters, which consisted of diffractive stripe microstructure similar to twin crystal. Orientation deviation was observed between two （110）o planes in diffractive stripes, which results in light and shade contrast. Furthermore, formation mechanisms of the nanometre stripe microstructure were discussed in terms of the interaction of Cu and Fe atoms in the Fe-Cu binary alloys.

Fe-Zn supersaturated solid solution prepared by mechanical alloying and laser sintering to accelerate degradation

The slow degration of iron limits its bone implant application.The solid solution of Zn in Fe is expected to accelerate the degradation.In this work,mechanical alloying(MA)was used to prepare Fe-Zn powder with supersaturated solid solution.MA significantly decreased the lamellar spacing between particles,thus reducing the diffusion distance of solution atoms.Moreover,it caused a number of crystalline defects,which further promoted the solution diffusion.Subsequently,the MA-processed powder was consolidated into Fe-Zn part by laser sintering,which involved a partial melting/rapid solidification mechanism and retained the original supersaturated solid solution.Results proved that the Fe-Zn alloy became more susceptible with a lowered corrosion potential,and thereby an accelerated corrosion rate of(0.112±0.013)mm/year.Furthermore,it also exhibited favorable cell behavior.This work highlighted the advantage of MA combined with laser sintering for the preparation of Fe-Zn implant with improved degradation performance.

Mossbauer Spectroscopic Studies on a Supersaturated Solid Solution of Fe-Cu Formed by Mechanical Alloying

Mechanical alloying (MA) was employed to produce supersaturated solid solutions of Fe1-xCux,which is virtually immiscible under an equilibrium condition at ambjent temperature. The X-ray diffraction results show that the solutions formed in the concentration ranges of x≤0.1 5 and x≥0.40 are of bcc structure of iron and fcc structure of copper. respectively. For the region in between.however, the alloy obtained is a mixture of bcc plus fcc phases. The Mossbauer spectrum of the solid solution of a single phase could be fitted by two sub-spectra with hyperfine magnetic fields of 200 and 250 kOe. respectively. suggesting that there must exist two forms of coordination in the solution. While to fit the spectrum for the solution with mixed structu re. three Sub-spectra. including a spectrum of α-Fe, should be used. The variation of the Mossbauer spectra of Fe60Cu40 with milling time as well as annealing temperature was systematically studied. This may be ascribed to the changes of the number of nearest neighboring atoms of iron in the processes of formation and decomposition of the solid solution during milling and annealing

Effect of solid-solution temperature on the microstructure of Fe-Ni based high strength low thermal expansion (HSLTE) alloy

The influence of solid-solution temperature on the dissolution of carbide precipitates, the average grain size and the microhardness of the austenite matrix in an Fe-Ni based high strength low thermal expansion （HSLTE） alloy was investigated to obtain the proper temperature range of the solid-solution process. The XRD analysis, microstructure observations, and the theoretical calculations showed that the Mo-rich M2C-type precipitates in the Fe-Ni based HSLTE alloy dissolve completely at about 1100℃. The average grain size of the studied alloys increases from 14 to 46 μm in the temperature range of 1050 to 1200℃. The microhardness of the matrix decreases gust for the sake of solid-solution treatment, but then increases later with increasing solution temperature because of the solution strengthening effect.

Tensile properties of 2024 Al alloy processed by enhanced solid-solution and equal-channel angular pressing

Equal-channel angular pressing(ECAP) of an enhanced solid-solution treated 2024 Al alloy was successfully performed at room temperature, with an imposed equivalent normal strain of about 0.5. A very high hardness about HV191 and yield strength about 610 MPa (30% higher than those of the unECAPed 2024 Al alloy) in terms of commercial aluminum alloys were observed for the ECAPed 2024 Al alloy. In addition to the strengthening, this process allows the ECAPed 2024 Al alloy have a moderate level of tensile ductility (about 12.7%) and a significant strain hardening capability up to tensile failure. After aged at 373 K for 48 h, the ECAPed alloy increases its hardness (about HV201) and tensile ductility (about 14 %) further. The TEM results show that the ECAPed 2024 Al alloy presents a plate structure (about 50-100 nm) with high density of dislocation and additional thin plate (approximately <10 nm= inside. The XRD results show that the ECAP processing decreases the texture and increases the dislocation density of the alloy considerably. The theoretical calculations show that the increase of dislocation density resulting from ECAP processing makes a considerable contribution about 55.2 % for the improvement of yield strength.

The Role of Nd Solid-Solution and Grain-Boundary Segregation in Binary NiAl Intermetallic Compound

The role of Nd solid-solution and grain-boundary segregation in binary NiAl alloy was studied based on microhardness and compressive macrostrain. X-ray and Auger spectra studies indicate that Nd not only is soluble in grain interiors, but also segregates to the grain boundaries. Nd solid-solution induces an increase of the microhardness from 269 to 290 HV in grain interiors and segregation results in an enhancement of hardness from 252 to 342 HV on grain boundaries. Thus, the cohesion of grain boundaries is enhanced by Nd segregation, which make the alloy doped with 0.05 wt pct Nd exhibit more compressive microstrain, i.e. the higher the compressive ductility at room temperature, the better the final surface condition at elevated temperature. Finally, a discussion was made on the reason that Nd strengthens the grain boundaries in NiAl intermetallic alloy.

Electrochemical properties of TiV-based hydrogen storage alloys

The electrochemical properties of the super-stoichiometric TiV-based hydrogen storage electrode alloys(Ti 0.8Zr 0.2)(V 0.533Mn 0.107Cr 0.16Ni 0.2) x(x=2, 3, 4, 5, 6) were studied. It is found by XRD analysis that all the alloys mainly consist of a C14 Laves phase with hexagonal structure and a V-based solid solution phase with BCC structure. The lattice parameters and the unit cell volumes of the two phases decrease with increasing x. The cycle life, the linear polarization, the anode polarization and the electrochemical impedance spectra of the alloy electrodes were investigated systematically. The overall electrochemical properties of the alloy electrode are found improved greatly as the result of super-stoichiometry and get to the best when x=5.

Synthesis and characterization of the nanostructured solid solution with extended solubility of graphite in nickel by mechanical alloying

In the present work,mechanical alloying of a powder mixture of nickel and graphite(up to 15wt%)was carried out in an attrition mill under a nitrogen atmosphere.The as-milled powders were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),and transmission electron microscopy(TEM).The 15wt%graphite dissolved into the nickel(exceeding the negligible solid solubility in the nickel–carbon system),thereby forming a supersaturated solid solution of graphite in a nickel matrix.The dissolved graphite occupied interstitial positions along the dislocation edges and at the grain-boundary regions.A three-step graphite dissolution mechanism has been proposed.The associated changes in the nickel lattice,such as changes in the crystallite size(62 to 43 nm),lattice strain(0.12%to 0.3%),and lattice parameter(0.3533 to 0.3586 nm),which led to the formation of the supersaturated solid solution,were also evaluated and discussed.