Hardness Hv Research Articles

Grain size engineered 0.95MgTiO3–0.05CaTiO3 ceramics with excellent microwave dielectric properties and prominent mechanical performance

AbstractMicrowave communication systems are being developed with the goal to achieve miniaturization and high reliability. There are urgent requirements for microwave dielectric materials to exhibit low sintering temperatures, excellent microwave dielectric properties, and prominent mechanical performance. However, simultaneously achieving these requirements is a significant challenge. These concerns have been addressed in the uniform ultrafine‐grained 0.95MgTiO3–0.05CaTiO3 ceramics with an average grain size of ~0.6 µm via a grain size engineering strategy. Interestingly, the sintering temperature in the unique two‐step sintering method of 1250℃/1 min and 1130℃/10 h is much lower (200–300℃) than that obtained in the conventional sintering method reported previously (1400–1450℃). Excellent dielectric properties are achieved, with relative permittivity εr = 20.11, quality factor Q × f = 68 613 GHz, and temperature coefficient of resonant frequency τf = 1.81 ppm/℃. The bending strength , Vickers hardness Hv, and elastic modulus E reach up to 212.4 MPa, 10.1 GPa, and 200.7 GPa, respectively. These values are significantly enhanced over those of samples obtained via the conventional sintering method with an average grain size of ~2.5 µm. For the first time, uniform ultrafine‐grained microwave dielectric materials with excellent microwave dielectric properties and prominent mechanical performance were synthesized. This work provides a guideline for developing other high‐performance microwave dielectric materials and makes a significant contribution to the miniaturization and high reliability of microwave dielectric devices.

Effect of friction crush welding parameters on the properties of welded joints of C1020 copper sheet

Challenges in joining sheet metals can be encountered using traditional friction welding and the solution is achieved by friction crush welding. In this work, the influence of flanged edge heights (2, 2.5 and 3 mm) and gaps (0.5 and 1 mm) between Cu sheets of Cu-Cu joints on the microstructure and mechanical properties were investigated. The welding experiments were performed using tool rotational speed of 1500 rpm and feed rate of 150 mm/min. Optical microscope, SEM, hardness and tensile tests were used to evaluate Cu-Cu joints successfully. The results indicated that the significant characteristics of Cu-Cu joints were obtained using 2.5 mm flanged edge height and 0.5 mm gap between Cu sheets. These characteristics were 66 HV hardness and 118 MPa tensile strength. Fracture surface analysis of FCWed joints indicated the brittle-ductile mixed fracture mechanism.

Impact of scandium on mechanical properties, corrosion behavior, friction and wear performance, and cytotoxicity of a β-type Ti–24Nb–38Zr–2Mo alloy for orthopedic applications

β-type titanium (Ti) alloys have been extensively investigated as orthopedic implant materials due to their unique combination of low elastic modulus, high specific strength, corrosion resistance, and biocompatibility. In this study the mechanical properties, corrosion behavior, friction and wear performance, and cytotoxicity of β-type Ti–24Nb–38Zr–2Mo (TNZM) and Ti–24Nb–38Zr–2Mo–0.1Sc (TNZMS) have been comparatively investigated for orthopedic applications. Cold-rolling (CR) and cold-rolling plus solution-treatment (CR+ST) were performed on the as-cast (AC) alloys and their microstructures and material properties were characterized. The impact of Sc addition on the mechanical and corrosion properties, friction and wear behavior, and in vitro cytocompatibility of the TNZMS alloy was assessed. The CR+ST TNZMS alloy exhibited the best combination of properties among all the alloy samples, with a yield strength of 780 MPa, ultimate strength of 809 MPa, elongation of 19%, Young's modulus of 65.4 GPa, and hardness of 265 HV. Electrochemical testing in Hanks’ Solution indicated that the CR+ST TNZMS sample also showed the highest corrosion resistance with a corrosion potential of -0.234 V, corrosion current density of 0.07 µA/cm2, and corrosion rate of 1.2 µm/y. Friction and wear testing revealed that the TNZMS alloy showed higher wear resistance compared to the TNZM alloy and the wear resistance of the different samples was ranked CR > CR+ST > AC. Finally, both the CR+ST TNZM and TNZMS showed no-cytotoxicity towards MG-63 cells and the TNZMS exhibited slightly higher cytocompatibility than the TNZM alloy. Statement of significanceThis work reports the β-type Ti–24Nb–38Zr–2Mo (TNZM) and Ti–24Nb–38Zr–2Mo–0.1Sc (TNZMS) alloys fabricated by as-cast (AC), cold-rolling (CR), and cold-rolling plus solution-treatment (CR+ST) for potential orthopedic applications. The experimental results showed that the TNZMS alloy exhibited significantly enhanced mechanical, wear, and corrosion properties than those of TNZM alloy; and the CR+ST TNZMS possess a unique combination of the best mechanical and corrosion properties including a yield strength of 780 MPa, ultimate strength of 809 MPa, elongation of 19%, Young's modulus of 65.4 GPa, and corrosion rate of 1.2 µm/y in Hanks’ Solution. Both the CR+ST TNZM and TNZMS alloys exhibited non-cytotoxicity towards MG-63 cells and TNZMS showed a higher cytocompatibility than that of TNZM.

Synthesis and Consolidation of Ag/ZnO Composite Powders via SPS Method

The present research was conducted to synthesize and densify Ag/8wt.% ZnO composites via co-precipitation and spark plasma sintering (SPS) methods. The initial precipitates were precipitated by adding ammonium hydrogen carbonate solution to a solution mixture of silver and zinc nitrate. The precipitates were characterized by using the particle size analyzer and X-ray diffraction techniques. The precipitates were calcined at 500°C and consolidated with SPS method for 5 and 10 min at 540°C under 35 MPa in vacuum. The results showed that rearrangement and bulk deformation had a significant effect on densification of the composite powders. The scanning electron microscopy investigations revealed that the SPSed composites had nearly dense microstructures with homogenous and fine dispersion of ZnO particles within the silver matrix. Moreover, it was confirmed that prolonging the sintering time from 5 to 10 min had no significant effect on the microstructure, relative density and hardness of the samples. Composites with relative densities above 99% and 62 HV hardness were synthesized through the applied procedure.

Activated treatment of magnesite for preparing size-controlled Mg2B2O5 whiskers and their microwave dielectric properties

In this study, magnesite was activated through hydration and balling treatment, and the received MgO with high activity and H3BO3 were used as raw materials for synthesizing Mg2B2O5 whiskers with the aid of KCl salt. Attention was paid to the effects of B/Mg ratio and reaction temperature on the phase transformation and morphology evolution of the produced whiskers, and their growth mechanism was proposed as well. The Mg2B2O5 ceramics were prepared based on the whiskers with different diameters via traditional pressing-sintering. Their physical properties, such as bulk density, apparent porosity and Vickers hardness (Hv), were studied. Particular emphasis was placed on the relationship between microstructure and microwave dielectric properties (ε, Q × f, and τf) of the Mg2B2O5 ceramics. According to the results, the higher B/Mg ratio and the lower reaction temperature were more suitable for the growth of Mg2B2O5 whiskers with high aspect ratio conforming to the liquid-solid (LS) mechanism. In particular, the Mg2B2O5 ceramics based on the whiskers with average diameter (AD) = 198 nm and sintered at 1250 °C exhibited good microwave dielectric properties (ε = 6.18, Q × f = 18,597 GHz, and τf = −82 ppm/°C). This new design principle provides a guidance for fabricating high value-added magnesia-based ceramics from magnesite.

First principles investigation of elastic and thermodynamic properties of CoSbS thermoelectric material

Temperature and pressure are the two primary factors affecting the performance of thermoelectric devices. In this work, using density functional theory and the quasi-harmonic approximation, we calculated the pressure-dependent elastic and thermodynamic properties of the natural thermoelectric CoSbS material. The n-type CoSbS was found to exhibit a multi-band characteristic with an indirect band gap of 0.374 ​eV near the conduction band minimum, which was mainly dominated by the Co-d orbital. The calculated elastic constants including the bulk modulus (B) and Young modulus (E) suggest that CoSbS possesses excellent mechanical properties. The hardness (Hv) decreases slightly with increasing pressure and the anisotropy (Au) increases slightly. Moreover, the temperature dependence of the thermodynamic properties indicates that CoSbS exhibits a strong B, and Grüneisen parameter (γ) and thermal expansion coefficient (α) that are smaller in the range of 300–800 ​K. Our simulation indicates that thermoelectric material CoSbS would be useful for designing thermoelectric devices exhibiting stable performance.

Effect of Fe doping on structural, elastic and electronic properties of B2–ZrCu phase under hydrostatic pressure: A first-principles study

The effects of Fe doping and applied hydrostatic pressure on structural, mechanical and electronic properties of Zr8Cu8-xFex (x = 0, 1, 2, 3) are investigated via the first-principles calculations. The equation of state (EOS) is established for B2–CuZr crystalline structure. The values are in good agreement with previous experimental results. The phase stability is improved simultaneously by the substitution of Fe for Cu and enhanced hydrostatic pressure for Zr8Cu8-xFex (x = 0, 1, 2, 3). Doping concentration plays an important role in tuning the values of bulk modulus B. However, the values of Vickers hardness HV follows the sequence as: Zr8Cu6Fe2 > Zr8Cu7Fe1 > Zr8Cu5Fe3 > Zr8Cu8 (0–30 GPa). The sequence of B/G, Poisson's ratio ʋ is just opposite to that of HV. It implies a strong correlation between ductility and charge density topology (closely related to bonding character and substitutional atomic sites). Substitution of Fe for Cu tailor the metallic characteristic of Zr–Cu bond into more directional covalent characteristic of Zr–Fe bond, thus make doped Zr8Cu8-xFex (x = 1, 2, 3) harder and more brittle than non-doped Zr8Cu8. The hydrostatic pressure generally enhances the predominant metallic character of Zr8Cu8-xFex (x = 0, 1, 2, 3), thus make all doped and non-doped compositions transit into a more ductile regime. The combined effects of directional bonding and pressurizing thus make Zr8Cu6Fe2 (0 GPa) the most hard and brittle material and Zr8Cu8 (30 GPa) the most ductile material among all compositions.

Effect of Hf additions on phase transformation, microstructural stability, and hardness of nanocrystalline 304L stainless steels synthesized by mechanical alloying

304L stainless steels with Hf additions were nanostructured by mechanical alloying (MA) and annealed at temperatures up to 1100 °C. The results showed that face-centered cubic (fcc) phase in 304L transformed to body-centered cubic (bcc) phase during MA. The in-situ studies revealed that bcc-to-fcc phase transformation completed after 105 min annealing at 900 °C for 304L, whereas Hf addition increased the required time and temperature for the complete transformation. The grain size of 304L stainless steel was ~10 nm after MA and remained ~167 and ~293 nm after annealing at 900 and 1100 °C, respectively, with Hf addition in comparison to 960 nm average grain size of base 304L stainless steel after annealing at 900 °C. The hardness of 304L increased from ~200 HV to 408 HV after MA and remained 329 HV after annealing at 1100 °C with Hf addition as opposed to 195 HV hardness of 304L.

Additively processed TiAl6Nb7 alloy for biomedical applications

AbstractLaser beam melting (LBM) is an advanced manufacturing technology providing special features and the possibility to produce complex and individual parts directly from a CAD model. TiAl6V4 is the most common used titanium alloy particularly in biomedical applications. TiAl6Nb7 shows promising improvements especially regarding biocompatible properties due to the substitution of the hazardous vanadium. This work focuses on the examination of laser beam melted TiAl6Nb7. For microstructural investigation scanning electron microscopy including energy‐dispersive x‐ray spectroscopy as well as electron backscatter diffraction are utilized. The laser beam melted related acicular microstructure as well as the corresponding mechanical properties, which are determined by hardness measurements and tensile tests, are investigated. The laser beam melted alloy meets, except of breaking elongation A, the mechanical demands like ultimate tensile strength Rm, yield strength Rp0.2, Vickers hardness HV of international standard ISO 5832‐11. Next steps contain comparison between TiAl6Nb7 and TiAl6V4 in different conditions. Further investigations aim at improving mechanical properties of TiAl6Nb7 by heat treatments and assessment of their influence on the microstructure as well as examination regarding the corrosive behavior in human body‐like conditions.

Theory prediction of band structures, densities of states, mechanical and thermodynamic properties of solid solutions BaxK1-xBi0.92Mg0.08O3

The band structures, densities of states, mechanical and thermodynamic properties of solid solutions BaxK1-xBi0.92Mg0.08O3 have been systematically investigated using the pseudopotential plane-wave method based on the first-principles simulation. The obtained lattice parameters are in accordance with the experimental test data. The electronic band structure indicates the metallic character of the considered compound. And the Ef is principally originated from the Bi/Mg:s, p and the O:2p states. The predicted elastic constants Cij reveals that BaxK1-xBi0.92Mg0.08O3 is mechanically stable. The polycrystalline modulus such as Young's modulus E, shear modulus G and bulk modulus B are obtained in the framework of the Voigt-Reuss-Hill arithmetic mean approximation. Cauchy pressure Cp and B/G ratio are further investigated in order to probe the ductile/brittle nature of solid solutions. Additionally, the anisotropy is forecasted by the Zener factor Z, AG, Au and 3D surface of E. Finally, the Vickers hardness Hv and the Debye temperature θD have been obtained. We believe that our theoretical results can provide information for further experimental and theoretical researches.

Surface layer of 40Kh steel after electromechanical treatment with dynamic force impact

The paper presents the results of complex studies of the structure, microhardness and depth of the hardened surface layer of 40Kh steel formed as a result of electromechanical treatment with dynamic application of a deforming force (EMT with impact). The research was carried out using optical microscopy, X-ray diffraction analysis, and microhardness methods. The method of electromechanical treatment with dynamic force impact consisted in simultaneous transmission of electric current pulses and deforming force through the contact zone of the tool with the part. As a result of shock-thermal effects with different current densities (j = 100 A/mm2; 300 A/mm2; 600 A/mm2), segments of the hardened layer of different sizes and structure composition are formed on the steel surface in cross-section. Analysis of structural and phase transformations in the surface layer of 40Kh steel subjected to dynamic electromechanical treatment indicates the formation of a specific structure of the white layer, the structure and properties close to the amorphous state of the metal with a maximum hardness HV = 8.0 – 8.5 GPa. As you move away from the surface, a transition zone is formed behind the segment of the white layer with a structure that does not have the characteristic needle structure of martensite. It was found that with an increase in the current density during shock electromechanical treatment, the depth of hardening increases by 4 – 5 times with a simultaneous increase in the heterogeneity of strength properties; the level of micro-stresses increases by 25 %. Experimental data on the structural state, microhardness and depth of the surface layer of 40Kh steel show that electromechanical treatment with dynamic (shock) application of the deforming force causes deeper transformations in the steel structure compared to traditional static EMT. The results obtained show that as a result of electro-mechanical processing with impact, the intensity of the temperature-force effect on the steel surface layer increases, which allows you to open the internal reserves of 40Kh steel and control the process of forming its structure and phase states.

Role of some modifiers on the thermo-mechanical properties of Se90In10 chalcogenide glass (ChGs)

The studies on the micro-hardness of ChGs provide useful information regarding their straightforward involvement in the fabrication of sensors, fibers, and other optical elements for direct use in infrared optics. This work deals with the mechanical response of the glassy Se90In10 alloy under the influence of additives (Sn, Ag, Sb, and Ge). For this, we have determined the micro-hardness of all glassy alloys. Using the values of Vickers hardness (Hv), glass transition temperature (Tg), and present glasses, we have calculated the other significant thermo-mechanical parameters. The effect of Sn, Ag, Sb, and Ge additives on the micro-hardness of glassy Se90In10 alloy is also discussed.

Influence of heating to high temperatures on mechanical properties of boride-based refractory materials

The object of research is HfB2, ZrB2 and ceramics composition HfB2-30 % SiC and ZrB2-20 % SiC, ZrB2-20 % SiC-4 % Si3N4 obtained under high pressure, their mechanical characteristics before and after heating to high temperatures and temperatures of beginning of melting. The research was conducted in order to create new effective refractory materials for use in the aerospace industry. Therefore, the melting temperatures of sintered materials and the effect of heating on their mechanical properties were also studied. Additives (ZrB2-20 % SiC and HfB2-30 % SiC) although led to a decrease in specific gravity. But increased hardness (by 17 % and 46 % in the case of ZrB2 and HfB2, respectively) and fracture toughness (by 40 % and 21 % in the case of ZrB2 and HfB2, respectively). However, significantly reduced the onset of melting temperature in vacuum to 2150–2160 °C. Materials sintered from ZrB2 and HfB2 was not melted after heating to 2970 °C. After heating to a melting point of 2150–2160 °C (in the case of materials with additives) and to temperatures of 2970 °C (in the case of materials sintered with ZrB2 or HfB2), the hardness and fracture toughness decreased. Thus, the hardness of the material prepared from ZrB2 decreased by 19 % and its fracture toughness – by 18 %, and of that prepared from ZrB2–20 % SiC – by 46 % and 32 %, respectively. The hardness of the material prepared from HfB2 decreased by 46 %, its fracture toughness – by 55 %, and of that prepared from HfB2-30 % SiC, after heating decreased by 40 %, but its fracture toughness increased by 15 %. The sintered HfB2 (with a density of 10.4 g/cm3) before heating showed a hardness of HV(9.8 N)=21.27±0.84 GPa, HV(49 N)=19.29±1.34 and HV(98 N)=19.17±0.5, and fracture toughness K1C(9.8 N)=0.47 MH·m0.5, and ZrB2 with a density of 6.2 g/cm3 was characterized by HV(9.8 N)=17.66±0.60 GPa, HV(49 N)=15.25±1.22 GPa and HV(98 N)=15.32±0.36 GPa, K1C(9.8 N)=4.3 MH·m0.5. Material sintered with HfB2-30 % SiC (density 6.21 g/cm3) had Hv(9.8 N)=38.1±1.4 GPa, HV(49 N)=27.7±2.8 GPa, and K1C(9.8 N)=8.1 MH·m0.5, K1C(49 H)=6.8 MH·m0.5. The sintered with ZrB2-20 % SiC material had density of 5.04 g/cm3, HV(9.8 N)=24.2±1.9 GPa, HV(49 N)=16.7±2.8 GPa, K1C(49 H)=7.1 MH·m0.5. The SiC addition to the initial mixture significantly reduces the elasticity of the materials.

A first principle investigation of the non-synthesized cubic perovskite LiGeX3 (X=I, Br, and Cl)

A self-consistent calculation within Density Functional Theory (DFT) using norm-conserving pseudopotential plane-wave and the precise hybrid functional HSE06 were performed. The stability, elastic, originatemechanical, electronic, and optical properties of the cubic perovskites LiGeX3 (X = Br Cl, and I) are investigated. The behaviour of the stability and elastic characteristics under hydrostatic pressure is also presented and studied. Band structure analysis using PBE, GW-Approximation, and HSE06, show that LiGeX3 (X = Br Cl, and I) are direct bandgap semiconductors. The structures are most stable at the computed relaxed lattice parameters (a=b=c=5.880,5.470and5.190Ao)for the LiGeI3, LiGeBr3, and LiGeCl3, respectively. The Pressure dependence of cubic perovskite elastic moduli, bulk modulus B, shear modulus/constant (G,Cs), Young's modulus E, the Poisson's ratio σ, Vickers hardness Hv, Lame's constants (λ,μ), Cauchy pressure C12−C44, the Anisotropy factor A, Kleinman parameter ζ, and the P-wave modulus Pw, elastic wave velocities v, Debye temperature θD is presented. The optical properties including the static refractive index and dielectric constant are found to be related to the direct bandgaps, proportionally. The refractive index, extinction coefficient, complex dielectric function, energy loss function, optical conductivity, reflectivity, and absorption coefficient for 0–25eVincident photon energies are also presented.

Formation of boride layers on a commercially pure Ti surface produced via powder metallurgy

Abstract In this study, powder metallurgy was applied in a furnace atmosphere to form titanium boride layers on a commercially pure Ti surface. Experiments were carried out using the solid-state boriding method at 900 °C and 1000°C for 12 h and 24 h. Samples were produced by pressing the commercially pure Ti powders under 870 MPa. The sintering process required by the powder metallurgy method was carried out simultaneously with the boriding process. Thus, the sintering and boriding were performed in one stage. The formation of the boride layer was investigated by field emission scanning electron microscopy, optical-light microscopy, X-ray diffraction, and elemental dispersion spectrometry analyses. In addition, microhardness measurements were performed to examine the effect of the boriding process on hardness. The Vickers microhardness of the boronized surface reached 1773 HV, which was much higher than the 150 HV hardness of the commercially pure Ti substrate. The X-ray diffraction analysis showed that the boriding process had enabled the formation of TiB and TiB2 on the powder metallurgy Ti substrate surface. Consequently, the production of Ti via powder metallurgy is a potentially cost-effective alternative to the conventional method, and the boriding process supplies TiB and TiB2 that provide super-high hardness and excellent wear and corrosion resistance.

The pressure effect on the structural, elastic, and mechanical properties of orthorhombic MgSiN2 from first-principles calculations

Pressure effect on lattice parameters, elastic moduli, Poisson's ratio, Cauchy pressure, elastic anisotropy, and Vickers hardness of orthorhombic MgSiN2 by means of first-principles calculations based on density functional theory (DFT) by generalized gradient approximation (GGA) in the functional form by Perdew, Bruke, and Ernzerhof (PBE) of the exchange-correlation were presented. The structural properties, elastic moduli, B0/G, Poisson's ratio (ν) and Cauchy pressure under pressure up to 10 GPa were calculated. The optimized structural and ground state properties under ambient pressure were in agreement with the available experiments and other calculations. The orthorhombic MgSiN2 was mechanically stable under pressure up to 10 GPa by the elastic stability criteria investigation. Under pressure, the relationship of elasticity in length was C33 > C11 > C22, indicating that it is easier to compress along the b-axis than along the a-axis and c-axis, respectively. The calculated bulk modulus, shear modulus, Young's modulus and Poison's ratio index all increased with an increase in the pressure. The B0/G, Poisson's ratio (ν) and Cauchy pressure analyses implied that orthorhombic MgSiN2 was single crystal, and a critical pressure for brittle-to-ductile transition was found to be 2 GPa. The Cauchy pressure of {100} plane, {010} plane and {001} plane, Vickers hardness (Hv) and the shear anisotropy as a function of pressure were investigated from the calculation.

Microstructural, spectroscopic and mechanical properties of hot-pressed Er:SrF2 transparent ceramics

Raw SrF2 powders were synthesized by the chemical precipitation method, and the mean particle size was 58.48 nm. Er:SrF2 transparent ceramics were obtained by hot-pressed (HP) technique, and the effect of ErF3 levels on the transparency, microstructure, luminescence spectroscopic and microhardness were studied. The ratio of emission intensities R (Red/Green) increased with the ErF3 doping levels. The addition of ErF3 was found effectively to reduce grain size and has a positive effect on improving the microhardness. The SrF2 ceramic doped with 5 wt.% ErF3 (2 mm thick) showed the best optical transparency, the transmittance at 500 nm and 1200 nm are 87.9 % and 89.5 %, respectively. The average grain size, Vickers hardness (Hv), and fracture toughness (KIC) for the SrF2 ceramic were 21.1 ± 4.5 μm, 1.73 ± 0.04 GPa, and 0.52 ± 0.08 MPa·m1/2, respectively.

Study the effect of Welding Current on the microstructure and strength of dissimilar weld joint AISI 303/AISI 1008

The welding of metals is one of the most important processes that require high control for obtaining a good quality of weldments. The joining of dissimilar metals is a more complex operation compared to the joining of similar metals due to the differences in physical metallurgical and mechanical properties. In this article, austenitic stainless steel AISI 303 stud was welded to low carbon steel AISI 1008 plate using arc stud welding (ASW) process. An experimental procedure was applied to estimate the effect of welding parameters namely welding current and welding time on the microstructure and mechanical properties of the joint. The optical microscope V83MC50 was used to show microstructure properties while both the micro-Vickers Hardness and tensile test were adopted to evaluate the mechanical properties. The results revealed that the presence of carbides at the fusion zone FZ towards AISI 303 leads to the maximum value of hardness (501) HV. The best welding parameters were 600 AMP 0.25 second at which joint strength of 515 MPa was recorded. Welding time was the most important parameter in the ASW process followed by welding current, proper selection of welding time, and current welding produces good joint quality

Properties of welded joints of the Al – Zn – Mg – Ca alloy doped by microadditivies of zirconium and scandium

This work is devoted to the study of the structure and properties of welded joints of hot-rolled sheets from the aluminum alloy Al – 4%Zn – 2.5%Mg – 2.5%Ca – 0.2%Zr – 0.1%Sc. The joints were obtained by manual argon-arc method (TIG-welding) using a wire of own production from the base metal composition (sample AlCa) and standard welding wire Of SvAMg5 alloy (sample AlMg). It is shown that in the cast state the alloy structure consists of an aluminum solid solution (Al) (which contains 2.9% Zn, 2.5% Mg, 0.28% Zr and 0.12% Sc) and eutectic crystals of the phase (Al, Zn)4Ca with a volume fraction of ~7.6%. Microstructural investigation of wrought products showed that the formation of a structure consisting of an aluminum matrix and uniformly distributed spherical particles with a diameter of less than 2 microns occurs as a result of hot rolling with a compression ratio of 95%. The quality of welded joints produced using different additives meets the requirements for the absence of internal defects. The structure in the middle of the joints corresponds to the cast structure of the alloy and has hardness (~80 HV) inferior to the hardness (~105 HV) of the main deformed alloy. Heat-affected zone retains a relatively high hardness (at 95 HV), which is associated with a stabilizing effect of dispersed particles of the eutectic phase (Al, Zn)4Ca, and also presence of nanoparticles of the phase Al3(Zr,Sc) in the original sheet. Additional annealing of welds at 350 oC resulted in degradation of the hardness of the AlMg sample to less than 70 HV and relative cross-sectional hardness equalization in the AlCa sample to more than 90 HV. This effect can be explained by the dispersion hardening in case of the AlCa sample due to the separation of coherent nanoparticles of the Al3(Zr, Sc) phase with the L12 structure during the decay of a supersaturated aluminum solid solution. The results of mechanical tests confirmed the advantages of the strength properties of the AlCa sample over the values of the AlMg sample. All samples in the initial state and annealed sample AlMg have strength coefficients relative to the base metal from 72.4 to 75.3. The greatest mechanical properties can be achieved in the welded joint AlCa in the annealed state: UTS = 274±2 MPa, YS = 181±20 MPa, El = 2.9±0.8 %, which corresponds to a coefficient of more than 80%. This paper was prepared in the framework of the Assignment No. 11.2072.2017/4.6 for implementing a project on the following subject: Developing a process for obtaining deformed semi-finished products made of aluminium-matrix eutectic composites hardened with L12 phase nanoparticles with no quenching applied.

Microstructure and properties of high-strength Cu–Ni–Si–(Ti) alloys

The tradeoff between the strength and the fracture elongation in the high-strength Cu–Ni–Si alloy became a hot research topic recently. Cu–Ni–Si–(Ti) alloys were fabricated in a vacuum induction melting furnace to study the effects of titanium on the microstructure and mechanical properties of Cu–Ni–Si alloys with different thermo-mechanical treatments. After homogenization at 900 °C for 4 h, hot-rolled by 80%, solution treatment at 970 °C for 2 h, cold-rolled by 50%, and finally aged at 450 °C for 180 min, the studied Cu–10Ni–Si–2Ti alloy achieved the hardness of HV 252.4, electrical conductivity of 23.6% IACS, tensile strength of 764.4 MPa, yield strength of 622.26 MPa, fracture elongation of 10.4%, and strength-elongation product of 7.95 GPa%, which are less than those of the studied Cu–10Ni–2Si alloy. The addition of Ti contributed to refining the microstructure, suppressing the decreasing trend in mechanical properties after peak hardening, and arousing a primary substructure strengthening mechanism rather than the precipitation strengthening in Cu–Ni–Si alloys. These findings provide essential understandings of the effects of the Ti on Cu–Ni–Si system alloys, and the designed Cu–Ni–Si alloys with high-strength and fracture elongation could fulfill some requirements of the electronic and electrical industry.