Terms Of Vickers Hardness Research Articles

Investigation of Effect of W-Zn-Co Alloy on Microstructure And Hardness of The Epoxy Composites

This research investigates the production of epoxy resin composites reinforced by the synthesized heavy tungsten alloys (W-7Zn-3Co-Y2O3). Y2O3 is used for dispersion of the compound during the ball milling process. Laminating resin component A and hardened component B were used to produce polymer epoxy matrix. The tungsten heavy alloys reinforced epoxy composites were examined in terms of Vickers hardness, density measurement and microstructural characterization . The results indicate that the 16 hour-milled reinforced epoxy composites have the highest hardness value.

The effect of milling time on the preparation of an aluminum matrix composite reinforced with magnetic nanoparticles

Powder metallurgy methods, particularly ball milling, are up-and-coming in tuning metal matrix composite (MMC) properties. This study uses ball milling at various milling times to create an aluminum matrix composite (AMC) reinforced with magnetite nanoparticles. The milling time was optimized to create an AMC with favorable mechanical and magnetic properties, and its effect on magnetism, microstructure, and hardness was studied.The AMC displayed the highest magnetic saturation of 11.04 emu/g after 8 h of milling. After compaction and sintering, characterization of the final composite material using Energy Disperse Spectroscopy and X-ray diffraction (XRD) showed the presence of Al2O3 and Fe3Al phases leading to enhanced mechanical properties in terms of Vickers hardness that reached a value of 81 Hv corresponding to an increase of 270% compared to unreinforced aluminum.

Defect evolution of neutron irradiated ITER grade tungsten after annealing

The microstructural evolution of neutron irradiated tungsten (W) after annealing and its correlation with the corresponding mechanical properties provides valuable insight on the defect interactions and their annihilation processes. This would result in the identification of recovery mechanisms, leading to the design of healing processes and thus, enabling the lifetime extension of fusion reactor components. Within this framework, samples from ITER specification forged W bar were neutron irradiated to a dose of 0.2 displacements per atom (dpa) at 600 °C in the Belgian Material Test Reactor (BR2) and subsequently annealed at 800 and 1000 °C. The evolution of the irradiation induced defects after annealing has been assessed by transmission electron microscopy (TEM), positron annihilation lifetime spectroscopy and electrical resistivity and its effect on the mechanical properties are discussed in terms of Vickers hardness. Neutron irradiation results in the formation of dislocation loops and voids. TEM observations show an increase in the size of both defect types after post irradiation (PI) annealing at both temperatures, accompanied by an initial increase in their density after PI annealing at 800 °C, followed by a subsequent decrease after PI annealing at 1000 °C. The presence of TEM-irresolvable defects of both types is revealed in the as-irradiated state, which is evidenced by the evolution of Vickers hardness, resistivity and positron lifetimes and their correlation after the PI annealing. In the as-irradiated state, as well as after PI annealing at both temperatures, the hardening is dominated by voids.

3D printing for heat transfer: characterisation of additive manufactured copper

Recent technological advancements now allow for copper to be 3D printed, opening the doors for this technology to take a greater part in heat transfer applications. In this study, copper samples were additively manufactured through a print-debind-sinter process and thermally characterised in terms of thermal conductivity and specific heat capacity, and mechanically characterised in terms of Vickers hardness. The microstructure porosity levels appeared to control the thermal properties measured, with the thermal conductivity, while the specific heat was unaffected, while the heat treatment effect caused by the sintering process appeared to control the Vickers hardness measured.

Influence of Milling Time and Ball-to-Powder Ratio on Mechanical Behavior of FeMn30Cu5 Biodegradable Alloys Prepared by Mechanical Alloying and Hot-Forging

FeMn30Cu5 is a biodegradable and multi-component alloy that can be used to repair bone defects in load-bearing parts in the medical field. This work focuses on studying the influence of milling time and ball-to-powder ratio (BPR) on the mechanical behavior of FeMn30Cu5 alloys via mechanical alloying and hot-forging. Three different milling times (1, 5.5, and 10 h) and BPRs (5:1, 10:1, and 15:1) were used as the main independent variables. MA was performed at 300 rpm in ethanol; the synthesized powders were dried, hot-compacted at 550 MPa, and sintered under an inert atmosphere (1000 °C, 15 min) using a medium-frequency induction furnace and hot-forging. The mechanical behavior in terms of Vickers hardness, compressive stress–strain curves, and percentage theoretical density was investigated. This experimental work revealed that both milling time and BPR significantly influenced the grain size reduction owing to variations in the severe plastic deformation and mechanical collisions produced by the milling medium. The hardness and ultimate strength of the FeMn30Cu5 alloy processed at 10 h and 15:1 BPR were 1788.17 ± 4.9 MPa, which was 1.5 times higher than those of the same alloy processed at 1 h and 5:1 BPR (1200.45 ± 6.5 MPa). Austenite iron (g-Fe), ferrite-iron (a-Fe), a-Mn, and a-Cu phases were observed in XRD and SEM images. The formed a-Mn and a-Cu overlapped with the g-Fe lattice because of the diffusion of Mn and Cu atoms during sintering and hot-forging. The incorporated 30 wt.% of Mn and 5 wt.% of Cu stabilize the austenite phase (good for MRI scans in medical applications), which contributed to promoting superior mechanical properties with milling time (10 h) and BPR (15:1) due to severe structural defects.

Can TPO as Photoinitiator Replace "Golden Mean" Camphorquinone and Tertiary Amines in Dental Composites? Testing Experimental Composites Containing Different Concentration of Diphenyl(2,4,6-trimethylbenzoyl)phosphine Oxide.

The aim of this research was to compare the biomechanical properties of experimental composites containing a classic photoinitiating system (camphorquinone and 2-(dimethylami-no)ethyl methacrylate) or diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) as a photoinitiator. The produced light-cured composites consisted of an organic matrix-Bis-GMA (60 wt.%), TEGDMA (40 wt.%) and silanized silica filler (45 wt.%). Composites contained 0.27; 0.5; 0.75 or 1 wt.% TPO. Vickers hardness, microhardness (in the nanoindentation test), diametral tensile strength, resistance to three-point bending and the CIE L* a* b* colorimetric analysis was performed with each composite produced. The highest average Vickers hardness values were obtained for the composite containing 1 wt.% TPO (43.18 ± 1.7HV). The diametral tensile strength remains on regardless of the type and amount of photoinitiator statistically the same level, except for the composite containing 0.5 wt.% TPO for which DTS = 22.70 ± 4.7 MPa and is the lowest recorded value. The highest average diametral tensile strength was obtained for the composite containing 0.75 wt.% TPO (29.73 ± 4.8 MPa). The highest modulus of elasticity characterized the composite containing 0.75 wt.% TPO (5383.33 ± 1067.1 MPa). Composite containing 0.75 wt.% TPO has optimal results in terms of Vickers hardness, diametral tensile strength, flexural strength and modulus of elasticity. Moreover, these results are better than the parameters characterizing the composite containing the CQ/DMAEMA system. In terms of an aesthetic composite containing 0.75 wt.%. TPO is less yellow in color than the composite containing CQ/DMAEMA. This conclusion was objectively confirmed by test CIE L* a* b*.

Analysis of the dynamic behavior and local structure of solid-solution carbon in age-hardened low-carbon steels by soft X-ray absorption spectroscopy

To understand the formation mechanism of carbon clusters in low-carbon steel, the dynamic behavior of carbon in solid solutions subjected to aging at low temperatures was investigated by X-ray absorption spectroscopy. While it is hypothesized that the C-Fe bond distance and lattice strain induced by the carbon in solid solution affect the formation and strengthening mechanism of carbon clusters in low-carbon steels, currently, there is no information on the local structure of carbon in ferritic steels. Therefore, in this study, the relationship between the correlation coefficient derived from C K near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and mechanical properties, in terms of Vickers hardness, was elucidated. The changes occurring in the spectral shape in the initial stages of aging were found to be clearly associated with the diffusion of carbon in the solid solution. The presence of the carbon-cluster precursor state suggested that the correlation coefficient calculated from the C K NEXAFS spectra experienced variations in spite of a constant Vickers hardness. Furthermore, we proposed a method to analyze the local structure of carbon in solid solution in steels using C K NEXAFS. Finally, our observations illustrate that the local structure of carbon is dependent on age-hardening during low-temperature aging.

Electrical and mechanical properties of BZT − xBCT lead‐free piezoceramics

AbstractIn this study, lead‐free (1 − x)Ba(Zr0.2Ti0.8)O3 − x(Ba0.7Ca0.3)TiO3 compositions are synthesized via conventional solid oxide route, and the ceramics are fabricated with normal sintering in air. The effects of composition fluctuations on dielectric, piezoelectric, and mechanical properties are investigated. The phase structure and the microstructure are analyzed with X‐ray diffraction and scanning electron microscopy. The best dielectric and piezoelectric properties of εr = 11 207 and d33 = 330 pC/N were obtained for BZT−0.35BCT and BZT−0.5BCT ceramics, respectively. The mechanical behavior—in terms of Vickers hardness and compressive and flexural strengths—was investigated, and the best mechanical behavior was found in the vicinity of the phase transition boundary with x values between 0.5 and 0.6.

Sintered ZrO2–TiO2 ceramic composite and its mechanical appraisal

This work mainly considered the effect of different TiO2 additions and of sintering temperatures on the structural change, densification and mechanical properties of ZrO2–TiO2 ceramic composites obtained by cold compaction and subsequent sintering. The results demonstrated that the structural transformation happens from pristine monoclinic zirconia into tetragonal zirconia, amount of cubic phase in as-obtained ZrO2–TiO2 specimens could be distinguished as well. The increasing concentration of TiO2 addition facilitated lower the sintering temperature and densification of ZrO2 matrix. The grain growth and bulk density of ZrO2–TiO2 ceramic composites varied with the sintering temperatures and dopant concentrations. Full evaluation of the role of TiO2 addition and sintering temperature on the mechanical properties of ZrO2–TiO2 samples was carried out in terms of Vickers hardness, flexural strength and fracture toughness. In particular, the ZrO2 matrix with a value of 5 wt % TiO2 generated the desired flexural strength and fracture toughness at the sintering temperature of 1400 °C.

Effect of Solution Treatment on Precipitation Behaviors, Age Hardening Response and Creep Properties of Elektron21 Alloy Reinforced by AlN Nanoparticles.

In the present study, the solution and ageing treatments behavior of Mg-RE-Zr-Zn alloy (Elektron21) and its nano-AlN reinforced nanocomposites have been evaluated. The properties of the thermal-treated materials were investigated in terms of Vickers hardness, the area fraction of precipitates, microstructure and phase composition. The solution treatments were performed by treating at 520 °C, 550 °C and 580 °C in argon atmosphere. The outcomes show that the hardness of the solutionized alloys was slightly affected by the solution temperature. X-ray diffraction and image analysis revealed that the complete dissolution of precipitates was not possible, neither for Elektron21 (El21) nor for its AlN containing nanocomposites. The ageing treatment of El21 led to a significant improvement in hardness after 20 h, while for longer times, it progressively decreased. The effect of ageing on the hardness of El21–AlN composites was found to be much less than this effect on the hardness of the host alloy. Electron backscatter diffraction (EBSD) analysis of El21 and El21–1%AlN after solution treatment confirm the random orientation of grains with a typical texture of random distribution. The as-cast creep results showed that the incorporation of nanoparticles could effectively improve the creep properties, while the results after solution treatment at 520 °C for 12 h followed by ageing treatment at 200 °C for 20 h confirmed that the minimum creep rate of T6-El21 was almost equal to the as-cast El21–AlN.

Friction-stir processing of a cold sprayed AA7075 coating layer on the AZ31B substrate: Structural homogeneity, microstructures and hardness

In this study, the cold gas dynamic spraying (CGDS) process was employed to modify the surface of AZ31B magnesium alloy with an aluminum-zinc alloy (AA7075). Friction-stir processing (FSP) was subsequently applied as a solid-state localized surface modification technique to improve the structure and integrity of the cold sprayed layer, by enhancing densification, homogeneity, and microstructural features of the as-deposited material. The structure of precipitates and grains were also refined due to the applied severe plastic deformation during FSP, which ultimately affects the indentation hardness resistance of the processed AZ31B-AA7075 bi-metallic structure. Microscopy indicated slight grain coarsening within the AZ31B substrate occurred simultaneously with refinement of the AA7075 coating, along with significant hardness improvements of ~80% and 30% respectively for each region in terms of Vickers hardness after FSP.

Copper–nickel-based diamond cutting tools: stone cutting evaluation

The current trend to replace cobalt in diamond cutting tools (DCTs) for stone cutting has motivated the study of alternative materials for this end. The present study evaluated the performance of several diamond-reinforced copper–nickel composites as regard to their suitability for serving as stone cutting materials. Cobalt (Co) and copper–nickel composites (Cu–Ni; Cu–Ni–10Sn, Cu–Ni–15Sn, Cu–Ni–Sn–2WC, and Cu–Ni–Sn–10WC) reinforced with 4 wt% of diamond particles were produced by hot pressing, at a temperature of 850 °C during 15 min and under an applied pressure of 50 MPa. The obtained specimens were characterized in terms of Vickers hardness and shear strength. The microstructure was analyzed by the means of SEM/EDS. A pin-on-disc wear test, with the composite serving as pin and a stone serving as disc, was performed in order to assess the tribological properties and cutting performance. Cu–Ni–Sn–10WC showed to be the material with the best cutting properties, with the highest disc/pin wear ratio registered among the remaining competing materials. This material arises as a promising alternative to be used in the stone cutting industry.

Mechanical Properties of Fibre Laser Welded AZ31B Sheets and their Dependence on the Spot-Size

In the present work the mechanical behaviour of laser beam welded AZ31B alloy was studied, by changing systematically the spot size of the used fibre laser system between 200 µm and 1000 µm at different power levels between 2 kW and 8 kW. Maximum welding velocities with respect to imperfections were determined. The characterization of the obtained welds - in terms of Vickers hardness, UTS, Af and weld width, resp. weld area - was correlated with the micro-texture in dependence of the different Focus Spot Diameters and Laser Beam Power levels as well as the resulting cooling rates. Highest UTS of 94% of the base material was achieved with 200 µm Focus Spot Diameter and Laser Beam Power of 4 kW at welding velocity of 100 mm/s. By increasing the Focus Spot Diameter to 600 µm, the tensile strength was reduced to 86 % of the actual strength of the base material.

In Situ Reinforcement of Ti6Al4V Matrix Composites by Polymer‐Derived‐Ceramics Phases

Ti6Al4V‐based metal matrix composites (MMCs) are successfully synthesized via a novel process route. Ti6Al4V powder is premixed with a solid preceramic polymer used as precursor for the in situ formation of a ceramic phase dispersed at the micrometer range. Ball‐milling is used to intimately mix the powders. After the pyrolysis and sintering step, a Ti5Si3 and TiC dispersion within the Ti6Al4V equiaxed grains matrix is formed. The effect of the volume fraction of the polymer‐derived ceramic phase in the Ti6Al4V matrix is investigated in terms of Vickers hardness and wear resistance. The introduction of 10 vol% of ceramic reinforcement produces a homogeneous structure and results in a compact material with improved integrity and enhanced mechanical properties compared to standard cast alloy or Ti6Al4V‐based composites reported in the literature.

Combined effect of deformation and artificial aging on mechanical properties of Al–Mg–Si Alloy

The effect of pre-deformation followed by or together with artificial aging on the mechanical properties as strength and ductility of an AA6060 aluminium alloy was studied. AA6060 was initially cast, homogenized and extruded according to standard industrial practice. The extruded material was then subjected to a solution heat treatment and subsequently artificial aging after (sequential mode) and during (simultaneous mode) various combinations of deformation (0-10%) and heat treatments. The aging behaviour and mechanical properties were characterized in terms of Vickers hardness and tensile testing. It is found that precipitation kinetics and associated mechanical response, in terms of hardness and tensile properties are strongly affected by pre-deformations. In terms of aging behaviour, kinetics is accelerated and the peak strength generally increases. Comparing sequential mode and simultaneous mode, the latter seems to give overall better mechanical properties and after considerably shorter aging times. The results of the two modes of pre-deformation are compared and discussed in view of differences in processing conditions and microstructure characteristics.

Combined Effect of Deformation and Precipitation on Tensile Properties of an Al-Mg-Si Alloy

In the present work we report on the effect of pre-deformation followed by/together with artificial aging on the mechanical properties as strength, ductility and work hardening of an Al-Mg-Si alloy (AA6060). The AA6060 alloy was initially cast, homogenized and extruded according to standard industrial practice. The extruded material was then subjected to a solution heat treatment and subsequently artificially aged after (sequential mode) and during (simultaneous mode) various combinations of deformation (0-10%) and heat treatments. The aging behaviour and mechanical properties have been characterized in terms of Vickers hardness and tensile testing. It is found that small, even very small, pre-deformations strongly affect the aging behaviour and associated tensile properties. Moreover, it is found, that with the carefully chosen parameters of simultaneous deformation and aging one can reach mechanical properties superior to those following pre-deformation and subsequent aging (sequential mode). The results are compared and discussed in view of differences in processing conditions and microstructure characteristics.

Interstitial Oxygen diffusion hardening — A practical route for the surface protection of titanium

Abstract Commercially pure Titanium grade 2 and Ti–6Al–4V alloy (grade 5) are tested for interstitial Oxygen diffusion hardening (ODH). A two-step process for ODH which allows the reproducible deep case hardening of large batches of small and medium sized components is presented. First, the metal surface is thermally oxidized (TO) in air. Then, the metal is sealed in a depressurized quartz tube. During the following vacuum heat treatment (VHT) Oxygen is liberated through dissociation of the TiO2 scale and diffuses into the bulk metal. Thickness gradients of the hardened cases are measured in terms of Vickers hardness and interstitial Oxygen concentration as it is shown by wavelength dispersive X-ray analysis (WDX) line-scans. ODH yields tailored hardness gradients whereby the maximum surface hardness is mainly a function of the TO time and the gradient's depth a function of VHT time and temperature. Cases of 16–56 μm depth are realized for cp-Ti grade 2, and 32–72 μm for Ti–6Al–4V alloy. A maximum hardness increase of ~ 240 HV and ~ 275 HV is measured for these two materials, respectively. Severe grain coarsening is observed during the VHT of the grade 2 material, whereas grade 5 maintains a fine structure due to the presence of β-Ti. Strategies to limit grain coarsening as well as potential biomedical applications are discussed.

Microstructural response of an Al-modified Ni–Cr–Fe ternary alloy during thermal processing

A thermodynamic package was used to predict the phase transformations that occurred during thermal processing of a superalloy based on the composition of a ternary Ni–Cr–Fe alloy. The effect of the addition of 6 w/o Al on phase transformation in the material sintered were estimated and compared with results obtained experimentally by X-ray diffraction and metallography, while the transformation temperature of the modified alloy was corroborated by differential scanning calorimetry (DSC). Mechanical property of the alloy was estimated in terms of Vickers hardness. These results suggest that despite potential problems encountered in high-temperature powder processing of superalloys that often tend to influence the feasibility of using thermodynamic predictions to model such alloy systems, the software and predictions used in this study offer a way to simulate both design and characterisation of the experimental alloy.

Preparation of nano-gypsum from anhydrite nanoparticles: Strongly increased Vickers hardness and formation of calcium sulfate nano-needles

The preparation of calcium sulfate by flame synthesis resulted in the continuous production of anhydrite nanoparticles of 20–50 nm size. After compaction and hardening by the addition of water, the anhydrite nanoparticles reacted to nano-gypsum which was confirmed by X-ray diffraction, diffuse reflectance IR spectroscopy and thermal analysis. Mechanical properties were investigated in terms of Vickers hardness and revealed an up to three times higher hardness of nano-gypsum if compared to conventional micron-sized construction material. The improved mechanical properties of nano-gypsum could in part be due to the presence of calcium sulfate nano-needles in the nano-gypsum as showed by electron microscopy.

Role of grain size on the strength and ductile–brittle transition temperature in the dual-sized ferrite region of the heat-affected zone of ultra-fine grained steel

The softening region in the heat-affected zone of ultra-fine grained steels consists of coarse and fine ferrite grains. The strength and toughness of the dual-sized ferrite region were evaluated in terms of Vickers hardness and ductile–brittle transition temperature, respectively. In this study, the average grain size of the dual-sized ferrite region was expressed in terms of arithmetical average d ar and weighted average d wt, respectively. It was found that the strength proportionally varied with d ar − 1 / 2 while the ductile–brittle transition temperature showed a monotonic relation with d wt − 1 / 2 for the dual-sized ferrite region.