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In the production of cement, raw materials can be partially substituted by regenerable waste provided from glasses, construction and demolition waste in order to reduce the environmental problem and burden of landfills. In this study, limestone–silicate composites were synthesized using starting materials such as glass waste and lime, brick, autoclaved aerated concrete (ACC), mortar or plaster waste. The structure and mechanical properties of the nano-composite materials have been studied. The mean CaCO3 crystallite sizes are higher for composites containing ACC and brick than for doping with lime, mortar and plaster. Cement-based materials are formed by replacing 2.5% of the Portland cement with limestone–silicate composites. The results indicate new possibilities for introducing 2.5%of composites in cement paste because they promote the formation of the C-S-H network, which provides strength and long stability for the cement paste. The influence of varied types of mix composites in the expired cement on the initial cracking strain and stress, tensile strength and compressive strength were investigated. The compressive strength values of composite-expired cement specimens are situated between 11.8 and 15.7 MPa, respectively, which reflect an increase from 22.9 up to 63.54% over the compressive strength of expired cement matrix. [ABSTRACT FROM AUTHOR]

Recently, dissimilar metals have found applications in the process of resistance spot welding (RSW), particularly within the electric vehicle industry. Notably, copper and aluminum have gained significant importance in these sectors due to their advantageous characteristics for the industry requirements. The mechanical behavior of these materials is essential to maintaining structural integrity. The study aims to estimate the mechanical behavior of dissimilar RSW joints and optimize welding parameters for Cu-Al joints. Hence, understanding the joining processes in the electric vehicle industry to design reliable components. Combining different types of materials, such as T2-grade commercially pure copper sheets and aluminum AA1050 with the same thickness of 1 mm has been welded. The determination of optimal welding conditions takes into account material thicknesses and types. Through tensile-shear testing, welding parameters that yield maximal joint strength were identified. Using Minitab 19 software, the Taguchi method helped achieve optimized welding parameters. The hardness, fracture characteristics, and weld strength have been investigated. Hardness measurements were conducted across the nugget thickness and surface, offering insights into potential failure modes. The welding process involves the transition to a liquid state for the aluminum components, resulting in the formation of intermetallic compounds. Consequently, crack initiation was observed within the aluminum segments, leading to a plug-out fracture mechanism. In contrast, copper exhibits superior strength and hardness compared to aluminum, where increased hardness correlates with heightened strength. The discrepancy in hardness, especially the lower values observed on the aluminum side, caused fractures to appear within the heat affected zone (HAZ). Subsequently, this fracture propagated until pull-out failure was realized. The study revealed that dissimilar joining of Cu and Al resulted in an ultimate tensile stress of 26 MPa, while similar joining of copper showcased a strength of 98 MPa. Additionally, the symmetric join in aluminum exhibited a strength of 93 MPa. The maximum tensile shear force is equal to 512 N at a maximum welding current of 14000 A. The pull-out failure mode occurs in the Cu-Al RSW joint. The maximum hardness was noted in the fusion zone (FZ). Relevant literature sources have supported and confirmed these outcomes. [ABSTRACT FROM AUTHOR]

The preparation of dense single-phase boride ceramics has always been a challenge. In this paper, single-phase W 2 B 5 ceramic with excellent performance was successfully prepared using W 2 B 5 powder and SPS-HF technology. Under the sintering condition of 1800 °C and 50 MPa, a nearly dense W 2 B 5 ceramic material with excellent mechanical properties was obtained. The relative density of the as-sintered W 2 B 5 ceramic achieved 96.72 % without any sintering additive. Additionally, the Vickers hardness, fracture toughness as well as bending strength were 30 GPa (9.8 N), 5.39 MPa·m1/2 and 522.7 MPa, respectively. The outstanding hardness and bending strength of W 2 B 5 ceramic could be attributed to its monophase W 2 B 5 structure and high densification degree. The primary fracture mode of W 2 B 5 ceramic was transgranular fracture, and the toughening mechanisms included crack deflection, crack bridging, and crack branching. [ABSTRACT FROM AUTHOR]

(1) Background: Digital technologies are available for denture base fabrication, but there is a lack of scientific data on the mechanical and chemical properties of the materials produced in this way. Therefore, the aim of this study was to investigate the residual monomer content, flexural strength and microhardness of denture base materials as well as correlations between investigated parameters. (2) Methods: Seven denture base materials were used: one conventional heat cured polymethyl methacrylate, one polyamide, three subtractive manufactured materials and two additive manufactured materials. High-performance liquid chromatography was used to determine residual monomer content and the test was carried out in accordance with the specification ISO No. 20795-1:2013. Flexural strength was also determined according to the specification ISO No. 20795-1:2013. The Vickers method was used to investigate microhardness. A one-way ANOVA with a Bonferroni post-hoc test was used for the statistical analysis. The Pearson correlation test was used for the correlation analysis. (3) Results: There was a statistically significant difference between the values of residual monomer content of the different denture base materials (p < 0.05). Anaxdent pink blank showed the highest value of 3.2% mass fraction, while Polident pink CAD-CAM showed the lowest value of 0.05% mass fraction. The difference between the flexural strength values of the different denture base materials was statistically significant (p < 0.05), with values ranging from 62.57 megapascals (MPa) to 103.33 MPa. The difference between the microhardness values for the different denture base materials was statistically significant (p < 0.05), and the values obtained ranged from 10.61 to 22.86 Vickers hardness number (VHN). A correlation was found between some results for the material properties investigated (p < 0.05). (4) Conclusions: The selection of contemporary digital denture base manufacturing techniques may affect residual monomer content, flexural strength and microhardness but is not the only criterion for achieving favourable properties. [ABSTRACT FROM AUTHOR]

A series of homogeneous hybrid BPA.DA-NVP@Eu2L3 materials were obtained through an in situ approach where the luminescent dopant was formed at the molecular level with different contents (0.1; 0.2; 0.5; 1; and 2% by weight). A Europium(III) complex (Eu2L3) with quinoline-2,4-dicarboxylic acid was applied as a luminescence additive while a polymer matrix consisted of a combination of bisphenol A diacrylate (BPA.DA) and N-vinylpyrrolidone (NVP) monomers. Synthesis steps and the final materials were monitored by NMR and Fourier transform infrared spectroscopy (FTIR). The emission, excitation spectra, lifetime, and quantum yield measurements were applied for the determination of the photophysical characteristics. The thermal and mechanical properties of the obtained materials were tested via thermal analysis methods (TG/DTG/DSC and TG-FTIR) in air and nitrogen atmospheres, dynamic mechanical analysis (DMA), and hardness and bending measurements. Generally, even a small addition of the metal complex component causes changes in the thermal, mechanical, and luminescent properties. Hybrid materials with a greater europium complex content are characterized by a lower stiffness and hardness while the heterogeneity and the flexibility of the samples increase. A very small amount of an Eu2L3 admixture (0.1% wt.) in a hybrid material causes an emission in the red spectral range and the luminescence intensity was reached for the BPA-DA-NVP@1%Eu2L3 material. These materials may be potentially used in chemical sensing, security systems, and protective coatings against UV. [ABSTRACT FROM AUTHOR]

The research was focused on developing new materials using natural products, which is the valuable or suitable way to solve environmental related issues and increase the income of farmers and industries. The work was carried out using corn fibres polyester composites. The composites were produced by adding fibres at different weight fractions as FRP10, FRP20, FRP30, FRP40 and FRP50 percentages. The optimum fibre mass fraction required for flexural strength using corn fibre is 18.05(MPA) and the impact energies and Hardness of the composites were lower than that of the control which were 1.41(J/mm²) and 2.01(BHN) respectively. In the results from the analysis of the mechanical properties of corn fibers reinforced composites greatly influenced by the fiber percentages with the observed strength from flexural and hardness. The impact of the polyester samples was improve the flexure responses of the developed composite materials. Likewise the work justifies the economic consumption of these otherwise waste materials that are detrimental as environmental pollution agent. [ABSTRACT FROM AUTHOR]

Cu-P-Sn-Ag quaternary alloy brazing material is prone to brittle fracture of wire during industrial production, which seriously affects product quality. To improve its mechanical properties, Cu-P-Sn-Ag quaternary alloy ingots and brazing materials with different P contents were prepared. The effects of P content on the microstructure, hardness, tensile strength, and elongation of the brazing material were systematically studied. The results show that when the P content is between 5.0% and 5.2%, the brittle phase Cu3 P structure in the alloy is small and short rod-shaped, with grain size less than 5 µm. When the P content is between 5.4% and 6.0%, some Cu3 P structures in the alloy gradually transform into coarse fishbone like structures, with grain sizes greater than 30 µm. When the P content ranges from 5.2% to 5.4%, the hardness of the solder increases significantly with the increase of P content, from 247.7 HV to 260.4 HV; Its tensile strength and elongation significantly decreased from 844.38 MPa and 3.60% to 815.08 MPa and 3.07% respectively. The evolution relationship between P content and microstructure is the main factor affecting the mechanical properties of brazing materials. [ABSTRACT FROM AUTHOR]

High-pressure torsion (HPT) is an effective severe plastic deformation method to produce ultrafine-grained (UFG) and nanocrystalline (NC) materials. In the past, most studies have focused on the evolutions in the microstructure, texture and mechanical properties of HPT-deformed materials at peripheral regions. The corresponding evolutions at a special area were observed in this study to reveal the potential plastic deformation mechanism for face-centred cubic (FCC) material with high stacking fault energy. A decreasing trend was found in grain size, and the final grain size was less than 1 μm. However, close observation revealed that the general trend could be divided into different sub-stages, in which grain elongation and grain fragmentation were dominant, respectively. Additionally, microhardness demonstrated a non-linear increase with the development of plastic deformation. Finally, the microhardness reached a high level of ~64 HV. At the early stages of HPT, the C component was transformed into a cube component, suggesting the material flows around the shear plane normal (SPN) axis at these stages. However, finally they will be replaced by ideal simple shear orientations. [ABSTRACT FROM AUTHOR]

Composite materials represent a category of new materials, with superior properties, used in many fields of activity. In the present work, reference is made to such a material, this material being studied under certain conditions, in order to highlight its special properties. [ABSTRACT FROM AUTHOR]

The shear cutting of electrical steel sheets has a significant influence on the magnetic and mechanical material properties. Due to plastic deformation and strain hardening in the area of the punched edge, the electrical steel sheets exhibit a characteristic hardness profile. This study deals with the modelling of the resulting hardness profile by means of finite‐element simulations. Elastic‐plastic material properties are obtained from spherical nanoindentation testing as a function of the local hardness. In particular, representative stress‐strain values are determined by applying Tabor's concept of indentation stress‐strain curves. The choice of the appropriate stress‐ and strain‐constraint factors is discussed with respect to the nanoindentation test setup used. Following this, the representative stress‐strain values are analytically described to determine true stress‐strain curves for the local assignment of different material models depending on the hardness. The implementation of the modelling approach in a finite‐element simulation is presented for a punched electrical steel sheet specimen under monotonic loading. The simulation results are basically in good agreement with experimental data and confirm the expected influence on the mechanical material behaviour due to the shear cutting process. [ABSTRACT FROM AUTHOR]

Short-range order is a new strengthening effect that can significantly affect the mechanical properties of high-entropy materials. Furthermore, simulation results show that this strengthening effect at a quasi-atomic scale can suppress the grain size softening, leading to the disappearance of inverse Hall-Petch behavior in nanocrystalline high-entropy materials. In this work, the evident inverse Hall-Petch behavior is confirmed in the translucent nanocrystalline high-entropy ceramic (HEC) with an average grain size below 10 nm, fabricated by a high-pressure low-temperature sintering technique. Besides, the as-obtained nanocrystalline HEC also shows an improving fracture toughness compared with the corresponding coarse-crystalline HEC. [ABSTRACT FROM AUTHOR]

In this study, the effects of different welding filler materials were examined in the case of repair welding of pressure infiltration casting tool made out of Böhler W350 ISOBLOC hot forming tool steel. Three additional welding filler materials were used: Böhler W350 ISOBLOC (same as the raw material), Böhler W300 ISOBLOC and Anviloy® 1150 tungsten alloy. The welds were created with TIG welding method. The used welding filler material has an impact on the mechanical and corrosive properties of the tool. The hardness of the weld was measured to determine its resistance against mechanical stress. The corrosion rate was measured because molten aluminium corrodes workpieces due to its high chemical activity. It was concluded that a single-pass weld corrosion speed is 0.142 ± 0.010 mm/year while a weld containing multiple layers and passes has the corrosion speed of 0.069 ± 0.005 mm/year which is approximately 48% of the corrosion speed of the single-pass weld. Furthermore, the hardness of a weld made with W350 welding filler material significantly drops in the upper layers of the weld, down to 273 HV1 while the hardness of the base material is 495 ± 8 HV1. The results show that the multiple layers and passes welds have better corrosion resistance and less hardness than the single-pass weld. [ABSTRACT FROM AUTHOR]

The so‐called lower tungsten carbides W2C and Fe3W3C often appear in tungsten carbide–reinforced iron matrix (WC–Fe) composites. The effect of their presence on the mechanical properties of the material, such as hardness, is not well understood. In this study, we extensively measured the hardness distribution in the WC–Fe composites and also performed hundreds of microhardness measurements to determine the hardness values for the lower carbides. The hardness values calculated by ab initio were compared, where the theoretical values of Fe3W3C had little difference from the experimental values. However, the experimentally obtained hardness data for W2C were significantly smaller than the reported theoretical data. Moreover, the experimental hardness values for W2C reported in the literatures are very different. To understand the origin of the discrepancy, the focused‐ion‐beam–transmission‐electron‐microscopy technique was used to obtain the high‐resolution images of W2C, which revealed a high density of planar defects. As a further comparison, ab initio molecular dynamics simulations illustrate that the complex interactions between different atomic pairs in Fe3W3C make it difficult for this type of crystal defect to occur. The lattice of W2C can adjust—resulting in shuffle defects and stacking faults—to a certain degree affecting its hardness, which was not revealed in previous studies. [ABSTRACT FROM AUTHOR]

Clad rebar is one of the key structures of marine and construction services. Therefore, it is of great importance to acknowledge the mechanical property parameters of the composite region in the structural integrity evaluation of clad rebar. The different base materials of clad rebar (20MnSiV/316L steel, 35#/316L steel, 45#/316L steel, and 55#/316L steel) are researched in this study. The composite area is further refined, and simultaneously, a refinement model of the composite region of clad rebar is established. In view of the fact that a surface hardness experiment is quite easy to conduct, a proposed method consists of obtaining the mechanical property parameters of materials using the surface hardness test. The mechanical property parameters are acquired; moreover, the relationship between yield stress and surface hardness of the stainless steel clad rebar is set up. We used this method to acquire the mechanical parameters of a composite surface uneven area of clad rebar, and we established a mechanical parameters mathematics model of clad rebar, it is a significant basis for a structural integrity evaluation of cladding materials. [ABSTRACT FROM AUTHOR]

The objectives of this study were to evaluate the mechanical properties of lithium disilicate components produced by additive manufacturing (AM) and to assess the effect of build orientation on the resistance to fracture. Oversized bars were printed with a glass-filled photoactive resin using a digital light processing technique. After sintering and post-processing, flexure and chevron notch fracture toughness bars were obtained in three principal orientations (0°, 45°, and 90°) with respect to the build direction. Mechanical properties were obtained according to the relevant ASTM standards. The hardness, indentation fracture resistance, and elastic modulus were measured for each orientation, and a Weibull analysis was conducted with the flexure responses. Fractography of the fracture surfaces was performed to identify the failure origins. The 0° orientation exhibited characteristic strength, Weibull modulus, and elastic modulus of 313 MPa, 4.42, and 168 ± 3 GPa, respectively, which are comparable to lithium disilicate materials from traditional processes. However, build orientation contributed significantly to the flexure strength, elastic modulus, and Weibull modulus; the characteristic strengths for the 45° and 90° build orientations were 86 MPa and 177 MPa, respectively. The primary contribution to the orientation dependence was the number of residual build layer-related flaws from incomplete union between printed layers. Of note, hardness and the fracture toughness were not dependent on build orientation. AM of lithium disilicate materials can achieve the mechanical properties of materials produced by traditionally processing. Thus, while further process development is warranted, the outlook for dentistry is promising. [ABSTRACT FROM AUTHOR]

Objectives: To analyze and compare, in vitro, the microhardness, sorption, solubility, color stability, and cytotoxicity of three types of resin composites: self-adhesive (SARC) (Dyad Flow (DF)/Kerr), bulk-fill (Filtek Bulk Fill Flow (FBF)/3 M ESPE), and conventional (Filtek Z350XT Flow (Z350)/3 M ESPE). Materials and methods: Thirty cylindrical specimens were prepared using a split metal mold (15 mm × 1 mm), divided into 3 groups (n = 10) according to the material used. Vickers hardness (VH) was calculated from three indentations (300gf/15 s) per specimen. The sorption and solubility were measured according to the ISO 4049:2009 specification after storing in distilled water for 7 days. The color of each resin composite was measured using a portable digital spectrophotometer according to the CIELAB system. After a 7-day immersion in coffee, the color variation (∆E) was calculated. Following the ISO 10993:2012, the cytotoxicity in Vero cells was evaluated through the MTT assay. The results were analyzed using the Kruskal–Wallis test to compare the studied groups. The Wilcoxon test was used to compare the assessments in each studied group. For cytotoxicity analysis, the data were compared by the ANOVA test (α = 0.05). Results: DF showed the lowest VH (28.67), highest sorption (0.543 µg/mm3) and solubility (1.700 µg/mm3), and higher ∆E after 7 days of coffee immersion (p = 0.008). The resin composites studied were considered non-cytotoxic. Conclusions: The SARC presented inferior mechanical and physical–chemical properties than bulk-fill and conventional resin composites, with comparable cytotoxicity against Vero cells. Clinical relevance: The simplification of the clinical protocol of SARC can minimize the number of possible failures during the restorative technique. However, considering their inferior physical and mechanical properties, their coverage with materials of higher mechanical properties and physical–chemical stability should be considered. [ABSTRACT FROM AUTHOR]

Objective: medium and low alloy steel have good mechanical properties and are widely used in the manufacture of key parts such as high-speed rail, automobiles, and aircrafts. Hardness is an important physical property of metal materials, which directly affects the mechanical properties of metal materials as key components. Therefore, the detection of hardness is of great significance. The traditional hardness testing method is to apply force to the sample to produce indentation and then determine the hardness of the sample by the depth of the indentation. Due to the existence of indentation in this method, the sample will be destroyed, so it can only be used for the random inspection of sample hardness parameters, which cannot meet the reality of the hardness testing of the key parts of the equipment in a running state. Therefore, it is necessary to explore a non-destructive testing method for the hardness of low and medium alloy steel based on LIBS testing technology. Method: based on laser-introduced breakdown spectroscopy (LIBS) technology and combined with chemometrics, this study took the medium-and-low alloy steel as the research object to monitor the quality of train wheels. Firstly, LIBS spectra of 12 standard steel samples with different hardness characteristics were acquired and compared. Secondly, the original spectrum was preprocessed using methods such as smoothing correction, multiplicative scatter correction, AsLS, and AirPLS to select the optimal preprocessing method. It was found that the model established by means of multiplicative scatter correction (MSC) combined with baseline estimation and de-noising using sparsity (BEADS) showed the best performance, in which the cross-validation of correlation coefficient (Rcv) was 0.9909 and the standard deviation of cross-validation (RMSECV) was 14.6935. To simplify the calculation and improve model accuracy, the uninformative variable elimination (UVE), competitive adaptive reweighted sampling (CARS), and successive projections algorithm (SPA) were used to select the effective spectral bands and create the partial least squares and partial minimum support vector machine (SVM) models, respectively. The results showed that the CARS-LS-SVM model obtained more accurate prediction results than the CARS-PLS model, whose Rp and RMSEP values were 0.9966 and 9.4800, respectively. Conclusion: it is concluded that the wavelength selection can not only eliminate the interference information, and simplify the modeling and calculation process of LIBS spectral data but also improve the accuracy of the detection model, thus making it feasible to rapidly detect steel hardness. The results show that it is feasible to predict the hardness of the medium-and-low alloy steel using LIBS combined with the LS-SVM model, which can be further used as a technical method to detect the quality of steel and the performance of the key components for the quality supervision of steel. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) formed through pyrolysis of preceramic polymers loaded with SiC particles has gained significant attention for applications such as coatings, composite matrix modifications, and most importantly additive manufacturing. This work presents combined synchrotron XRD, Raman spectroscopy, scanning electron microscopy, nano-indentation, and Vickers indentation of pyrolysis bonded SiC to shed light on the changes of composition and mechanical properties of these materials. Characterization was performed on samples that were heat treated ranging from the synthesis 850 °C up to 1500 °C. Pre-treatments of the powders prior to pellet synthesis, such as heat treatment and etching using a hydrofluoric acid (HF), were investigated. It is shown that the degradation of mechanical properties when exposed to higher temperatures is due to the burnout of amorphous carbon clusters remnant of the pyrolysis process of the preceramic polymer. Furthermore, prior HF etching and removal of the native oxide layer of the powders showed improved density and hardness values in the final pellets. The average Vickers hardness of the control samples were 4.59 GPa and later 3.74 GPa when exposed to 1500 °C, while the samples synthesized using powders that were etched with HF had an average hardness value of 9.37 GPa and later 6.86 GPa when exposed to 1500 °C. [ABSTRACT FROM AUTHOR]

The identification of ancient worked materials is one of the fundamental goals of lithic use wear analysis and one of the most important parts of understanding how stone tools were used in the past. Given the documented overlaps in wear patterns generated by different materials, it is imperative to understand how individual materials' mechanical properties might influence wear formation. Because isolating physical parameters and measuring their change is necessary for such an endeavor, controlled (rather than replicative) experiments combined with objective measurements of surface topography are necessary to better grasp how surface modifications formed on stone tools. Therefore, we used a tribometer to wear natural flint surfaces against five materials (bone, antler, beech wood, spruce wood, and ivory) under the same force, and speed, over one, three, and five hours. The study aimed to test if there is a correlation between surface modifications and the hardness of the worked material. We measured each raw material's hardness using a nano-indentation test, and we compared the surface texture of the flint bits using a 3D optical profilometer. The interfacial detritus powder was analyzed with a scanning electron microscope to look for abraded flint particles. We demonstrate that, contrary to expectation, softer materials, such as wood, create a smoother surface than hard ones, such as ivory. [ABSTRACT FROM AUTHOR]

The effect of reinforcement with ceramic microparticles of SiC, B4C and Al2O3 on the microstructure and mechanical properties of composite materials with an aluminum matrix produced by powder metallurgy is studied. It is shown that an increase in reinforcing particle concentration gives rise to a substantial increase in composite compressive strength and hardness with an insignificant increase in density. The connection of microstructure morphology with composites properties is demonstrated. [ABSTRACT FROM AUTHOR]

In this study, the impacts of the heating temperature and bending angle on springback were experimentally examined in the V-bending of Docol 1400 steel sheets. The bending angle (30°, 60°, 90° and 120°) and the temperature (Room Temperature-RT, 200°C, 300°C, 400°C, 500°C, 600°C) of the bending zone were determined as the variable experimental parameters. The springback was measured using a coordinate measuring machine (CMM). The springback was observed to decrease by 7.7% on average between RT and 200 °C, to increase by 8% between 200 °C and 300 °C and by 18% between 300 °C and 600 °C. The material data used in the analyses were attained from the tensile test results conducted at different temperatures. The analysis shows that the springback values decreased linearly at elevated temperatures. It was seen that the mechanical properties of the material decreased within the temperature range of RT to 600°C in the heated bending zone. [ABSTRACT FROM AUTHOR]

Ductile wear is highly desirable in manufacturing and machining operations to achieve a high quality of finish. In a ductile regime of operation, a characteristic transition from ploughing to cutting is often observed in materials with different mechanical properties. We unveil the origin of this transition through a plastic, debris-free model of a tip causing wearing of a flat surface. The abraded volume depends on the equilibrium depth which is reached once the normal force is balanced by the lifting force during scratching. We show that the dependence of the equilibrium depth on the lifting force is highly non-linear and diverges above a threshold force that depends on the hardness, friction force and geometry of the tip. The threshold corresponds to a characteristic depth marking the ploughing–cutting transition. When this characteristic depth is below the ductile–brittle depth of cut, ploughing, cutting and brittle modes of operation are all possible. These abrasive wear modes are summarised in a unified mechanism map. The findings of this model, derived from theoretical considerations, are validated by DEM simulations and literature data from experiments. [Display omitted] • Emergence of severe wear is related to an incipient ploughing–cutting transition. • The transition is due to the load-bearing area's inability to counterbalance the load. • The theoretical model is validated by DEM simulations and experimental data. • A mechanism map predicts ploughing, cutting and brittle fracture wear modes. [ABSTRACT FROM AUTHOR]

The paper addresses the investigation of microstructures from AISI 52100 and AISI 4140 in hardened as well as in quenched and tempered conditions. The specimens are compared in terms of their magnetic hysteresis and their microstructural and mechanical properties. Material properties were determined by hardness, microhardness, and X-ray diffraction measurements. Two different approaches were used to characterize magnetic properties via a hysteresis frame device, aiming, on the one hand, to record the magnetic hysteresis with established proceedings by setting a constant magnetic flux and, on the other hand, by offsetting a constant field strength to facilitate reproducibility of the results with other micromagnetic measurement systems. Comparable differences in both the micromagnetic and the mechanical material properties could be determined and quantified for the specifically manufactured specimens. The sensitivity of the magnetic hysteresis and, determined from that, the relationship between magnetic flux and magnetic field strength were confirmed. It was shown that a consistent change in hysteresis shape from hardened to high temperature tempered material states develops and that this change allows the characterization of different materials without the need to adjust magnetization parameters. Repeatedly, an increase in remanence with decreasing hardness was found for both test approaches. Likewise, a decreasing coercivity and increasing maximum magnetic flux could be detected with decreasing retained austenite content. The investigated correlations should thus contribute to the calibration of comparable measurement systems through the holistic characterized specimens. [ABSTRACT FROM AUTHOR]

In surface mechanical attrition treatment (SMAT), the processing parameters like the diameter of hardened steel balls/shots (D) and their impact velocity (V) are crucial in affecting the mechanical properties of the materials. This study is focused on understanding the effect of D and V on microstructural and hardness variation during the SMAT process. The SMAT has been performed on AISI 304L steel using 3-mm and 8-mm diameter balls with a combination of 1 m/s and 10 m/s impact velocity. Microstructure of the SMATed material shows twin distribution near the top surface changeover from coarser to finer when V increases from a low to significantly high value, whereas it changes marginally with an increase in D. Nanoindentation experiments performed along the depth of SMATed material reveal that the near-surface hardness is mainly governed by V and weakly influenced by D. However, the hardened layer thickness is enhanced by increasing either of these parameters. The complementary finite element (FE) simulations of the single impact SMAT process are performed using the rate-dependent Johnson–Cook plasticity model to provide the mechanistic reasons for the behavior observed from the experiments. A strategy to determine the hardness-depth profile of SMATed steel through FE simulations is developed. The hardness behavior of the SMATed steel is linked to the effects of D and V on the residual equivalent stress and equivalent plastic strain at the surface. The hardness away from the surface is influenced by the shot size and shot velocity. The empirical relations that show the dependence of hardness on the SMAT parameters are determined. [ABSTRACT FROM AUTHOR]

A356 alloy, which is a commercial Al–Mg–Si alloy, was solidified with different magnitudes (0.42–1.25 kV cm−1) and directions of static electrical fields (E+: positive and E−: negative) to study the influences of E+ and E− on irregular interflake structure and mechanical property of Al–Mg–Si alloy. The direction of E is parallel or antiparallel to the solid–liquid (S–L) interface growth direction. The secondary dendrite arm spacing (λ2), Alα average grain surface area (Sα), sphericity ratio of Si into matrix (fSi) and Brinell hardness (HB) were measured for A356 alloy solidified with different E+ and E− values. The static electrical field force (F) affects the atomic mass flux at the S–L interface during the solidification and thus the microstructure, and physical and mechanical properties of the material are changed with E+ and E−. While the values of λ2, Sα and fSi increase with increasing the value of E−, the HB value decreases with increasing E−. However, the values of λ2, Sα and fSi decrease with increasing the E+ and the HB value increases with increasing E+. The relationships between them were determined with linear regression analysis. Optical images of microstructure for the A356 alloy solidified with different directions and magnitudes of static electric fields; (a) 0.0 kV cm−1 (b) 1.25 kV cm−1 (c) − 1.25 kV cm−1. [ABSTRACT FROM AUTHOR]

[Display omitted] • Temperature-dependent yield strength and hardness models were developed. • The models consider the indentation size effect under different loading conditions. • Predictions were well validated by more than 30 sets of experimental data. • A new finding is the loading mode dependence of the indentation size effect. • The influence of various factors on the indentation is systematically considered. The development of theoretical models to facilitate access to the mechanical properties of materials has been a long-standing pursuit of scholars. In this study, temperature-dependent yield strength models and temperature-dependent hardness models considering indentation size effects were developed under different loading modes (loading to the same displacement or the same load at different temperatures), respectively. Based on the Force-Heat Equivalence Energy Density Principle, the proposed models are free of any adjustable fitting parameters, and the quantitative relationships among temperature, yield strength/hardness, Young's modulus, and indentation load/displacement were successfully captured. All the available 36 groups of experimental data validate the accuracy of the proposed models over a wide temperature range. The yield strength and hardness of metallic materials over a wide temperature range can be easily predicted by using the developed models. Based on the parametric analysis of the models, it has been theoretically clarified for the first time that the two loading modes have opposite indentation size effects for the same material. Although the indentation size effect all decreases gradually with increasing temperature for different loading modes. The influence of loading modes should be noted in future studies where temperature-dependent indentation size effects need to be considered. This work systematically considers the effects of temperature, loading mode, indentation load/displacement, and Young's modulus on the indentation yield strength and hardness, which is important to facilitate the study of the deformation behavior of materials at different temperatures by indentation methods. [ABSTRACT FROM AUTHOR]

The impact of warm-rolling at 773 K to 76% and 90% thickness reduction on the microstructure and mechanical properties of an equiatomic CrMnFeCoNi high entropy alloy is compared to material that is cold-rolled and subsequently annealed between 673 and 1173 K. While cold-rolling significantly improves hardness and yield strength, subsequent annealing with increasing temperature improves ductility due to stress-relaxation, recovery, and recrystallization of the elongated grain structure which simultaneously reduces hardness and strength. Compared to the cold-rolled condition, however, annealing at 773 K increases hardness and strength as well as ductility which may be associated with the onset of chemical ordering combined with a lack of the formation of precipitates. Warm-rolling at 773 K, on the other hand, results in partially recrystallized microstructures without mechanical nanotwins. While the 76% deformed material exhibits mechanical properties that are comparable to the cold-rolled and annealed materials, the 90% warm-rolled material shows significantly improved hardness compared to the cold-rolled material, similar strength, but improved plastic failure strains. These properties are associated with the formation of a fine lamellar deformation structure and the onset of the precipitation of Cr-rich particles during rolling. Our results reveal that warm-rolling may enable an efficient pathway to obtain structure-property relationships in HEAs that can otherwise only be obtained in a multi-step processing procedure. • Annealing the cold-rolled alloy at 773 K leads to an increase in both yield strength and ductility. • The warm-rolled material shows comparable mechanical resistance to the cold-rolled, but improved plastic failure strains. • Warm-rolling provides an efficient pathway to improve structure-property relationships in HEAs. [ABSTRACT FROM AUTHOR]

The current trend in scientific researches is to improve the performance of mechanical and physical properties of polymeric compounds, one of these methods is to add nanoparticles to polymeric composites. In this work, the wear behaviour (pin to disc) of nanocomposites composed of vinyl ester reinforced glass fibers and nanoparticles was evaluated under three different factors, such as specimen content, load applied, and distance sliding using a sliding time constant, as well as studying the hardness shore for these nanocomposites. The (hand-lay) method was used for the purpose of preparing the nanocomposites from vinyl ester filled with 10% vf. glass fiber and (0.5%, 1%, 1.5%, and 2% vf. of nano-Fe3O4 and ZrO2). The results are tabulated and analysed using Taguchi experiments (L9) (Minitab 18) for the purpose of determining which of the factors under consideration had the greatest influence on the wear behaviour. From the results, it was found that the specimens (vinyl ester-10% vf. glass fibers-2% ZrO2) and (vinyl ester-10% vf. glass fibers-2% Fe3O4) give the best wear resistance 0.003×10-5, 0.012×10-5 mm³ /Nm respectively under the factors (load 20 N, sliding distance 45 cm). It was found that the specimen content is the most important factor influencing the wear behaviour, followed by the factors of the applied load and then the sliding distance. The addition of nanoparticles (0.5-2% vf. ZrO2, Fe3O4) to the vinyl ester resin improved the hardness values. Furthermore, the findings show that the addition of nanoparticles (ZrO2, Fe3O4) had a positive effect on the (wear and hardness) tests, implying that the nanoparticles improved the bonding between the base material and reinforcing material. [ABSTRACT FROM AUTHOR]

Electrical discharge machined surfaces inherently possess recast layer on the surface with heat affected zone (HAZ) beneath it and these have a detrimental effect on the mechanical properties viz., hardness, elastic modulus, etc. It is very difficult to experimentally characterize each machined surface. Therefore, an attempt is made in this study to numerically calculate the mechanical properties of the parent material, HAZ and the recast layer on a hemispherical protruded micro feature fabricated by reverse micro EDM (RMEDM). In the first stage, nano indentation was performed to experimentally determine the load-displacement plots, elastic modulus and hardness of the parent material, HAZ, and the recast layer. In the second stage, finite element analysis (FEA) simulation was carried out to mimic the nano indentation process and determine the load-displacement plots for all the three cases viz., parent material, recast layer, and HAZ. Results demonstrated that the load-displacement plots obtained from numerical model in each case was in good agreement with that of the experimental curves. Based on simulated load-displacement plots, hardness was also calculated for parent material, HAZ, and the recast layer. A maximum of 11% error was observed between simulated values of hardness and experimentally determined values. This model can be utilized to predict the mechanical properties of surfaces fabricated by micro scale EDM process and this will help in reducing the number of experiments thereby saving time and cost. [ABSTRACT FROM AUTHOR]

We measured hardness, modulus of elasticity, and, for the first time, loss tangent, energy of fracture, abrasion resistance, and impact resistance of zinc- and manganese-enriched materials from fangs, stings and other "tools" of an ant, spider, scorpion and nereid worm. The mechanical properties of the Zn- and Mn-materials tended to cluster together between plain and biomineralized "tool" materials, with the hardness reaching, and most abrasion resistance values exceeding, those of calcified salmon teeth and crab claws. Atom probe tomography indicated that Zn was distributed homogeneously on a nanometer scale and likely bound as individual atoms to more than ¼ of the protein residues in ant mandibular teeth. This homogeneity appears to enable sharper, more precisely sculpted "tools" than materials with biomineral inclusions do, and also eliminates interfaces with the inclusions that could be susceptible to fracture. Based on contact mechanics and simplified models, we hypothesize that, relative to plain materials, the higher elastic modulus, hardness and abrasion resistance minimize temporary or permanent tool blunting, resulting in a roughly 2/3 reduction in the force, energy, and muscle mass required to initiate puncture of stiff materials, and even greater force reductions when the cumulative effects of abrasion are considered. We suggest that the sharpness-related force reductions lead to significant energy savings, and can also enable organisms, especially smaller ones, to puncture, cut, and grasp objects that would not be accessible with plain or biomineralized "tools". [ABSTRACT FROM AUTHOR]

The mechanical properties possessed by surface layers of metal alloys hardened by severe plastic deformation methods were studied by indentation. The test materials were AISI O2 and AISI 316L steels and D16 aluminum alloy. Most scientific papers evaluate the mechanical properties of hardened surface layers and thin coatings only by hardness measurement. Hardness alone cannot characterize the ductility of a material without using modern concepts for determining the physical ductility from hardness. The mechanical behavior of a material can only be characterized by determining both the ductility and the yield stress. These quantities can be found by micro- or nanoindentation. We developed indentation methods to find the physical ductility δH and yield stress σSH of the surface layers of metal alloys hardened by various techniques (with analysis of changes in these characteristics across the hardened layer) to select the optimal hardening method. The hardening characterized by the ratio between the yield stresses of the hardened layer and the starting material σ SH hard / σ SH start was much greater for all studied alloys than the hardening characterized by the hardness ratio (HVhard/HVstart). Thus, the use of δH and σSH obtained from standard microhardness measurements enhanced the informative nature and efficiency of the indentation method in studying the mechanical behavior of metal alloy layers hardened by various techniques. [ABSTRACT FROM AUTHOR]

The conversion of waste to wealth has recently grossed high attention as it possesses the ability to boost the economy of any nation; hence, this research. In this study, the characterization and investigation of mechanical properties of nano-flux (CaO) welding powder developed from bio-agrowaste (eggshell) was carried out. Mild, galvanized and stainless steel of plates and rods were used as parent metals for the experiment. Results obtained from hardness test in the base metal, weld joint and heat affected zone for the galvanized and mild steel plates with nano-flux powder gave the best hardness of 111.95, 120.30, 182.99 and 206.21, 164.85, 110.56 BHN respectively. The tensile stress obtained both for mild and stainless steel was 88.14 MPa while the tensile strain obtained for both plates were 0.0155 mm/mm. Microstructural analysis results shows an improvement in the structure, surface and patterns of the weld with the use of developed flux compared with imported flux. Hence eggshells can be recycled and used for developing flux powder for welding processes. [ABSTRACT FROM AUTHOR]

Multilayered bulk Al–Cu–Al metal-matrix composite was fabricated by means of high-pressure torsion and subsequent annealing. The resulting composite had a heterogeneous structure consisting of ductile aluminum matrix and hard intermetallic inclusions with a gradient decrease in grain size and layer thickness when moving from the center to the periphery of the sample. Precipitation of Al 2 Cu intermetallic phase was revealed at the edge of the sample in the as-deformed state. Post-deformation annealing initiated the emergence of AlCu and Al 4 Cu 9 intermetallic precipitates with increased hardness compared to strain-induced Al 2 Cu particles. The growth kinetics of intermetallic compounds was obtained using precise X-ray phase analysis. It was found that the initial growth of intermetallic phases at temperatures 150–210 ∘ C depends on time t 1 / 2 , indicating the bulk diffusion-controlled growth. The growth activation energy of Al 2 Cu and AlCu phases was calculated to be 0.48 and 0.33 eV, respectively. The results obtained contribute to an understanding of the kinetics of annealing-induced growth of intermetallic phases and the corresponding evolution of strength characteristics in Al–Cu–Al composites. It was revealed that thermal treatment regimes resulting in enhanced mechanical properties are associated with moderate time and temperature of annealing, which allows avoiding partial dissolution of strengthening phases. The applied approach of phase kinetics analysis can become the basis for the development of new energy-efficient heat treatment modes of in situ Al-based composites allowing to govern their heterogeneity type and tailoring the mechanical properties of the material. [ABSTRACT FROM AUTHOR]

Mechanical properties of materials are enhanced by different methods to increase the usage of the materials. In this research spray pyrolysis method is employed to increase the mechanical characteristics of three different materials. The tin oxide is chosen as coated material and aluminium, brass, mild steel are selected as substrate materials. The 500nm thin film is developed over the substrate materials by spray pyrolysis. The substrate temperature are chosen as 300° C for aluminium, 400° C for brass and mildsteel. Nozzle to substrate distance is 0.4 m, substrate temperature is 300° C for aluminium and 400° C for solution concentration as 0.2 mole and solution flow rate is 1ml/min are selected for constant deposition parameters. The hardness and tensile strength result clearly shows that strength is increased by adding the coating over the surface. The material is heated above crystallization temperature and SnO² increases the tensile and hardness strength of the materials. The triangular metrological microscope is used to examine the microstructure of non coated and coated substrate materials. The microstructural analysis is showed that the uncoated surface of the substrate material is full of rough and pores. And displays that the tin oxide coated surface of the substrates after the initial deposition disclosed a surface with a agglomeration of tin oxide in homogeneous and uniform than the uncoated substrates. [ABSTRACT FROM AUTHOR]

Refractory high entropy alloys (R-HEAs) are becoming prominent in recent years because of their properties and uses as high strength and high hardness materials for ambient and high temperature, aerospace and nuclear radiation tolerance applications, orthopedic applications etc. The mechanical properties like yield strength and ductility of TaNbHfZr R-HEA depend on the local nanostructure and chemical ordering, which in term depend on the annealing treatment. In this study we have computationally obtained various properties of the equimolar TaNbHfZr alloy like the role of configurational entropy in the thermodynamic property, rate of evolution of nanostructure morphology in thermally annealed systems, dislocation simulation based quantitative prediction of yield strength, nature of dislocation movement through short range clustering (SRC) and qualitative prediction of ductile to brittle transition behavior. The simulation starts with hybrid Monte Carlo/Molecular Dynamics (MC/MD) based nanostructure evolution of an initial random solid solution alloy structure with BCC lattice structure created with principal axes along [1 1 1], [− 1 1 0] and [− 1 − 1 2] directions suitable for simulation of ½[1 1 1] edge dislocations. Thermodynamic properties are calculated from the change in enthalpy and configurational entropy, which in term is calculated by next-neighbor bond counting statistics. The MC/MD evolved structures mimic the annealing treatment at 1800 °C and the output structures are replicated in periodic directions to make larger 384,000 atom structures used for dislocation simulations. Edge dislocations were utilized to obtain and explain for the critically resolved shear stress (CRSS) for the structures with various degrees of nanostructure evolution by annealing, where extra strengthening was observed because of the formations of SRCs. Lastly the MC/MD evolved structures containing dislocations are subjected to a high shear stress beyond CRSS to investigate the stability of the dislocations and the lattice structures to explain the experimentally observed transition from ductile to brittle behavior for the TaNbHfZr R-HEA. [ABSTRACT FROM AUTHOR]

This research is about manufacturing brake pads from a polymeric composite material composed of domestic materials, which are cheaper and available in the market. An unsaturated polyester is used as the basic material. Styrene--butadiene rubber and montmorillonite clay materials available in the market are used as the fillers. The Kevlar fibers, the nylon, and the steel fibers are used as reinforcing materials to improve the mechanical properties. The Shore hardness, compressibility, thermal conductivity, impact, and wear resistance tests have been implemented. The results show that the hardness, compressive, and impact resistance of the samples increase with the increase of the reinforcement ratio by Kevlar fibers, nylon fibers, and steel fibers. The rate of wear decreases with the increase of reinforcement ratio. The thermal conductivity decreases with an increase in the reinforcement ratio by Kevlar fibers and nylon fibers while the thermal conductivity increases with an increase in the reinforcement ratio by Kevlar fibers and steel fibers. Compared to the commercial brake pads, high strength, high wear resistance, high impact resistance, high hardness, high compressive strength, low thermal conductivity, and low-cost brake pads have been proposed. [ABSTRACT FROM AUTHOR]

The relationship between the mechanical properties of anisotropic materials and their thermophysical characteristics was experimentally revealed using the example of Scots pine (Pınus sylvéstris L) wood. By measuring the hardness and principal components of the thermal diffusivity tensor, on three sections (normal to the fibers, tangential, and radial) at different wood moisture content, it has been shown that this relationship can be described by linear functions. This makes it possible to carry out an express assessment of the mechanical properties of anisotropic materials, which normally require labor- and material-intensive destructive tests, by means of contactless nondestructive determination of their thermophysical characteristics using the method of dynamic thermography. [ABSTRACT FROM AUTHOR]

The effect of TiB2 additions on the structure, phase composition, and mechanical and tribological properties of materials in the Fe–FKh800 system was studied. The introduction of titanium boride additions activated compaction of the iron-based composites through sintering with participation of the liquid phase that emerged with the formation of low-melting Fe–C–B (Tm ~ 1050°C) and γ-Fe–Fe2B–TiB2 (Tm ~ 1162) eutectics and led to a 50–70°C decrease in the sintering temperature of the compacts. Titanium boride additions between 0.38 to 0.74 wt.% provided 20–25% higher bending strength of the 65 wt.% Fe–35 wt.% FKh800 composite with a slight increase in hardness. Metallographic studies, X-ray diffraction, and electron microprobe analysis of the Fe–35 wt.% FKh800–TiB2 materials showed that titanium boride additions promoted a multiphase, microheterogeneous matrix-reinforced composite, consisting of Kh17 chromium steel, double M7C3 and M3C iron–chromium carbides, and complex Me3(CB) carboborides. The influence of TiB2 additions on the wear resistance of the composites subjected to dry friction against fixed diamond wheel particles and ShKh15 steel was studied. The study showed that the abrasive mass wear (Im) of carbide steels decreased from 36.94 to 14.8 mg/km and their linear wear (Il) decreased from 0.197 to 0.079 mm/km with TiB2 additions increasing from 0.38 to 1.48 wt.%. Titanium boride additions ranging from 0.38 to 2.2 wt.% reduced the mass wear rate from 4.9 to 1.9 mg/km in dry friction of the composite against a ShKh15 steel counterface with 50–55 HRC hardness and decreased the friction coefficient from 0.49 to 0.38. [ABSTRACT FROM AUTHOR]

[Display omitted] • The exceptional hardness of Ti-based materials, 40% plus above the hardness of the base alloy, was achieved without compromise to low specific weight of the material. • The addition of TiC to the alloy Ti-6Al-4 V in an amount of 40% leads to the formation of a discontinuous composite and an increase in the hardness of the material; with a higher particle content, the composite becomes continuous, exhibiting very fragile behavior. • TiC chemically reacts with the matrix alloy and forms a strong interfacial bond with the base alloy. • As a result of high temperature aging of the composite, the hard phases of Ti 2 C and Ti 3 AlC formed in the expense of a relatively soft matrix alloy and further contribute to a significant increase in hardness. Titanium alloy composites, reinforced with a light second phase and made using inexpensive powder metallurgy, attract considerable attention due to the directness of their intentional hardness increase without compromising low weight of materials. In this study the metal-matrix composites (MMC) of Ti-6Al-4V alloy reinforced with light and hard particles of TiC (up to 80%, vol.) were made using blended elemental powder metallurgy of hydrogenated titanium. Post-sintering solution treatment for 45 min. at 880 °C and 1000 °C and water quenching followed by the 5 hrs. aging at 550 °C was used to additionally refine the microstructure and properties of MMC. For the duration of thermal exposure throughout solution treatment and additional aging the matrix and reinforcement phase underwent distinct structural changes that modified the mechanical properties of materials. It has been shown that the used reinforcement presents an exceptional opportunity for hardening of Ti-based composites without compromising their low specific weigh. It can increase the hardness of material by more than 40% due to the ability of TiC to chemically react with the matrix to form a strong interfacial bond and its ability to form hard compounds of Ti 2 C and Ti 3 AlC in the expense of the relatively soft matrix alloy. [ABSTRACT FROM AUTHOR]

The monocrystalline Cu material mechanical properties at the micro and nano scale show complex anisotropy and size effects. However, the anisotropy of scratch hardness and coefficient of friction (COF) in micro-nano scratching monocrystalline Cu has not been well explained. In this paper, we conducted the nano-scratching experiments and corresponding molecular dynamics (MD) simulation under ramp normal force mode along two representative crystal orientations thereby investigating the anisotropy origins of scratch hardness and COF. The research results indicate that, for monocrystalline Cu materials, the scratch hardness and COF are closely related to the atomic slip resistance F slip caused by the activated <1 1 0> {1 1 1} slip systems. [Display omitted] • The transformation of plastic deformation behavior exhibits anisotropy during nano-scratching monocrystalline Cu. • The COF decreases with scratch depth in rubbing stage, but is stable in ploughing and chip stages. • The scratch and lateral hardness both decrease with the scratch depth in rubbing stage, but increase in ploughing and chip stages. • The anisotropy for scratch depth, scratch hardness, and COF can be analyzed by the atomic slip resistance F slip. [ABSTRACT FROM AUTHOR]

The elastic compliance of the instrument (hardness tester) should be taken into account when determining the mechanical properties of materials by means of instrumented indentation with registration of indentation diagrams. The values of Young's modulus of the tested materials significantly depend on the method for evaluating and accounting for elastic compliance. Therefore, the methods should be verified during instrumented indentation of materials with known but very different Young's moduli. Successful experience in evaluating and accounting for elastic compliance of the instrument during the instrumented indentation of materials with a diamond pyramid has already been accumulated to date. This is reflected in the relevant standards. However, this experience cannot be applied to instrumented indentation with a steel ball or hard-metal ball without additional research and experimental verification. We propose a method for evaluating the elastic compliance of the hardness tester using the instrumented diagram of ball indentation based on the Hertz equation in the case of elastic contact of the ball with the plane. It is found that additional elastic deformations of the links of instrument are directly proportional to the indentation load; this dependence is typical of each instrument and the diameter of the ball does not affect it. This dependence allows one to take into account the elastic compliance of the instrument using software when registering and processing diagrams of ball indentation. Experiments to determine Young's modulus and hardness by instrumented ball indentation of various materials (steel, aluminum alloy, magnesium alloy, and titanium alloy) using the known and proposed methods to account for the elastic compliance of the instrument are performed. The main criterion confirming the reliability of the method is the coincidence or proximity of the values ​​of Young's modulus of the same material determined from the diagram of ball indentation and the diagram of tension of the sample. The advantages and disadvantages of the known and proposed methods are described. Practical recommendations for use of these methods are given. [ABSTRACT FROM AUTHOR]

An experimental method for alloy development that allows to systematically scan multicomponent alloy systems is presented using the Cu–Ga–Sn system as an example. Rods with homogeneous concentration distribution of different initial compositions are annealed in a steep temperature gradient with temperatures in the range from above liquidus to below solidus temperature. During resolidification of the initially formed mushy-zone, a continuously varying composition over the length of the rods develops. Further concentration gradients of the alloying elements are generated during subsequent directional solidification. The graded samples are evaluated for different properties. Vickers hardness as a function of composition was measured along the length of the samples to get first information on the mechanical behavior of bulk samples. The melting range of selected compositions (cylindrical disks of 1 mm thickness cut out of the rods) was determined by differential scanning calorimetry and compared to liquidus temperatures extrapolated from the binary systems with a fitting method and the Calphad method. With the procedure introduced here, it is possible to determine several alloy properties over an extended composition range of a multicomponent system with significantly reduced experimental effort. [ABSTRACT FROM AUTHOR]

Uniaxial compressive strength (UCS) and some physical properties of rock materials are very important input parameters used in rock mechanics and engineering. Samples with standard shape and dimension are used in physical and mechanical tests. However, it is difficult to determine the UCS values in case of difficult sample preparation conditions. To overcome this limitation prediction of UCS values from indirect test methods is preferred. One of the most common parameters used to predict the UCS values of rock materials is surface hardness. In this study, the usability of hardness values (HL) of selected ignimbrite, travertine and syenite rocks in the prediction of some physical and mechanical properties were investigated by using the Leeb hardness test which has much lower impact energy than the Schmidt hardness hammer has. Firstly, petrographic and some physical and mechanical properties of the samples were determined and then the HL measurements of all samples were taken. Test results were correlated and correlation equations for dry (γdry) and saturated (γsat) unit weights, apparent porosity (nA), water absorption (wS), sonic wave velocity (VP) were presented and prediction equation of UCS from HL measurements were proposed. In the context of the study, the effect of L/D ratio on HL measurements were also investigated and minimum length to diameter (L/D) ratio of 1.5 on samples with 50 mm in diameter was suggested for consistent HL measurements. [ABSTRACT FROM AUTHOR]

Indentation hardness and brittleness are the important factors to be considered in the study of rock-like materials' mechanical crushing behaviors. The brittleness of rock-like materials is defined as the ratio of uniaxial compressive strength to tensile strength in this paper. In order to investigate the influences of hardness and brittleness on rock-like materials' crushing behaviors, quartz sand and high strength α-hemi-hydrated gypsum were used to prepare rock-like materials with different hardness and brittleness through different mass ratios. The artificial rock-like materials can eliminate the effects of natural rock's weak structure plane on experimental results. The indentation test, Uniaxial compressive test, and Brazilian tensile test were conducted for characterizing the indentation hardness and brittleness of this artificial rock-like materials. The experimental results showed that brittleness increased with the increase of indentation hardness with high correlation coefficient. The confining stress presented a positive impact on the indentation hardness of the rock-like materials. Based on those mechanical properties, the numerical rock models were calculated to study rock crushing behaviors using discrete element method (DEM). A series of rock crushing tests were conducted to investigate the influences of hardness and brittleness of rock-like materials on rock crushing behaviors using a conical pick cutter. The numerical results showed that the normalized specific energy was negatively correlated with indentation hardness index (IHI). The normalized specific energy decreased with the increase of brittleness index (BI) with a high correlation coefficient. This study is beneficial in utilizing IHI and BI to evaluate the mechanical properties, failure patterns, and mechanical crushing efficiency of rock-like materials. [ABSTRACT FROM AUTHOR]

Residual stress can strongly affect the mechanical behaviors of engineering components. In this work, the authors revisit the role of equi-biaxial residual stress in the spherical indentation of elastoplastic solids by the finite element method. When specified residual stress remains in the body, the material hardness and the corresponding indentation depth at the inception of fully plastic deformation are examined for the first time. It is found that the hardness is remarkably dependent on the value of residual stress, especially for materials with a relatively small ratio of modulus to yield strength. Based on the dimensional analysis as well as numerical calculations, explicit expressions of the hardness and the critical indentation depth are generalized with respect to residual stress, indentation modulus, and yield strength. These results can be employed in the analysis and determination of residual stress by spherical indentation tests. [ABSTRACT FROM AUTHOR]

Background: The antibacterial properties are beneficial and desired for dental restorative composite materials. The incorporation of various antimicrobial agents into resin composites may compromise their physical and mechanical properties hence limiting their applications.Objective: The aim of the current study is to evaluate the antibacterial activity and the hardness of microhybrid and flowable resin based composites (RBCs) modified using novel antimicrobial agent chitosan (CS).Methods: The antibacterial activity of microhybrid and flowable RBCs modified with 0, 0.25, 0.5 and 1% w/w chitosan (CS) against Actinomyces viscous bacteria was explored using agar diffusion test and direct contact methods. The hardness of control and experimental RBCs was determined by Vickers hardness (VH) tester.Results: The results revealed that control and experimental flowable and microhybrid RBCs did not demonstrate growth inhibition zone in the lawn growth of Actinomyces viscous. The direct contact test revealed that colony forming unit (CFU) count of Actinomyces viscous was comparable among the experimental and control materials. The flowable RBCs containing 1% CS had significantly higher VH compared to control and other experimental flowable RBC groups. The microhybrid RBCs consisting of 0.50% CS exhibited significantly higher VH compared to experimental microhybrid RBC group containing 1% CS. [ABSTRACT FROM AUTHOR]

Despite advances in mechanical testing at small scales and testing at high strain rates, studies of mechanical behavior of materials remain largely qualitative in the regimes where these two conditions overlap. Here, we present an approach based on microparticle impact indentation to determine material hardness at micron scales and at high strain rates. We employ laser ablation to impact ceramic alumina microparticles (as indenter) onto two model materials, namely copper and iron. We use real time measurements of impact and rebound velocities together with post-impact measurements of indentation volume to determine material hardness at strain rates beyond 106 s−1. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Discontinuous reaction of nano-Al3Sc particles in Al-Sc alloys is investigated in detail, with a goal of developing high-level Sc-containing Al alloys used for aerospace and aeronautics industry. This reaction is of interest because it generally has a deleterious effect on the mechanical property of materials. Requirements for the occurrence of discontinuous precipitation in this Al-Sc alloy are distinct from the prior investigations of other Al-Sc alloys. It was found that discontinuous precipitation of nano-Al3Sc particles occurred widely when the alloys were aged at the intermediate temperature ranges of 300–400∘C, while did not occur at relatively low (250∘C) and high (500∘C) temperatures. The discontinuous precipitation of nano-Al3Sc particles can be suppressed by continuous precipitation through controlling the heat treatment process, which helps to control the microstructures of the Al-Sc alloys. Furthermore, the effects of both continuous precipitation and discontinuous precipitation of nano-Al3Sc particles on the hardness of Al-Sc alloys were discussed. Finally, the morphologies of these nano-Al3Sc particles were also analyzed. [ABSTRACT FROM AUTHOR]

Fully dense β-SiAlON ceramics with excellent mechanical properties and good thermal conductivity were fabricated by two-stage spark plasma sintering (SPS) processes without and with applying pressure respectively, using α-Si 3 N 4 powder and 6 Al 2 O 3 -3 AlN-6 Y 2 O 3 (in wt.%, label with 636), 424 and 422 additives. In the first stage SPS process without pressure, the relative dense β-SiAlON ceramics with interlock microstructures of elongated grains and density of 3.14˜3.18 g cm−3, hardness of 14.00˜14.82 GPa and fracture toughness of 6.00˜6.63 MPa m1/2 were obtained by sintering at about 1600 °C for 20 min. In the second stage SPS process at about 1425 °C for 5 min under pressure of 24 MPa, the fully dese β-SiAlON ceramics with density of 3.22˜3.24 g cm−3, high hardness of 15.68˜15.95 GPa, high fracture toughness of 6.38˜7.03 MPa m1/2 and thermal conductivity of 13.5˜19.6 Wm-1K-1 were obtained. The reaction between the samples and the graphite mold can be avoided in this fabrication method. [ABSTRACT FROM AUTHOR]

Metal matrix composites have been used in recent times to achieve better mechanical properties of materials and welded structures. Aluminium and its alloys provide unique properties which makes it one of the most attractive metallic, economical, versatile material for a broad range of uses in engineering applications, such as aerospace, automobile and mineral processing industries. Against this background, aluminium is not suitable for all engineering applications, and it sometimes requires some degree of reinforcement, particularly in a corrosive environment and/or at elevated temperatures. This study focuses on ascertaining the integrity of MIG welded AA1100 reinforced with copper powder at the weld zone. This was achieved through tensile testing, microhardness profiling and microstructural investigation via the scanning electron microscope, the energy-dispersive spectroscopy and optical microscope, followed by corrosion test by electrochemical polarization method. The results revealed that the addition of copper powder significantly increased the hardness property of the welds, as the welds with copper powder particle reinforcement showed higher hardness values when compared to those without the copper powder particle reinforcement. The highest tensile strength was obtained from the copper reinforced sample. Furhermore, the microstructures revealed finer grain structures for the reinforced samples. The samples with reinforcement also exhibited better corrosion properties. It was therefore concluded that the aluminium (Al) and copper (Cu) metal matrix composite welded via MIG welding produced better mechanical properties, as well as increased corrosion resistance behaviour, and it can definitely be recommended for typical applications. [ABSTRACT FROM AUTHOR]