Hardness Test Results Research Articles

Thermodynamic–kinetic calculations and dilatometric verification of the martensitic and bainitic transformations in 4% medium-Mn steel

AbstractThe present study investigated the theoretical and experimental phase transitions phenomena during continuous cooling and isothermal holding above and below Ms temperature in 4 mass. % Mn medium-Mn steel. The thermodynamic–kinetic calculations were performed using JMatPro software, and phase transformations were recorded using a BÄHR high-resolution DIL805A/D dilatometer. The research covered continuous cooling rates from 60 to 0.05 °C s–1 and isothermal holding temperatures in a range between 420 °C and 230 °C. The issues related to both modelling and dilatometric methodology were discussed. The CCT and TTT diagrams were prepared on the basis of dilatometry and compared with the results of light microscopy and hardness tests. The alloy containing about 4 mass.% Mn and 0.22% Mo exhibited very high hardenability as only continuous cooling with rates lower than 1 °C s–1 allowed the bainitic transformation to be initiated. The bainitic transformation is accelerated after passing the Ms temperature. Both the incubation time and the time needed to complete the transformation were significantly reduced (the incubation time from 100 s to below 1 s and the completion time from over 4000 s to below 1000 s). The obtained microstructures were homogeneous and refined.

Effects of Gd on the microstructure and mechanical properties of GdxCoCrFeNiV0.4 high-entropy alloys

This study investigated the microstructure and mechanical properties of GdxCoCrFeNiV0.4 alloys. Various techniques such as XRD, SEM, EBSD, and TEM were utilized, alongside hardness and compression tests at room temperature. The findings revealed that the high-entropy alloy without Gd element exhibited a single face-centered cubic (FCC) phase. Upon the introduction of Gd element, the phase composition shifted to FCC + hexagonal structure (HS) phases, and further addition of Gd resulted in the presence of FCC + HS + body-centered cubic (BCC) phases. Additionally, the inclusion of Gd element led to the precipitation of Gd-rich particles within the alloy. The Vickers hardness test results revealed a significant increase in alloy hardness as the Gd content rose, from 177.5 HV for Gd0 to 848.4 HV for Gd0.4. This suggests that the presence of the HS phase and BCC phase notably influences alloy hardness. Furthermore, compressive test outcomes demonstrated that the alloy's yield strength rose from 173.74 MPa for Gd0 to 1356.17 MPa for Gd0.3 with increasing Gd content. However, the excessive addition of Gd elements results in significant precipitation of V and Cr elements, leading to grain coarsening, adversely affecting its mechanical properties. The high strength of Gd-containing high-entropy alloys can be attributed to various strengthening mechanisms, such as solid solution strengthening, the presence of the HS phase, the precipitation of a small number of Gd-rich particles, and the grain refinement caused by the addition of Gd.

Evaluation of the Mechanical Properties of PLA Material Used For 3D Printing Solar E-Hub Component

The advent of additive manufacturing (AM) technologies revolutionized design and production processes across various industries. In renewable energy, AM enabled new possibilities for optimizing solar e-hub (solar energy harvesting module) configurations, enhancing efficiency and performance. This study examined critical considerations such as material selection, durability, and cost-effectiveness in solar hub development. This fast-prototyping technique was controlled by computer-aided design (CAD) software like CREO Parametric 7.0 and Creality Slicer 4.8. Experimental results indicated that PLA (Polylactic acid) materials exhibited superior strength, with an impact energy of 4.8 Joules. The deformation study revealed that the maximum load of 22 MPa aligned with the ultimate tensile strength of PLA, and a hardness test result of 83.1 HRF featured its exemplary hardness properties. These findings advanced the understanding of using AM to investigate mechanical behaviours of PLA materials and optimize solar e-hub configurations for portable device applications, promoting sustainable energy solutions and the adoption of renewable energy technologies. In addition, the successful implementation of this approach will enable the renewable energy sectors to minimize the carbon foot-prints towards helping the global net-zero emissions by aligning the circular economy approach.

Development and Mechanical Characterization of a CoCr-Based Multiple-Principal-Element Alloy

The development and mechanical characterization of a CoCr-based multiple-principal-element alloy are presented and discussed. In this work, ab initio synthesis and mechanical characterization of the (CoCr)100-x(TiNbZr)x (x = 0, 48 60, 78 and 100 % at) alloy family is reported; these include the calculation of thermodynamic parameters such as mixing entropy (ΔSmix), mixing enthalpy (ΔHmix), valence electron concentration (VEC), Ω and δ factors. The alloys were melted in a vacuum arc furnace; rod-shaped ingots were produced by suction casting. Phase characterization was carried out using optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction. Mechanical characterization was done via compressive and hardness tests. Calculation of phase diagrams was performed using Thermo-Calc © software. Yang’s model for phase prediction predicted a BCC solid solution. Multicomponent simulations predicted a more complex structure, with Laves (C14 and C15), Theta (C16), BCC 1, 2 and 3, Mu, CoTi2, CoZr3 and TiZr2. Contrary to Yang’s model for phase prediction, the experimentally obtained phases agreed reasonability well with those obtained by the Thermo-Calc simulation. The suction cast process cooling rate suppressed the nucleation and growth of some equilibrium phases, i.e., Laves (C14) or BCC 3 for the (CoCr)100-x(TiNbZr)x (x = 0, 48 60, 78 and 100 % at) alloys. The hardness test results were strongly related to the intermetallic phase formation, showing an increase of 331% with the x = 78 alloy. The BCC 1 phase played an important role in the yield strength behavior, as the (CoCr)22(TiNbZr)78 alloy, with a considerable amount of this phase, showed the highest yield strength value.

Tensile test and hardness test on FCAW-GS welding results of AB/EH36Z35 material in 3G downhill position

Welding is a crucial aspect of the modern construction industry as it allows for efficient and reliable joining of metals. The purpose of this research is to evaluate the FCAW-GS welding process on AB/EH36Z35 material in the 3G downhill position. Additionally, the study aims to analyze the tensile and hardness test results of the welding. The research utilized the FCAW-GS welding method, with tensile testing conducted by the AWS D1.1/D1.1 M:2015 standard. Hardness testing was performed using the Vickers hardness test method with a test load of 10 Kgf, following the ASTM E92:2017 standard. The results of the tensile tests demonstrate that both specimens achieved high tensile strength. Furthermore, the hardness testing indicated no significant changes in material hardness in the HAZ and Line 3 areas. Consequently, this study's findings adhere to the quality standards outlined by AWS D1.1/D1.1M:2015 and ASTM E92:2017, making them a valuable reference for industrial welding processes

Weldability and Mechanical Properties of Pure Copper Foils Welded by Blue Diode Laser.

The need to manufacture components out of copper is significantly increasing, particularly in the solar technology, semiconductor, and electric vehicle sectors. In the past few decades, infrared laser (IR) and green laser (GL) have been the primary technologies used to address this demand, especially for small or thin components. However, with the increased demand for energy saving, alternative joint techniques such as blue diode laser (BDL) are being actively explored. In this paper, bead-on-plate welding experiments on 0.2 mm thick pure copper samples employing a BDL are presented. Two sets of parameters were carefully selected in this investigation, namely Cu-1: Power (P) = 200 W; Speed (s) = 1 mm/s; and angle = 0°, and Cu-2: P = 200 W; s = 5 mm/s; and angle = 10°. The results from both sets of parameters produced defect-free full penetration welds. Hardness test results indicated relatively softer weld zones compared with the base metal. Tensile test samples fractured in the weld zones. Overall, the samples welded with Cu-1 parameters showed better mechanical properties, such as strength and elongation, than those welded with the Cu-2 parameters. The tensile strength and elongation obtained from Cu-1 were marginally lower than those of the unwelded pure copper. The outcomes from this research provide an alternative welding technique that is able to produce reliable, strong, and precise joints, particularly for small and thin components, which can be very challenging to produce.

The effects of austenitization temperature on the microstructural characteristics and mechanical properties of Cr–Mo–V hot work tool steels with different nitrogen contents

Two kinds of Cr–Mo–V hot work tool steels with different nitrogen contents, i.e. High-N steel and Low-N steel, were heat treated to investigate phase transformation phenomena in the present study. Microstructure characterization revealed the existence of numerous particles within both steels, which could be further categorized as the following three types: large- (>150 nm), medium- (50–100 nm), and tiny-sized (<10 nm) particles. It should be noted that numerous nanometer-sized V (C, N) precipitates were randomly dispersed within the tempered martensite matrix. Fewer V (C, N) precipitates were found in the High-N steel than in the Low-N steel, which was consistent with the hardness test results. Microstructure analysis (EBSD) also revealed that the matrixes of both hot work tool steels consisted of primarily tempered martensite matrix with extremely low amounts of retained austenite, indicating that the retained austenite could be eliminated effectively by suitable tempering treatment, even in the High-N steel. On the other hand, from the impact toughness and hardness tests, it was found that a higher nitrogen content was beneficial in achieving higher impact toughness, especially at higher austenitizing temperatures, which could be ascribed to the smaller austenite grains in the High-N steel.

Heat-balance control of friction rolling additive manufacturing based on combination of plasma preheating and instant water cooling

Friction rolling additive manufacturing (FRAM) is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head. The thermal efficiency of FRAM, which depends only on friction to generate heat, is low, and the thermal-accumulation effect of the deposition process must be addressed. An FRAM heat-balance-control method that combines plasma-arc preheating and instant water cooling (PC-FRAM) is devised in this study, and a temperature field featuring rapidly increasing and decreasing temperature is constructed around the tool head. Additionally, 2195-T87 Al-Li alloy is used as the feed material, and the effects of heating and cooling rates on the microstructure and mechanical properties are investigated. The results show that water cooling significantly improves heat accumulation during the deposition process. The cooling rate increases by 11.7 times, and the high-temperature residence time decreases by more than 50 %. The grain size of the PC-FRAM sample is the smallest, i.e., 3.77±1.03 µm, its dislocation density is the highest, and the number density of precipitates is the highest, the size of precipitates is the smallest, which shows the best precipitation-strengthening effect. The hardness test results are consistent with the precipitation distribution. The ultimate tensile strength, yield strength and elongation of the PC-FRAM samples are the highest (351±15.6 MPa, 251.3 ± 15.8 MPa and 16.25 %±1.25 %, respectively) among the samples investigated. The preheating and water-cooling-assisted deposition simultaneously increases the tensile strength and elongation of the deposited samples. The combination of preheating and instant cooling improves the deposition efficiency of FRAM and weakens the thermal-softening effect.

The dynamic recrystallization microstructure characteristics and the effects on static recrystallization and mechanical properties of Al–Mg–Si alloy

It is essential to clarify the dynamic recrystallization microstructure characteristics of age-hardened aluminum alloys and the effects on the static recrystallization microstructure and aging mechanical properties, with the aim of selecting the deformation conditions reasonably. This work investigated the evolution of the hot deformation and solid solution microstructures and aging mechanical properties of Al–Mg–Si alloy with deformation temperatures of 400–550 °C, strain rates of 0.01–10 s−1, and true strains of 0.2–0.8. Research has shown that it is advantageous for the DDRX and CDRX mechanisms to annihilate and rearrange dislocations simultaneously for forming deformation microstructure with uniform grain size at higher deformation temperatures and lower strain rates (such as 500 °C, 0.01 s−1). Additionally, the lower dislocation density in deformation microstructure facilitated the inhibition of static recrystallization during subsequent solid solution treatment, whereas lower deformation temperature and higher strain rate conditions should result in a greater degree of static recrystallization and reduce the uniformity of the solid solution microstructure. Hardness test results demonstrated that the deformation temperature of 480–520 °C and strain rate of 0.03–0.2 s−1 were the appropriate conditions for Al–Mg–Si alloy to attain finer and uniform grains and superior properties after solid solution treatment. The extruded samples within the above conditions (500 °C, 0.032 s−1) exhibited higher UTS and YS after solid solution and aging treatment, reaching 444 ± 2 MPa and 426 ± 4 MPa, respectively.

Effect of copper addition on mechanical properties and microstructures of LM25 cast alloys

The use of aluminum alloys in automobiles is expanding, and the potential for additional increases is significant. Further growth will be determined by improvements in material qualities for existing applications or the discovery of new applications. Alloy A-356 (LM25) is commonly employed for high-quality alloy wheel rims in various motor vehicles, constituting 40% of global car usage. This study introduces 0.2% Cu into the Al–Si–Mg alloy system to enhance the mechanical properties. The alloy blend is cast into a metal mold, subjected to a 4-h cure at 540 °C, quenched with water, and precipitation hardened for 12 h at 1800 °C. Optical and scanning electron microscopes are utilized to analyze the alkali microstructure. The mechanical properties of alloyed and unalloyed castings, including hardness and tensile test results, are examined in untreated and heat-treated states. Fracture surfaces of tensile specimens are scrutinized. Intermetallic compounds formed during solidification are studied using scanning electron microscopy and x-ray diffraction analysis. The tensile strength under unalloyed (LM25) and alloyed (LM25 + 0.2 wt. % Cu) conditions before and after heat treatment [(72, 165.4 and 88.3, 237.1) and (78, 179.6 and 98, 252.9, respectively)] shows a significant increase.

THE EFFECT OF FRICTION TIME VARIATIONS ON DISSIMILAR MATERIAL WELDING JOINTS AND HARDNESS VALUE USING A BAR-PLATE ROTARY FRICTION WELDING MACHINE

This research aims to determine the effect of variations in friction time on welded joints of dissimilar materials and hardness values. The method used is the friction welding method. One of the materials widely used in industrial products is mild steel AISI 1037 and stainless steel 304. One of the tools used is a bar-plate upright rotary friction welding machine. The parameters used are friction time variations of 25-35 seconds, 55-65 seconds and 115-125 seconds with a rotational speed of 2,484 rpm, friction pressure of 0.5 MPa, forging pressure of 0.7 MPa, forging time of 10 seconds. From the results of the connection several tests were carried out, namely liquid penetrant , macro observation and hardness test. The results of liquid penetrant testing and macro observations showed no influence on the welding area. The results of hardness testing have an influence on the hardness value. In the interface area, the friction time variation of 120 seconds has the highest hardness value of 161.67 VHN. The lowest hardness value in the interface area with a friction time variation of 30 seconds is 152.90 VHN. Where the longer the friction time, the hardness value also increases.

Scratch resistance and in-vitro biocompatibility of plasma-sprayed baghdadite coatings reinforced with carbon nanotubes

Hydroxyapatite (HA, Ca10(PO4)6(OH)2) coatings, commonly used for metallic implants, have limitations such as excessive brittleness, low fracture toughness, inadequate wear resistance, and slow osseointegration properties. In contrast, baghdadite (BAG, Ca3ZrSi2O9), a calcium zirconium silicate-based bioceramic, exhibits outstanding biological properties, to promote cell proliferation and differentiation of human osteoblasts along with adequate mechanical strength. In this study, plasma-sprayed HA, BAG, and carbon nanotubes (CNT, 1 wt%, and 2 wt%) reinforced BAG coatings are deposited on titanium (Ti) substrate to enhance its mechanical as well as biological properties. The microhardness values of CNT-reinforced BAG coatings increase due to a decrease in porosity and the retention of CNT inside the BAG matrix. Progressive loading scratch tests are performed, revealing a reduction in wear volume loss from 15.051 mm3 to 12.574 mm3 and scratch rate from 43.262 mm3N−1 m−1 to 36.172 mm3N−1 m−1 with the addition of 2 wt% CNT in BAG coatings. The scratch hardness test results demonstrated that introducing CNT into BAG coating significantly enhances its performance, showing a remarkable 38.7 % improvement. In-vitro cell culture studies indicate excellent cell adhesion, growth, and proliferation of MC3T3-E1 osteoblast cells on the surfaces of the CNT-reinforced BAG coatings.

PENGARUH PENAMBAHAN PROSES INOKULASI TERHADAP STRUKTUR MIKRO DAN KEKERASAN PRODUK COR DENGAN MATERIAL FC 250

The inoculation process in metal casting is needed to make grey cast iron or nodular cast iron. Inoculation aims to increase the number of freezing nuclei and promotes the formation of a homogeneous microstructure. This research aims to determine the effect of the inoculation addition process on the microstructure and hardness of PP products with FC-250 material. The changes made include changes to the inoculation process and changes to the chemical composition of the induction furnace. Changes in the inoculation process include changing the inoculation process which was initially only carried out on ladles with an inoculation material weight of 0.5 kg to 2 processes, namely on ladles with an additional weight of 0.8 kg of inoculation material and an inoculation process on crucible (kowi) with an additional material weight of 0.4 kg. The results of the metallography test after the additional inoculation process showed that the pearlite and ferrite graphite spread evenly and fell into Type-A graphite. The hardness test results show that the effect of adding inoculation changes the level of hardness so that it complies with ASTM 40 specifications/standards, namely 180 – 302 HB. The hardness value after the addition of the inoculation process was 190 HB.

Effect of cobalt addition on thermal cycling behaviour of Ti50Ni(50−x)cox shape memory alloys

The effect of adding Co on the temperature cycling behaviour of ternary Ti50Ni(50−x)Cox (x = 1, 2, 3) alloys was experimentally studied in this work. The alloys were prepared using a vacuum induction furnace, followed by subjecting them to homogenization, hot-rolling and annealing processes. The alloys were subjected to thermal cycling experiments in a nitrogen atmosphere by differential scanning calorimetry under stress-free conditions between their transformation temperatures. The results indicate that adding Co to NiTi alloys decreases their transition temperatures, improves the thermal cycling stability apart from suppressing the R-phase formation on cooling during cycling. The changes are due to the addition of Co introducing solid solution strengthening and generation of dislocations during cyclic phase transformations, as confirmed by the hardness test results and TEM micrographs, respectively.

Effect of Solution Concentration and Anodizing Coating Time on Hardness and Thickness Coating Of 7075-O Aluminum Alloy

One of the materials used in ship propellers is aluminum alloy. The advantages of aluminum are that it is easy to cast and relatively resistant to corrosion. This research aims to determine the effect of heat treatment and the effect of variations in the concentration of H2SO4 and immersion time in optimal of the anodizing process on the hardness value of 7075-O aluminum alloy (as-cast aluminum alloy). The method used is solution heat treatment at a temperature of 490ºC with a holding time of 6 hours, quenching using water or oil, with artificial aging at a temperature of 120ºC with a holding time of 24 hours. In the anodizing process, a sulfuric acid solution with various concentrations of 10%, 15%, and 20% with variations in immersion time of 10, 15, and 20 minutes. The results of vickers hardness test on heat-treated specimens with water quenching accompanied by artificial aging is 137.54 HV, it is increased by 47.44%. While the results of the vickers hardness test after anodizing is 213.09 HV, it is increased by 128.42%. Where the optimum hardness value was achieved at a concentration of 15% H2SO4 and an immersion time of 20 minutes. The coating thickness is equal to 25.79 µm.

Explosion Cracking Analysis of Sulfur Resistance Induction Heat Bend Pipe

The explosion cracking reason on induction heat bend pipe was analyzed through macroscopic analysis, chemical composition analysis, mechanical properties testing, metallographic analysis, scanning electron microscopy and XRD. The results showed that the chemical composition, tensile test, Vickers hardness results of the straight section of the bent pipe met the requirements of the technical specifications, and the metallographic structure of the straight section of the bent pipe was pearlite and ferrite. The Charpy impact test in the neutral zone of the bend section had a low shear fracture ratio, and the Vickers hardness test results were on the high side. The metallographic structure was granular bainite. The fracture surface of the failed bent pipe exhibited brittle fracture characteristics on the macro level. The metallographic analysis and hardness test results of the crack source area showed that the fracture surface had typical intergranular propagation characteristics and high hardness values. Energy spectrum analysis of the crack source area revealed the presence of S element. The XRD analysis of the product on the inner wall of the pipe contained sulfides. The comprehensive results indicated that the failed bend pipe undergoes stress corrosion and initiates corrosion cracks on the surface under the combined action of operating pressure, additional bending stress, residual stress, etc. in a sulfide corrosive medium, the cracks continued to propagate along the grain boundaries and ultimately caused the bend pipe to explode.

Multi-pass friction hardening treatment of Ti6Al4V alloy toward improved tribological properties

Abstract Multi-pass surface friction hardening was employed to modify the microstructure and enhance the tribology characteristics of the Ti6Al4V alloy. The process was performed by reciprocated sliding a flat-head WC-Co cylindrical pin tool on the alloy surface under different applied loads of 350, 700, 1050, and 1400 N. The sliding was conducted at different speeds of 45, 90, 180, 360, 720, and 900 mm min−1 for 30, 60, 90, 120, and 150 passes, respectively. Based on the hardness test and microstructural characterization results, the applied load of 1050 N, the sliding speed of 900 mm min−1, and the pass number of 60 (900-60 sample) were chosen as the optimum economic process parameters for the subsequent experiments. Performing surface friction hardening under the optimized conditions increased the surface hardness of the annealed sample from 350 HV1 to 564 HV1 showing an increase of about 60 %. Surface friction hardening was also found to substantially improve the tribology characteristics of the Ti6Al4V alloy. According to the obtained results, under the applied loads of 1 and 6 N, the wear rate and the average friction coefficient of the 900-60 sample were lower than those of the annealed one by 58 and 83 %, and 33 and 50 %, respectively.

“Evaluation of microstructure and mechanical properties of Al6005 MMCs reinforced with B4C via stir casting route and optimisation through ANOVA DOE technique”

ABSTRACT MMCs are used in variety of applications due to their distinctive characteristics, including superior stiffness, wear resistance and service temperatures, brake rotor, cylinder liners, automobile drive shaft, and connecting rod. In the present studies, Al6005-B4C composites were developed using the gravity die-casting technique to investigate mechanical properties (hardness and tensile strength). Later, microstructural characterisation is conducted using an optical microscope. Also, fracture surface analysis was carried out using SEM. The optical micrographs revealed that Al6005 alloy has a fine-grained, uniform microstructure and Al6005-B4C MMCs. Also, SEM fractographs of Al6005 displayed ductile fracture due to more dimples, and Al6005-B4C MMCs exhibited brittle fracture. From the hardness and tensile test results, it is noticed that the addition of B4C enhances the mechanical properties of Al6005-B4C MMCs. Overall, it is observed that the hardness and strength value steadily increase up to 4% B4C as the reinforcement percentage grows and then somewhat decrease when the B4C addition is improved to 6%. The accumulation of particles in the matrix may be the cause. The regression analysis results confirm that the coefficient of determination was achieved with an 86% of confidence interval, and the P-values is less than 0.05 for all the combination considered.

Possibilities to modify the properties of the AW7075 aluminum alloy for the automotive industry

The paper investigated the AW7075 aluminum alloy that is used in the automotive industry. The alloy is widely used, among others, in the production of heads and engine blocks. The possibility of obtaining various properties of the alloy (material states) by appropriate heat treatment (saturation and aging) was demonstrated. The results of strength, hardness, abrasion and fracture toughness tests of the alloy in the T73, RRA and HTPP aging treatments, in comparison with the T651 reference state, are presented. The need to select the appropriate parameters of heat treatment in relation to the load conditions of the structural element, especially in elements with notches, was indicated. Depending on the state of the AW7075 alloy, the results prove the wide and diverse possibilities of its use, and should be used consciously in the design and production processes of modern automotive drivetrain components.

Development and Analysis of Biomaterial Based on Calcium Sulfate Hemihydrate and Epoxy Resin

Bone deformation and the degradation of the joint are one of the most common problems faced around the world, especially after the age of 50. Materials like Allograft and Polymethyl-Methacrylate (PMMA) are used in traditional orthotics and prosthetics, and for bone grafting/filling procedures, however, these materials can be expensive. This research proposes, the fabrication of a novel material by utilizing Calcium-Sulfate Hemihydrate (CaSO4. 1/2H2O), and epoxy resin, which can be used as a cost-effective orthotic and prosthetic material. The materials are already used as bone adhesives and bone grafts, hence, are compatible and non-toxic. The fabricated composite material possesses physical properties closest to the natural human bone and is also hydrophilic. Samples with different ratios of the constituents were fabricated and tested for their hardness, compression, and contact angle values using a Hardness tester, PASCO compression tester, and Image J software. The hardness test results indicate that sample 1 has the hardness value i.e., 29.5 ± 2.50 HV in contrast the hardness value of a human bone is found to be 33.3