Hardness Values Of Samples Research Articles

Evaluation of hardness and microstructural features in piston aluminum-silicon alloys after different ageing heat treatments

Contemporarily, aluminum alloy is widely used in automobile industries, especially in engine parts, due to the properties of mentioned alloy like low weight ratio and proper thermal conductivity. In the presented research, twelve different heat treatments procedure were conducted on piston aluminum-silicon alloy to examine the influences of time and temperatures of ageing and quenching processes on the hardness values of the aluminum alloy. In addition, the effect of the aforementioned treatments on the microstructures of aluminum alloy was investigated. Therefore, the optical microscopy investigation was conducted to study the microstructural alternation. Moreover, hardness tests were performed to measure the differences in hardness. In addition, the test results were discussed to choose the optimum heat treatment parameters in order to achieve enhancement in hardness values of samples besides the fewer size of Si and intermetallic phases, which could result in better fatigue performance.

Production of Brake Pad from Epoxy Resin: From Polymerization Concept to the Experiment with Analysis of Mechanical Properties

The purpose of this study was to determine the effect of variations in the use of catalysts on the performance of brake pads. The performance testing is compressive strength and puncture strength. The resin is formed from a mixture of Bisphenol A-epichlorohydrin and cycloaliphatic amine. Based on the results of the study, it was found that brake pads with samples B and C had better performance. The hardness values of samples A, B, and C are 307.4; 331.1; and 334.3 N, respectively. The ratio of resin and catalyst mixture affects the performance of the brake pad. The more catalysts added, the faster the hardening process. It is hoped that this research can be the basis for developing brake pads.

The influence of surface finishing on laser heat treatments of a tool steel

Laser heat treatments (LHT) has received growing attention in the last years because of highly localized precision and manufacturing efficiency related to laser processing of moulds steel. Due of its strong resistance and ability to maintain hardness and strength at high temperatures, AISI P20 steel is one of the most widely used tool steel in the plastics injection mould industry.This work presents an experimental investigation on LHT using P20 mod. steel produced with different surface finishes. After mechanical surface finishing, the diode laser beam with 15 mm width was applied to the P20 specimens at 1060 ⁰C using a feed rate of 8.8 mm·s-1in an air and argon ambient. The influence of different LHT atmosphere conditions and specimen initial surface finishing on characteristics such as final roughness, microhardness and microstructure were comprehensively analyzed. The use of a controlled atmosphere during processing showed an increment in depth and hardness values of samples. Through 3D profilometer, it was possible to determine the samples roughness. Results showed that lower average roughness leads to higher hardness values close to the surface, while higher average roughness lead to a deeper heat-treated zone. Macroscopical analysis revealed the depth and width afftected by LHT. The microhardness results showed an increment from 300 HV to around 750 HV on laser heat-treated zone using a controlled environment. Optical microscopy analysed the microstructural changes into martensite between LHT and non LHT zones for all samples.

Effects of Homogenized Treatment on Microstructure and Mechanical Properties of AlCoCrFeNi2.2 Near-Eutectic High-Entropy Alloy

A 4 kg AlCoCrFeNi2.2 near-eutectic high-entropy alloy ingot was prepared by vacuum medium frequency induction melting. The effects of homogenized treatment on microstructure and mechanical properties of AlCoCrFeNi2.2 were studied. The results showed that all the alloys consisted of the primary FCC phases and eutectic FCC/B2 phases. After homogenized treatment, lots of precipitated phases appeared in the primary phase. The hardness of the as-cast alloy was HV296. The hardness values of samples were decreased and were around HV250 after homogenized treatment. The tensile fracture strength of the as-cast alloy reached 900 MPa, while the elongation was 18%. After homogenized treatment at 900 °C, the alloy showed the most excellent mechanical properties with the fracture strength 880 MPa and the elongation was 29%, respectively. All the alloys displayed a mixture fracture mechanism, including ductile fracture in primary FCC phases and eutectic FCC phases, and brittle quasi-cleavage fracture in eutectic B2 phases. Through a simple heat treatment method, the strength of the alloy was not reduced but the plasticity was greatly enhanced, which was more conducive to the industrial application prospects.

Influence of grains and grain boundaries on hardness values

Many physical and mechanical properties of materials are connected with their microstructure. Recently, technologies to control the microstructure of materials have been well developed in order to more accurately determine the necessary properties. Therefore, the hardness values of samples from technically pure copper with different average grain sizes are determined. The effect of grain boundaries on the hardness values of a sample from a homogeneous copper structure is studied. The grains effect of different structural components and grain boundaries effect on the hardness values of a sample from steel C45 were also investigated. The grains number in the indentation zone was determined to more correctly obtain the hardness of materials with grains of different structural components, for example, perlite and ferrite.

The effect of high-energy methods of forming on the sintering behaviour and properties of Si3N4-based materials

In the study, Si3N4-Al2O3-Y2O3 samples were obtained in two stages. In the first stage, the materials were compacted using different methods: Isostatic Pressing, UHP (Ultra High Pressure), and SC (Shock Compaction). In the second stage, the green body samples obtained were sintered using the free sintering method.Powder mixtures, in wt%, 88 Si3N4 - 6 Al2O3 - 6Y2O3, were based on commercial nano - and micropowders. The parameters of green bodies compaction and sintering processes were optimised using the criteria of highest density, hardness, and Young's modulus. When compared to theoretical density values, the density of green body samples was 58% for the Isostatic Pressing and 82% for UHP and Shock Compaction. The Vickers hardness was measured only for Shock Compacted green body samples and was ~10.8–14 GPa depending on the applied load during the measurement. The largest changes in lattice constant parameters were measured for the Y2O3 phase for the dynamic compaction method (a = 0.02% - 2.26%).The highest relative density was measured for materials which were compacted by UHP method and subsequently free sintered (95%). Young's modulus for UHP and Isostatic green body free sintered samples was 284 GPa and 241 GPa, respectively. The hardness values of samples after free sintering were as follows: 11.7GPa for Isostatic, 14.8 GPa for UHP, and 17.6 GPa for Shock Compaction samples.

Effect of cooling rates on T6 Treatment of B390 Aluminium-Silicon Hypereutectic alloys

This research aimed to study an effect of cooling rates on T6 treatment process of B390 aluminium hypereutectic alloy. B390 casting samples were casted with pouring temperature of 710°C and solidified in three different cooling rates of 33.33, 28.60 and 22.22°C/s, respectively using three metal moulds. After that samples were subjected to T6 treatment: solution treated at 510°C for 30 min and aged at 200°C at various times. However, after ageing, hardness values of as-casted samples reduced with increasing cooling rate. It was found that the specimen cooled with the highest cooling rate exhibited the highest hardness. Peak hardness values of samples cooled with cooling rate of 33.33, 28.60 and 22.22°C/s after ageing obtained from ageing time of 3, 6 and 8 hour, respectively. Furthermore, the result showed that morphology of primary silicon, eutectic silicon and Ali5(Mn, Fe)3Si2 phase presented in the aged specimen cooled with the highest cooling rate exhibited more globular, finer and distributed more evenly compared with the slower cooled samples. It can be concluded that rapid cooling rate increases concentration of a-solid solution resulted in shorter aging time.

Temperature dependence of nickel ion irradiation damage in GH3535 alloy weld metal

Bulk samples of the GH3535 alloy weld metal have been characterized by transmission electron microscopy, X-ray diffraction and nanoindentation to determine their microstructural evolution and mechanical property changes after 8 MeV Ni3+ ions irradiation. The irradiation experiments were carried out at room temperature and 600 °C, and the ion fluences correspond to a calculated peak damage dose of 0.5, 2 and 12 dpa, respectively. TEM results show the formation of solute clusters or dislocation loops with a number density of approximately 5–14 × 1022 m−3 and sizes between 3 and 10 nm at room temperature due to irradiation induced defects and their evolution. Moreover, the peak shift with increasing ion dose observed in XRD diffraction patterns reveals the lattice distortion induced by ion irradiation. As far as the case of high temperature irradiation, several solute clusters with the same size were observed, whereas the number density was smaller than that of the former case. The calculated indentation values in irradiated samples were found to be much higher in comparison to the unirradiated one, indicating the dose dependent effect of irradiation on hardness. However, in the case of the ion irradiation at 600 °C, the hardness value of samples was significantly decreased. The relationship between ion irradiation induced microstructural evolution and the changes in the mechanical properties of this weld metal is discussed in the context of ion dose and irradiation temperature.

Effect of Continuous and Pulsed Currents on Microstructural Evolution of Stainless Steel Joined by TIG Welding

Abstract In this study, AISI 316L series austenitic stainless steel sheets were joined by tungsten inert gas welding method in continuous and pulsed currents. Regarding microstructural investigation and hardness values of weld metal, samples were welded to investigate the effect of current type on grain structures of weld metal. Results showed that samples welded by using pulsed current had considerable different properties compared to the samples welded by using continuous current. While the weld metals of joinings obtained by using continuous current displayed a coarse-grained and columnar structure, weld metals obtained by using pulsed current had a finer-grained structure. It was also found that hardness values of samples, which were welded with continuous and pulsed current, were quite different.

Production of globular microstructure of A356 aluminium alloy by cooling channel and strain induced melt activation processes: morphological and hardness studies

Processing of alloys in the semisolid state has several advantages over conventional casting processes, such as reduction in macrosegregation, porosity and improved mechanical properties. In this study, produced A356 alloy by means of cooling channel and strain induced melt activation (SIMA) processes has been investigated, and their microstructures and hardness were evaluated. At first, in cooling channel process, the grain size is smaller than that in the conventional cast processes and increases with increasing time. Before heat treatment, the microstructure of the SIMA sample is elongated towards the rolling side in contrast to spherical structure in the cooling channel process. The hardness value of sample in the SIMA process is greater than that in the cooling channel process without heat treatment. When the solution annealing was carried out within 2 h, the globular microstructure in both samples was observed. Finally, the grain size and the hardness of samples were determined as 150 μm and 60 HV respectively.

Effect of Rehydration Temperature on Functional Properties, Antioxidant Capacity and Structural Characteristics of Apple (Granny Smith) Slices in Relation to Mass Transfer Kinetics

AbstractApple slices dried at 60C were rehydrated at 20, 40 and 60C to analyze the influence of processing temperature on quality attributes and rehydration kinetics. Diffusion coefficient increased with process temperature from 1.36 to 2.37 × 10−9 m2/s. The Weibull model obtained the best fit quality for the experimental data based on statistical test, chi square. Color was not recovered during rehydration and the results indicated that the use of low temperatures is more adequate. Water‐holding capacity decreased, while rehydration ratio increased with increasing rehydration temperature, indicating structural modifications. Increasing rehydration temperatures led to a reduction in the glass transition temperature and hardness values of samples. The radical‐scavenging activity showed higher antioxidant activity at higher rehydration temperatures rather than at lower temperatures. It was found that rehydration temperature modifies the cell structure and antioxidant capacity of final product.

Pressureless Sintering of Hexagonal Boron Nitride Powders

Pressureless sintering of hexagonal boron nitride (BN) with and without additives was performed using a powder which was previously nitrided at 900oC and then heat treated at 1400oC. Sintering additives were B2O3 (2, 4, 6 wt %) and Y2O3 (2, 4, 6 wt %) and sintering temperatures was 1900oC. Sintered samples were characterized by XRD, SEM, micro hardness, density and mercury porosimeter measurements. Maximum density values of samples were 1.56 g/cm3 without additives and 1.63 g/cm3 with additives. Hardness values of samples were found to improve with the presence of additives.