In this study, the effect of equal-channel angular pressing process on the mechanical properties of a dual-phase 60–40 brass alloy was investigated. The samples were processed up to six passes ...through the route C at 350 °C. Optical microscopy and tensile tests were employed for the investigation of microstructure and mechanical properties. Increasing the number of passes caused the increase in both strength and elongation. It was observed that by the sixth pass, the elongation at the room temperature was increased up to 85% and the tensile strength was obtained to be 1.5 times more than that of the annealed sample. Micro-hardness test results also showed that the hardness was increased to 100% for the specimen processed to the sixth pass. Since the process temperature was less than
T
m
/2, due to the low stacking-fault energy of this alloy, continuous recrystallization was expected to occur in the microstructure. However, it was observed that recrystallized grains were formed near the grain boundaries for the first pass. To determine the type of the recrystallization, primary specimens were rolled up to 95% and then annealed at different temperatures. The obtained samples microstructures confirmed that both static and dynamic recrystallizations occurring in the primary passes were the reason for the bimodal structure formation in these passes. To study the fracture surfaces, scanning electron microscope was employed. The results showed the ductile fracture in all the specimens. By increasing the passes, this type of fracture was expanded.
In this research, two phase brass alloy as one of the most important copper base alloys was processed by equal channel angular pressing as a severe plastic deformation process. The process was ...performed at 350 °C in route C up to 6 passes. Microstructural study showed that discontinuous recrystallization initiated at the first pass in the alpha phase. Recrystallization fraction enhanced by increasing the amount of strain and grain size decreased to less than one micron after the fifth and sixth passes. Investigations of beta phase showed that recrystallization in this phase began after the third pass and enhanced with increasing the number of passes. Separate investigation of macro-texture for two phases of alpha and beta well proved the different deformation behavior in both phases. Furthermore, it was observed that Goss, Rotated Goss and Rotated cube texture components were dominant for alpha phase, and cube and {112} texture components were dominant for beta phase that had a direct impact on the results of mechanical properties. Micro-hardness and tensile test were used in order to study the mechanical properties of the alloy. The results indicated a massive increase in micro-hardness and tensile strength after the process. Also, total elongation in the processed specimens was higher than expectations in a manner that after the final pass, it reached more than 80% which was only approximately 35% less than the primary anneal specimen.
Ni–Al bronze (NAB) was coated with Stellite-6 through gas-fueled high-velocity oxyfuel spraying. Scanning electron microscopy observations revealed the accumulation of Tungsten-rich particles at the ...substrate-coating interface. These areas played an important role in the enhancement of the mechanical properties of the coating. The coating hardness increased 5 times with respect to the substrate one. The tribological analysis of the coating was done via pin on disk method. Results showed that abrasive wear is the dominant mechanism for the substrate; on the contrary, delamination is the dominant wear mechanism in the coating. The corrosion performance of bare and coated alloy was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. The corrosion potential of coated sample increases in comparison with bare alloy, corrosion current density decreases from 3.91 to 1.82 µA/cm
2
and the capacitive resistance is much larger.
Graphic abstract
Precipitation strengthening of body-center cubic (A2) alloys via ordered B2 nanoprecipitates is expected to achieve a desirable combination of strength and ductility. In this work, the A2/B2 ...configuration is manipulated by adjusting Fe content in medium-entropy AlCrFexNi (x = 0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0) alloys fabricated via arc-melting for improved mechanical properties and wear resistance. As Fe content increases, the fraction of A2 phase increases, and A2 nanoprecipitates in the B2 matrix change to a weave-like A2/B2 structure. Continuously increasing Fe content leads to a mixture of BMAP (B2 matrix with A2 precipitates) and AMBP (A2 matrix with B2 precipitates), and finally to a complete AMBP structure. The yield strength decreases and fracture strain increases with increasing Fe content except x = 0. The alloy of x = 0 displays slightly higher hardness because of its relatively brittle B2 matrix. Cracks tend to propagate along A2/B2 interfaces. AMBP structure exhibits greater toughness than the BMAP structure. The alloy of x = 0 displays the second-greatest wear volume loss due to its relatively brittle B2 matrix. When Fe is added, the wear volume loss decreases considerably but shows a trend of an upward parabola with respect to the Fe content. After achieving the highest volume loss at x = 1.5 with a mixture of AMBP and BMAP, the volume loss decreases again. A completely uniform AMBP structure at x = 3.0 shows the least volume loss.
In this study, the surface nanocomposite containing graphene oxide was produced on the Al5083 alloy surface, using Friction Stir Processing (FSP) in liquid cooled condition, in order to improve the ...microstructure and mechanical properties. For this purpose, FSP was carried out up to 3 passes on a base alloy with and without reinforcing particles. Microstructural features and mechanical properties of the obtained surface nanocomposite, FSPed Al 5083 and base alloy were investigated. In order to study the microstructure, Electron Back Scatter Diffraction (EBSD) was used. It was revealed that the grain size nanocomposite was about 1 m after the process. This was while the grain size of the specimen with no reinforcement, after the process was 6 1.1 m and the size of the base alloy was 23 2.3 m. The substantial effect of the reinforcing particles in preventing the grains growth in the nanocomposite specimen was the main reason for this difference. Study of mechanical properties of base alloy, FSPed specimen, and the nanocomposite revealed that the simultaneous use of cooling environment and performing the process, increased the hardness of stir zone compared to the base alloy. This increase was raised in the presence of graphene oxide particles and reached to 123 1.7 HV. It was also observed that the nanocomposite had a better tensile behavior than the base alloy and the FSPed specimen. SEM images of the fracture surfaces indicated the existence of dimples and voids at the surface of the base alloy specimens and the FSPed specimen which showed their ductile fracture, but at the nanocomposite surface, in addition to the ductile fracture, a brittle fracture was occurred.
The effect of diamond-like carbon (DLC) coating (fabricated by cathodic arc deposition) on mechanical properties, tribological behavior and corrosion performance of the Ni−Al−bronze (NAB) alloy was ...investigated. Nano-hardness and pin-on-plate test showed that DLC coating had a greater hardness compared with NAB alloy. Besides, the decrease in friction coefficient from 0.2 for NAB substrate to 0.13 for the DLC-coated sample was observed. Potentiodynamic polarization and EIS results showed that the corrosion current density decreased from 2.5 μA/cm2 for bare NAB alloy to 0.14 μA/cm2 for DLC-coated sample in 3.5 wt.% NaCl solution. Moreover, the charge transfer resistance at the substrate–electrolyte interface increased from 3.3 kΩ·cm2 for NAB alloy to 120.8 kΩ·cm2 for DLC-coated alloy, which indicated an increase in corrosion resistance due to the DLC coating.
The purpose of this study was to determine the prevalence of bovine leukemia virus (BLV) in Khorasan Razavi and Khorasan Shomali provinces which are the main provinces located in the northeast of ...Iran. Total number of 429 blood samples were collected from industrial dairy herds. The samples were categorized based on province, age (2-3, 4-6, and 7-10 years old), calving (≤ 2, 3-5, and > 5) and herd size (≤ 100, 101-250, and > 250) and examined by indirect ELISA. The results of this study showed that 109 (25.4%) out of 429 serum samples were BLV seropositive. The BLV prevalence among cattle of dairy herds of Khorasan Razavi and Khorasan Shomali provinces were 29.8% and 1.5%, respectively. The results showed that the number of seropositive animals was increased significantly with the age (p < 0.05). The infection rate in animals 2-3, 4-6 and 7-10 years old were 12.1%, 26.7% and 45.6%, respectively. It was shown that BLV prevalence according to calving ≤ 2, 3-5 and > 5 was 15.5%, 33.0% and 42.9%, respectively, with a significant difference between calving ≤ 2 and > 5 (p < 0.001). The prevalence of BLV among herd size of ≤ 100, 101-250 and > 250 was 19.7%, 14.3% and 42.1%, respectively, which was significantly higher in herds with more than 250 cattle (p < 0.05). This study revealed that BLV infection in dairy herds of northeast of Iran was influenced by geographical location (province), age, calving and herd size.
Precipitation strengthening of body-center cubic (A2) alloys via ordered B2 nanoprecipitates is expected to achieve a desirable combination of strength and ductility. In this work, the A2/B2 ...configuration is manipulated by adjusting Fe content in medium-entropy AlCrFesub.xNi (x = 0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0) alloys fabricated via arc-melting for improved mechanical properties and wear resistance. As Fe content increases, the fraction of A2 phase increases, and A2 nanoprecipitates in the B2 matrix change to a weave-like A2/B2 structure. Continuously increasing Fe content leads to a mixture of BMAP (B2 matrix with A2 precipitates) and AMBP (A2 matrix with B2 precipitates), and finally to a complete AMBP structure. The yield strength decreases and fracture strain increases with increasing Fe content except x = 0. The alloy of x = 0 displays slightly higher hardness because of its relatively brittle B2 matrix. Cracks tend to propagate along A2/B2 interfaces. AMBP structure exhibits greater toughness than the BMAP structure. The alloy of x = 0 displays the second-greatest wear volume loss due to its relatively brittle B2 matrix. When Fe is added, the wear volume loss decreases considerably but shows a trend of an upward parabola with respect to the Fe content. After achieving the highest volume loss at x = 1.5 with a mixture of AMBP and BMAP, the volume loss decreases again. A completely uniform AMBP structure at x = 3.0 shows the least volume loss.
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