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Showing 25 results for Strength
Investigating the Effect of Equal Channel Angular Extrusion on Microstructure and Mechanical Properties of the 60-40 Two-phase Brass Alloy
S. E. Mousavi, M. Meratian, A. Rezaeian,
Volume 36, Issue 4 (3-2018)
Abstract
Equal Channel Angular Pressing (ECAP) is currently one of the most popular methods for fabricating Ultra-Fine Grained (UFG) materials. In this study, mechanical properties of the 60-40 two phase brass processed were evaluated by ECAP. The samples were repeatedly ECAP-ed to strains as high as 2 at a temperature of 350 ◦C using route C. The microstructure of the samples showed that small grains were formed in the boundaries which indicates the occurrence of recrystallization in different passes. Observation of slip trace in the microstructure of the samples showed that even in such alloy with a low-stacking fault energy, dislocations slip trigger the deformation. Investigation of mechanical properties showed that with increasing the number of passes, tensile strength, microhardness and ducility improved at the same time.
 

Synthesis and Characterization of Mechanical Behavior and Thermal Shock Resistance of Macro-Porous SiC Solar Absorber
A. R. Parvanian, H. R. Salimijazi, M. H. Fathi,
Volume 38, Issue 4 (1-2020)
Abstract
The concentrated solar power (CSP) is one of the renewable energy sources in which solar irradiation heat energy will be used in a steam turbine to generate electrical grid. Solar radiation is absorbed by a solar receiver reactor on the surface of a porous solar absorber. In this survey, synthesis and mechanical/thermal characterization of micro-porous silicon carbide (SiC) absorber to be used in solar reactor is carried out. SiC foams were synthesized and categorized based on three different pore sizes i.e. 5, 12 and 75 ppi. Mechanical behavior and thermal shock resistance of porous foams in the working temperature range for absorber (25-1200 °C) were evaluated. Results revealed that the specific compressive strength (σc/ρ) of foams increase exponentially by a decrement in the porosity percentage and the average pore size. Moreover, for foams with smaller pore size, a considerable decrease in mechanical strength due to thermal shock was observed. This could be due to increase in the number of struts per unit volume i.e. more weak struts to withstand the mechanical loading. So, porous foams with coarser pore sizes were distinguished to be more capable of tolerating thermal shock while serving as solar absorbers.

Investigating the Joining of Ni3Al Intermetallic Compound, using Transient Liquid Phase (TLP) Method with Cu Interlayer
M. Soltani Samani, A. Bahrami, F. Karimzadeh,
Volume 38, Issue 4 (1-2020)
Abstract
In this study, joining of Ni3Al intermetallic compounds using the transient liquid phase (TLP) process with Cu interlayer was investigated. The binding process was carried out in a vacuum furnace at a temperature of 1050 °C for different times of 30, 60, 90 and 120 minutes. The effect of time variation on microstructure and mechanical properties of the joint zone was investigated. The EDS analysis results of the joints proved formation of the athermally solidified zone (ASZ), isothermally solidified zone (ISZ) and diffusion affected zone (DAZ) at different times. After 90 minutes, brittle eutectic phases still exist in the joint line. However, by increasing the process time to 120 minutes, a copper-rich solid solution was formed in the joint line. Maximum hardness was attained in DAZ region and due to formation of more brittle compounds. By increasing the process time to 90 min, the hardness in the joint center-line increased. After 120 min, the hardness in the joint center-line decreased to about 224 HV. Maximum shear strength was achieved to be about 60 MPa at a process time of 30 minutes and due to formation of Ni-rich matrix at the joint. With increasing time to 90 min, the shear strength decreased to about 34 MPa. After 120 minutes and due to formation of copper-rich solid solution as well as disappearance of eutectic compounds, shear strength again increased to about 44 MPa. Investigation of fracture surfaces showed that until 90 minutes, fracture mode was mainly brittle whereas by increasing time to 120 minutes, a more ductile fracture occurred.

Effect of Temperature and Time on the Joint Properties of AISI420 Steel to SAF2507 Steel Produced by Transient Liquid Phase Process
M. Jafari, M. Rafiei, H. Mostaan,
Volume 39, Issue 2 (8-2020)
Abstract
In this research, the effect of temperature and time on the properties of AISI420/SAF2507 dissimilar joint produced by transient liquid phase bonding process was investigated. A BNi-2 interlayer with 25 μm thickness was inserted between two dissimilar steel samples. The bonding process was performed at 1050 oC and 1100 oC for different bonding times. The microstructures of the joints were studied using optical microscope, scanning electron microscope and energy dispersive X-ray spectroscopy. Microhardness and tensile shear strength of bonded samples were investigated. Isothermal solidification was completed for the joints bonded at 1050 oC and 1100 oC for 45 min and 30 min, respectively. ASZ and ISZ areas of the bonding zone at the bonding temperature of 1050 oC indicated the highest (520 HV) and the lowest (300 HV) microhardness values, respectively. Sample bonded at 1050 oC for 1 min indicated the lowest tensile strength (196 MPa) and sample bonded at 1100 oC for 60 min indicated the highest tensile strength (517 MPa).

Synthesis of Al7075/TiB2-Al2O3 In-Situ Hybrid Composite by Stir Casting Method
B. Sharifian, G. H. Borhani, E. Mohammad Sharifi,
Volume 41, Issue 2 (11-2022)
Abstract
In this study, mechanically milled (MM) Al-24TiO2-20B2O3 powder in molten Al7075 matrix was used in order to fabricate in-situ TiB2 and Al2O3 reinforcements in Al7075 matrix. Differential thermal analysis (DTA) examination was adopted to find reaction temperature between milled Al, TiO2, and B2O3 powders. X-Ray Diffraction (XRD) patterns showed the existence of TiB2 and Al2O3 peaks (750 °C at Ar atmosphere) in MM powder. Scanning Electron Microscopy (SEM) results revealed the uniform distribution of TiO2 and B2O3 particles in the aluminum matrix. 6 wt.% MM powder was added to molten Al7075 at 750 °C. The molten Al7075/TiB2-Al2O3 composite was poured in copper mold. The stir casted composites were hot extruded at 465 °C with extrusion ratio of 6:1 and ram speed of 5 mm/s. The microstructures (optical microscopy and TEM) and mechanical properties (hardness and tensile testing) of samples were evaluated. TEM results showed that in-situ TiB2 nanoparticles were formed. The tensile strength of extruded Al7075/TiB2-Al2O3 composite was reached the value of 496 MPa. This result was around four times greater than that of the as cast Al7075 alloy.

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