Showing 7 results for Composite
B. Sadeghi, M. Shamanian, F. Ashrafizadeh, P. Cavaliere,
Volume 4, Issue 2 (1-2019)
Abstract
Solid state joining of powder metallurgy (P/M) processed and sintered by spark plasma sintering through friction stir welding (FSW) was studied. The nanocomposites were prepared via mechanical milling followed by spark plasma sintering. The microstructural and mechanical of the joints were evaluated as a function of the different processing parameters such as rotating and advancing speeds of the tool. The achieved finding revelled that the FSW of the nanocomposites produced by P/M containing bimodal sized Al2O3 reinforcement have a working window are affected by the heat input. The joint evolution revelled that the microstructure and mechanical properties of those was related to the generated heat input during the welding. It is known that dynamic recrystallization (DRX) caused grain size refinement of aluminium into stir zone. Meanwhile, it was revealed that the pinning effect of Al2O3 nanoparticles retarded grain growth of the recrystallized grains caused by dynamic recrystallization (DRX)
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Volume 5, Issue 1 (9-2019)
Abstract
In this paper experimentally, the friction-stir welding of the polypropylene sheets with 40% glass fiber has been investigated. Comparison to other welding methods, the strength of the joint is the most important feature in this process. Many parameters such as tool geometry, rotational speed, linear velocity, and tilt angle are very important as input parameters in this type of welding. Therefore, in the present study, the effect of these parameters on the friction-stir welding of the polypropylene composite sheets have been extracted. Experiments are based on the Taguchi method and the orthogonal L9 array that are suitable for three-level designs. Statistical analysis have been performed as variance (ANOVA) and signal-to-noise ratio. Based on the results, the tool with a screw cone-cylindrical pin has a better apparent quality and higher tensile-shear strength. Results analyze show the rotational speed has the most significant effect on the tensile-shear strength and appearance of the weld. The joint with maximum tensile strength is obtained at rotational speed of 1000 rev/min, welding speed of 20 mm/min and tilt angle of 1 degree.
S.e. Moosavi, M. Movahedi, M. Kazeminezhad,
Volume 8, Issue 1 (8-2022)
Abstract
In this study, thermo-mechanical stability of two-pass constrained groove pressing (CGP) AA1050 sheets towards friction stir welding (FSW) employing hybrid powder (%50vol. micrometric graphite powder+%50vol. α-Al2O3 nanoparticles) was investigated by examining its microstructural evolutions and mechanical properties. FSW was carried out via different process variables in order to reach the highest ultimate mechanical properties of joints. The welding variables employed in this study were single-pass and multi-pass FSW, and different rotation speed to traverse speed ratios (ω/v) were. In order to appraise the powder effect on mechanical properties in the fabricated hybrid metal matrix composite (HMMC), some CGPed sheets were also welded with no powder. Besides optical microscopy and field emission scanning electron microscopy (FESEM) observations, Vickers microhardness and transverse tensile tests were conducted to examine mechanical properties of the weld zone. It was revealed that the effect of graphite powder as a solid lubricant was substantially influenced by the welding variables. More precisely, by employing graphite powder during the FSW, the peak temperature decreased to 224 ℃, while the peak temperature of 489 ℃ was resulted by welding without any powder. Thus, the thermo-mechanical stability of CGPed aluminum and their mechanical properties were enhanced. On the other hand, graphite powder can be responsible for mechanical properties drop due to deteriorating material flow. In addition, different strengthening mechanisms, including grain boundary Zener-pinning and particulate stimulated nucleation (PSN) mechanism, were provided and governed by both powders. However, increasing the ω/v ratio was a practical approach to obtain uniform powder distribution, and consequently, to attain ultimate mechanical properties. Moreover, weld soundness was perceived to be achievable by increasing the number of FSW passes due to eliminating the cavities and improved material flow, resulting in an ultimate tensile strength of 101 MPa, as an optimum efficiency of ~ %80, in three-pass FSW at ω/v=70.
Gh. Khalaj, E. Asadian,
Volume 8, Issue 2 (1-2023)
Abstract
In this paper, the microstructure and mechanical properties of the plain carbon steel-bronze interface of explosive welding and rolling were investigated. Explosive connection was done at two stop distances and with two different thicknesses of explosive material. Rolling of the welded composite was done at both ambient and preheated temperatures of 300 °C and with a constant thickness reduction of 33.3%. The results showed that the wave interface of the steel-bronze connection includes different parts. By rolling, the connection interface was stretched and flattened and the vortex areas were compressed together and in some cases entered the steel field. The steel particles separated from the background along the wave crest and remained as isolated islands in the bronze background. On the other hand, in the areas near the vortex, a part of the bronze flying metal was caught under the wave and was observed as islands separated from the bronze background inside the steel. Porous areas were crushed and compressed as a result of rolling. The rolling force and temperature had partially removed the diffusion barriers and a metal bond had been formed between bronze and steel. During the connection, the voids and shrinkage pores were pressed together due to rolling and the separate borders were close to each other. Explosive joining and cold rolling had increased the hardness in the interface, and hot rolling has led to a decrease in the hardness in the interface. In the hardness test, the welding samples are arranged in the order of the highest impact energy. The effects of welding parameters remain after cold and hot rolling and the hardness rating does not change.
M.h. Nourmohammadi, M. Movahedi, A.h. Kokabi, M. Tamizi,
Volume 9, Issue 1 (5-2023)
Abstract
The miniaturization and compaction trends in electronic equipment and the removal of lead (Pb) element from solder alloys due to environmental considerations have created a great challenge in the field of designing and developing of new solder alloys. Therefore, researchers have recently focused on composite solder alloys using reinforcing particles to improve the reliability of lead-free solders. In this research, SAC0307 solder alloys (99 wt.% Sn, 0.3 wt.% Ag, and 0.7 wt.% Cu) with different percentages of cobalt microparticles were made by the Accumulative Roll Bonding (ARB) method. Then, the effect of the particles on wettability, microstructures and mechanical characteristics of solder alloys was investigated. The lowest contact angle was 23◦in 0.2 wt.% cobalt sample. By adding cobalt to the solder matrix, the size of intermetallic compounds (IMCs), Cu6Sn5 and Ag3Sn, decreased and the percentage of eutectic phases increased. The shape of the interfacial intermetallic compounds changed from scallop to layer shape by adding cobalt, and their average thickness increased about 13-71% in composite samples. The shear strength of solders increased up to 38% by enhancement of cobalt microparticles in the solder alloy containing 0.4 wt.% cobalt; however, shear strength was decreased in the composite solder containing 1 wt.% cobalt due to the agglomeration of microparticles. The shear fracture surfaces showed that the nature of the fracture changed from ductile fracture in the form of elongated dimples to brittle fracture in the form of cleavage with the increase in the percentage of cobalt microparticles. The composite solder alloys containing 0.2-0.4 wt.% Co have the best wettability behavior and tensile shear strength.
Dr Mojtaba Movahedi, Dr Amir Hossein Kokabi, Engineer Mohammad Hadi Nourmohammadi,
Volume 9, Issue 2 (8-2024)
Abstract
Soldering plays a crucial role in the electronics industry, driving the need for constant improvements in physical and mechanical properties and the management of intermetallic compound formation. Research in composite materials aims to achieve a uniform distribution of reinforcing particles within solder matrices to enhance their performance. This study investigates the integration of cobalt microparticles into SAC0307 lead-free soft solder alloy using the accumulative roll bonding (ARB) method. Microstructural analysis confirmed a homogeneous dispersion of cobalt particles within the solder after three ARB passes. Moreover, increasing cobalt content led to a reduction in the size of Cu6Sn5 intermetallic compounds, from 9 µm to 5 µm with 1% cobalt by weight. Examination of β-Sn grain morphology revealed the impact of cobalt particles on recovery and recrystallization kinetics in the solder. Mechanical testing indicated a 20% decrease in interlayer strength within composite solder sheets. Tensile tests showed a 28% increase in strength and a 31% decrease in elongation for composite solder alloy containing 1% cobalt. Differential scanning calorimetry (DSC) results revealed minimal change in the melting temperature of composite solder foil
M. Bozorgmehr, A. Heidari, K. Amini, M. Loh Mousavi, F. Gharavi,
Volume 9, Issue 2 (1-2024)
Abstract
In the present study, friction stir process (FSP) was used to produce AL/ZrO2/ZrSiO4 surface hybrid composite at a fixed rotation speed of 1400 rpm and traverse speeds of 20, 25, 31.5 and 40 mm/min. Therefore, the purpose of the mentioned study is to investigate the effect of tool traverse speed on the microstructure, hardness and wear behavior of the above-mentioned surface hybrid composite and compare it with base material aluminum 5052. Investigations showed that as a result of FSP operation, a fine-grained structure is created, which improves the hardness and wear resistance of the samples compared to the base sample with the presence of ZrO2 and ZrSiO4 particles. Also, the results showed that among the FSP samples, the sample with a speed of 20 mm/min has the highest hardness and wear resistance. The reason for this is that in this sample, due to the lower traverse speed compared to other samples, more heat has been generated, which has led to more suitable particle distribution and more fine particles. Therefore, in the sample with the traverse speed of 20 mm/min, the hardness and wear resistance increases by 27.3% and 68.9% respectively compared to the base material sample. Also, the examination of the wear surfaces of the samples showed that the wear mechanism in the base sample is strong adhesive wear, and as a result of the FSP operation and surface compositing due to the fineness of the grains and the increase in hardness, the wear mechanism has become weak adhesive, so the wear resistance of the sample is FSPs have been improved.
