•Nanosecond laser ablation characteristics were compared between composite and homogeneous materials.•Interface effect and dispersed distribution of particles contribute to composite’s machining ...feasibility.•Thresholds for matrix and reinforcement were different from that of homogeneous materials.•Surface roughness for homogeneous materials showed stepwise but exponential increase for composite.•Oxidization and accumulation of oxides on SiC's ablated surface deteriorates its processing by nanosecond laser.
This study performed comparative experiments on ablation behavior and surface quality obtained by nanosecond laser processing of silicon carbide (SiC) particle-reinforced 2024 aluminum alloy matrix composite (SiCp/AA2024), homogeneous SiC, and 2024 aluminum alloy. A nanosecond laser with a pulse fluence range of 0.68 ∼ 6.83 J/cm2 was used at irradiate samples of these materials, which were then ablated by various numbers of scanning passes (1 to 10) at a fluence of 6.83 J/cm2. The material melting could be achieved only for homogeneous AA2024. The ablation depth for SiC exceeded that of the composite, and the former could be ablated with a pulse fluence exceeding 3.42 J/cm2. The composite ablation threshold was higher than 4.10 J/cm2. Due to the thermal transition between the reinforcement and matrix, the melting threshold of the composite’s AA2024 matrix was lower than that of homogeneous AA2024 alloy. Moreover, the ablation threshold of SiC particles exceeded that of homogeneous SiC. The ablated surface roughness for the homogeneous material showed a sudden increase because of melting or oxidization, while that of the composite exhibited a gradual increase. For homogeneous SiC, oxidization accompanied by ablation and the accumulation of oxidization products on the surface deteriorated the laser pulse processing quality, especially in multipass scanning. In contrast, the dispersed distribution of SiC particles in the composite improved the composite’s machining feasibility.
The present work investigates Rotary Friction Welding (RFW) of AA2024 similar joints, where the welding operations were carried out using an adapted device to a column-drilling machine (SUPEMEC ...J320). This work aims to determine the optimal RFW parameters from an experimental study based on mechanical tests and microscopic observations of weld joints. The best compromise, which offers the highest tensile strength value (499 MPa) corresponds to the joint obtained by using a rotational speed of 2000 rpm, a friction pressure of 12 MPa, and a forging pressure of 17 MPa. The EDX results indicate the presence of the intermetallic compounds (IMCs) in each zone of the weld joints, with varying sizes and a random distribution. This study focuses also on the microscopic analyses of the interface of weld joints and the fracture surfaces that indicates a dominant ductile fracture mode.
Abstract
In this investigation, AA2024 alloy was welded by tungsten inert gas welding. Access the influence of pitting corrosion on TIG weld; the joints were heat-treated after welding with different ...techniques. Moreover, the corrosion test was carried out with 3.5% NaCl solution under different pH values such as pH:5, pH:7, and pH: 12. From the experimental results, the joint treated with solution treatment with pH: 7 showed high corrosion resistance than its counterparts.
In this study, AA2024-(X vol.% SiO2np + Y vol.% TiO2np) (X, Y = 0.5, 1.0) hybrid nanocomposites were fabricated the via stir casting process and their structural and mechanical properties were ...examined. The results indicated that the grain sizes of the hybrid nanocomposites were reduced by the addition of nanoparticles into the matrix alloy. The analysis of mechanical properties also showed an increase of about 30, 36 and 7% in the hardness, tensile strength, and tensile yield strength, respectively. In the larger amounts of nanoparticles, scanning electron microscopy studies showed that there were more quantities of nanoparticles agglomerates in the structure, reducing the mechanical properties of the nanocomposite with 1 vol.% of SiO2 nanoparticles, as compared to the nanocomposite with 0.5 vol.% of SiO2 nanoparticles. The main strengthening mechanisms were estimated to be Hall-Petch strengthening, Orowan strengthening, and the coefficient of thermal expansion mismatch and elastic modulus mismatch between the reinforcements and the metal matrix. There was also some evidence showing some of the singular and agglomerated nanoparticles in the matrix on the fractured surfaces of the nanocomposites.
The effects of Ag on the microstructure, mechanical properties, and electrical conductivity of AA2024 aluminum alloy coating were investigated. It was fabricated by friction surfacing as an additive ...manufacturing process. To carry out this investigation, Ag was added by 5.3, 10.6, and 16.0 wt.% to an AA2024 consumable rod by inserting holes in it. It was found that due to the strengthening by solid solution and the formation of precipitates and intermetallic containing Ag, the driving force for grain growth is reduced and consequently the grain size of the coating is decreased. After artificial aging heat treatment, the electrical conductivities of the coatings containing 0 and 16.0 wt.% Ag are increased by 4.15% (IACS) and decreased by 2.15% (IACS), respectively. While considering a linear relationship, it can be proposed that for a 1 wt.% Ag increase, the strength and hardness of the coating will be increased by 1.8% and 1.0%, respectively. It was established that the effect of Al6(Cu,Ag)Mg4 precipitate formation on strengthening is greater than that of Ag-rich intermetallic.
In this study, corrosion properties of AA2024 aluminum alloy matrix composite materials reinforced with Al2O3 in three different ratios were investigated. After mixing the aluminum alloy matrix ...material powders and the reinforcement material powders at 10%, 20% and 30% Al2O3 ratios homogeneously, composite materials were produced by keeping them in an axial mold under 50 MPa pressure and 550 °C for 1 hour by hot pressing method. According to the corrosion test results, the corrosion resistance of the composite materials containing 20% and 30% Al2O3 reinforcement was very close to each other. The corrosion rates of these two samples were determined to be lower than the sample containing 10% Al2O3 reinforcement.
Given the nonuse of TiO2 nanoparticles as the reinforcement of AA2024 alloy in fabricating composites by ex-situ casting methods, it was decided to process the AA2024−xTiO2(np) (x=0, 0.5 and 1 vol.%) ...nanocomposites by employing the stir casting method. The structural properties of the produced samples were then investigated by optical microscopy and scanning electron microscopy; their mechanical properties were also addressed by hardness and tensile tests. The results showed that adding 1 vol.% TiO2 nanoparticles reduced the grain size and dendrite arm spacing by about 66% and 31%, respectively. Also, hardness, ultimate tensile strength, yield strength, and elongation of AA2024− 1vol.%TiO2(np) composite were increased by about 25%, 28%, 4% and 163%, respectively, as compared to those of the monolithic component. The agglomerations of nanoparticles in the structure of nanocomposites were found to be a factor weakening the strength against the strengthening mechanisms. Some agglomerations of nanoparticles in the matrix were detected on the fractured surfaces of the tension test specimens.
We reported an investigation of the influence of B4C contents on microstructure and mechanical behavior of AA2024/B4C composites. In our work, nearly full-dense AA2024/B4C composites with various B4C ...contents were fabricated by plasma activated sintering. Our results indicated that the B4C particles exhibit a network distribution in the composites with 7.5 wt % and 17.5 wt % B4C particles, adjacent particles of monolithic alloy are continuous or interpenetrated among the B4C particles in the powder boundary region. However, for the composite with 27.5 wt % B4C particles, the adjacent particles of monolithic alloy are interdicted due to the formation of severe aggregations. Improving the content of B4C particles will increase the hardness and compressive yield strength of the composites. However, the yield strength of the composite failed to be further improved when adding too much B4C because of the agglomeration of the reinforcements. With the content of 17.5 wt % B4C, the Vickers hardness and compressive yield strength of the consolidated composites were 203.2 HV and 564 MPa, respectively. In addition, quantitative analysis of the strengthening mechanisms revealed that increasing the weight fraction of the B4C particles results in larger augment in dislocation strengthening and load-bearing strengthening.
•AA2024/B4C composites were fabricated by plasma activated sintering.•The high compressive strength of AA2024/B4C composites was measured.•Quantitative analysis of strengthening mechanism of the composites was discussed.
In this study, the effect of various process control agents (PCAs), including Methanol, Ethanol, Stearic acid, and Zinc stearate, on the properties of AA2024-B4C composite powders during the milling ...was investigated. Through comprehensive analyses encompassing morphological imaging, EDS assessments, particle size measurements, hardness evaluations, apparent density calculations, XRD, TGA examinations, and subsequent hardness and tensile strength tests on bulk samples derived from these composite powders, intriguing findings emerged. The employment of methanol as a PCA manifested an 85% reduction in the average particle size, decreasing from 220 μm (initial powder size) to 35 μm after 5 h of milling. In contrast, the use of zinc stearate resulted in a more conservative 21% reduction, with an average particle size of 174 μm. Notably, methanol usage resulted in superior hardness (144.5 HB) and tensile strength (262 MPa) compared to zinc stearate, which yielded lower values (107.8 HB and 204.5 MPa).
Display omitted
•AA2024-B4C composite powders were milled using different PCA types for the first time.•Liquid (Methanol and Ethanol) and solid (Stearic acid and Zinc stearate) PCA types were used.•The effect of PCAs on the morphological, physical, thermal and mechanical properties of composite powders was investigated.•The most effective PCA in the examination of all morphological, physical and mechanical properties is methanol.
PDF
