| 1. |
- Guo, Rui'E, et al.
(författare)
-
The Effect of Eco-Friendly Inhibitors on the Corrosion Properties of Concrete Reinforcement in Harsh Environments
- 2022
-
Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 15:14
-
Tidskriftsartikel (refereegranskat)abstract
- In the present research, the synergistic effect of Arabic and guar gum inhibitors on the corrosion efficiency of concrete reinforcement was investigated. Thus, eight types of Arabic and guar gum combinations with 100, 250, 500, 750, and 1000 ppm were added to the steel reinforcement for 1, 7, 28, 48, and 72 days. The corrosion behavior of the samples was investigated by the electrochemical impedance (EIS) test. Water transmissibility, electrical resistivity, and compressive strength of concrete were also studied. The results showed that adding inhibitors generally increased the compressive strength of concrete. It was also found that water transmissibility was reduced by the addition of inhibitors. The electrical resistivity of the samples increased slightly with increasing time up to 72 days. EIS and Tafel results have demonstrated that Arabic and guar gums are effective inhibitors for reinforced concrete structures. Furthermore, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) utilized to analyze the samples indicated that inhibitor grain size was enhanced by enhancing the concentration of the inhibitor combination, showing that the guar and Arabic inhibitor combinations were properly absorbed on the reinforcement surface. Results showed that a sample with 250 ppm Arabic gum and 250 ppm guar gum having a properly distributed inhibitor combination on the reinforcement surface creates a desirable cathode current.
|
|
| 2. |
- Kheradmand, Azam Beigi, et al.
(författare)
-
Tribological Characterization of Reinforced Fe Matrix Composites with Hybrid Reinforcement of C, Cu, and SiC Particulates
- 2022
-
Ingår i: Crystals. - : MDPI AG. - 2073-4352. ; 12:5, s. 598-
-
Tidskriftsartikel (refereegranskat)abstract
- This study sought to design and characterize the Fe, SiC, Cu, and C metal matrix composite (MMC) with optimum SiC content to obtain sufficiently good wear resistance performance. For this purpose, Fe, Cu, graphite, and BaSO4 (Fe-11Cu-6.5G-6BaSO(4)) with 2, 4, 6, 8, and 10 wt.% SiC powders (in the range of 45-150 um) were milled for the fabrication of the composite. Then, sintering was performed by hot press at 1000 degrees C under 400 MPa in a controlled atmosphere furnace. Wear, and coefficient of friction (COF) were then carried out on the samples under 20 N and 700 rpm for 1000 m. SEM micrographs and EDS analysis were also utilized for the wear mechanism. According to the studies of worn surfaces, it was found that at the beginning of the sliding distance, the abrasion mechanism was predominant, and by increasing the sliding distance of plastic deformation, adhesive wear and oxidation were activated. It was concluded that the weight loss decreases less and has a constant and more appropriate COF due to an increase in SiC to an optimal value, i.e., 10%. In addition, wear resistance and hardness increase due to increased SiC. Therefore, due to the low wear rate and suitable coefficient of friction, composite Fe-11Cu-10SiC-6.5G-6BaSO(4) can be introduced as brake pad applications.
|
|
| 3. |
- Mousavi, Seyed Fereidon, et al.
(författare)
-
Thermal cycles behavior and microstructure of AZ31/SiC composite prepared by stir casting
- 2022
-
Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- In the present work, the effect of thermal cycles on the physical and thermal properties of AZ31 alloy and AZ31/5wt%SiC and AZ31/10wt%SiC composites was investigated. Samples were prepared using the stir casting method and then subjected to precipitation hardening. Thermal cycles were done for as-cast and aged samples with V-shaped notch under 300, 600, and 900 heating and cooling cycles at 150 and 350 degrees C. The crack length (CL) was evaluated using optical microscope (OM), scanning electron microscope (SEM), and energy-dispersive scanning electron (EDS) analysis. Also, density, porosity, thermal expansion coefficient of the samples were evaluated. X-ray diffraction (XRD) analysis was employed to assess the phases present in the material. The results demonstrated that by increasing the number of thermal cycles up to 600 at 150 degrees C and 350 degrees C, the porosity and density of the as-cast and aged AZ31 alloy decreased and increased, respectively; however, the density and open porosity were remained constant for the composite samples. The crack's length enlarged with increasing the thermal cycles from 300 to 600 mu m at 150 degrees C and 300 to 900 mu m at 350 degrees C. It was found that the reinforcement and precipitates prevented the rapid growth of the crack in the magnesium matrix. All in All, composite and the aged samples demonstrated better thermal fatigue resistance compared with that of the unreinforced alloy and as-cast samples, respectively.
|
|
| 4. |
- Wang, Yang-Yang, et al.
(författare)
-
Microstructural Evolution during Accelerated Tensile Creep Test of ZK60/SiCp Composite after KoBo Extrusion
- 2022
-
Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 15:18
-
Tidskriftsartikel (refereegranskat)abstract
- In the current study, the creep properties of magnesium alloy reinforced with SiC particles were investigated. For this purpose, ZK60/SiCp composite was produced by the stir casting method following the KoBo extrusion and precipitation hardening processes. The creep tests were performed at 150 degrees C under 10-110 MPa. The results showed that the stress exponent (n) and the average true activation energy (Q) was changed at high stresses, was found with increasing stress, the creep mechanism changing from grain boundary sliding to dislocation climb. The results of microstructure characterization after the creep test showed that at low stresses, the dynamic recrystallization resulting from twinning induced the GBS mechanism. However, at high stresses, with increasing diffusion rates, conditions are provided for dynamic precipitation and the dislocation climb of the dominant creep mechanism. Examination of the fracture surfaces and the surrounding areas showed that the cavity nucleation in the ternary boundary and surrounding precipitation was the main cause of damage. The evaluation of the samples texture after creep showed that the unreinforced alloy showed a moderately strong fiber texture along the angle of phi(1) = 0-90 degrees, which was tilted about phi = 10 degrees. A new strong texture component was observed at (90 degrees, 5 degrees, 0 degrees) for the composite sample, which crept due to minor splitting of the basal pole by similar to 5 degrees toward RD.
|
|
| 5. |
- Zuo, Zhaoyang, et al.
(författare)
-
Microstructure, Fractography, and Mechanical Properties of Hardox 500 Steel TIG-Welded Joints by Using Different Filler Weld Wires
- 2022
-
Ingår i: Materials. - : MDPI. - 1996-1944. ; 15:22
-
Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the effects of three low-carbon steel filler metals consisting of ferritic and austenitic phases on the weld joints of the tungsten inert gas (TIG) welding of Hardox 500 steel. The correlation between the microstructure and mechanical properties of the weld joints was investigated. For this purpose, macro and microstructure were examined, and then microhardness, tensile, impact, and fracture toughness tests were carried out to analyze the mechanical properties of joints. The results of optical microscopy (OM) images showed that the weld zones (WZ) of all three welds were composed of different ferritic morphologies, including allotriomorphic ferrite, Widmanstätten ferrite, and acicular ferrite, whereas the morphology of the heat-affected zone (HAZ) showed the various microstructures containing mostly ferrite and pearlite phases. Further, based on mechanical tests, the second filler with ferritic microstructure represented better elongation, yield strength, ultimate tensile strength, impact toughness, and fracture toughness due to having a higher amount of acicular ferrite phase compared to the weld joints concerning the other fillers consisting of austenitic and ferritic-austenitic. However, scanning electron microscopy (SEM) images on the fracture surfaces of the tensile test showed a ductile-type fracture with a large number of deep and shallow voids while on the fracture surfaces resulting from the Charpy impact tests and both ductile and cleavage modes of fracture took place, indicating the initiation and propagation of cracks, respectively. The presence of acicular ferrite as a soft phase that impedes the dislocation pile-up brings about the ductile mode of fracture while inclusions may cause stress concentration, thus producing cleavage surfaces.
|
|
