نشریه مهندسی متالورژی و مواد
سال سی و چهارم شماره 2 (تابستان 1402)

In this research, the tensile properties of polypropylene/natural rubber composite reinforced with perlite nanoparticles were studied. The mathematical modeling of analysis of variance using the surface response method was used to confirm the experimental results. The role of each materials variable and the weight percentage of natural rubber and pearlite nanoparticles on the tensile properties of the nanocomposite samples was investigated. It was observed that the values of tensile strength and elongation at break by increasing the amount of natural rubber from 20 wt.% to 40 wt.% and the constant amount of perlite nanoparticles at 3 wt.%, decreased by 14.68% (from 8.92 to 7.61 MPa) and increased by 72% (from 51.05% to 87.81%), respectively. The results obtained from the parameters optimization showed that the maximum values of tensile strength and elongation at break are 8.332 MPa and 74.38% was obtained in the sample with 3.268 wt.% of natural rubber and 4.046 wt.% of perlite nanoparticles, respectively. The scanning electron microscope images showed the positive effect of adding nanoparticles to the polypropylene/natural rubber composite due to the reduction in the size of the elastomeric phase and as a result, the increase in the tensile strength of the composite samples. Also, the proper dispersion of nanoparticles in the polymer matrix phase occurred in the sample with 5 wt.% of perlite nanoparticles and 30 wt.% of natural rubber. However, with increasing the weight percentages of nanoparticles up to 9 wt.%, some agglomerations of pearlite nanoparticles were observed in the thermoplastic phase.

Co-doped ZnO thin films (CAZO) were prepared by DC magnetron sputtering. The structural, electrical and optical properties of thin films were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), optical spectrophotometer and Raderford Back Scattering (RBS) techniques. The CAZO thin films with different thicknesses had an amorphous structure. The particle distribution diagram showed that with the increase in thickness, the size of nanoparticles reached from 10 nm to 25 nm and the range of particle size changes also increased. The bandgap energy decreased with the increase in thickness, but the Urbach energy increased. The CAZO thin film with a thickness of 50 nm had lower activation energy and a higher concentration of donor carriers, but with increasing thickness, the concentration of this type of carriers (n-type) decreases, because the conduction in the layers decreases and the resistance in CAZO thin films with a thickness of 150 nm has increased.

Titanium alloy grade Ti–8Al-1Mo-1V (Ti-811) has been widely applied for many applications such as aerospace, automotive and military industries due to their high specific strength, low density, and excellent corrosion resistance. In this work, cylindrical specimens with a height of 12 mm and diameter of 8 mm were machined for the hot compression tests. the flow stress behavior of near-α alloy Ti-811 was investigated by hot compression testing under conditions of varying temperature (between 950, 975, 1000, 1025, 1050 and 1075 ◦C), strain rates ( 0.001, 0.01, 0.1 and 1s-1) and true strain up to 0. 6. The stress–strain curves of Ti-811 alloy revealed that the continuous flow softening occurs, anyway, the flow softening amount show greater flow softening in the two phase region as compared to the single phase region. Mechanical testing and optical microscopy analyses indicate that dynamic recrystallization occurred, for single-phase β microstructure. However; a broad variety of microstructure formation mechanisms including allotropic phase transformations, platelet kinking and globularization occurred for two- phase α + β region.

In the present study, metallurgical tests including quantometry, X-ray diffraction analysis, and microstructural investigations with optical and scanning electron microscopes were emplyed to investigate the effect of composition and microstructure on the mechanical properties of the cast ingots and extruded profiles manufactured in Balouch Aluminum Company. Results showed that the concentrations of Fe, Si and Cu were higher than the standard composition of 6063 Al alloy. Optical micrographs sowed that pores were mainly observed at the center of ingots. According to XRD analysis, in addition to FCC phase, an iron aluminide intermettalic phase was identified in the structure of ingots. The formation of intermetallic phase was confirmed by energy dispersive analysis attached to the scanning electron microscope. Tensile test results illustrated that the presence of pores and the distribution of intermetallic phases declined the strength and formability of the alloy. The ultimate tensile strengths at the surface and center of the ingot were 103 and 71MPa, respectively. Fractography of samples indicated that the presence of pores and the intermetallic phase led to a combination of ductile and brittle fracture durin tensile test.

In this study, the effects of zirconia and titania particles on the abrasion behavior and hardness of Ni-P and Ni-P-ZrO2 coatings on ST37 substrate by electroless technique were investigated. For this purpose, Ni-P-ZrO2 composite coatings were precipitated at five different concentrations of 1 to 5 g/l of reinforcing particle, and then, after examining the best specimen in terms of hardness, the effect of TiO2 particles in five concentrations of 1 to 5 g/l was studied as a booster alongside ZrO2 particles. The coatings were heat-treated for 1 hour at 400 °C. Resistance to wear and friction coefficient of coatings were evaluated by pin on disk test. The surface and cross-section of coatings, as well as the abrasion lines, were examined using a scanning electron microscope (SEM) equipped with an EDS test. The X-ray diffraction (XRD) test was also used to examine the coprecipitation of the reinforcing particles and phase transformations in the coatings. The results showed that the heat treatment resulted in increased hardness. Also, increasing the concentration of ZrO2 particles in the bath from 1 g/l to 3 g/l resulted in improved hardness of the coating and the use of TiO2 up to 2 g/l along with ZrO2 resulted in improved Ni-P-ZrO2 coating hardness, so that increasing TiO2 concentration to 2 g/l resulted in an increase in the hardness from 702 HV0.1 in the Ni-P-ZrO2 (3 g/l) sample to 813 HV0.1 in the Ni-P-ZrO2 (3 g/l) -TiO2 (2 g/l) sample.

The effects of rare earth Er additions on the microstructure and tensile properties of cast Al–3Mg–2.5Cu aluminum alloy have been investigated. The results show that by adding 1 wt.% Er grain refiner in the aluminum cast alloy, the grains can be refined to a fine degree. The microstructures and fracture surfaces of cast aluminum alloy samples were examined by scaning electron microscopy (SEM). In addition, the rare earth Er modified the eutectic structure from a coarse plate-like and acicular structure to a fine branched and fibrous one. The tensile properties were improved by the addition of rare earth Er, and good ultimate tensile strength (310 MPa) was obtained when the rare earth Er addition was 1 wt.%. Furthermore, fractographic examinations revealed that refined pore and spheroidized α-Al dendrite were responsible for the high ultimate tensile strength. Adding of 1 wt.% rare earth Er make about 38% enhancement in tensile strength compared to that of unreinforced aluminum alloy.