Papers by Keyword: Mechanical Property

Abstract: Microstructure and mechanical properties in QT-Treated 9Ni steel were investigated. The detail microstructures were observed by optical microscope (OM) and transmission electron microscope (TEM). The volume fraction of austenite was estimated by XRD. Tensile test at room temperature and Charpy-V-Notch (CVN) impact test at -196°C were carried out. The results showed that the microstructure of QT-treated 9%Ni steel was composed of tempered martensite and reversed austenite. The brittle cementite was absorbed gradually by the increasing reversed austenite as the tempering temperature increased. The optimum tempering temperature range was 560°C~580°C. The reversed austenite could improve the cryogenic toughness of 9Ni steel through the combination of the scavenging effect and the TRIP effect.

Abstract: The butt weld of 15CrMoR with the thickness of 55mm has been manufactured with the bonding methods of manual electric arc welding (SMAW) and submerged-arc welding (SAW), and the mechanical properties of which have been tested with the corresponding test, and the metallurgical structures have been analyzed with microscope. Conclusions have been obtained as following: the metallurgical structure of multi-layer butt weld is much more complicated than the monolayer ones; only the last weld layer has the obvious zones of weld zone, heat-affected zone (HAZ) and fusion area; the weld zone and the fusion area will be heat treated with the next layers weld finished; the mechanical property of the multi-layer butt weld is much better than the monolayer weld.

Abstract: The butt weld of Q345R with the thickness of 40mm has been manufactured with the submerged-arc welding (SAW). The mechanical properties of the weld seam have been tested and the metallurgical structures have been analyzed. Conclusions have been obtained as follows: the metallurgical structure of multi-layer butt weld is much more complicated than the monolayer ones; only the last weld layer has the obvious zones of weld zone, heat-affected zone (HAZ) and fusion area; the weld zone and the fusion area will be heat treated with the next layers weld finished; the mechanical property of the multi-layer butt weld is much better than the monolayer weld determined by the corresponding organization.

Abstract: Blending PPO and POE-g-MAH assisted by SCCO2 has been investigated. The in-line rheological behavior of PPO and POE-g-MAH containing SCCO2 were studied with the slit die and self made in line rheological testing system. The effect of SCCO2 on the reduction of shear viscosity of PPO is more obvious than that of POE-g-MAH. The shear viscosity of PPO reduced 36.7% with addition 4wt% CO2. Morphology of blends was inspected by SEM. The sizes of POE-g-MAH disperse phase decreased with the contents of CO2 increasing. As a result, the impact strength of blend is improved from 43.5KJ/m2 to 100.9KJ/m2 due to introduce 4wt% SCCO2 for PPO/POE-g-MAH (85/15) blends.

Abstract: Based on artificial neural network (ANN), a mechanical properties prediction model for automatic welding is built. The input parameters of the model consist of the chemical elements and the diameter of the welding material and the outputs is the mechanical properties, i.e. yield strength, tensile strength and elongation. The ANNs model is established by Visual C++ based on improved back-propagation (BP) arithmetic with momentum coefficients, in which the sample data used are from automatic welding materials for X70 pipeline steel. The influence of chemical compositions, such as C, S, P, Si, Mn, Cu, Ti and Ni on the mechanical properties of welding materials are analyzed. The results show that the influence of metallic elements is significantly greater than the nonmetallic. For nonmetallic elements, not all the value of mechanical properties decreases with the increase of the content. The influence of C is critical, followed by P and S. For metallic elements, the influence of different elements on mechanical properties, such as the yield strength, the tensile strength, the elongation and the average Charpy impact toughness, is difference.

Abstract: 7A60 aluminum alloy was treated under different retrogression time, and the micro-structure, mechanical properties and stress corrosion behaviors were observed and determined by optical microscopy, transmission electron microscopy and slow strain rate tester. The results shown that with the increasing of retrogression time the precipitates within the grains were gradually grown up, and the precipitates along the grain boundaries were changed from small and closely spaced into coarse and widely spaced ones. The elongation and toughness ratio of 7A60 alloy increased obviously with the retrogression time, whereas the tensile strength and hardness of 7A60 alloy decreased. The optimum retrogression time is about 60min, under which 7A60 alloy has a best combination of tensile strength, ductility and stress corrosion resistance.

Abstract: The objectives of this paper are study effect of dispersion of hard alumina (Al₂O₃) microparticles-filled polypropylene (PP) composites. Al₂O₃/PP composites containing 1.0 – 5.0 wt% of the Al₂O₃ were prepared through melt blending and specimens were produced through injection moulding technique. This study sets out to evaluate the influence of adding hard particles to the mechanical properties of the composite obtained while keeping the processing characteristics of the material. The material was characterized as thermo gravimetric analysis (TGA) and scanning electron microscopy (SEM). The tensile tests performed showed an increase in the mechanical properties of the composite (modulus and elongation (%)) by increasing the Al₂O₃ content. The SEM images show a change in the fracture behavior between pure PP (brittle fracture) and Al₂O₃/PP composites containing 3.0 and 5.0 wt % (ductile fracture). The research aims to establish a new parameter for the development of products and advances in the application of this material.

Abstract: Silicon carbide (SiC) has been employed in many different fields such as ballistic armor, thermal coating, high performance mirror substrate, semiconductors devices, among other things. Plasma application over the silicon carbide ceramics is relatively recent and it is able to promote relevant superficial modifications. Plasma expander was used in this work which was supplied by nitrogen and switched by a capacitor bank. Nitrogen plasma was applied over ceramic samples for 20 minutes, in a total medium of 1440 plasma pulses. SiC ceramics were produced by uniaxial pressing method (40 MPa) associated to isostatic pressing (300 MPa) and sintered at 1950°C under argon gas atmosphere. Silicon carbide (β-SiC - BF-12) supplied by HC-Starck and sintering additive (7.6% YAG - Yttrium Aluminum Garnet) were used in order to obtain the ceramics. Before and after the plasma application, the samples were characterized by SEM, AFM, contact angle and surface energy measurement.

Abstract: Si₃N₄ based ceramics are widely researched because of their low density, high hardness, toughness and wear resistance. Post-sintering heat treatments can enhance their properties. Thus, the objective of the present paper was the development of a Si₃N₄ based ceramic, suitable for structural applications, by sintering in nitrogen gas pressure, using AlN, Al₂O₃, and Y₂O₃ as additives and post-sintering heat treatment. The green bodies were fabricated by uniaxial pressing at 80 MPa with subsequent isostatic pressing at 300 MPa. The samples were sintered at 1900°C for 1 h under N₂ gas pressure of 0.1 MPa. Post-sintering heat treatment was performed at 1500°C for 48 h under N₂ gas pressure of 1.0 MPa. From the results, it was observed that after post-sintering heat treatment there was a reduction of α-SiAlON phase and increase of β-Si₃N₄ phase, with consequent changing in grain size, decrease of fracture toughness and increase of the Vickers hardness.

Abstract: This work has as its objective to evaluate the influence of a granite waste into a clayey ceramic body for obtaining of rustic wall tiles. As raw materials, a clayey ceramic body for red ceramic production and a granite waste, resulting from ornamental stones cutting with the multi-wire technology were used. Compositions using 0, 10, 20 and 30% of waste incorporated into ceramic body were prepared. Specimens were fabricated by uniaxial press-molding at 20 MPa and sintered at 1050°C. The following properties were determined: linear shrinkage, water absorption and flexural rupture strength. In general, within the error bar, there was no influence of the waste in the values of water absorption of the clayey ceramic body. The results showed that all investigated formulations used in this work for the production of rustic wall tiles attend the standards for water absorption and mechanical strength.