Abstract: It is clearly seen that the magnetic induction of the amorphous ribbon produced by conventional technology implying heating up to 1490 °С increases as the thickness of specimens increases, with this growth being especially intensive at the 100 А/m magnetic field strength. At the same time, the melt preparation supplemented by overheating contributes to the magnetic induction stabilization, i.e. magnetic induction is essentially independent of the ribbon’s thickness. It is only at high values of h that a slight increase in magnetic induction becomes evident. The fracture diameter of the free side surface is linearly increasing as the annealing temperature increases. The structure has been shown to influence magnetic and mechanical properties of the material in preparing the melt before casting.
Abstract: Sliding friction is one of the most powerful processes for microstructural evolution in the sub-surface, including grain refinement and recrystallization of deformed structure. Pin-on-disc sliding tests were carried out for 0.45 mass % carbon steels, and TEM microstructure and hardness of the specimens were investigated. Particularly effects of friction conditions on the microstructure at the surfaces and wear properties of the friction induced microstructure were studied. It was found that ultra-fine equi-axed grains in the 30 - 50 nm size range were produced in the case of a high friction speed of 5.0 m/s in an air atmosphere. Moreover, nano-crystalline microstructure can be produced in a vacuum atmosphere even if the friction speed was low. The friction induced nano-crystalline surface layers, which exhibited significant high hardness, showed good wear resistance.
Abstract: Palmtop tensile and fatigue testing machines were developed in-house for small and thin specimens that were fabricated by the LIGA process. The dimensions of the specimens were selected in accordance with the international standard IEC62047-3, and were 10 micrometers in thickness, 20 micrometers in width, and 500 micrometers in parallel length. Since the loading mechanism and methods of measuring the load and displacement were specially designed, the stiffness of the specimen is quite low compared to that of the conventional large-size specimens. The mechanical properties of electroformed Ni2Pd8 and Ni4Pd6 alloys were studied with these developed testing machines and excellent values of tensile and fatigue strengths of 2.7 GPa and 1.8 GPa, respectively were obtained in the case of the Ni4Pd6 alloy.
Abstract: The effect of Mg and Ca treatment on the modification of inclusions in GCr18Mo bearing steel at 1873K was studied by thermodynamic calculations. The stability phase diagrams among Mg, Ca, Al, and O were investigated to understand the fundamentals about the formation of inclusions. The calculated results showed that: (1) Both the alumina and spinel can be modified to MgO by Mg treatment in the case of the dissolved [Mg] = 5.9ppm ~ 40ppm, corresponding the dissolved [Al] ≤ 0.056%, which can control the [O] ≤ 3ppm. (2) The MgO·Al2O3 spinel can be modified to 12CaO·7Al2O3 liquid inclusion by Ca treatment in the case of the optimal [Al] = 0.07% ~ 0.31% and the dissolved [Mg] ≤ 5.2ppm, the [O] can be controlled at about 3ppm. (3) The alumina can be modified to liquid calcium aluminate inclusions by Ca treatment in the case of the dissolved [Al] = 0.03% ~ 0.29% and the dissolved [Ca] = 13ppm ~ 80ppm, correspondingly the equilibrium [O] is about 3ppm. These results of thermodynamic calculation will provide a detailed thermodynamic reference for GCr18Mo bearing steel smelting.
Abstract: Based on the predecessors of thermodynamic data, the relationship between aluminum contents and oxygen contents of the aluminum deoxidization reaction was calculated. And the influence of activity coefficient to the reaction equilibrium in bearing-steel is analyzed. First-order and second-order interaction coefficients were used to calculate and draw the equilibrium curves, respectively. The effects of different temperature and different interaction parameters on the deoxidization equilibrium curves were studied. And through the curve the influence of the change of aluminum contents to the activity can be known. The trend of the curve with first-order interaction parameters is consistent with the curve with first-order and second-order interaction parameters at the low Al concentration region. And the oxygen contents of curve with first-order interaction parameters are higher than the other curve at the high Al concentration region
Abstract: Polypropylene(PP)/nanoclay composites samples have been fabricated by melt compounding the PP pellets with nanoclay masterbatch (i.e. 50 wt% of nanoclay) using a mini extruder. The effect of three loadings of nanoclay (i.e. 5, 10, and 15 wt%) on the morphology, non-isothermal crystallization, and viscoelastic behavior of the PP/nanoclay composites were investigated. All the nanocomposites samples were characterized by using Scanning Electron Microscope (SEM), Differential Scanning Calorimetry (DSC), and an oscillatory rheometer. The SEM results showed that the distribution of nanoclay in the PP was relatively good at all level of loadings. The DSC analysis results showed that the nanoclay has dramatically enhanced the crystallization temperature, from 117°C (for neat PP) to 127-129°C (for nanocomposites). Additionally, the frequency sweep test results exhibited that the presence of nanoclay increased the viscoelastic behavior of the PP matrix.
Abstract: The present research aimed to develop natural rubber (NR) hybrid composites reinforced with calcium carbonate/carbon black (CC/CB) and calcium carbonate/silica (CC/SC). The influence of CC/CB and CC/SC with various filler ratios (120/0, 90/5, 60/10, 30/15 and 0/20) on cure characteristics and mechanical properties of the vulcanizates was investigated and their reinforcing efficiency was compared. It has been found that incorporation of CB in the hybrid filler decreases the scorch time and cure time but increases crosslink density, whereas the incorporation of silica showed cure retardation. As CB or SC content increases, stiffness, tensile strength and tear strength increase, while elongation at break and compression set decrease. Scanning electron microscopy studies also reveal poor filler dispersion and poor adhesion between filler particles and matrix in the vulcanizates with increasing in CC content in a weight filler ratio which causes inferior mechanical properties. Incorporation of CB or SC content enhanced the mechanical properties of the vulcanizates, where CC/CB hybrid system exhibited higher reinforcing efficiency compared with CC/SC hybrid system.
Abstract: Poly(ethylene-co-trimethylene terephthalate) is an engineering material that has recently gained attention for use in fused filament fabrication (FFF). Although the properties of this thermoplastic are well suited for this process, the porosity of the components made remains a barrier to wider use of this approach in the additive fabrication of tight components for medical and food applications. This study investigated the effects of four tool path parameters of the FFF process – road width, air gap, layer thickness, and outer contours – on the void fraction in the structures made. It was revealed that the porosity was reduced from above 9% to below 2% when the extrusion rate was increased from initially 5.00 mm3/s to at least 5.75 mm3/s. A similar outcome was observed when a negative air gap between two adjacent strands of -15% or less was applied. In addition, these results were obtained without extending the print times. By contrast, altering the layer thickness and number of contours had only marginal or no effects on part porosity.
Abstract: This study investigated the effects of the extrusion temperature and volumetric flow rate settings in a fused filament fabrication (FFF) process on the tensile properties of specimens made of poly(ethylene-co-trimethylene terephthalate). The tensile strength almost doubled from 13.5 MPa at 230°C to 26.7 MPa at 260°C extrusion temperature, while the elongation at break improved to 5.4% and the tensile modulus rose to 641.8 MPa at the highest temperature. Similar observations were made when the extrusion flow rate was augmented to 115% of the initial value, with part strength greatly improving to 795.9 MPa and part elasticity increasing by 22%. These results illustrate two effective strategies to enhance the mechanical properties of components made in an engineering material that is increasingly being utilized in filament-based 3D printing.
Abstract: Edge trimming process is needed for finishing CFRP components to the required accuracy and surface quality. The bouncing–back effect of CFRP components is very challenging owing to spring back of trimmed edge after cutting tool pass. Ultrasonic assisted machining (UAM) is an efficient method used to enhance the quality of CFRP parts due to the reduced contact time between the tool and workpiece. This paper experimentally investigates the effect of edge trimming variables on the cutting forces and the magnitude of the bouncing back. Diamond abrasive end mills were utilized during ultrasonic assisted edge trimming of CFRP. The processes variables include spindle speed, feed rate, radial depth of cut, fiber orientations, and up/down strategy. Statistical analysis was conducted to determine the most significant factor on performance characteristics. Regression equation was also developed to predict the value of bouncing back. The results showed that depth of cut and feed rate have a significant effect on bouncing back among the process variables.