Search

This study investigated the hot workability of an experimental, non-toxic, low-cost Ti-3.4Fe alloy using flow stress analysis, constitutive modelling, processing maps and microstructural examination. Hot compression tests were performed on Ti-3.4Fe alloy samples at different deformation temperatures (750, 800, 850 and 900 °C), strain rates (0.05, 0.1, 1 and 10 s−1) and a total strain of 0.6. The compression tests were performed using a Gleeble® 3500 thermomechanical simulator. The isothermally compressed samples were analysed using a scanning electron microscope to assess the microstructure. An Arrhenius-based model was used to derive the constitutive constants. From the results, the stress exponent and activation energy were 4.91 and 611 kJ.mol−1 under the steady-state stress condition and 5.32 and 675 kJ.mol−1 at peak stress. The stress exponents suggested a dislocation climb and glide mechanism controlling deformation. The processing map showed that the optimum conditions to deform Ti-3.4Fe were 850 °C at a strain rate of 0.1 s−1 for both steady-state and peak stresses. The microstructure revealed kinked, rotated and bent lamella at the safe region (850 °C at 0.05 s−1), confirming the dominance of dynamic recovery as the softening mechanism. Instabilities manifested as cracks and inhomogeneity at 750 °C and 1 s−1 and at 850 °C and 10 s−1. [ABSTRACT FROM AUTHOR]

This work investigates the microstructure characterization and mechanical properties of Al alloy fabricated by additive friction stir deposition (AFSD). Microstructure characterizations of the Al alloy 5B70 base material (BM) and build were compared using optical microscope (OM) and electron back scattered diffraction (EBSD). The hardness distribution in the direction perpendicular to the cross-section of the deposited area was systematically evaluated. Tensile tests were performed on the BM and the build using digital image correlation (DIC), and the real-time stress distribution states of the specimens were analyzed. After the tensile tests, the fracture micromorphology was characterized using scanning electron microscope (SEM). The results indicated that a high degree of recrystallization occurred in the deposition zone, where fine, equiaxed, and differently oriented grains are formed. It was found that the strength of the deposition layer was lower compared to that of the BM, but its toughness was significantly improved. Also, obvious anisotropy of mechanical properties was identified in the deposition layer. [ABSTRACT FROM AUTHOR]

Titanium and its alloys (especially Ti6Al4V) are widely employed in aerospace and biomedical industry. Wire electric discharge machining is common in practice to machine this difficult-to-cut material. But owing to the thermo-electric nature of the process, it is challenging to have adequate level of surface integrity. This primary concern needs to be addressed as it mainly influences the surface mechanical characteristics. Therefore, the present research aims to address the aforesaid issues using well-known multipass strategy. Understanding the multipass process dynamics and requirements, the potentiality of brass wire diameters was comprehensively examined and explored during WEDM of Ti6Al4V. Considering higher cost, unavailability, environmental hazards, and straightness issues of novel zinc-coated wire electrodes, readily available brass wires provide a cheaper and widely acceptable solution to enhance surface integrity of machined parts if equivalent results can be somehow made possible. For that sake, three different brass wire diameters; 0.15 mm, 0.2 mm, and 0.25 mm have been considered to evaluate their impact on surface roughness, recast layer thickness, overcut, machined surface microhardness, and cutting speed using multipass cutting technique. Experimental results revealed that 0.15 mm uncoated brass wire can produce white layer result equivalent to Topas Plus X wire (Cu core-double Zn-rich layer coating) which outperformed among all zinc-coated wires used in previously published research. Moreover, among different diameter brass wires, surface roughness is improved by 25% using multipass cutting with 0.15 mm diameter in comparison to its counterparts. Scanning electron microscope (SEM) analysis depicts that the said combination reduces recast layer thickness from 39.04 µm to 14.6 µm (~ 1.5 times lesser value). In addition to that, smaller diameter (0.15 mm) provides the maximum cutting rate in rough cuts (which consume maximum machining time) and dimensional accuracy. [ABSTRACT FROM AUTHOR]

Metallic powder alloys for additive manufacturing (AM) are required to have a certain particle size and shape distribution in different processes such as laser powder bed fusion for metallic alloys (LPBF-M). For reasons of sustainability and cost-effectiveness, it is common to recycle powder that was not melted in the build construction process. As usual in a LPBF-M process, the metal powder undergoes a heuristical designed sieving and blending procedure to maintain a certain particle distribution. However, keeping track of the powder's mean age during each building cycle can be obscure or laborious. To overcome this challenge, the authors of this research propose a theoretical model and an experimental methodology to track the powder morphology evolution with respect to a specific number of building cycles and the sieved and solidified amount of powder Such morphological investigation was carried out through a scanning electron microscope, analyzing the morphological evolution of nickel-chromium alloy metal (Inconel 718) powder. The powder analysis gives a close fit of its mean age to the span of the retained particle solidity measurements and the evolution of the mean major diameter. Recycling and thereby modifying the ageing rate of the powder, under monitoring the morphologic evolution of the particles, could be considered as a key criterion for a more effective powder usage lifetime. The findings from this methodology give insight on a predictive model for aging rate, capable of retrieving information about the effective powder's lifetime, impacting positively in the organization and storage of metal powders for AM. [ABSTRACT FROM AUTHOR]

Wear behavior of titanium alloys of Ti-4.5wt%Al + xFe (x: 2,4,6,8) produced by spark plasma sintering was investigated in order to highlight the effects of the iron additive on wear rate and coefficient of friction (COF). These research objectives were accomplished by a dry sliding experimental technique using the Tribometer (version 8.1.8) Anton Paar machine, which was carried out under normal loads at 10 N and 20 N with a linear speed of 0.06 cm/s. Scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques were used to characterize the titanium alloy specimens. The results indicated that the wear rate increases with an increase in the applied normal load. A minimal coefficient of friction of 0.047 and a wear rate of 1.033 × 10−5 (mm3/N/M) were observed for Ti-4.5 wt% Al + 4 wt% Fe with respect to sliding at 10 N. While at a normal load of 20 N, a minimal friction coefficient of 0.015 and a wear rate of 1.74 × 10−5 (mm3/N/M) were obtained for Ti-4.5 wt% Al + 4 wt% Fe. [ABSTRACT FROM AUTHOR]

The beryllium bronze guide sleeve and the aluminum alloy valve body are assembled to form a beryllium bronze-aluminum alloy stepped hole which requires multiple positioning and tool changes during machining, resulting in lower machining efficiency and accuracy. The geometry error and surface quality of beryllium bronze-aluminum alloy stepped holes after reaming were studied in this research. The geometric error (cylindricity, concentricity and verticality) and diameters of the stepped holes were measured by using a three-coordinate measuring machine. The experimental results show that the PCD forming cutters has high geometric error and diameter stability when reaming beryllium bronze-aluminum alloy stepped holes. Under various cutting parameters, the cylindricity of stepped holes was guaranteed to be within 6μm, and the concentricity of stepped holes was guaranteed to be within 6μm, and verticality of stepped holes was guaranteed to be within 2μm. With the increase of spindle speed and feed per tooth, the diameters of beryllium bronze holes increase while the diameters of aluminum alloy holes decrease and then increase. As the cutting allowance increases, the diameters of the beryllium bronze holes and aluminum alloy holes decrease. The laser confocal microscope and scanning electron microscope were used to detect and analyze the surface quality of beryllium bronze-aluminum alloy stepped holes after reaming. The experimental results show that the surface roughness of the beryllium bronze-aluminum alloy stepped holes reamed by using the PCD forming cutter were less than 0.3μm, and the surface roughness of the beryllium holes were slightly larger than the aluminum holes. The fourth group of experimental parameters (spindle speed 1290r/min, feed per tooth 0.01mm/z, cutting allowance 0.06mm) was selected as the actual processing parameters. There are cavities on the surface of the initial stepped holes before reaming and the cavities basically disappear after reaming, so the surface quality of the beryllium bronze-aluminum alloy stepped holes has been greatly improved. [ABSTRACT FROM AUTHOR]

In this study, the machining characteristics of pulse short arc milling (SEAM) Ti6Al4V alloy were studied. In this regard, the influence of SEAM parameters on the material removal rate (MRR), relative electrode wear ratio (REWR), and surface integrity of Ti6Al4V is studied. A wide variety of processing parameters, including different voltages, frequencies, duty cycles, flushing pressures, electrode rotation speeds, and electrode feed rates, are considered in the investigation. Scanning electron microscope (SEM), energy dispersive spectrograph (EDS), and micro-hardness analysis are applied to analyze results. Moreover, a multichannel data acquisition system is used to measure gap voltage and gap current. Obtained results cover the variation of MRR, REWR, surface roughness (Ra), average resolidified layer thickness, and average heat-affected zone thickness with different processing parameters. Furthermore, the electrode surface morphology and chemical composition of the negative growth of REWR are studied. Based on the obtained results, the microstructure of the resolidified layer and heat-affected zone of the workpiece cross-section is confirmed. This study provides a basis for the high-quality pulse SEAM technology of difficult-to-machine (DTM) materials to enter the semi-finishing field. [ABSTRACT FROM AUTHOR]

In this study, friction stir processing (FSP) is utilized to fabricate FeCoNiCrAl high-entropy alloy reinforced Al5083 composites. The role of the reinforcement and processing pass on microstructure, microhardness, and wear properties of the composites are studied. The surface of the composites was analyzed via scanning electron microscope. The number of the processing passes acts an important role in the production of the composites via FSP technology. XRD result shows that FSP technology can be used for producing FeCoNiCrAl high-entropy alloy reinforced 5083 aluminum matrix composites which does not contain any harmful intermetallic. The properties of the composites are evaluated by microhardness and wear test. The results show that the composites possess higher microhardness and wear resistance than the Al5083 base alloy and FSPed samples without the FeCoNiCrAl high-entropy alloy particles. In all the composites, the sample produced by 5 passes reveals the highest microhardness, the best wear resistance, and the lowest friction coefficient. [ABSTRACT FROM AUTHOR]

AlSi10Mg alloys reinforced by TiC particles were fabricated on 5052 aluminum alloys by laser additive manufacturing. The surface morphology, microstructure, microhardness, and tensile properties of the alloys fabricated with different processing parameters were investigated by optical microscope (OM), scanning electron microscope (SEM), Vickers hardness tester, and high-precision electronic universal testing machine. The results show that appropriate laser energy input leads to uniform distribution of TiC particles in the alloy. Fine needle-like TiC particles are precipitated from the grain boundary, which is beneficial to the improvement of mechanical properties of the alloy. The optimum process parameters are found to be 2500–3500 W for laser power, 600 mm/min for scanning velocity, and 2.0 mm for hatch spacing. For lower or higher laser energy input, aggregations are formed in the coatings. At the optimum processing parameters, the maximum microhardness and tensile strength of the TiC/AlSi10Mg alloys are much higher than those of others, which are 139.1 HV0.05 and 278.8 MPa, respectively. A large number of dimples have been found on the fracture surface of the alloys, which indicates the fracture mechanism of the alloy is ductile fracture. [ABSTRACT FROM AUTHOR]

Titanium alloy (Ti-6Al-4V) is one of the materials used in most engineering applications due to its excellent combination of mechanical and corrosion properties. However, the extend application of Ti-6Al-4V alloy is limited because of low hardness and poor wear resistance. In order to overcome this alloy's limitations, coatings could be fabricated on the surface of the alloy through surface modification technique. In this work, Ti and Al2O3 powders were deposited using laser cladding at different admixed ratios (95Ti-5Al2O3, 92Ti-8Al2O3 and 90Ti-10Al2O3) on Ti-6Al-4V alloy. The coatings were laser cladded at laser power of 900 W, powder feed rate 2.0 g/min, beam spot size 2 mm and gas flow rate 8.0 L/ min while scan speed was varied at 0.6 and 0.8 m/min. The produced coatings were characterized for microstructures and phase constituents by using optical microscope (OPM), scanning electron microscope (SEM) and X-ray diffractometer (XRD). Moreover, Vickers hardness tester and and pin-on-disk Anton Paar tribometer were respectively used to measure hardness and wear resistance. The results showed that hardness values and reduction in wear loss were improved by increasing the Al2O3 content from 5 to 10 wt% in Ti-Al2O3. However, high scan speed of 0.8 m/min prompted non-uniform distribution of Al2O3 which in resulted low hardness and wear resistance compared to coatings fabricated at 0.6 m/min. [ABSTRACT FROM AUTHOR]

To solve problems such as insufficient energy and effective arc burning during the injection of a working medium in a short arc discharge channel, the application of a W-Cu alloy as the electrode material in short electrical arc machining (SEAM) is explored in this paper. Using the surface roughness, material removal rate, and tool electrode wear rate as technical indices, the effects of voltage, frequency, and duty cycle on W-Cu alloy materials are studied to explore machining characteristics in SEAM. Contrast experiments on a graphite electrode were conducted using a SU8010 scanning electron microscope and energy spectrum analysis to study the erosion mechanism of the W-Cu alloy material. This paper addresses applications of copper-based composites in SEAM and provides a theoretical basis for the development of electrode materials in the SEAM. [ABSTRACT FROM AUTHOR]