In the first part of this two-part study, filament wound hybrid composite pipes with various stacking sequences were manufactured and mechanical properties such as hardness, ring tensile strength, ...and burst strength were experimentally investigated. After determining mechanical properties, drilling tests were performed to research machinability characteristics. The second part of the study consists damage analysis and surface quality examination including ring test damage analysis, push-out delamination analysis, borehole damage examination and borehole surface quality. The experimental data suggested that cutting parameters, stacking sequence, and the use of back-up were impactful on the formation and propagation of various types of damages. Especially, the effect of stacking sequence was remarkable. A larger delamination area was formed in Glass-Glass-Carbon (GGC) sample after the ring tensile tests compared to Glass-Carbon-Glass (GCG) and Carbon-Glass-Glass (CGG) samples. In all cases, the utilization of back-up lead to decrease of delamination with 9–40% reduction in surface roughness. When the back-up is not used during drilling, an excessive push-out delamination occurred in all drilling tests. Moreover, CGG samples represented lower push out delamination. In addition, position of the hole depending on the winding angle plays a key role on damage formation and surface quality.
Bismuth telluride based thermoelectric materials have been commercialized for a wide range of applications in power generation and refrigeration. However, the poor machinability and susceptibility to ...brittle fracturing of commercial ingots often impose significant limitations on the manufacturing process and durability of thermoelectric devices. In this study, melt spinning combined with a plasma‐activated sintering (MS‐PAS) method is employed for commercial p‐type zone‐melted (ZM) ingots of Bi0.5Sb1.5Te3. This fast synthesis approach achieves hierarchical structures and in‐situ nanoscale precipitates, resulting in the simultaneous improvement of the thermoelectric performance and the mechanical properties. Benefitting from a strong suppression of the lattice thermal conductivity, a peak ZT of 1.22 is achieved at 340 K in MS‐PAS synthesized structures, representing about a 40% enhancement over that of ZM ingots. Moreover, MS‐PAS specimens with hierarchical structures exhibit superior machinability and mechanical properties with an almost 30% enhancement in their fracture toughness, combined with an eightfold and a factor of six increase in the compressive and flexural strength, respectively. Accompanied by an excellent thermal stability up to 200 °C for the MS‐PAS synthesized samples, the MS‐PAS technique demonstrates great potential for mass production and large‐scale applications of Bi2Te3 related thermoelectrics.
Melt‐spinning combined with plasma activated sintering is adopted to design hierarchical nanostructured BiSbTe alloys. Because of the hierarchical configuration and nanodispersion, the lattice thermal conductivity is reduced significantly, leading to superior thermoelectric performance and robust mechanical properties. Accompanied by an excellent thermal stability, the melt‐spinning‐based synthesis approach offers great potential for commercial applications.
It is tedious to machine high strength materials such as titanium alloy for making engineering products related to aerospace and medical applications due to its high corrosion resistance and low ...density. In this study, an endeavor was made to analyze the influence of tool electrodes in electrical discharge machining process for enhancing the machinability of Titanium α- β alloy. Copper, brass and tungsten carbide electrodes were utilized with iso energy pulse generator. It was observed that the use of copper electrode could enhance material removal mechanism due to its higher electrical conductivity. The better surface topography with tiny craters could be observed on machined specimen with tungsten carbide electrode owing to its high melting point. The IEPG generator can produce tiny craters with lower pulse energy and uniform energy distribution. Since it produces tiny crater and has higher melting point, the tungsten carbide tool electrode can create lower surface roughness than other electrodes. Brass electrode can create larger craters on the machined surface of titanium alloy specimens due to its low melting point. Hence it could create higher surface roughness and electrode wear.
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•Effects of micro/nanostructures on the machinability of metallic materials is critically reviewed.•Micro/nanostructures include crystal orientations, grains, phases, multilayers, ...amorphous, reinforcements and porosities.•Main challenges and opportunities faced in machining of metallic materials are discussed for further development.
Metallic materials have long been used in a wide range of industrial applications due to their outstanding physical and mechanical properties as well as high process latitudes. Mechanical machining is one of the important steps in manufacturing of metallic components because it directly influences the surface quality of the final products. To date, extensive studies have been conducted on the investigation of factors affecting the machinability of metallic materials, such as cutting parameters, cooling conditions and material micro/nanostructures. Contributory factors of cutting parameters and cooling conditions have been extensively reviewed in previous studies, but there is still a lack of a fundamental review to clearly understand the effects of material micro/nanostructures on the machining. Therefore, this review highlights the influences of different micro/nanostructures on the machinability and discusses the materials deformation mechanism in machining of metallic materials. The micro/nanostructures mainly include crystalline anisotropies of single crystals, grain sizes of polycrystals, phase compositions of single/multiphase materials, layer-by-layer structures of additive manufactured materials, amorphous structures of bulk metal glasses, micro reinforcements of metal matrix composites, and porosities of porous metal foams. Besides, the challenges and opportunities faced in machining of metallic materials are discussed from the perspective of micro/nanostructures.
Laser-assisted turning (LAT) involves locally heating a rotating workpiece using a focused laser beam before the removal of material. A key aspect in optimising productivity with laser-assisted ...turning is understanding the thermal relationship between laser heating, the improved material removal rate, and machinability. Consequently, in this paper, a thermal heating and laser-assisted turning finite element model and experiments were conducted to assess the machinability of an Al/SiCp MMC workpiece, considering the circumferential location of the laser beam from the cutting point. The results confirm that laser power and cutting velocity influence the temperature profile from the laser spot to the tool point and the heat-affected depth. Positioning the cutting tool closer to the laser spot effectively reduces the Von Mises stress during cutting at higher cutting temperatures. At the same time, the experiment indicates an increased risk of directly heating the tool, which can affect the integrity of the cutting tool. The work further reveals that at specified cutting velocities, lower specific cutting energy improves the tool condition and surface quality of the machined parts. Based on a range of material removal rates and laser-specific energy density, a new criterion for optimal laser-tool circumferential distance was determined. Establishing this distance can act as a guide for the laser-assisted turning of Al/SiCp metal matrix composites and potentially other materials.
Although covalent organic frameworks (COFs) with a graphene‐like structure present unique chemical and physical properties, they are essentially insoluble and infusible crystalline powders with poor ...processability, hindering their further practical applications. How to improve the processability of COF materials is a major challenge in this field. In this contribution, we proposed a general side‐chain engineering strategy to construct a gel‐state COF with high processability. This method takes advantages of large and soft branched alkyl side chains as internal plasticizers to achieve the gelation of the COF. We systematically studied the influence of the length of the side chain on the COF gel formation. Benefitting from their machinability and flexibility, this novel COF gel can be easily processed into gel‐type electrolytes with specific shape and thickness, which were further applied to assemble lithium‐ion batteries that exhibited high cycling stability.
We propose a general gelation strategy for the construction of highly processible covalent organic framework (COF)‐Gel materials through side‐chain engineering. The COF‐Gel is compatible with electronic devices with diverse functionality, including in lithium‐ion batteries.
The present work deals with the machining application of one of the aerospace material i.e., Inconel-800 alloy by considering the social, economic and environmental effects. The turning tests were ...done under four sustainable machining conditions i.e., dry, vegetable oil with minimum quantity lubrication (MQL) system, graphene nanofluid plus vegetable oil with MQL (NMQL) system and liquid nitrogen (N2) cooling. Then, the energy consumption, carbon emissions, cost per part, average surface roughness and cutting tool wear have been measured for varied cutting speed and feed rate under selected sustainable environments. The outcomes of this study revealed that the N2 cooling conditions reduced the total machining cost up to 9.3%, total energy consumption up to11.3%, carbon emissions up to 49.17% and tool wear up to 46.6% as compared to other cooling conditions. Significant improvement in surface roughness and tool wear have also been noticed from the outcomes of N2 cooling conditions. Hence, it is worthy to mention that these cooling conditions promote sustainability in the aerospace sector by saving resources and extending environmental benefits.
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•Turning of Inconel-800 alloy under dry, MQL, NMQL and liquid N2 conditions were performed.•Sustainability in terms of machining efficiency, carbon emissions, energy consumption and cost modelling were evaluated.•Overall sustainability aspects were improved with liquid nitrogen cooling.•Machinability indicators such as surface roughness and tool wear were also improved with liquid nitrogen cooling.
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High-power direct laser deposition (HP DLD) was utilized to fast generate AISI 316L stainless steel parts with large size and excellent mechanical properties. In order to efficiently ...manufacture the stainless steel parts with high surface quality and dimensional accuracy, a dry milling finish was applied. During the DLD process, heat retaining powder was employed to prevent buckling deformation. The effect of building direction on the microstructure, mechanical properties and machinability of the stainless steel was investigated. It was found that the microstructure was homogeneous, at the building direction of 0°, while a number of larger dendritic grains were present in the microstructure, at the building direction of 90°. The tensile properties and hardness values at the building direction of 0° were higher than those at the building direction of 90°. For both building directions, the decrement in surface roughness and the increment in cutting force and tool wear, were observed with the increase in cutting speed. The cutting force, tool wear and surface roughness of the additive manufactured stainless steel at the building direction of 0° were relatively higher, which implies that the anisotropy in the machinability could be utilized to increase efficiency and reduce production cost.
Machining of metal matrix composite is a difficult task as compared to monolithic materials due to hard-to-cut reinforced materials. However, metal matrix composites are gaining worldwide importance ...in the field of manufacturing industries due to their high strength-to-weight ratio, high ultimate tensile strength, temperature resistance, excellent structural stability. To improve the machining conduct of metal network composites, various methods were adopted, including conventional, non-conventional, and hybrid machining processes. This paper centres around the examination and investigation of different machining cycles of metal matrix composites to get the upgraded result and it is observed that hybrid machining plays an important role in machining metal matrix composite as compared to other methods due to its better machining ability. Since the availability of hybrid-machine is not common and also skilled people are required to run hybrid machines so, non-conventional machining also plays a vital role in achieving the goal.
3D printing of bulk metallic glasses Zhang, Cheng; Ouyang, Di; Pauly, Simon ...
Materials science & engineering. R, Reports : a review journal,
July 2021, 2021-07-00, 20210701, Volume:
145
Journal Article
Peer reviewed
Bulk metallic glasses (BMGs) being metallic materials without long-range order have attracted a considerable amount of interest from academia and industry in the past three decades due to their ...unique and outstanding properties. However, the manufacturing of glassy components with large dimension and complex geometries has remained a considerable challenge. The main obstructions in this regard arise from the oftentimes limited glass-forming ability (GFA) of most metallic systems, which requires extremely fast quenching of the corresponding melts and, consequently, limits the obtainable dimensions. In addition, BMGs generally have a poor machinability due to their intrinsic high hardness and extreme brittleness. The emerging 3D printing technology (also called additive manufacturing), as an advanced bottom-up manufacturing process, seems to be a viable route to circumvent these deficiencies inherent to conventional processing routes. Additive manufacturing theoretically allows the fabrication of large-sized BMGs and components with complex geometries, greatly extending the range of applications of BMGs as both structural and functional materials. The 3D printing technology has given fresh impetus to the field of BMGs and represents an approach, which is intensely explored in the BMG’s scientific community at the moment. In this review, we present a comprehensive overview of the state-of-the-art research on various aspects related to 3D printing of BMGs. It covers various 3D printing techniques for manufacturing BMGs, the microstructures (e.g. structural heterogeneities and fused-related defects) found in 3D-printed BMGs, the crystallization behavior in additively manufactured glasses and the associated alloy selection criterion, the observed mechanical properties and deformation mechanisms, and finally the functional properties and potential applications of 3D-printed BMGs and BMG matrix composites, in terms of catalysis, wear, corrosion, and biocompatibility. This article also identifies a number of key questions to be answered in the future in this important research direction in order to successfully bridge the gap from fundamental research to large-scale application of additively manufactured bulk metallic glasses.
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