Materialwissenschaft und Werkstofftechnik最新文献

Additive manufacturing, or 3D printing technique, is a technology that uses computerized information to generate three-dimensional solid objects. These objects are produced by feed-stocking and fusing materials layer by layer. Compared to conventional manufacturing, additive manufacturing can make geometrical shapes that are very complex within a short time with less material wastage. Remarkable applications of manufacturing technology are found in automobile, aerospace, medicine, and natural/synthetic fibre-reinforced composites. Manufactured parts are fabricated using metals, ceramics, and mainly polymers or composites. Advancements in research have recently been implemented to optimize the process. This review focuses on the research progress on current methods applied to optimize 3D printed biopolymer medical implants and natural/synthetic fibre-reinforced composites. The objective of this article is to review new opportunities to produce multifunctional materials and suggest solutions to solve persisting challenges in additive manufacturing of medical implants using natural/synthetic fiber reinforced composites. The influence of process parameters on output performance measures, as well as the modelling and simulation techniques applied, are critically established in this paper. Current 3D printing processes and technologies, including the status and future of additive manufacturing, are also critically presented. Finally, challenges and research opportunities for improved high-performing and less costly printed parts are also illustrated.

In the present work, we demonstrate the development of a cost-effective hybrid composite of aluminium 6063 alloys by utilizing some industrial wastes like fly ash and red mud as reinforcement. Alloy composites have been produced with varying concentrations of reinforcement by a two-step stir-casting method. X-ray diffraction (XRD) confirmed the presence of fly ash and red mud whereas microstructural analysis through optical microscopy showed a uniform distribution of the reinforcements within the alloy matrix. The composite formed with optimized weight fractions of red mud and fly ash exhibited higher ultimate tensile strength in comparison with base aluminium alloy. Furthermore, the dry sliding wear behaviour of the alloy and its composites have been investigated at low sliding speed against a hardened disk at three different loads (2 kg, 3 kg and 4 kg). The wear rate increases with increasing load in the alloy as well as in the composite. Sem images of worn surfaces of the hybrid composite exhibit fewer grooves when 5 wt.-% of both reinforcements are present. Essentially, the overall wear rate of the composite is found lower than the base alloy. Hybrid composites with 5 wt.-% of both reinforcements show maximum wear resistance.

Metal joining can perhaps be said as one of the most indispensable manufacturing processes, with applications across a variety of engineering streams ranging from automobile to day-to-day construction activities. The conventional techniques primarily rely on melting the two joining surfaces and solidifying them to create a fresh cast joint. Though the plates being welded are wrought the joints inevitably are cast and hence result in heterogenous mechanical properties between the base metal. In alloy systems with eutectic phase, the high heat input involved in melting the joining surfaces often degrades the strength of the material in the vicinity of the weldment resulting in the formation of a heat-affected zone. In the welding of heat-treatable aluminium alloys, heat-affected zone degradation is often the weakest point of the welded sample The mechanical properties of a weldment can be improved by extensive plastic deformation. Studies show that such strengthening of AA6061 alloys is a combined influence of the grain refinement of the primary matrix as well as the redistribution of the secondary eutectic phase. Weldments fabricated by gas tungsten arc welding and rotary friction welding were subjected to severe plastic deformation, and the effects were studied. Improved mechanical properties thereby providing an alternative solution to post-weld heat treatment were observed.

Using plasma as an energy source in thermal spraying allows the processing of feedstock materials with high melting temperatures. In plasma spraying, hydrogen or nitrogen is commonly injected into the argon plasma, which increases the specific enthalpy and thermal conductivity. The objective of this study is to improve the understanding of this process through numerical simulation and to investigate the impact on the plasma properties. A comprehensive modelling approach for the electrodes in the three-cathode plasma generator is built upon the previous work of the authors. The plasma is described as an electromagnetically reactive fluid in local thermodynamic equilibrium using temperature-dependent thermodynamic and transport properties. The increase of flow temperature and velocity as well as the temperature distribution at the electrodes can be successfully simulated. The simulation model could accelerate parameter development for new coating systems in the future. This study completes the simulation model for multi-arc plasma spraying using binary gas mixtures.

This article proposes the development of a novel polymer composites using non-conventional materials, specifically constructional wastes such as red brick dust, in different weight percentages (0 wt.-%, 10 wt.-%, 20 wt.-%, and 30 wt.-%) and their erosion wear characteristics has been studied. Solid particle erosion test equipment is employed to evaluate the erosion wear characteristics of the composites. According to the study, adding red brick dust to epoxy resin enhances its erosion resistance. The influence of input parameters has also been evaluated using Taguchi approach. The results of this experiment show that the most important variables influencing the composites′ wear rate are impact velocity and filler content. The factor combinations A₂B₄C₄D₂E₃ exhibit the lowest erosion wear. Moreover, a commercial finite element method tool called ANSYS 2019 R2 is utilized to estimate the wear rate of epoxy/red brick dust composites. After that, the experimental and predicted wear rates of the composites are compared, and it is discovered that the two sets of data accord better. Scanning electron microscopy is utilized to examine the eroded composite samples, and the potential wear causes are explored.

Herein, the type of latex and its ratio to nano-zinc oxide have been investigated for the effectiveness of latex-assisted dispersion of nano-zinc oxide. By analyzing the mixed state of latex and nano-zinc oxide after the addition of coagulants, as well as physical and scanning electron microscope of corresponding composite materials, it was determined that natural rubber latex has the best auxiliary dispersion effect. Based on this result, the effect of the ratio of natural latex to zinc oxide nanoparticles was further investigated. Result showed that when the ratio of the two was too small, the nano-zinc oxide in the rubber particles would cause the natural rubber latex to fail to solidify rapidly. When the ratio of the two was 2 : 1, the natural rubber latex rapidly solidify and encapsulate the nano-zinc oxide. Eventually dispersed uniformly in the high density polyethylene matrix. Based on these results, the corresponding composites have a corrected notched impact strength of 142.6 kJ⋅m⁻² and a tensile strength of 24.2 MPa. They also have excellent electrical insulation properties. These two properties are retained at a high rate after aging., This work further refines the latex-assisted dispersion method and can improve the potential of the method for industrial applications.

This study first employed a vacuum isothermal gas quenching process to heat-treat Cr12MoV in an attempt to achieve a mixed structure of martensite and lower bainite. Based on an analysis of the impact of different isothermal gas quenching process parameters on the properties and microstructure of Cr12MoV steel, with a focus on material impact toughness and Rockwell hardness, the particle swarm optimization method was used to optimize the vacuum gas quenching process parameters for Cr12MoV steel. Using the optimized process parameters, Cr12MoV steel was subjected to vacuum isothermal gas quenching treatment. Microstructure observations and phase analysis revealed that the post-quenching structure consisted of an excellent combination of martensite and lower bainite dual-phase structures, with reduced carbide content and even distribution. After two tempering processes, it was observed that the residual austenite content significantly decreased. The vacuum isothermal gas quenching-tempering process effectively reduced material anisotropy and tool deformation.

Die Kombination von Effizienz und Dauerhaftigkeit ist im Hinblick auf die Gestaltung nachhaltiger Konstruktionen von besonderer Bedeutung, entsprechend sind Kenntnisse zur Verzinkung hochfester Stähle von zunehmendem Interesse. Im Rahmen einer vertiefenden Studie wurde am Baustahl S620QH der Einfluss der Verzinkung unter Variation der Verzinkungstemperatur und -dauer auf die mechanischen Eigenschaften untersucht. Hierzu wurden sowohl Zug- und Kerbschlagbiegeversuche als auch begleitende Materialsimulationen durchgeführt. Im Ergebnis zeigt sich, dass bei der klassischen Verzinkung im Bereich üblicher Prozessparameter, nämlich einer Verzinkungstemperatur im Bereich von 440 °C bis 460 °C sowie Tauchdauern bis 20 Minuten, keine nennenswerten Effekte auf die Eigenschaften des Stahls auftreten. Bei der Hochtemperaturverzinkung wirkt sich die Temperatur in Höhe von 550 °C bei langen Tauchdauern nicht auf die Festigkeit und Duktilität, jedoch zähigkeitsmindernd auf die Stahlsorte S620QH aus. Die parallelen simulativen Untersuchungen weisen darauf hin, dass durch eine erneute Erwärmung die Ausscheidungshärtung mit steigender Temperatur, temperaturabhängig beschleunigt und weitere feine Ausscheidungen ermöglicht werden und dies für den Effekt ursächlich ist. Daraus wird die Empfehlung zur Einhaltung einer Anlasstemperatur von mindestens 580 °C für die letzte Wärmebehandlung des Vergütungsprozesses von warmgefertigten Hohlprofilen nach DIN EN 10210-3 abgeleitet.

Studies on the development of energy absorbing systems that minimize vehicle chassis damage in traffic accidents are increasing day by day. Many designs have been made in the studies on crushboxes used to absorb the energy released in the event of an accident. These design works are quite costly and take a long time. In this study, to design crushboxes faster and more economically was estimated using artificial neural network. The input layer of the artificial neural network model consists of three different materials, thicknesses (between 0.8 and 2.2 mm) and three different initial speeds. In the artificial neural network model, 42 different models were created by changing the different training functions (training, trainlm and trainrp), transfer functions (tansig and logsig) and the number of neurons in the hidden layer (between 9 and 33). R² and root mean square error (RMSE) methods were used to evaluate the efficiency of artificial neural network models. The training function was found to be highly accurate (R²: 0.99999 and root mean square error: 0.314727E-05) when the training function was “trainlm” and the number of neurons in the hidden layer was 33. The training and testing results of the artificial neural network model show that artificial neural networks can be used to estimate the specific energy absorption/energy/peak crush force value of crushboxes.