Materialwissenschaft und Werkstofftechnik最新文献

This investigation studied the effect of different heat treatment routes on the microstructural behavior and mechanical properties of a high manganese steel. The 0.12 % carbon – 15 % manganese steel was manufactured from a commercial 1018 steel. It was hot rolled in successive stages until a 90 % reduction. The samples subjected to different heat treatment conditions were analyzed using conventional characterization techniques. The results showed that the mechanical behavior of the steel depends on the stacking fault energy but to a greater extent on the initial microstructure. The mechanical properties increased to tensile strength values > 1070 MPa and 70 % elongation when the steel was exposed to quenching and tempering treatment. The above was attributed to the twinning-induced plasticity mechanism verified in the zone with the highest load in the stress-vs.-strain curve and microstructurally evaluated in the deformation zone, where a completely twinned structure was observed. Nevertheless, martensite phases were also present. In contrast, when low cooling rates are used, the mechanical properties are not recovered. However, the hardening mechanisms and deformation-induced phase transformation are the same as hot rolling, quenching, and annealing conditions.

Gypsum can be decomposed at low-temperature by adding reductant, which is beneficial to obtain cement. The effects of different reductant on the phases of belite cement raw meals were studied by calcining at 1300 °C for 2 hours and using phosphogypsum as raw materials. Diffraction peaks of calcium sulfate were not observed in the samples when 10 wt.-% activated carbon was added and the molar ratio of calcium sulfide (CaS) to calcium sulfate (CaSO₄) was 3, respectively. The Sulfur trioxide contents in the clinkers were 0.80 wt.-% and 0.64 wt.-%, respectively. The effect of carbonation curing on the cement properties was also studied. Carbonation curing can promote cement hydration and increase strength at 20 °C, 75 % relative humidity and 20 % carbon dioxide (CO₂) concentration. As the carbonation curing age increased, the compressive strengths of the samples gradually enhanced. When 10 wt.-% carbon was employed as the reductant, compressive strengths of the samples were 15.5 MPa, 15.6 MPa, and 15.6 MPa after carbonation curing at 3 day, 7 day and 28 day, respectively. When calcium sulfide was employed as the reductant, the compressive strengths of the samples were 19.8 MPa, 27.2 MPa, and 34.1 MPa after carbonation curing for 3 day, 7 day and 28 day, respectively. The carbon dioxide sequestration contents of the samples prepared with a 10 wt.-% carbon and calcium sulfide reductant, were 11.6 % and 9.2 % after carbonation curing for 28 days, respectively. These findings demonstrate the potential to use phosphogypsum with various reductants to enhance the quality of belite cement and at the same time consume more carbon dioxide in the atmosphere during curing process.

The growing global demand for sustainable and renewable energy sources has intensified research efforts in biodiesel production. This study investigates the optimization and simulation of biodiesel production from Chlorella algae oil using a supercritical transesterification process without any catalyst. Avoiding the use of a catalyst eliminates potential issues associated with water content in the algae oil and reduces pretreatment costs. The research involves a two-step approach: conducting a simulation study to develop a validated process simulation model, followed by process optimization using response surface methodology (RSM). The input parameters - temperature, pressure, and residence time - are analyzed to maximize the biodiesel yield, which is the response function. A face-centered central composite design is utilized for experimental setup and statistical analysis of the results. Analysis of variance (ANOVA) is used for the optimization procedure. The statistical analysis highlights temperature as the most significant process parameter compared to residence time and pressure. This optimization process results in a maximum biodiesel yield of 99.6 % at an optimum temperature of 343.5 °C, 43.2 bar pressure, and 139.5 minutes of residence time. This study provides significant insights into non-catalytic biodiesel production from algae oil, presenting an effective method for improving biodiesel yield.

The high sintering temperature of tungsten heavy alloys is one of the problems in the production of this alloy. In this research, with the aim of reducing the sintering temperature, W-(10-x) Ni-x Si alloy with different amounts of silicon (x = 0.8 wt.%, 1.2 wt.% and 1.6 wt.%) were designed. These alloys were pressed at 1050 °C, 1100 °C and 1150 °C under a pressure of 30 MPa. The microstructure, composition, density and compressive properties of the samples were examined. The highest relative density was about 99.52% for W-8.8Ni-1.2Si alloys at 1150 °C. By increasing the silicon, the density and tungsten particle size initially increased and then decreased. Intermetallic and unwanted compounds were observed in the microstructure of the W-8.4Ni-1.6Si alloy. At 1100 °C, the compressive yield strength decreased with an increase in silicon, but at 1150 °C, it did not change significantly. In both temperatures, the compressive strain decreased with increasing silicon. At 1100 °C, the compressive yield strength of alloys with 0.8 wt. %, 1.2 wt. % and 1.6 wt. % silicon were about 1303 MPa, 1231 MPa, and 670 MPa, respectively. The results showed that W-Ni-Si alloys had higher density and compressive yield strength than common W-Ni-Fe alloys, although the sintering temperature was lower.

Every functional component in current industries requires unique and adaptable behavior for the materials. The process of forming new composite materials requires time and significant cost. The goal of this study is to fabricate novel materials using alternative layers of various materials, such as poly-lactic acid (M1), wood reinforced poly-lactic acid (M2) and ceramic reinforced poly-lactic acid (M3), fabricated using fused deposition modeling. The evaluation of fracture toughness is essential for materials to ensure its applicability for their intended use. Extended finite element method and experimentation were used to evaluate fracture toughness. The results show that, when compared to poly-lactic acid M1 (fracture toughness at mode I = 4.84 MPa√m), wood reinforced poly-lactic acid M2 (fracture toughness at mode I = 3.25 MPa√m), and ceramic reinforced poly-lactic acid M3 (fracture toughness at mode I = 5.76 MPa√m), the innovative material exhibits superior fracture toughness at mode I = 16.54 MPa√m (experimentally) and fracture toughness at mode I = 17.15 MPa√m (simulation). Equivalent experimental and extended finite element method outcomes provide two levels of assurance, giving fidelity and allowing incorporation of innovative material potential in lightweight application that demand high fracture resistance. This study offers first-hand experience for implementing innovative material in a variety of industrial and structural application.

RETRACTION: I.C. Ezema and V.S. Aigbodion, “Explicit Microstructural Evolution and Electrochemical Performance of Value Added Palm Kernel Shell Ash Nanoparticle/A356 Alloy Composite [Explizite Mikrostrukturelle Entwicklung Und Elektrochemisches Verhalten Eines Verbundwerkstoffes Aus Palmkernschalenasche-Nanopartikeln in Der Aluminiumlegierung AlSi7Mg],” Materials Science and Engineering Technology 51, no. 3 (2020): 324-329, https://doi.org/10.1002/mawe.201900071.

The above article, published online on 17 March 2020 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the journal Editor-in-Chief, Jörg Ellermeier; and Wiley-VCH GmbH. The retraction has been agreed upon following an investigation into concerns raised by a third party. The investigation revealed that elements from Figures 2, 3, and 4 were found to be duplicated in articles published elsewhere by one of the same authors. The figures containing the duplicates are described as representing different materials. The authors acknowledged the presence of the duplications and indicated that they occurred inadvertently. However, they were unable to produce any original data. Due to the extent and nature of the duplications, the editors consider the results and conclusions reported in this article unreliable. The authors were informed of the retraction.

Nanofluids present unique characteristic density and surface behavior and they can be applied in many devices for better performances due to their enhanced thermophysical properties. Herein, a literature survey of the experimentally determined values for the density and surface tension of nanofluids has been carried out. In addition, accuracy and uncertainty measurements of the reviewed articles are analyzed and compared. Some of the well-known empirical models for estimating density and surface tension are included as well. The results revealed that density of nanofluids followed a same trend, where it showed a direct and an inverse relationship with concentration and temperature, respectively. But for surface tension of nanofluids, inconsistencies have been reported in results for the influence of concentration and temperature. Therefore, due to the increasing importance and use of nanofluids in various industries, it is vital to compile and compare studies on these thermophysical properties to practically utilize nanofluids to their full potential for industrial use.

Selective laser melting technology has demonstrated significant advantages in the processing of TC4 titanium alloy. While TC4 alloy exhibits outstanding properties, the economic viability of recycling its high-cost powder has become a focal point of interest. Experimental results indicate that as the number of powder recycling cycles increases, the microstructure of the TC4 components tends to degrade gradually. After multiple recycling cycles, the intensity of the crystal diffraction peaks diminishes, and the crystal structure undergoes changes due to oxidation, stress accumulation, and microstructural damage. The hardness of the components fluctuates with the increasing number of recycling cycles. Components made from non-recycled powder exhibit high tensile strength, but this strength gradually declines with additional recycling cycles, showing a brief recovery after 20 cycles. The impact toughness slightly improves after five recycling cycles, but it then continues to decrease, stabilizing after 30 cycles of recycling.

With the increasing demand for lightweight and high-performance components in industries such as aerospace, automotive, and marine, wire arc additive manufacturing has become an attractive manufacturing method due to its cost-effectiveness and ability to produce complex geometries. This review provides an in-depth analysis of the microstructure and mechanical properties of aluminum alloy walls produced using wire arc additive manufacturing. It explores the influence of various process parameters including voltage, current, travel speed, wire feeding rate, and shielding gas. The review emphasizes the importance of selecting suitable aluminum alloys, particularly highlighting the 5xxx series for their strong weldability and mechanical performance. Findings from recent research are compiled and presented in structured tables and figures to guide optimization of the process. Furthermore, the review identifies a need for further investigation into the 2xxx and 7xxx aluminum series, which offer higher strength but present challenges in terms of weldability and defect control. This work provides essential insights for improving outcomes in aluminum alloy manufacturing.

This study presents the development of boron-doped lignin-based composites reinforced with textile waste as a sustainable alternative to conventional insulation materials. By utilizing lignin, a byproduct of the paper industry, and textile waste from cotton and polyester blends, composites with varying boron concentrations (0 %, 5 %, and 10 %) were fabricated, evaluated for their thermal, acoustic, and fire-resistant properties. Among the samples, alb10 (10 % boron addition to pink cotton/polyester waste) exhibited exceptional performance, achieving a burning speed of 20 mm·s⁻¹, a significant reduction compared to 160 mm·s⁻¹ in the non-doped alb0 and a thermal conductivity of 0.04 W·mK⁻¹, comparable to commercial insulation materials. Compared to the reference material yltm (commercial felt), alb10 demonstrated superior fire resistance, enhanced thermal regulation, and improved acoustic insulation, underscoring boron's critical role as a flame-retardant additive. This work highlights the potential of boron-doped lignin-textile composites to address energy efficiency, fire safety, and waste management challenges, aligning with circular economy principles and offering a cost-effective, eco-friendly solution for future insulation applications.