Materialwissenschaft und Werkstofftechnik最新文献

This paper describes an aging treatment based on alloying the traditional high-carbon high-manganese steel to improve its initial wear resistance (wear resistance after water toughening treatment only). The changes in structure and mechanical properties of alloyed high-manganese steel after aging treatment at different temperatures were investigated using various experimental methods such as metallographic analysis, mechanical property testing, and fracture morphology observation.

The austenite grain boundary began to have the appearance of grain carbide at 550 °C; a large number of pearlites nucleated at the grain boundary and within grain at 600 °C, most phase transitions occur at 650 °C; and the pearlite and carbide began to revert to a soluble state at 700 °C, leaving only a small amount of pearlite in the austenite grain boundary. The hardness and yield strength of alloyed high-manganese steel increase and then decrease with the increasing aging temperature, and the high peaks appear in the range of 600 °C–650 °C; while the tensile strength and plasticity decrease and then slightly increase, with the highest and lowest peaks being approximately 550 °C and 650 °C, respectively.

At the aging temperature of 550 °C, the alloy high manganese steel has good comprehensive mechanical and deformation strengthening properties, with yield strength, tensile strength, elongation, and section shrinkage of 536 MPa, 1058 MPa, 51 % and 35 %, respectively. The changes in the properties of alloyed high-manganese steel are related to the pattern of structural changes that occur during the aging process.

The purpose of this study is to investigate the features and properties of stone mastic asphalt in the context of its potential for practical application in road repair works, aiming to create a high-quality road surface and replace outdated structural materials with newer alternatives. The leading approach combines a systematic analysis of the issues submitted for consideration and an experimental study of the properties of stone mastic asphalt, which are important in the context of the practical use of this building material to ensure high quality parameters of the roadway and the timeliness of its repair, if necessary. Within the framework of this study, results were obtained that indicate a significant variety of approaches to determining the characteristics and properties of the material under consideration, clearly demonstrating current solutions to the problem of improving the performance of stone mastic asphalt by introducing special admixtures into its composition. The findings and conclusions of this research are valuable for road service employees and developers of modern construction materials, aiding in high-quality road surface repair and creating durable asphalt for safe road use in the future.

The application of wire arc additive manufacturing (WAAM) for the production of large size components is currently limited, due to strong distortion and unprecise filling behavior. The resulting geometric and metallurgical irregularities pose a challenge to the process. The current approach of a layered structure cannot be adopted without adjustments when using wire arc additive manufacturing. Reasons include incompleteness, material accumulation and deformation. The combination of experimental weld geometry-determination and its numerical estimation is presented here as solution to this challenge. The procedure is based on the measurement of a weld bead cross-section-area. By convolution of a path matrix with a weld-geometry-function, the planned path is filled with the seam geometry. Subsequent summation of multiple matrices results in a height profile showing discontinuities and accumulations. Further validation tests show a good agreement between the method and experimentally determined problem areas. The presented optimisation procedure can be extended with material parameters. A local compensation for deformation can be achieved.

The present work discusses the voltage difference as a measure for electrostatic charge generated from the contact-separation and sliding of polymeric textiles on polyamide textile. It is proposed to blend polyester by carbon fiber to decrease the electrostatic charge generated on the contact surfaces. Because polyester acquires a negative charge and polyamide gains a positive one, carbon fiber is proposed to conduct the negative electrostatic charge from polyester to polyamide and conducts the positive one from polyamide to polyester, so that the resultant electrostatic charge decreased. The effect of carbon fiber to decrease the electrostatic charge depends on its area of contact, interaction, and distribution with polyester. Polyester double weaved by carbon fiber showed the lowest voltage. Based on those observations, it can be recommended to use double weaves of carbon fiber with polyester. The reduction in voltage was relatively lower for braided polyester by carbon fiber than that detected for double-weaved polyester by carbon fiber.

In this paper, a nanosecond laser was used to etch the surface of graphene nanoplatelets reinforced ZK60 (GNPs/ZK60) matrix composites, and the effects of different scanning speeds, pulse repetition frequency and laser power on the etched morphology of the machined surface were investigated. The experimental results show that the etched groove width and heat affected zone width of GNPs/ZK60 composites are significantly increased compared with ZK60 material due to the influence of graphene, and the growth rate of the difference in heat affected zone width between GNPs/ZK60 composites and ZK60 materials is most significantly affected by the pulse repetition frequency. In addition, the dross height increases with the increase of laser power, while the scaly dross structure becomes increasingly clear.

Scientific studies involving hafnium have grown significantly in recent years due to the potential applications that this metal has. These potential applications come from the properties of this element, which for many years since its discovery were neglected in research. Among the factors that contributed to this was the high cost of extracting its ores from nature. One of the properties is the solubility of this metal in concentrated sulfuric acid, reacting to form hafnium(IV) sulfate and hydrogen gas. This acid is one of the few that can dissolve this metal, since hafnium is highly resistant to corrosion. The present work reports a chemometrically planned study on the surface of hafnium metal during its dissolution in sulfuric acid at different temperatures (13 °C, 25 °C and 97 °C) and for different times (5 minutes, 60 minutes and 120 minutes). Samples of metallic hafnium were completely immersed in sulfuric acid, subsequently characterized by scanning electron microscopy and the mass variation of the samples was analyzed. The corrosion of hafnium occurs only after the rupture of the protective film of hafnium(IV) oxide of the material, this rupture being faster as the temperature increases.

Quality machining on stainless steel AISI 304 is achieved by reducing the interface temperature generated due to high hardness and compressive frictional force. Temperature rise during the turning operation was observed to cause a weak tool nose, and machining surface. Enhanced lubricant properties can alleviate these issues and help reduce tool nose wear while increasing machined surface quality. Nano-lubricants have been prepared to meet the functional requirements for machining. Emulsifier oil-based nanofluids perform exceptionally well in heat transfer during machining. The present investigation focuses on copper oxide nanoparticles addition in “Society of Automotive Engineers 30” emulsifier oil at two different weight percentage: 1.5 wt.-% and 2.25 wt.-%, aiming to improve heat transfer and machined surface quality. In this experimental study, a computer numerical control machine tool, DCMT120404 insert, tool dynamometer, and infrared pyrometer are utilized for the machining operation. It was observed that 2.25 wt.-% copper oxide mixed emulsifier-nano cutting fluid exhibited minimum cutting force and work-tool interface temperature while enhancing the surface quality.

High-chromium cast iron is a good wear-resistant material. Its heat treatment regime has an important influence on the evolution of its microstructure and properties. This study investigates the microstructural attributes and properties of Fe–4.0 C–35.0Cr–0.5Si (wt.%) low-silicon hypereutectic high-chromium cast iron subsequent to quenching at 1050 °C, followed by tempering at diverse temperatures. The microstructure was examined using optical microscopy, scanning electron microscopy, and X-ray diffractometry across varied tempering conditions. Furthermore, microhardness and wear resistance were conducted via a microhardness tester and a wear testing machine. The results show that the quenching heat treatment promotes the transformation of the matrix from austenite to martensite, while also promoting the precipitation of secondary carbides of M₂₃C₆-type. The subsequent tempering heat treatment engenders transformations involving retained austenite to martensite, amplifies the precipitation and enlargement of secondary carbides, and induces martensite decomposition. As the tempering temperature increases, primary and eutectic carbides exhibit minimal changes, while the secondary carbide morphology evolves from granular to reticular. The matrix composition predominantly comprises martensite, interspersed with a minor fraction of austenite. It is worth noting that the alloy has the highest hardness and wear resistance after quenching at 1050 °C and then tempering at 400 °C.

Sensor placement is one of the vital concerns in civil structure monitoring. A sensor placement strategy based on a damage assessment method has been introduced for beam-like structures. An existing damage detection method adapted to multi-modes and different types of beam-like structures. Then, it is numerically verified to be suitable for detecting any damage location in a 100 degrees of freedom mass-spring system. Depending on the noise in the response and the limited measurements, the results demonstrate the validity of using the multi-mode damage indicator. However, there are limitations to this method due to mode shape saddle points. Sensor deployment schemes have been proposed to address the restriction. In contrast to the corresponding procedure, this method does not rely on the optimization algorithm. Sensor placement strategies involve the simultaneous use of accelerometers and large-area electronics.

Conventional liquid lubricants prove inadequate for effective lubrication in conditions characterized by high temperatures and high vacuum environments. In such extreme scenarios, powder lubricants emerge as a more viable solution. The present study is to conduct a series of experiments using a reciprocating wear test setup and evaluate the capability of four different machine learning models in analysing the tribological attributes of metals when lubricated with three distinct powder types: zirconium dioxide, copper oxide, and molybdenum disulfide, specifically under conditions of elevated contact pressures and dry environments. The experiments were systematically carried out encompassing a range of load and temperature combinations. Four different machine learning models (MLP, KNN, extreme gradient boosting and light gradient-boosting machine) were used for predicting the coefficient of friction of metals lubricated with different powders. Extreme gradient boosting machine learning model gives better result than the other models with mean absolute error, root mean squared error, R² value and average absolute deviation percentage of 0.0215, 0.0278, 0.9962 and respectively.