Materialwissenschaft und Werkstofftechnik最新文献

This paper presents the parametric investigation and optimization of various chemical treatment parameters that affect the mechanical performance of the green composite. The injection moulding method was used to produce the green composites using flax fibre (FF) and polylactic acid (PLA). The chemical parameters chosen to investigate their effects are chemical type (sodium hydroxide, sodium carbonate, and potassium hydroxide), chemical concentrations (1 %, 2 %, and 3 % (w/v)), and duration for fibre treatment (2 h, 4 h, and 6 h). The mechanical performance of the green composites was assessed by evaluating the various properties namely strength, modulus, and elongation under tensile, share, flexural, and compression loading conditions. The morphological study was also performed to examine the failure behavior of the composite after mechanical testing. The effect of fibre length (2 mm, 3 mm, 4 mm, 5 mm, and 6 mm) and fibre loading (10 wt.%, 20 wt.%, and 30 wt.%) on the performance of the flax fibre (FF)/polylactic acid (PLA) composite was also investigated. The fibre dispersion, fibre orientation, and fibre length retention were investigated to assess the characteristics of fibre during injection moulding of the developed flax fibre (FF)/polylactic acid (PLA) composite.

The corrosion behavior of Q345qNH steel and Q420qNH steel in simulated industrial atmospheric environment medium was studied by periodic immersion+infrared aging corrosion experiment. The results show that the corrosion type of both samples is uneven comprehensive corrosion, and the rust layer formed in the later stage of corrosion is relatively dense. But average corrosion rate of Q345qNH steel is always lower than that of Q420qNH steel, and the ratio of I_α-FeOOH/I_γ-FeOOH in rust layer is always higher. Compared with Q420qNH steel, Q345qNH steel has fewer surface pits but deeper local pits. The self-corrosion potential of Q345qNH steel increases obviously, the resistance of the rust layer is larger, and protection to the matrix is stronger. This is because the formation of a large number of corrosion microcells induced by fine lamellar sorbite tissue that uneven distributed in Q420qNH steel, which increases the corrosion rate and makes corrosion uneven, while the larger pearlitic group in Q345qNH steel increases the local corrosion rate. However, the higher chromium/carbon ratio in Q345qNH steel promotes the conversion of lepidocrocite to goethite and inhibits the cathode reaction in the infrared drying stage, improving the density and stability of the rust layer.

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.