Materialwissenschaft und Werkstofftechnik最新文献

In this paper, pre-oxidation treatment was carried out at 950 °C under oxygen pressure of 10⁻¹⁶ atm for nickel-10 % chromium-x % aluminium-1 % silicon-0.5 % yttrium(x=0 wt.–%, 1 wt.–%, 3 wt.–%, 5 wt.–%) alloys. Morphology and structure of oxide layers on the alloys after pre-oxidation were analyzed by scanning electron microscopy and electron discharge spectroscopy. The results showed that a chromium oxide film was formed on the surface of the alloy without aluminium addition, while the oxide layer on the surface of the alloy with aluminium addition gradually transformed into M₂O₃ (M=aluminium and chromium) oxide film. The oxidation behavior was analyzed by means of chemical thermodynamics, and it was seen that because the interaction coefficient,εijof aluminium and chromium is a positive value, the increase of aluminium addition will strengthen the interaction and increase the diffusion coefficient,Diof aluminium and chromium. The diffusion of chromium and aluminium in each other therefore promotes their interaction, which is beneficial to the formation of the outer oxide film. Thus, with the increase of aluminium addition, the thickness of the outer oxide film gradually increased, and the aluminium content in M₂O₃ (M=aluminium and chromium) increased significantly, and with 5 % aluminium added, the aluminium oxide of the outer oxide film became the main body.

Rapid evolution in engineering and manufacturing demands light weight material with enhanced mechanical properties. Aluminium metal matrix composites with ceramic reinforcement particulates serve this demand due to their reduced density, improved strength and hardness along with higher resistance to wear and corrosion. However, the material cost and reduced machinability hinders the full potential of utilization. To overcome these challenges, in this work cupola slag, an industrial waste generated as by product of cast iron production, has been incorporated as reinforcement of aluminium composites using low cost stir casting method. The enhancement of material properties and machinability by cupola slag inclusion on base alloy has been investigated in detail. Moreover, introspection about the underlying mechanisms responsible for the improvement in material properties has been studied using detailed microstructure and fractographic analysis. The results show improvement of in material properties and machinability up to 7 wt.–% cupola slag inclusion, beyond which the reduced wettablity prohibits sound castings. The ultimate tensile strength and specific strength observed to be improved by 18.20 % and 33.23 % respectively for 7 wt.–% slag reinforced composites when compared with base alloy. This work can be a successful addition to the knowledge pool of ongoing research on low-cost novel material with enhanced properties.

The effect of equal channel angular pressing combined with inter-pass and post-process annealing on the microstructure and mechanical properties of the Al-7075 alloy has been studied. The samples underwent successful equal channel angular pressing for three passes using the B_c route. The most significant changes in mechanical properties were observed after the first pass. Despite an 88 % reduction in grain size, the hardness of the alloy increased by 45 % and the fracture toughness decreased by 75 %. Post-process annealing was found to be an effective method for enhancing the alloy‘s toughness. Annealing the one-pass sample at 310 °C resulted in a 33 % increase in fracture toughness; from 15.8 J to 21.02 J. Inter-pass annealing had a lesser impact on improving fracture toughness compared to post-process annealing. It can be concluded that a balanced combination of strength and toughness can be achieved by utilizing a combination of equal channel angular pressing and inter-pass or post-process annealing. Examination of the fracture surfaces of the samples revealed intragranular fractures, with the annealed samples exhibiting higher energy absorption during impact and better toughness compared to the non-annealed sample.

In this paper, three-phase composites were made by combining N220 carbon black rubber powder with open-cell aluminum foam and epoxy resin with mass fractions of 3 %, 5 %, and 7 %, respectively. The mechanical and energy absorption properties of three groups of epoxy resin/rubber powder/aluminum foam three-phase composites with added aluminum foam and different mass fractions of N220 carbon black rubber powder were analyzed during quasi-static compression at a compression rate of 2 mm/minute. The mechanical parameters in the quasi-static compression experiments were compared with those of the two-phase composites of epoxy resin/rubber powder with no added aluminum foam. Finally, the micro-morphology of the composites after quasi-static compression damage was observed by scanning electron microscopy. The results show that the collapse deformation of aluminum foam during compression affects the stability of the epoxy resin/rubber powder composite matrix and reduces the toughness of the epoxy resin/rubber powder composite matrix.

Polymer alloying is particularly important due to the possibility of choosing a wide range of materials and the ability to design a product with desired properties. In case of incompatibility between the components, the resulting alloy cannot meet the set of desired properties and shows poor performance. In this research, alloys of polyvinyl chloride and polylactic acid were prepared in an internal mixer and nanoclay and maleic anhydride-grafted styrene-ethylene/butylene-styrene (SEBS-g-MAH) compatibilizer were used to improve the properties. In order to investigate the morphology and phase distribution of polylactic acid, scanning electron microscope images were taken. Tensile and dynamic mechanical thermal analysis tests were performed to evaluate the properties of the samples. The scanning electron microscope test images show the improvement of system uniformity by adding compatibilizer to the alloy. Adding nanoclay to the alloy increased the storage modulus and uniformity of the system. An increase in glass transition temperature and storage modulus was observed in the samples containing compatibilizer, and the uniformity of the system was also improved. The tensile test results showed that by adding nanoclay up to 3 % by weight, the tensile strength and Young′s modulus increase. Addition of compatibilizer up to 5 % by weight increased the physical and mechanical properties.

Automobile and aviation industries require lightweight solutions in the suspension system to improve overall performance and payload capacity. This can be achieved by materials having high strength to weight ratio. Fiber composites, known for their lightweight and high strength, face a major issue of delamination, which shortens the lifespan of fiber-reinforced polymer leaf springs. Current researchers are emphasizing the use of functionally graded materials as a promising alternative to tackle this problem. In the present work, a functionally graded leaf spring plate was fabricated using stir casting technique with five layered gradations in the mid portion. The amount of molten material required for each gradation was ensured using a novel experimental technique. On the other hand, the matrix and reinforcement have been adopted from the output of the analysis conducted using CES EduPack 2019 software. Low density and high fatigue strength were primary focal point for the consideration of matrix and reinforcement materials. Aluminium 7075 and boron carbide were considered as matrix and reinforcement materials respectively. Stir casting technique, used in the present work, is simple, suitable and cost effective technique which creates a gradation at central part of the leaf.

High velocity oxyfuel coatings have been sprayed on aluminium (Al) alloy composites substrate with varying coating thickness and tested for their wear behavior. The density and micro- hardness of the coatings found to increase with increase in coating thickness. The air erosion wear test has been conducted using quartz sand of size up to 75 μm as erodent. The steady state experiments indicate that the greatest specific erosion rate is at 60° and minimum at 30°. Due to the presence of interlayer, specific erosion rate decreases with the increase in the thickness of the coatings. Surface topography of the eroded samples indicate a decrease in surface roughness with increase in impact velocity. Thereafter, Taguchi (L₁₆) orthogonal array has been utilized in order to optimize the input parameters. Analysis of variance has been applied to determine the contribution of individual control factors. The results from Taguchi experiments and analysis of variance find the order of dominance of control factors and their individual contribution as: velocity (47.31 %) > coating thickness (29.94 %) > angle (13.26 %) > erodent feed rate (7.65 %). Coatings have exhibited a semiductile wear behavior.