Materialwissenschaft und Werkstofftechnik最新文献

GH4169 is a precipitation-strengthened nickel-based high-temperature alloy, and its mechanical behavior at different temperatures is of significant importance for practical applications. Here, an in situ study on the mechanical properties and microstructural evolution of the GH4169 alloy at different temperatures was conducted using scanning electron microscopy in combination with digital image correlation. The results demonstrate the existence of a linear relationship between the local average strain and the macroscopic strain. At temperatures of 20 °C, 100 °C, 180 °C, and 260 °C, the local average strain is 1.96, 2.13, 2.26, and 2.30 times the macroscopic strain, respectively, which shows a clear trend. This indicates that the temperature has a significant influence on the plasticity of the alloy. Additionally, the strain is concentrated below the notch, whereby at a macroscopic strain of 1.7 % at 20 °C and 260 °C, the local maximum strain at the notch is 52 % and 83 %, respectively. Furthermore, when the macroscopic strain reaches 2.12 %, the local maximum strain at the notch is 72 % and 103 %, respectively. At this point, cracks start to initiate and gradually propagate. In situ observations show that at the beginning of the tensile plasticity stage, the plastic strain rate in the grains is twice the rate at the grain boundaries; subsequently, both rates tend to stabilize, and a high-strain zone appears inside the grains and is coordinately transferred to the surrounding grains through the grain boundaries. The final stage of damage of the alloy consists of perforation fracture, and the presence of a large number of cracked carbides at the fracture results in specimen cracking.

M. Gamerdinger, F. Akyel, S. Olschok, C. Kahve, D.C. Fritsche, U. Elliesen, C. Hopmann, U. Reisgen. Use of a low transformation temperature effect for the targeted reduction of welding distortion in stainless chromium-nickel steel for an application in rail vehicle construction. Materialwiss. Werkstofftech. 2024, 55, 1005–1017.

In paragraph “Acknowledgements” the following text is missing:

“The presented investigations were carried out at RWTH Aachen University within the framework of the Collaborative Research Centre SFB1120-236616214 “Bauteilpräzision durch Beherrschung von Schmelze und Erstarrung in Produktionsprozessen” and funded by the Deutsche Forschungsgemeinschaft e. V. (DFG, German Research Foundation). The sponsorship and support is gratefully acknowledged. The data that support the findings of this study are available at http://hdl.handle.net/21.11102/777fe674-4446-445c-ab21-b38f5b0b37b5 upon request”

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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.