Filters

2018 - 20192

More filters

20202
Reset filters

Settings

Author: Eckert, J. × End date: 2019 × Start date: 2010 × Has files: Yes × Sponsor: Leibniz_Fonds ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    High strength nanostructured Al-based alloys through optimized processing of rapidly quenched amorphous precursors
    (London : Nature Publishing Group, 2018) Kim, S.-Y.; Lee, G.-Y.; Park, G.-H.; Kim, H.-A.; Lee, A.-Y.; Scudino, S.; Prashanth, K.G.; Kim, D.-H.; Eckert, J.; Lee, M.-H.
    We report the methods increasing both strength and ductility of aluminum alloys transformed from amorphous precursor. The mechanical properties of bulk samples produced by spark-plasma sintering (SPS) of amorphous Al-Ni-Co-Dy powders at temperatures above 673 K are significantly enhanced by in-situ crystallization of nano-scale intermetallic compounds during the SPS process. The spark plasma sintered Al84Ni7Co3Dy6 bulk specimens exhibit 1433 MPa compressive yield strength and 1773 MPa maximum strength together with 5.6% plastic strain, respectively. The addition of Dy enhances the thermal stability of primary fcc Al in the amorphous Al-TM -RE alloy. The precipitation of intermetallic phases by crystallization of the remaining amorphous matrix plays important role to restrict the growth of the fcc Al phase and contributes to the improvement of the mechanical properties. Such fully crystalline nano- or ultrafine-scale Al-Ni-Co-Dy systems are considered promising for industrial application because their superior mechanical properties in terms of a combination of very high room temperature strength combined with good ductility.
  • Thumbnail Image
    Item
    Optimizing mechanical properties of Fe26.7Co26.7Ni26.7Si8.9B11 high entropy alloy by inducing hypoeutectic to quasi-duplex microstructural transition
    (London : Nature Publishing Group, 2019) Zhang, Z.-Q.; Song, K.-K.; Guo, S.; Xue, Q.-S.; Xing, H.; Cao, C.-D.; Dai, F.-P.; Völker, B.; Hohenwarter, A.; Maity, T.; Chawake, N.; Kim, J.-T.; Wang, L.; Kaban, I.; Eckert, J.
    High-entropy alloys (HEAs) have inspired considerable interest due to their attractive physical and mechanical properties. In this work, the microstructural evolution induced by different heat treatments on rapidly solidified hypoeutectic precursors of a Fe26.7Co26.7Ni26.7Si8.9B11 HEA is investigated and correlated with the corresponding mechanical properties. The microstructures of the rapidly solidified precursors are composed of primary fcc solid solution dendrites embedded in a eutectic matrix. When the samples are annealed at different temperatures after furnace cooling or quenching, respectively, the eutectic structure gradually decomposes into fcc, tetragonal (Fe,Co)2B, and hexagonal Ni31Si12 crystals with increasing annealing temperature, leading to a gradual increase of the content of the fcc crystals and both their aggregation and coarsening. Then the dominant structural framework gradually transforms from eutectic structures to fcc dendrites and ultimately the (Fe,Co)2B crystals become isolated as dominant reinforcement particles distributed in the interdendritic regions. This gradual microstructural transition from hypoeutectic to quasi-duplex structures leads to the change of the dominant deformation mechanism from crack-controlled to dislocation-dominated deformation, which allows to control both ductility and strength in a wide range. Hence, this study provides some guideline for how to tune the microstructure and mechanical properties of HEAs.