2 research outputs found
Substitutional silicon content effect on the structural/mechanical modification of metastable triplex high entropy alloys
No full textThe phase metastability and precipitation are now considered to be an important strategy in designing Fe-rich high entropy alloys (HEAs). In this study, the influence of silicon addition on the initial and strain-induced microstructure evolution and related mechanical property of Fe52-xMn27Cr15Co6Six ( x = 0, 0.3, 0.5, 1.0, 1.5, at.%) HEAs was systematically investigated by utilizing the in-depth microstructural characterization coupled with X-ray diffractometer (XRD), secondary electron microscopy (SEM), and transmission electron microscopy (TEM). The addition of Si to Fe52-xMn27Cr15Co6Six HEAs facilitates the triplex structure consisting of fcc-y matrix, thermally-induced s-martensite and sigma phase ( a). The lattice distortion energy by Si atoms is suggested to promote the formation of a phase consisting of Cr, Si and Co and consequently influence the metastability of the matrix. In 0.3 at.% Si HEA, the strain-induced body-centered tetragonal (bct)-type a'-martensite were observed at the intersection of bi-directional strain-induced s-martensite laths, enhancing the ultimate tensile strength to similar to 851 MPa from similar to 618.3 MPa with ductility increment (similar to 73.1% from similar to 71%). In 0.3 at.% Si and 0.5 at.% Si alloys, the granular-type a phase was observed both at grain boundaries and in grain interior, and the size of granular-type a phase at grain boundary and intra-granular a phase were found to be similar. The deformation mode altered from the transformation-induced plasticity (TRIP) to twinning-induced plasticity (TWIP) with an increase of Si content to 1.5 at.%, due to the enhanced fcc-y stability induced by the compositional modulation driven by increased a phase formation. The propagation of microcracks inside brittle a phase could be suppressed by homogeneous slip through strain-induced martensite transformation (SIMT) in HEAs with low Si addition of 0.3at.% -0.5 at.%. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.
The Growth of ZnO on CrN Buffer Layer Using Surface Phase Control by Plasma Assisted Molecular-beam Epitaxy
No full textABSTRACTEpitaxial ZnO films are successfully grown on Al2O3 substrates with phase controlled CrN buffer layer using Zn and O-plasma pre-exposures on CrN layers by plasma assisted molecular beam epitaxy (P-MBE). The Zn exposures on CrN layers prior to ZnO film growth result in the formation of rocksalt CrN without surface oxidation. On the other hand, the surface of the initially deposited CrN layers with rocksalt structure changes into hexagonal structured Cr2O3 after O-plasma exposure as confirmed by reflection high-energy electron diffraction (RHEED) and high resolution transmission electron microscopy (HR TEM). Etching studies show that the ZnO films grown on CrN have +C polarity, while the polarity of ZnO on Cr2O3/CrN double buffer is -C polarity. The interdiffusion of Zn and Cr occurs at the ZnO/CrN interface, while the interdiffusion is negligible at the ZnO/ Cr2O3 interface. The interdiffusion of Cr and Zn can be suppressed by inserting a low-temperature ZnO buffer layer in between ZnO and CrN layers, which helps improve the crystal quality of ZnO layers grown with CrN buffer.</jats:p
