The Use of Selective Laser Melting to Increase the Performance of AlSi9Cu3Fe Alloy

For the first time, the comprehensive characterization of the additively manufactured AlSi9Cu3Fe alloy is reported in this paper. Conventionally, the AlSi9Cu3(Fe) alloy is prepared by high-pressure die casting (HPDC), but this technology largely does not offer such opportunities as additive manufacturing (AM) does, especially in the design of new lightweight parts. In the present paper, testing samples were prepared by selective laser melting (SLM), one of the AM technologies, and characterized in terms of their microstructure (by means of light microscopy, scanning electron microscopy and transmission electron microscopy in combination with analytical techniques for evaluation of chemical and phase composition) and mechanical properties (static tension, compression, and hardness). All the characteristics were compared with the HPDC reference material. Our study showed an excellent improvement both in strength (374 ± 11 MPa compared to 257 ± 17 MPa) and plasticity (1.9 ± 0.2% compared to 1.2 ± 0.5%) of the material thanks to its very fine and distinctive microstructure

The synthesis of Au-NPs by ion implantation in the crystalline GaN and characterisation of their optical properties

Nanostructured surfaces with embedded noble metal nanoparticles is an attractive way for manipulation with the optical properties of wide bandgap semiconductors applied in optoelectronics, photocatalytic processes or for Surface-Enhanced Raman spectroscopy. Ion implantation offers an effective way for nanoparticle preparation without the use of additional chemicals that offers precise control of nanoparticle depth distribution. The aim of this study is a synthesis of the gold nanoparticles in GaN by implantation of 1.85 MeV Au ions with high fluences up to 7×1016 cm-2 and study of optical properties of Au implanted GaN. Implanted crystals were annealed at 800 °C in an ammonia atmosphere for 20 min to support Au nanoparticle creation and GaN recovery. The structure characterisation has been realized by Rutherford backscattering spectroscopy in channelling mode and it showed the formation of two separated disordered regions – the surface region and buried layer. The lower implantation fluences induce damage mainly in a buried layer; however, the increase of the Au-ion fluence leads to the increase of surface disorder as well. Further, the increase of the Au-ion fluence induces the Au dopant shift to the surface and multimodal Audepth profiles. TEM analyses confirmed the formation of Au nanoparticles in the implanted samples after annealing with sizes up to 14 nm. The increase of light absorption and modification of GaN bandgap of the Au modified GaN was deduced from the change in optical transmission spectra between 370 – 1400 nm

Nanotwinned (inter)martensite transformation interfaces in Ni50Mn25Ga20Fe5 magnetic shape memory single crystal foil

Publisher Copyright: © 2022 Elsevier Inc.Using common and high resolution transmission electron microscopy (TEM), we study the magnetic and crystal phase structures as well as their evolution in Ni50Mn25Ga20Fe5 magnetic shape memory material with high Curie point. The particular alloying by Fe and changing thickness of the TEM foil enable us to observe all martensitic phases known in Ni-Mn-Ga Heusler alloy system and their respective transitions simultaneously. Starting from cubic austenite at about 10 nm foil thickness, the structure evolves via peculiar interleaved stripes of austenite and five-layered modulated 10M martensite to pure 10M phase with a low density of stacking faults at 40 nm thickness. With further increasing thickness, the 10M phase transforms gradually to seven-layered modulated 14M martensite with an increased density of stacking faults. Finally, the non-modulated tetragonal NM phase appears within the 14M phase by detwinning of nanotwins forming the modulated phases. High resolution TEM further confirms that nanotwinning and stacking faults are inherent structure features tightly connected with the lattice modulation and intermartensite transformations. Overall, the evolution of average lattice shows the same general trend, an increasing simple shear with (11¯0) shuffling plane, across the whole phase sequence. Additionally, we found large local variation of lattice parameters in all phases, which is is ascribed to strong lattice softening in the vicinity of the martensitic transformation and high density of stacking faults in 14M martensite lattice.Peer reviewe

Observation of anomalously large magnetoelectric coupling in the hexagonal Z-type ferrite films

Although the bulk hexaferrites are known to exhibit strong magnetoelectric (ME) effects near room temperature, the same effects are not realized in a thin film form. Herein, the growth of nearly epitaxial Co2Z-type hexaferrite Ba0.3Sr2.7Co2Fe24O41 (BSCFO) thin films on a SrTiO3 (111) substrate by a chemical solution deposition method is reported. The reciprocal space mapping on the annealed BSCFO films reveals broadening along the qx directions in the (0014) and (0018) peaks, indicating that the oxygen planes belonging to the off-centered octahedra have randomly distributed out-of-plane tilt to indicate significant disorder in the crystallographic orientation. Quantitative investigations reveal that both ME susceptibility and modulated electric polarization (ΔP) by magnetic field up to 370 K in the BSCFO films are always larger than those of the Co2Z-type single crystal by ≈2–15 times and further increase upon having enhanced qx broadening in the (0014) and (0018) peaks. As the off-centered octahedral sites can be a primary source of ΔP as predicted by the p–d hybridization mechanism, these results indicate that effective off-centering could be further enhanced by the orientational disorder. This study identifies the potential of applying the ME hexaferrite films for multifunctional devices.This work was financially supported by the National Research Foundation of S. Korea through 2019R1A2C2090648, 2019M3E4A1080227, and by the Ministry of Education of S. Korea through 2021R1A6C101B418. The works in Czech were supported by the GACR (Czech Science Foundation) Project Nos. 19-06433S and H2020-MSCA-RISE-2016 SPICOLOST under Grant No. 734187 for TEM analysis at LMA-INA, University of Zaragoza, and by the Nanomaterial Center for Advanced Applications(NANOCENT), No. CZ.02.1.01/0.0/0.0/15_003/0000485.Peer reviewe

Data publication: Radiation damage evolution in pure W and W-Cr-Hf alloy caused by 5MeV Au ions in a broad range of dpa

Positron annihilation lifetime spectroscopy data taking for ELBE proposal POS19101496 by Sandrina Fernandes, Rez, CZ. Role of open volume defects in irradiated structural materials for fusion applications. Measurements performed 16.3.2019 at the MePS facility