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23. High-strength and thermally stable TiB2-modified Al–Mn–Mg–Er–Zr alloy fabricated via selective laser melting.

Author

Yu, Jiang, Geng, Yaoxiang, Chen, Yongkang, Wang, Xiao, Zhang, Zhijie, Tang, Hao, Xu, Junhua, Ju, Hongbo, and Wang, Dongpeng

Abstract

To increase the processability and plasticity of the selective laser melting (SLM) fabricated Al–Mn–Mg–Er–Zr alloys, a novel TiB2-modified Al–Mn–Mg–Er–Zr alloy with a mixture of Al–Mn–Mg–Er–Zr and nano-TiB2 powders was fabricated by SLM. The processability, microstructure, and mechanical properties of the alloy were systematically investigated by density measurement, microstructure characterization, and mechanical properties testing. The alloys fabricated at 250 W displayed higher relative densities due to a uniformly smooth top surface and appropriate laser energy input. The maximum relative density value of the alloy reached (99.7 ± 0.1)%, demonstrating good processability. The alloy exhibited a duplex grain microstructure consisting of columnar regions primarily and equiaxed regions with TiB2, Al6Mn, and Al3Er phases distributed along the grain boundaries. After directly aging treatment at a high temperature of 400°C, the strength of the SLM-fabricated TiB2/Al–Mn–Mg–Er–Zr alloy increased due to the precipitation of the secondary Al6Mn phases. The maximum yield strength and ultimate tensile strength of the aging alloy were measured to be (374 ± 1) and (512 ± 13) MPa, respectively. The SLM-fabricated TiB2/Al–Mn–Mg–Er–Zr alloy demonstrates exceptional strength and thermal stability due to the synergistic effects of the inhibition of grain growth, the incorporation of TiB2 nanoparticles, and the precipitation of secondary Al6Mn nanoparticles. [ABSTRACT FROM AUTHOR]

Published
2024
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49. Insights into the oxidation resistance mechanism and tribological behaviors of multilayered TiSiN/CrVxN hard coatings.

Author

Ju, Hongbo, Athmani, Moussa, Luan, Jing, AL-Rjoub, Abbas, Cavaleiro, Albano, Yaqub, Talha Bin, Chala, Abdelouahad, Ferreira, Fabio, and Fernandes, Filipe

Abstract

In the last decades, vanadium alloyed coatings have been introduced as potential candidates for self-lubrication due to their perfect tribological properties. In this work, the influence of V incorporation on the wear performance and oxidation resistance of TiSiN/CrN film coatings deposited by direct current (DC) reactive magnetron sputtering is investigated. The results show that vanadium incorporation significantly decreases the oxidation resistance of the coatings. In general, two layers are formed during the oxidation process: i) Ti(V)O2 on top, followed by a protective layer, which is subdivided into two layers, Cr2O3 and Si-O. ii) The diffusion of V controls the oxidation of V-containing coatings. The addition of vanadium improves the wear resistance of coatings, and the wear rate decreases with increasing V content in the coatings; however, the friction coefficient is independent of the chemical composition of the coatings. The wear of the V-containing coatings is driven by polishing wear. [ABSTRACT FROM AUTHOR]

Published
2023
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50. Microstructure and Mechanical Properties of Magnetron Sputtering TiN-Ni Nanocrystalline Composite Films.

Author

Ma, Bingyang, Yuan, Haitian, He, Zongqian, Shang, Hailong, Hou, Yanjie, Ju, Hongbo, and Fernandes, Filipe

Subjects
NANOCOMPOSITE materials, TRANSMISSION electron microscopes, MICROSTRUCTURE, MAGNETRON sputtering, SCANNING electron microscopes, CRYSTAL grain boundaries
Abstract

In this paper, TiN-Ni nanostructured composite films with different Ni contents are prepared using the magnetron sputtering method. The composition, microstructure, and mechanical properties of composite films are analyzed using an X-ray energy spectrometer (EDS), a scanning electron microscope (SEM), X-ray diffraction technology (XRD), a transmission electron microscope (TEM), and nanoindentation. All the films grow in a columnar crystal structure. There are only TiN diffraction peaks in the XRD spectrum, and no diffraction peaks of Ni and its compounds are observed. The addition of the Ni element disrupts the integrity of TiN lattice growth, resulting in a decrease in the grain size from 60 nm in TiN to 25 nm at 20.6% Ni. The film with a Ni content of 12.4 at.% forms a nanocomposite structure in which the nanocrystalline TiN phase (nc-TiN) is surrounded by the amorphous Ni (a-Ni) phase. The formation of nc-TiN/a-Ni nanocomposite structures relies on the good wettability of Ni on TiN ceramics. The hardness and elastic modulus of the film gradually decrease with the increase in Ni content, but the toughness is improved. The hardness and elastic modulus decrease from 19.9 GPa and 239.5 GPa for TiN film to 15.4 GPa and 223 GPa at 20.6 at.% Ni film, respectively, while the fracture toughness increases from 1.5 MPa·m1/2 to 2.0 MPa·m1/2. The soft and ductile Ni phase enriched at the TiN grain boundaries hinders the propagation of cracks in the TiN phase, resulting in a significant increase in the film's toughness. The research results of this paper provide support for the design of TiN-Ni films with high strength and toughness and the understanding of the formation mechanism of nanocomposite structures. [ABSTRACT FROM AUTHOR]

Published
2023
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