The effects of process parameters and aging treatment on the microstructure and mechanical properties of selective laser melting (SLM) fabricated high Mg-content Al-Mg-Sc-Zr aluminum alloy were ...systematically studied. Our experiment results show that the samples exhibit good processability with porosity less than 1%. The increase of Mg content in Al-Mg-Sc-Zr is beneficial to reduce the texture of the alloy. The laser scanning speed has a large influence on the Vickers hardness of as-fabricated samples. The maximum microhardness of as-fabricated sample reaches 148 ± 2 HV with a compression yield strength of 342 ± 7 MPa. After aging treatment, the distinction in microhardness of the samples obtained under different laser scanning speed is obviously reduced, and the mechanical properties of the samples are further improved with a maximum microhardness of 175 ± 5 HV and a maximum compressive yield strength of 476 ± 10 MPa, which are superior to the known Al-Mg-Sc-Zr alloy with same Sc and Zr content fabricated by SLM. In this study, a novel high Mg-content Al-Mg-Sc-Zr aluminum alloy specifically for SLM with good processability and mechanical properties was reported.
Graphic Abstract
•High Mg-content AlSiMg1.4 alloy was fabricated by selective laser melting.•YS and UTS of SLMed AlSiMg1.4 alloy reached 341 ± 14 MPa and 518 ± 6 MPa, respectively.•The strength of alloy are much ...higher than most known SLM fabricated Al-Si-Mg alloys.•The new strengthening mechanism was mentioned in the paper.
A high Mg-content AlSiMg1.4 alloy was designed for selective laser melting (SLM) processing. The SLMed AlSiMg1.4 alloy exhibits a high yield strength of 341±14 MPa and a high ultimate tensile strength of 518±6 MPa, along with a total elongation of 7.1±0.4%. The composition profile in the α-Al matrix of the alloy manifests in-phase concentration fluctuations of Mg and Si. The presence of high density Mg-Si atomic clusters as strong obstacles to dislocation gliding is suggested to provide an additional strengthening mechanism for the SLMed Al-Si-Mg alloy.
To address the high cost of raw materials for laser powder bed fusion (L-PBF) processed high-performance Al-Mn-Mg-Sc-Zr alloy, a novel Er- and Zr-modified Al-Mn-Mg alloy was fabricated by L-PBF using ...pre-alloyed powder in this study. The large internal stress and the existence of the keyhole together caused cracks in most of the L-PBF processed samples. The as-built sample exhibited a heterogeneous grain structure, including main columnar
α
-Al grains in the inner region of the molten pool and a few ultrafine
α
-Al equiaxed grains at the fusion boundary. Al
3
Er nanoparticles were attached to the Al
6
Mn phase, and both mainly precipitated at the grain boundary of
α
-Al. The existence of Mn in the alloy reduced the grain refining effect of Er elements. The yield strength (YS), ultimate tensile strength (UTS) and elongation of the as-built alloy were 327 ± 5 MPa, 502 ± 3 MPa, and 12.2 ± 1% respectively. When the aging temperature was over 350 ℃, the primary precipitates in the sample grew up, and needle-shaped secondary Al
6
Mn nanoparticles precipitated from
α
-Al. 350 ℃-6 h aging alloy exhibited maximum Vickers hardness of 171 ± 1 HV with YS, UTS and elongation of 339 ± 2 MPa, 508 ± 1 MPa and 8.1 ± 1%, respectively. During the tensile process of the alloy, micro-cracks mainly originated from the fusion boundary. At last, the authors also shared some prospects for future work.
Graphical Abstract
Transition metal dichalcogenides such as molybdenum disulfide (MoS2) were classified as excellent solid self-lubricant materials in vacuum or dry conditions. However, their poor mechanical and ...oxidation resistance properties limited their applications when used in humid air or at elevated temperature. In this paper, nitrogen was incorporated into the molybdenum disulfide matrix to synthesize the Mo–S–N films using RF magnetron sputtering system to improve above mentioned properties. The results showed the deposited nitrogen-free film was MoSx (x < 2), and due to its substoichiometry with respect to sulfur, both amorphous and crystalline state co-existed in MoSx film. Incorporation nitrogen into MoSx matrix induced the poor crystallinity and the formation of Mo–N, S–N and N–N bonds. All Mo–S–N films exhibit higher hardness and oxidation resistance temperature than that of MoSx mainly due to the Mo–N bonds. By comparison with MoSx film, all Mo–S–N films also had excellent tribological properties in the air at room temperature, 200 and 400 °C.
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•All Mo–S–N films exhibited higher hardness and oxidation resistance temperature than that of MoSx film.•Addition of nitrogen into MoSx matrix could improve room temperature tribological properties in humid air significantly.•Addition of nitrogen broadened the film's effective service temperature range from 200 to 400 °C.
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•A multilayered architecture of Mo2N-Ag and SiNx nanolayers in Mo2N-Ag/SiNx films.•Room temperature tribological properties were improved with increasing period thickness up to ...64 nm.•Multilayered Mo2N-Ag/SiNx films avoided the excessive diffusion of Ag at elevated temperatures.•Inserting SiNx layers avoided the excessive diffusion of Ag at high temperature.•Multilayer films exhibited excellent temperature-cycling tribological properties.
Nowadays there is the need to avoid the excessive consumption of liquid lubricant oils, as they are harmful to the environment and hard to disposal. Self-lubricant films have been seen as the sustainable solution to achieve a long-term lubrication under high temperature-cycling conditions. In this manuscript, multilayer Mo2N-Ag/SiNx films with a fixed modulation ratio (thickness of Mo2N-Ag to SiNx) of 3:1, with changing modulation period (Λ, thickness of Mo2N-Ag and SiNx) from 8 to 200 nm were produced to achieve an effective balance between the lubricious phase diffusion control and the adequate formation of the low friction tribo-layers. Results showed that a dual-phase of fcc-Mo2N and fcc-Ag co-existed in Mo2N-Ag layers, while the SiNx layer exhibited an amorphous character. Both room temperature (RT) lubricant and wear-resistance properties of the films were improved by increasing Λ from 8 to 64 nm, while a further increase of Λ degraded the wear-resistance properties. The multilayer film at Λ = 64 nm exhibited an excellent RT-500 °C temperature-cycling tribological properties. Mechanical properties and the synergistic effect of both modulation layers were the cause for the improvement of the tribological properties.
It is known that bulk metallic glasses follow simple composition formulas cluster(glue atom)
with 24 valence electrons within the framework of the cluster-plus-glue-atom model. Though the relevant ...nearest-neighbor cluster can be readily identified from a devitrification phase, the glue atoms remains poorly defined. The present work is devoted to understanding the composition rule of Fe-(B,P,C) based multi-component bulk metallic glasses, by introducing a cluster-based eutectic liquid model. This model regards a eutectic liquid to be composed of two stable liquids formulated respectively by cluster formulas for ideal metallic glasses from the two eutectic phases. The dual cluster formulas are first established for binary Fe-(B,C,P) eutectics: Fe-Fe
B
Fe + B-B
Fe
Fe ≈ Fe
B
for eutectic Fe
B
, P-Fe
P + P-Fe
P
Fe≈Fe
P
for Fe
P
, and C-Fe
Fe
+ C-Fe
C
Fe ≈ Fe
C
for Fe
C
. The second formulas in these dual-cluster formulas, being respectively relevant to devitrification phases Fe
B, Fe
P, and Fe
C, well explain the compositions of existing Fe-based transition metals-metalloid bulk metallic glasses. These formulas also satisfy the 24-electron rule. The proposition of the composition formulas for good glass formers, directly from known eutectic points, constitutes a new route towards understanding and eventual designing metallic glasses of high glass forming abilities.
The effects of minor alloying addition of Cu on the glass-forming ability and crystallization process of Fe
71.7−x
B
16.7
Si
8.3
Zr
3.3
Cu
x
and Fe
72.5−x
B
16.7
Si
8.3
Hf
2.5
Cu
x
(x = 0, 0.3, 0.7, ...1.0 and 1.3; at%) alloys were investigated. It was found that the critical glass formation size of rod samples gradually decreased from 2.5 to 1 mm with increasing Cu content in these alloys. Single
α
-Fe phase nanocrystalline alloys were obtained after isothermal annealing the Fe–B–Si–Zr/Hf–Cu glassy alloys containing 0.7–1.0 at% Cu. The Fe
71
B
16.7
Si
8.3
Zr
3.3
Cu
0.7
alloy exhibited good soft magnetic properties with a high saturation magnetization (~ 1.22 T) and a low coercive force (~ 0.6 A/m) after annealing at 853 K for 10 min due to the precipitation of
α
-Fe nanoparticles of 8 nm size in the glassy matrix. The structural evolution on annealing and the variation tendencies against Cu content of the glass transition temperature, thermal stability and glass-forming ability of the Fe–B–Si–Zr/Hf–Cu amorphous alloys were discussed using a dual-cluster local structure model.
Graphic Abstract
Selective laser melting (SLM) provides optimized lightweight structures for aircraft and space applications. However, the strength of the current SLMed aluminum alloys is still lower than that of the ...traditional high-performance aluminum alloys. This study presents an ultra-high-strength Al-Mn-Mg-Sc-Zr aluminum alloy specifically designed for SLM by increasing the (Mg + Mn) and (Sc + Zr) content simultaneously based on the rapid solidification characteristics of the SLM process. The alloy exhibits good SLM processability with a minimum porosity of 0.23%. After aging at 300 °C, the strength of the alloy was effectively improved, and the anisotropy of mechanical properties was reduced. Additionally, the tensile yield strength and ultimate tensile strength of the alloy reached 621 ± 41 MPa and 712 ± 28 MPa, respectively; these values are superior to those of most SLMed aluminum alloys reported previously. Multiple strengthening mechanisms including solid solution strengthening, precipitation strengthening and grain refinement strengthening contribute to the high strength of the present alloys.
Titanium nitride as a very representative ceramic film has been widely applied in cutting tools. Improvement the toughness and friction property of titanium nitride based films have been a research ...hotspot. In this paper, ruthenium was added into the titanium nitride brittle matrix and titanium ruthenium nitride composite hard films were synthesized using RF magnetron sputtering system and its crystal structure and room temperature tribological properties were investigated. The results showed that the addition of ruthenium above 1.3 at.% into the face-centered cubic (fcc) titanium nitride matrix exceeded the solid solubility limit and induced other phase of hexagonal close-packed (hcp) ruthenium. Addition of ruthenium into the titanium nitride matrix could enhance the fracture toughness, since it induced much more dislocations and interfaces. Compared with titanium nitride film, the content of adding ruthenium above 0.9 at.% reduced friction coefficient significantly without sacrificing the wear rate.
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•Titanium ruthenium nitride composite hard films were deposited using PVD system•The addition of ruthenium into the titanium nitride matrix enhanced the toughness.•Addition ruthenium into the titanium nitride matrix could improve the room temperature tribological properties.
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