A laser metal deposition (LMD) process has been applied to the fabrications of the (CrMnFeCoNi)1-xFex (x = 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) Multi-principal elements alloys (MPEAs). It is found that ...the LMD-fabricated (CrMnFeCoNi)50Fe50 alloy keeps a single-phase solid solution microstructure. Compared with the CrMnFeCoNi MPEA, the (CrMnFeCoNi)50Fe50 alloy obtains remarkably improved plasticity from 45% to 77%, while maintaining tensile strength (415 MPa to 470 MPa), due to the strain-induced FCC to BCC phase transformation. Furthermore, the (CrMnFeCoNi)50Fe50 alloy shows excellent mechanical properties at cryogenic temperatures. This alloy has lower cost and better mechanical property than the well-known CrMnFeCoNi MPEA by the addition of inexpensive Fe elements. The present work provides important pathways in the development of low-cost LMD-fabricated MPEA for cryogenic engineering applications.
Display omitted
•The (CrMnFeCoNi)50Fe50 multi-principal element alloy keeps an FCC solid solution.•The alloy shows excellent plasticity properties at cryogenic temperatures.•Strain- induced phase transformation was observed during tensile testing.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Titanium for additive manufacturing presents a challenge in the control of costs in the fabrication of products with expanding applications compared with cast titanium. In this study, ...hydrogenated-dehydrogenated (HDH) titanium powder with a low cost was employed to produce spherical Ti powder using the radiofrequency plasma (RF) technique. The spherical Ti powder was used as the raw material for laser directed energy deposition (LDED) to produce commercially pure titanium (CP-Ti). Microstructural analyses of the powder revealed that RF treatment, not only optimized the shape of the titanium powder, but also benefited in the removal of the residual hydride phase of the powder. Furthermore, the LDED-HDH-RF-produced samples showed an excellent combination of tensile strength and tensile ductility compared to the cast and the LDED-HDH-produced samples. Such an enhancement in the mechanical properties was attributed to the refinement of the α grain size and the dense microstructure. The present work provides an approach for LDED-produced CP-Ti to address the economic and mechanical properties of the materials, while also providing insights into the expanding application of HDH titanium powder.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this paper, a laser-based directed energy deposition (DED) technique is used to fabricate FeCoNiCr and CrMnFeCoNi multi-principal-element alloys (MPEAs). Comparing the above samples, the FeCoNiCr ...samples with coarse columnar grains cracked, while the CrMnFeCoNi samples with equiaxed grain were crack-free. The strategy that removes cracks is to induce a columnar-grain-to-equiaxed-grain transition (CET) with Mn addition to offer more grain boundaries to withstand residual stress in the process of DED-fabricated FeCoNiCr and to help minimize hot cracking. Furthermore, the yield strength, tensile strength, and tensile ductility of the DED-fabricated CrMnFeCoNi obviously improved compared with the DED-fabricated CoCrFeNi and exhibited better isotropic mechanical properties. The present work provides a novel strategy to utilize CET for resisting crack propagation in the process DED-fabricated MPEAs and improvement in mechanical properties of MPEAs.
To further strengthen the AlCoCrFeNi high-entropy alloy (HEA) coating prepared by high-speed laser cladding (HLC), laser remelting (LR) was chosen to reprocess it. The effects of LR on the ...topography, microstructure, growth orientation, phase distribution, and properties were investigated. It was revealed that there were a large number of liquid phase separation (LPS) zones in the HLC coating because of an ultrafast cooling rate. After LR, the LPS zones were eliminated. Compared to HLC coating, the microhardness increased from 622 HV to 762 HV, and the friction coefficient and the wear weight loss were reduced by 0.1 and 0.5 mg, respectively. In electrochemical testing, the self-corrosion potential increased by 45.9 mV and the self-corrosion current density decreased by one order of magnitude. Meanwhile, EBSD analysis indicated that the LPS zones were prone to recrystallization. The LPS zones were nickel-poor, low hardness, also BCC phase, and had a clearer (101) orientation. With the elimination of the LPS zones, the kernel average misorientation values were reduced, Taylor factor values and high angle grain boundaries were increased, and the average grain size was reduced from 2.43 μm to 2.12 μm. Eventually, for LR coatings, the combination of fine grain strengthening, solid solution strengthening, spalling reduction, and Cr element segregation resulted in better wear and corrosion resistances. The overall results show that a reasonable LR application can induce the microstructure of the HLC coating and improve its service properties.
● The AlCoCrFeNi high-entropy alloy coatings were prepared by high-speed laser cladding (HLC) and reprocessed by laser remelting (LR).● There were a large number of liquid phase separation (LPS) zones in the HLC coating. After LR, the LPS zones were replaced by fine equiaxed crystals.● The LPS zones were nickel-poor and low hardness, had a clearer (101) orientation, and tended to spall off in the wear test, causing a decrease in the overall wear resistance of the coating.● As a result of the elimination of the LPS zones, the microhardness and wear resistance of the LR coating were improved by solid solution strengthening and fine grain strengthening.● Appropriate undercooling and more high angle grain boundaries caused by LR provided a larger driving force for grain boundary segregation. The elemental content of Cr at the grain boundaries became higher, and the corrosion resistance of the LR coatings increased significantly. Display omitted
•HLC led to a large number of the LPS zones in the AlCoCrFeNi HEA coating.•LR could successfully eliminate the LPS zones.•Recrystallization made the grains of the LPS zones coarse and soft.•The microhardness and wear resistance of the coating were improved by LR.•Higher Cr content at grain boundaries boosted corrosion resistance of LR coating.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The negative effects of thermal cycles in the process of additive manufacture present a challenge for the control of microstructure so as to fabricate the products with improved properties compared ...with conventional casting technique. In this work, AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) was prepared by laser metal deposition (LMD). Compared with conventionally cast EHEA samples, the LMD-fabricated EHEA samples showed significantly enhanced tensile strength (by 19.7%) and increased tensile ductility (by 56.4%). Such enhancement in tensile properties was attributed to the refinement of the uniformly distributed eutectic-structure, which improved the strain hardening/dislocation accumulation capability of the EHEA. The present work provides a new strategy to utilize both the high cooling rates of LMD and the eutectic-structure characteristics for forming refined homogeneous structures and thus achieving superior mechanical properties to those prepared by traditional processing techniques.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The microstructural evolution, pitting performance, and passive-film properties of AlxCoCrFeNi high-entropy alloys (HEAs) fabricated via laser melting deposition (LMD) were investigated using ...material characterization techniques and electrochemical measurements. The substrates of the LMD HEAs transform from a face-centred cubic (FCC) to a body-centred cubic (BCC) structure with increasing Al addition. The BCC-structured B2 and A2 phases precipitate in the HEA substrate when the Al content reaches 10 mol.%. Ternary-phase HEA with Al addition of 10 mol.% exhibits the best corrosion resistance, which is attributed to favourable modifications in the Cr2O3 content and passive-film thickness.
•BCC-structured B2 and A2 phases are precipitated in the LMD HEAs with Al content higher than 5 mol. %.•Multi-phased HEAs with Al addition of 10–15 mol. % exhibit better corrosion resistance.•Corrosion resistance of the LMD HEA’s is improved by modifying the passive film chemistry and thickness..•Pitting will initiate at (Al, Ni)-rich B2 phase in multi-phased HEAs when passive film is broken down.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract Selective laser melting (SLM) can obtain metal magnetic materials with specific shapes and good mechanical properties, which has potential application value in the field of engineering. In ...this study, the soft-magnetic high-entropy alloy (HEA) Fe 33 Co 28 Ni 28 Ta 5 Al 6 was prepared via SLM. The microstructure, mechanical, and magnetic properties of the sample are investigated. The sample consists of a single face-centered-cubic (FCC) phase. The tensile yield strength, ultimate tensile strength, and elongation of the sample are 752 MPa, 1067 MPa, and 27% respectively. Furthermore, the sample has a low coercivity of 970 A m −1 , moderate saturation magnetization of 1.17 T, and high electrical resistivity of 121 μΩ cm. This work would provide a pathway for the rapid manufacturing high-performance soft-magnetic HEA.
AlxCoCrFeNi (x = 0, 0.2, 0.45, 0.7 and 1) high entropy alloys (HEAs) have been successfully synthesized by laser melting deposition (LMD). It is found that the microstructure of LMD-CoCrFeNi HEA with ...increasing the content of Al has been transformed from a single face-centered cubic (FCC) phase to mixture of FCC + BCC duplex phases, and then to body-centered cubic (BCC/B2) phases. The addition of Al (Al0.2, Al0.45 and Al0.7) remarkably improved the yield strength σ0.2 (from 138 MPa to 185 MPa, 262 MPa and 771 MPa) and the tensile strength σt (from 634 MPa to 675 MPa, 863 MPa and 1171 MPa) of the samples, with the prize of plasticity decrease from 46% to 45%, 41% and 11% in tension. This work provides an approach of LMD-fabricated CoCrFeNi-based HEAs with different Al addition to accommodate the microstructure and mechanical properties, and insights into the correlation of mechanical properties with the solid solution strengthening or/and the precipitation of hardening phase.
•AlxCoCrFeNi (x = 0, 0.2, 0.45, 0.7 and 1) HEAs have been prepared by LMD method.•The ΔHmix and VEC are used to predict the phase stability for LMD-fabricated HEAs.•The LMD HEA has been changed from a single FCC phase to BCC phase via Al addition.•With the increase of Al amount, σ0.2 and σt of the HEAs under the tensile and compression test have been obvious improved.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
High-entropy alloys (HEAs) have many attractive properties, while the thermodynamic mechanism and general behavior of the spinodal decomposition in HEAs remain unknown. In this work, we conduct an ...experimentally consistent calculation of the spinodal decomposition of HEAs. Against the “high mixing entropy” theory, we show that increasing the number of elements can increase the possibility of spinodal decomposition, and the effects of the temperature, entropy and enthalpy are clarified. The high entropy effect on the widely observed pseudo-binary decomposition is proposed. These results provide a necessary paradigm to understand and further harness the spinodal decomposition in HEAs.
Display omitted
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PDF
