Microstructure, corrosion and wear behavior of (AlCu)3.5CoCrNiFe and (AlCu)3.5CoCrNiTi high entropy alloy coatings prepared by laser cladding on AZ91 magnesium alloy

(AlCu)3.5CoCrNiFe and (AlCu)3.5CoCrNiTi high entropy alloy (HEA) coatings were prepared on AZ91 magnesium alloy by using laser cladding technology. The phase constitution, microstructure, microhardness, corrosion resistance and wear resistance of the prepared HEA coatings were investigated. Both the HEA coatings consisted of BCC and FCC phases. The microhardness of the (AlCu)3.5CoCrNiFe coating and (AlCu)3.5CoCrNiTi coating was 642.1 HV and 656.2 HV respectively, and both of them were about 9 times higher than that of the AZ91 substrate (71.9 HV). The addition of Ti element led to the formation of dense TiO2 passivation film, thus improving the corrosion resistance of the (AlCu)3.5CoCrNiTi coating. The wear loss of the (AlCu)3.5CoCrNiFe coating and (AlCu)3.5CoCrNiTi coating was 29% and 20% of that of the AZ91 substrate, respectively. The prepared HEA coatings could significantly improve the surface properties of the AZ91 alloy substrate, and the (AlCu)3.5CoCrNiTi coating showed better performance compared to the (AlCu)3.5CoCrNiFe coating

doi: 10.1093/jpe/rtn005 Advanced Access published

available online at www.jpe.oxfordjournals.org GeoSVM: an efficient and effective tool to predict species ’ potential distribution

A novel gradient composite material CrMnFeCoNiB2C0.5 prepared by laser melting deposition

A novel gradient composite of CrMnFeCoNiB2C0.5 was prepared by laser melting deposition (LMD). The heat accumulation during LMD results in thin-walled structure that exhibit significant structural gradients. The material was tested with an ultimate compressive stress of 1.56 ± 0.067 GPa and a compressive strain of 19.17 ± 1.96%. Such materials have the potential to prepare additive manufactured parts with locally-controllable strength and plasticity by simply varying the thermal input only

Effects of Laser Powers on Microstructures and Mechanical Properties of Al0.5FeCoCrNi High-Entropy Alloys Fabricated by Laser Melting Deposition

High-entropy alloys (HEAs) show great promise for various applications in many fields. However, it still remains a challenge to obtain the ideal match of the tensile strength and the ductility. In this paper, Al0.5FeCoCrNi walls were fabricated through laser melting deposition (LMD) technology with laser power ranging from 1000 W to 1800 W. Along with the increase in laser power, the average size of the Al0.5FeCoCrNi walls increased from 14.31 μm to 34.88 μm, and the B2 phase decreased from 16.5% to 2.1%. Notably, the ultimate tensile strength and the ductility of the 1000 W bottom wall were 737 MPa and 24.6%, respectively, while those of 1800 W top wall were 641 MPa and 27.6%, respectively, demonstrating that the tensile strength of the walls decreased and the ductility increased with the increase in laser power. Furthermore, quantitative calculation revealed that grain boundary strengthening and dislocation strengthening were the two major forms of strengthening compared to the others. This study concluded that the mechanical properties of HEAs could be regulated by laser power, enabling broader applications in industry with favorable tensile strength or ductility

Multi-scale comparison of topographic complexity indices in relation to plant species richness

Topographic complexity is a key component of habitat, which has been linked to increased species richness in many ecological communities. It can be measured in various ways and it is unclear whether these different measurements are mutually comparable when they relate to plant species richness at different spatial scales. Using a densely sampled set of observations for Rhododendrons (406 species and 13,126 georeferenced records) as a test case, we calculated eight topographic complexity indices from a 250-m resolution digital elevation model and examined their correlations with Rhododendron species richness in China at seven spatial scales: grain sizes 0.05 degrees, 0.1 degrees, 0.25 degrees, 0.5 degrees, 1.0 degrees, 1.5 degrees, and 2.0 degrees. Our results showed that the eight topographic complexity indices were moderately to highly correlated with each other, and the relations between each pair of indices decreased with increasing grain size. However, with an increase in grain size, there was a higher correlation between topographic complexity indices and Rhododendron species richness. At finer scales (i.e. grain size <= 1 degrees), the standard deviation of elevation and range of elevation had significantly stronger correlations with Rhododendron species richness than other topographic complexity indices. Our findings indicate that different topographic complexity indices may have positive correlations with plant species richness. Moreover, the topographic complexity-species richness associations could be scale-dependent. In our case, the correlations between topographic complexity and Rhododendron species richness tended to be stronger at coarse-grained macro-habitat scales. We therefore suggest that topographic complexity index may serve as good proxy for studying the pattern of plant species richness at continental to global levels. However, choosing among topographic complexity indices must be undertaken with caution because these indices respond differently to grain sizes. (C) 2015 Elsevier B.V. All rights reserved

Strain hardening and strengthening mechanism of laser melting deposition (LMD) additively manufactured FeCoCrNiAl0.5 high-entropy alloy

In order to develop the high-entropy alloy (HEA) with low cost and excellent mechanical properties for structural applications, the FeCoCrNiAl0.5 HEA has been fabricated by laser melting deposition, one of the advanced additive manufacturing methods. Strain hardening behaviour has been analysed and discussed using the combination of characterisation techniques. The LMD-ed FeCoCrNiAl0.5 had a true yield strength and strain of ∼463 MPa and 2.94%. Also, the true tensile strength of the LMD-ed FeCoCrNiAl0.5 reached 876 MPa, together with the ductility of 24.97% (engineering strain). The LMD-ed FeCoCrNiAl0.5 HEA exhibited a dual-phase structure of 93% face-centred cubic (FCC) phase and 6.9% ordered B2 phase. The phase boundary between the disordered FCC and ordered B2 phases played a key role in the barrier, which can block the movement of dislocations because of the lattice distortion, very large angle, and mismatch of the lattice. Dislocation pile-up and tangle caused the dislocation density near the phase boundaries to be higher than that in other areas, meanwhile, they further prevented the movement of dislocation under stress as they generated back stress, therefore LMD-ed FeCoCrNiAl0.5 HEA had a good strain hardening behaviour with a strain hardening exponent of 0.92. This study provided an innovative insight into the development of HEAs with ordered phase by laser additive manufacturing for structural applications

Strain hardening and strengthening mechanism of laser melting deposition (LMD) additively manufactured FeCoCrNiAl0.5 high-entropy alloy

In order to develop the high-entropy alloy (HEA) with low cost and excellent mechanical properties for structural applications, the FeCoCrNiAl0.5 HEA has been fabricated by laser melting deposition, one of the advanced additive manufacturing methods. Strain hardening behaviour has been analysed and discussed using the combination of characterisation techniques. The LMD-ed FeCoCrNiAl0.5 had a true yield strength and strain of ∼463 MPa and 2.94%. Also, the true tensile strength of the LMD-ed FeCoCrNiAl0.5 reached 876 MPa, together with the ductility of 24.97% (engineering strain). The LMD-ed FeCoCrNiAl0.5 HEA exhibited a dual-phase structure of 93% face-centred cubic (FCC) phase and 6.9% ordered B2 phase. The phase boundary between the disordered FCC and ordered B2 phases played a key role in the barrier, which can block the movement of dislocations because of the lattice distortion, very large angle, and mismatch of the lattice. Dislocation pile-up and tangle caused the dislocation density near the phase boundaries to be higher than that in other areas, meanwhile, they further prevented the movement of dislocation under stress as they generated back stress, therefore LMD-ed FeCoCrNiAl0.5 HEA had a good strain hardening behaviour with a strain hardening exponent of 0.92. This study provided an innovative insight into the development of HEAs with ordered phase by laser additive manufacturing for structural applications