Plasticity dependence on amorphous continuity in Fe-SiOC dual-phase nanocomposites

1.Introduction High strength and large deformability are greatly desirable for advanced structural metallic materials.Typically strengthening methods in crystalline materials rely on controlling the generation,propagation,and intersection of dislocations by introducing various internal defects[1-4].

Cooperative effect of Cr and Al elements on passivation enhancement of eutectic high-entropy alloy AlCoCrFeNi_(2.1)with precipitates

In conventional corrosion-resistant alloys,precipitation usually reduces corrosion resistance severely by weakening passive films locally.In this work,we found that the aging-treated AlCoCrFeNi_(2.1)sam-ples,which have abundant nanosized L 12 and body-centered cubic(BCC)precipitates in the lamellar face-centered cubic(FCC)and B2 phases,displayed better corrosion resistance than solution-treated AlCoCrFeNi_(2.1)samples without precipitates.In the AlCoCrFeNi_(2.1)alloy,the FCC phase with L1_(2)precipi-tates and the B2 phase with BCC precipitates were protected by passive films enriched with Cr and Al elements,respectively.Moreover,the Al-rich passive film of the B2 phase was less stable than the Cr-rich passive film of the FCC phase,so B2 phase dissolved preferentially.The Cr-rich passive film of the FCC phase remained stable with the formation of Al-rich L1_(2)precipitates inside the phase because those precipitates with the size of∼5 nm were too small to affect the composition of the Cr-rich passive film.The formation of Cr-rich BCC precipitates within the B2 phase increased the content of the Al element inside the phase,improving the stability of Al-rich passive film on the B2 phase.Furthermore,BCC precip-itates with the size of∼30 nm were protected by Cr-rich passive film,which could inhibit the expansion of corrosion pits.Thus,the corrosion resistance of eutectic high-entropy alloy AlCoCrFeN 2.1 was unprece-dentedly enhanced by the precipitation of BCC precipitates.Our study could provide an attractive strategy for designing high-entropy alloys with excellent corrosion resistance and high strength.

Intermediate Temperature Fatigue Induced Precipitation and Associated Corrosion in CrMnFeCoNi High Entropy Alloy

Understanding the corrosion behavior of high entropy alloys(HEAs)after intermediate temperature fatigue is critical to prevent their catastrophic failures from the reduction of corrosion resistance.Here,we investigated the corrosion behavior of CrMnFeCoNi HEA after 500℃ fatigue test with strain amplitudes of 0.2%and 0.5%.The intermediate temperature fatigue induced two types of precipitates,which were determined as Cr-richσphase and NiMn-rich L10 phase.Higher strain amplitude not only promoted precipitates generations but also spread the nucleation sites from intergranular to both intergranular and intragranular.Furthermore,we found that the deterioration in corrosion resistance of the alloy was derived from the increase of precipitates,which destroyed the stability of the passive film.The above results revealed that intermediate temperature fatigue impaired the stabilization of the solid solution state and subsequent corrosion resistance of CrMnFeCoNi HEA,where the higher strain amplitude led to more precipitates and more severe corrosion.

High-temperature strength-coercivity balance in a FeCo-based soft magnetic alloy via magnetic nanoprecipitates

Precipitation strengthening is an effective approach to enhance the strength of soft magnetic alloys for applications at high temperatures,while inevitably results in deterioration in coercivity due to the pinning effect on the domain wall movement.Here,we realize a good combination of high-temperature strength and ductility(ultimate tensile strength of 564 MPa and elongation of~20%,respectively)as well as low coercivity(6.97 Oe)of FeCo-2V-0.3Cr-0.2Mo soft magnetic alloy through introducing high-density magnetic nanoprecipitates.The magnetic nanoprecipitates are characterized by FeCo-based phase with disordered body-centered cubic structure,which enables the alloy to have a low coercivity.In addition,these nanoprecipitates can impede the dislocation motion and suppress the brittle fracture,which lead to a high tensile strength and ductility.This work provides a guideline to enhance strength and ductility while maintaining low coercivity in soft magnetic alloys via magnetic nanoprecipitates.

Dependence of Plastic Stability on 3D Interface Layer in Nanolaminated Materials

The nanolaminated materials generally exhibit poor plasticity due to the fast onset of shear instability.Engineering interface structure is an eff ective approach for enhancing plasticity via postponing or suppressing the shear instability.Here,we introduce 4 nm thick CuNb 3D amorphous interface layers and Nb 3D crystalline interface layers in Cu nanolaminated materials,respectively.In situ micro-pillar compression tests show that samples with crystalline interface layers exhibit shear instability,while the samples with amorphous interface layers display uniform deformation.Since the plastic deformation of the singlecrystal crystalline interface layer is anisotropic,except for well-aligned slip systems,dislocations on other slip systems have a poor ability to transmit the 3D crystalline interface layer,leading to localized dislocations pileups and shear instability.In contrast,the amorphous interface layer which is plastically isotropic accommodates dislocations from arbitrary slip systems of the matrix,which can alleviate the stress concentrations at the interface,and thus suppresses the shear instability.