Structure and Stability of TiC/γ Interface inFe-Cr-Ni Base Composite

The morphology. orientation relationship and stability of TiC/γ interface in Fe-Cr-Ni base composite synthesized with a liquid state in-situ process have been studied. The TiC/γ interface in as-cast sample is of coherent feature. Its orientation relationship is (020)γ／／(220)TiC, [001]γ||[001]TiC. During the aging at 1473 K, the TiC/γ interface may dissolve in matrix and lamellar M23C6 compound may precipitate from γ-matrix.

Enhanced dynamic deformability and strengthening effect via twinning and microbanding in high density NiCoFeCrMoW high-entropy alloys

High density alloys with enhanced deformability and strength are urgently required in energy,military and nuclear industries,etc.In this work,we present a new kind of NiCoFeCrMoW high entropy alloys(HEAs)which possess higher densities and sound velocities than copper.We systematically investigate the phase structure,quasi-static tensile,dynamic compression and related deformation mechanism of these HEAs.It is shown that single FCC or FCC+μdual phases were formed in the HEAs depending on Mo and W content and annealing temperature.Excellent quasi-static tensile and dynamic compression properties have been achieved for these HEAs,e.g.Ni_(30)Co_(30)Fe_(21)Cr_(10)W_(9)HEA annealed at 1573 K exhibited a yield and ultimate tensile strength and elongation of~364 MPa,~866 MPa and~32%,respectively,in quasi-static test;a yield strength of~710 MPa and no fracture under the dynamic strain rate of 4100 s^(-1).Superior strain rate sensitivity(SRS)of yield strength than that of previously reported FCC HEAs have been evidenced.The dynamic stress-strain constitutive relation can be described by the modified Johnson-Cook model.As for the dynamic deformation mechanism,it is envisaged that the regulation of stacking fault energy and Peierls barrier in current HEAs resulted in occurrences of abundant nanoscale deformation twins and microbands during high strain rate compression.The synergistic microbanding and twinning effectively contributes to the enhanced dynamic deformability and strengthening effect.Besides,the interactions of dislocations with precipitates,stacking faults(SFs)with twins,and between SFs also contribute to extraordinary work-hardening capacity.

High-throughput investigations of configurational-transformation-dominated serrations in CuZr/Cu nanolaminates

Metallic amorphous/crystalline(A/C)nanolaminates exhibit excellent ductility while retaining their high strength.However,the underlying physical mechanisms and the resultant structural changes during plastic deformation still remain unclear.In the present work,the structure-property relationship of CuZr/Cu A/C nanolaminates is established through integrated high-throughput micro-compression tests and molecular dynamics simulations together with high-resolution transmission electron microcopy.The serrated flow of nanolaminates results from the formation of hexagonal-close-packed(HCP)-type stacking faults and twins inside the face-centered-cubic(FCC)Cu nano-grains,the body-centered-cubic(BCC)-type ordering at their grain boundaries,and the crystallization of the amorphous CuZr layers.The serration behavior of CuZr/Cu A/C nanolaminates is determined by several factors,including the formation of dense dislocation networks from the multiplication of initial dislocations that formed after yielding,weak-spots-related configurational-transitions and shear-transition-zone activities,and deformation-induced devitrification.The present work provides an insight into the heterogeneous deformation mechanism of A/C nanolaminates at the atomic scale,and mechanistic base for the microstructural design of self-toughening metallic-glass(MG)-based composites and A/C nanolaminates.

Revealing the Local Microstates of Fe–Mn–Al Medium Entropy Alloy:A Comprehensive First-principles Study

Entropy-stabilized multi-component alloys have been considered to be prospective structural materials attributing to their impressive mechanical and functional properties.The local chemical complexions,microstates and configurational transformations are essential to reveal the structure–property relationship,thus,to promote the development of advanced multicomponent alloys.In the present work,effects of local lattice distortion(LLD)and microstates of various configurations on the equilibrium volume(V0),total energy,Fermi energy,magnetic moment(μMag)and electron work function(Φ)and bonding structures of the Fe–Mn–Al medium entropy alloy(MEA)have been investigated comprehensively by first-principles calculations.It is found that theΦandμMag of those MEA are proportional to the V 0,which is dominated by lattice distortion.In terms of bonding charge density,both the strengthened clusters or the so-called short-range order structures and the weakly bonded spots or weak spots are characterized.While the presence of weakly bonded Al atoms implies a large LLD/mismatch,the Fe–Mn bonding pairs result in the formation of strengthened clusters,which dominate the local microstates and the configurational transitions.The variations ofμMag are associated with the enhancement of the nearest neighbor magnetic Fe and Mn atoms,attributing to the LLD caused by Al atoms,the local changes in the electronic structures.This work provides an atomic and electronic insight into the microstate-dominated solid-solution strengthening mechanism of Fe–Mn–Al MEA.