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| 1 | A hidden precipitation scenario of theθ’-phase in Al-Cu alloys显示文摘Al-Cu binary alloys are important and interesting industry materials.Up to date,the formation mechanisms of the key strengthening precipitates,namedθ’-phase,in the alloys are still controversial.Here,we report that for non-deformed bulk Al-Cu alloys theθ’-phase actually has its own direct precursors that can form only at elevated aging temperature(>ca.200℃).These high-temperature precursors have the same plate-like morphology as theθ’-phase precipitates but rather different structures.Atomicresolution imaging reveals that they have a tetragonal structure with a=0.405 nm and c=1.213 nm,and an average composition of Al_(5-x)Cu_(1+x)(0≤x<1),being fully coherent with the Al-lattice.This precursor phase may initiate with a composition of Al5 Cu and evolve locally towards Al_(4)Cu_(2)in composition,eventually leading to a consequent structural transformation into theθ’-phase(Al4 Cu2=Al2 Cu).There are evidences that because of their genetic links in structure,such a high-temperature precursor may transform to theθ’-phase without having to change their morphology and interface structure.Our study reveals a well-defined and previously hidden precipitation scenario for theθ’-phase to form in Al-Cu alloys at an elevated aging temperature. | L.Zhou C.L.Wu P.Xie F.J.Niu W.Q.Ming K.Du J.H.Chen | 2021 | Journal of Materials Science & Technology2021，，16： | 4 |
| 2 | Unveiling anneal hardening in dilute Al-doped Al_(x)CoCrFeMnNi(x = 0,0.1) high-entropy alloys显示文摘Anneal hardening has been one of the approaches to improve mechanical properties of solid solution alloys with the face-centered cubic(FCC) structure,whereby a considerable strengthening can be attained by annealing of cold-worked alloys below the recrystallization temperature(T_(rx)).Microscopically,this hardening effect has been ascribed to several mechanisms,i.e.solute segregation to defects(dislocation and stacking fault) and short-range chemical ordering,etc.However,none of these mechanisms can well explain the anneal hardening recently observed in phase-pure and coarse-grained FCC-structured high-entropy alloys(HEAs).Here we report the observations,using high-resolution electron channeling contrast imaging and transmission electron microscopy,of profuse and stable dislocation substructures in a cold-rolled CoCrFeMnNi HEA subject to an annealing below T_(rx).The dislocation substructures are observed to be thermally stable up to T_(rx),which could arise from the chemical complexity of the high-entropy system where certain elemental diffusion retardation occurs.The microstructure feature is markedly different from that of conventional dilute solid solution alloys,in which dislocation substructures gradually vanish by recovery during annealing,leading to a strength drop.Furthermore,dilute addition of 2 at.% Al leads to a reduction in both microhardness and yield strength of the cold-rolled and subsequently annealed(≤500℃) HEA.This Al induced softening effect,could be associated with the anisotropic formation of dislocation substructure,resulting from enhanced dislocation planar slip due to glide plane softening effect.These findings suggest that the strength of HEAs can be tailored through the anneal hardening effect from dislocation substructure strengthening. | Q.Cheng X.D.Xu P.Xie L.L.Han J.Y.He X.Q.Li J.Zhang Z.T.Li Y.P.Li B.Liu T.G.Nieh M.W.Chen J.H.Chen | 2021 | Journal of Materials Science & Technology2021，，32： | 3 |
| 3 | Brain magnetic resonance imaging abnormalities in neuromyelitis optica显示文摘 | Y.Li P.Xie F.Lv J.Mu Q.Li Q.Yang M.Hu H.Tang J.Yi | 2008 | Acta Neurologica Scandinavica2008，，4： | 1 |
| 4 | Investigation on the ph-ase transformation of Bi-2223/Ag superconducting tapes during heating显示文摘 | K.-T.Huang T.-M.Qu P.Xie | | 0，，： | 1 |
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