Browsing by Author "Zhang, DL"

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    Annealing-induced strengthening and stabilization in ultrafine-grained Al and Al–Mg alloys prepared by rapid powder consolidation
    (Elsevier, 2022-01-26) Zhou, DS; Bu, YF; Muránsky, O; Geng, HW; Sun, BH; Yang, C; Zhang, DL
    Annealing usually softens Al–Mg based alloys due to grain coarsening. This work shows that annealing induces strengthening in bulk ultrafine-grained Al and Al-(2.5, 5 and 7.5) at.% Mg samples fabricated by mechanical alloying and rapid powder extrusion. Experimental investigation of the microstructure of the annealed samples reveals that the annealing promotes in-situ formation of nanoscale dispersoids which strongly suppresses grain growth and recrystallization. The in-situ formed nanodispersoids warrant high thermal stability of the ultrafine-grained matrix microstructure and improve the strength of the as-extruded samples while maintaining their good ductility. The present findings offer an exciting pathway in developing thermally stable ultrafine-grained Al–Mg based alloys with a notable combination of high strength and good ductility. © 2021 Elsevier B.V
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    In situ synchrotron high-energy x-ray diffraction analysis on phase transformations in Ti-Al alloys processed by equal-channel angular pressing
    (Wiley-Blackwell, 2009-11) Liss, KD; Whitfield, RE; Xu, W; Buslaps, T; Yeoh, LA; Wu, XL; Zhang, DL; Xia, KN
    Mixtures of 47-Al and 53-Ti powders (atomic %) have been consolidated using back pressure equal-channel angular pressing starting with both raw and ball-milled powders. In situ synchrotron high-energy X-ray diffraction studies are presented with continuous Rietveld analysis obtained upon a heating ramp from 300 K to 1075 K performed after the consolidation process. Initial phase distributions contain all intermetallic compounds of this system except Al, with distribution maxima in the outer regions of the concentrations (α-Ti, TiAl3). Upon annealing, the phase evolution and lattice parameter changes owing to chemical segregation, which is in favour for the more equilibrated phases such as γ-TiAl, α(2)-Ti3Al and TiAl2, were followed unprecedentedly in detail. An initial δ-TiH2 content with a phase transition at about 625 K upon heating created an intermediate β-Ti phase which played an important role in the reaction chain and gradually transformed into the final products. © 2009, Wiley-Blackwell.
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    Multiple strengthening mechanisms in high strength ultrafine-grained Al–Mg alloys
    (Elsevier, 2020-01-13) Wang, H; Geng, HW; Zhou, DS; Niitsu, K; Muránsky, O; Zhang, DL
    High strength has always been pursued in binary Al–Mg and 5xxx series Al alloys. However, these alloys usually provide medium strength due to lack of multiple strengthening methods. Here, this study reports on multiple strengthening effects existing in a binary ultrafine-grained (UFG) Al-7.5at.%Mg alloy prepared by mechanical alloying and hot extrusion. Different strengthening mechanisms, in particular, dispersoid strengthening and stacking fault strengthening, are analyzed and evaluated in terms of their respective contribution to the 511 MPa yield strength of the alloy. The strengthening analysis proves that the concurrent generation of nanoscale dispersoids and stacking faults (SFs) can be used as a new microstructural design in developing novel Al–Mg-based alloys with higher strength and enhanced ductility. © 2019 Elsevier B.V.
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    Towards the thermodynamic equilibrium of titanium aluminides after consolidation by back pressure equal channel angular pressing
    (ARC Centre of Excellence for Design in Light, 2007-12) Xu, W; Wu, X; Whitfield, R; Liss, KD; Buslaps, T; Yeoh, LA; Zhang, DL; Xia, K