Abstract

Selected magnesium and zirconium-based alloys reinforced by nanoprecipitation hardening and Nano dispersion strengthening mechanisms were examined in the power-law regime using long-term testing, strain-rate change measurements and constant structure steady-state creep tests to analyze the deformation and kinetic behavior of hcp Mg-Al-Ca-nm Al3Zr and hcp Zr-Sn-Nb-nm ZrO2 alloys at 423K and 673K, respectively. The microstructures generated in these hardened alloys have been assessed by proper techniques aiming at controlling and understanding the composition modification in the nanophase-reinforced and nanophase-free hcp magnesium and hcp zirconium alloys. The experimental studies were employed to optimize the composition-processing-microstructure-strength property relationship of the nano-reinforced composite materials in terms of extended uniform strain concept. Under the data of internal friction to be carried out isothermally in the hcp Mg-Ba and hcp Be-Fe, C alloys the deviations from Cottrell-Bilby time law have been revealed due to the non-isothermal kinetics of nanoparticulate nucleation by a pre-precipitate (cluster-forming) mechanism. A series of hcp metal alloys in the Mg-Al-Ca and Zr-Nb-Sn systems discontinuously nano-reinforced by Zr3Al and ZrO2, respectively have been developed as crystalline nanophase materials with more excellent heat and creep resistance as well as higher long-term strength. The observations and findings suggest that the principles of nanophase strengthening should be considered as an effective means of obtaining desirable combinations of mechanical properties due to the nanoparticle-induced delaying of time-dependent shear localization.

Keywords: Nanodispersoids; Strengthening mechanisms; Kinetics

Abbreviations: GBs: Grain Boundaries; EPMA: Electron Probe Microanalysis; XRD: X-Ray Diffraction (Analysis); AE: Alloying Element; Q-1: Internal Friction; Δ: Dislocation Damping; i.e. Amplitude- Independent Internal Friction; RE: Rare Earth; nm: Nano Meters; SAD: Selected are Diffraction Pattern