Compressive deformation behaviors of extruded SiCw/AZ91 were investigated in Gleeble-1500 thermal simulator at temperatures from 743 K to 783 K and strain rates from 6.4×10-2 s-1 to 1.0×101s-1. Results showed that high strain rate sensitivity (~0.5) occurred during compression; deformation activation energy normalized by threshold stress was higher than the lattice self-diffusion activation energy of magnesium. Dynamic recovery (DRV) and dynamic recrystallization (DRX) took place during compression, which refined the grains. The increase of deformation energy was attributed to non-basal planes slip and climbing of dislocations and also the presence of liquid phase.
The compressive behavior of squeeze cast SiCw/AZ91 composite in the temperature range of 423-723K and in the strain rate range of 0.001-0.25 s-1 was investigated. The compressive true stress-true strain curves were measured and hot deformation microstructures were observed. The strain rate sensitivity exponent (m) of the SiCw/AZ91 composite increased with the increasing of temperature. The activation energy of deformation varied over the range of test conditions
examined indicated that the deformation was controlled by more than one mechanism. The reorientation of SiC whiskers in the composite was observed during compression. During the compression, dynamic recovery and dynamic recrystallization occurred in the SiCw/AZ91 composite.
Compressive behaviors of SiCw/AZ91composite and AZ91 alloy were investigated at temperatures from 423 K to 723 K and strain rates from 0.002 s-1 to 0.25 s-1. Microstructure evolutions after compressed at 623 K and 0.01 s-1 were observed by SEM and TEM. Results showed that compressive flow stress decreased with the increase of temperature; whiskers were broken and redistributed to the direction normal to the compression direction. At the initial stage of compression, dislocation sliding is the mainly deformation mode for the composite, while for AZ91 alloy, twining was the dominant mechanism.
This paper proposes an improved PWM algorithm: SWEDE-PWM algorithm by combination of SWEDE and PWM algorithm. It can reduce the computation of 2-D searching and eigenvalue decomposition simultaneously. Application to noncircular signals to improve the performance is also considered.
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