Characteristics of superplasticity domain in the processing map for hot working of an Al alloy 201420vol.%Al2O3 metal matrix composite

doi:10.1016/0921-5093(94)90409-X

Materials Science and Engineering: A

Volume 189, Issues 1–2, 20 December 1994, Pages 137-145

https://doi.org/10.1016/0921-5093(94)90409-X Get rights and content

Abstract

The processing map for hot working of Al alloy 201420vol.%Al₂O₃ particulate-reinforced cast-plus-extruded composite material has been generated covering the temperature range 300–500 °C and the strain rate range 0.001–10 s⁻¹ based on the dynamic materials model. The efficiency η of power dissipation given by $2m (m + 1)$ , where m is the strain rate sensitivity, is plotted as a function of temperature and strain rate to obtain a processing map. A domain of superplasticity has been identified, with a peak efficiency of 62% occurring at 500 °C and 0.001 s⁻¹. The characteristics of this domain have been studied with the help of microstructural evaluation and hot-ductility measurements. Microstructural instability is predicted at higher strain rates above (1s⁻¹) and lower temperatures (less than 350 °C).

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Hot deformation mechanisms of 2009Al (Al-4.0 wt% Cu-1.5 wt% Mg) alloy and 17 vol% SiCp/2009Al composite prepared by powder metallurgy (PM) route were investigated using isothermal compression test at temperatures from 350 to 500 ºC and strain rates from 0.001 to 1 s⁻¹. Strain rate sensitivity map, temperature sensitivity map and processing map based on modiﬁed dynamic materials model (MDMM) were constructed to study the deformation mechanisms by combining with microstructural examination. The temperature sensitivity curves gave an identical equicohesive point, which was a strong and weak transition point of grain boundaries relative to grains, (T_eq) of 450 ºC both for the composite and unreinforced alloy. At high strain rate of 1 s⁻¹, dynamic recovery (DRV) and partial dynamic recrystallization (DRX) were the dominant mechanism, while at low strain rate of 0.001 s⁻¹, DRX was the dominant mechanism. The SiC particles accelerated dislocation multiplication and impeded the restoration below 450 ºC. The instability criteria based on Ziegler’s continuum principle and Lyapunov function were not applicable for the PM composite and the unreinforced alloy.
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Citation Excerpt :
It is, however, observed that there is little presence of matrix damage(as for example wedge cracking [35–37]) even in the intensely deformed area of bulge region. This observation is consistent with the numerous studies of hot deformation carried out on A6061 based PMMC reinforced with SiCP or Al2O3 at 500 °C, over wide strain rate range [35–41]. These studies mainly characterising the hot working behaviour of the A6061 PMMC in the framework of determining the processing map based on dynamic materials model show a high efficiency for power dissipation through microstructural changes at 500 °C deformed above 0.1 s−1 [38–40].
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Characteristics of superplasticity domain in the processing map for hot working of an Al alloy 201420vol.%Al2O3 metal matrix composite

Abstract

Scr. Metall.

Scr. Metall.

Scr. Metall.

Scr. Metall.

Compos. Sci. Technol.

Scr. Metall.

Scr. Metall.

Metall. Trans. A

Characteristics of superplasticity domain in the processing map for hot working of an Al alloy 201420vol.%Al₂O₃ metal matrix composite