Dissertation
Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Non - ferrous metals and their alloys > Light non-ferrous metals and their alloys > Aluminum

Dynamic Mechanical Properties of Ultra-strength and Ultra-ductile Aluminum Alloys at Extreme Temperature

Author HuJianDong
Tutor WangYongGang
School Ningbo University
Course Engineering Mechanics
Keywords Dynamic mechanical behaviour Aluminum alloy extreme temperature high strain rates
CLC TG146.21
Type Master's thesis
Year 2012
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In this paper, the SHPB experiment device with the refrigeration system and heating deviceare used to investigate the dynamic compression behavior of the2024-T4and7075-T6alloy at thedifferent temperature and different strain rates. The results of the study show that the strain rateeffect of2024-T4alloy is not obvious at room temperature, and the effect of temperature on thestrain rate has a significant effect. High temperature show some of the strain rate effect, and in lowtemperature is basically rate irrelevant. The mechanical properties of temperature on2024-T4alloyhas a significant impact depend on the temperature. The flow stress decrease with the rise oftemperature basic linear decreases. When the temperature is above573K, the flow stress has asudden decrease process due to the dynamic recrystallization effect. For7075–T6alloy, it is foundthat the flow stress increases with the strain rate, but the strain rate sensitivity is independent on thetemperature. Strain hardening is observed within the small strain range. When the strain exceeds aproper value, the strain soften occurs due to the increase of the adiabatic temperature, which canresult in the adiabatic shear fracture of aluminum alloy. At constant strain rate of3000s-1, thecompressive stress-strain response depends sensitively on the test temperature. While the testtemperature is lower than573K, the flow stress linearly decreases with the increase of the testtemperature. Otherwise, at temperatures greater that573K there is a distinct drop in the flow stress.This drop corresponds to the dynamic recrystallization of metal at high strain rate and hightemperature deformation.Using the SHTB experiment device with heating device and MTS universal test machine, thedynamic tensile mechanical properties of two kinds of aluminum alloy at different temperature anddifferent strain rates have been studied. The results of the study show that: The strain rate effect oftensile behaviour of2024-T4alloy is obvious. The strain rate effect of the tensile mechanicalproperties of7075-T6alloy is not obvious. At the same time, the strain hardening of7075-T6alloyis not obvious, and the temperature effect on the strain softening has not obvious influence.Based on the experimental results, the model parameters of Johnson-Cook (J-C) constitutivemodel for two kinds of aluminum alloy were obtained. The fitted curves agree with theexperimental ones very well. Using the ABAQUS program, numerical simulation are investigated about the dynamic compression tests. The simulation results are in good agreementwith experimental results.

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