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Lee, W.-S.; Chen, T.-H. |
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Publication |
Mechanical and microstructural response of aluminum-scandium (Al-Sc) alloy as a function of strain rate and temperature |
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Journal Article |
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2009 |
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Abstract |
Materials Chemistry and Physics |
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113 |
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2-3 |
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Summary Language |
734-745 |
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Al-Sc alloy; Strain rate sensitivity; Activation energy; Shearing; Dislocation; Precipitates |
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Abbreviated Series Title |
This study applies a compressive split Hopkinson bar to investigate the mechanical response, microstructural evolution and fracture characteristics of aluminum-scandium (Al-Sc) alloy at temperatures ranging from -100 °C to 300 °C and strain rates of 1.2 × 103 s-1, 3.2 × 103 s-1 and 5.8 × 103 s-1. The relationship between the dynamic mechanical behaviour of the Al-Sc alloy and its microstructural characteristics is explored. The fracture features and microstructural evolution are observed using scanning and transmission electron microscopy techniques. The stress-strain relationships indicate that the flow stress, work hardening rate and strain rate sensitivity increase with strain rate, but decrease with increasing temperature. Conversely, the activation volume and activation energy increase as the temperature increases or the strain rate decreases. Additionally, the fracture strain reduces with increasing strain rate and decreasing temperature. However, at room temperature under a low strain rate of 1.2 × 103 s-1 and at a high experimental temperature of 300 °C under all three tested strain rates, the specimens do not fracture, even under large strain deformations. The Zerilli-Armstrong fcc constitutive model is used to describe the plastic deformation behaviour of the Al-Sc alloy. Comparing the predicted flow stress values with the experimental values over all the considered strain rate and temperature conditions, the maximum error between the two sets of results is found to be less than 4%. SEM observations show that the specimens fracture predominantly as a result of a shearing mechanism. Moreover, the surfaces of the fractured specimens are characterised by transgranular dimpled features, which are indicative of a ductile fracture mode. Fine Al3Sc precipitates are found to be distributed in the matrix and at the grain boundaries. Finally, the TEM analysis results reveal that the dislocation density increases, but the dislocation cell size decreases, with increasing strain rate. However, a higher temperature causes the dislocation density to decrease, thereby increasing the dislocation cell size. |
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NU @ karnesky @ |
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10512 |
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