Microstructural Effects on the Spall Properties of 5083 Aluminum: Equal-Channel Angular Extrusion (ECAE) Plus Cold Rolli
5083 Aluminum alloy is a light weight and strain-hardened material used in high strain-rate applications such as those experienced under shock loading. Symmetric real-time (in-situ) and end-state (recovery) plate impact experiments were conducted to study
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Microstructural Effects on the Spall Properties of 5083 Aluminum: Equal-Channel Angular Extrusion (ECAE) Plus Cold Rolling C.L. Williams, T. Sano, T.R. Walter, and L.J. Kecskes Abstract 5083 Aluminum alloy is a light weight and strain-hardened material used in high strain-rate applications such as those experienced under shock loading. Symmetric real-time (in-situ) and end-state (recovery) plate impact experiments were conducted to study the spall response and the effects of microstructure on the spall properties of both 5083-H321 and 5083-ECAE + 30 % cold-rolled (CR) aluminum alloys shock loaded to approximately 1.46 GPa (0.2 km/s) and 2.96 GPa (0.4 km/s). The results show that mechanically processing the 5083-H321 aluminum by ECAE, followed by subsequent rolling significantly increases the Hugoniot Elastic Limit (HEL) by 78 %. However, this significant increase in HEL was at the expense of spall strength. The spall strength of the 5083-ECAE + 30 % CR aluminum dropped by 37 % and 23 % when compared to their 5083-H321 aluminum counterpart at shock stresses of approximately 1.46 GPa (0.2 km/s) and 2.96 GPa (0.4 km/s) respectively. This reduction in spall strength is attributed to the re-alignment of the manganese (Mn)-rich intermetallic second phase particles during mechanical processing (i.e., ECAE and subsequent cold rolling) which are consequently more conducive to spallation. Keywords Shock • Spall • Inclusions • Microstructure • Failure
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Introduction
5083 aluminum is a light weight, strain hardened, corrosion resistant, and high strength alloy commonly used in high strainrate applications such as those experienced under shock loading. It is not a heat treatable alloy but significant strengthening effects can be achieved through alloying with magnesium and manganese (Mn) followed by mechanical processing such as cold working. Magnesium is added for solid solution strengthening and manganese for refining the grain structure through the formation of dispersoid particles which pin grain boundaries. The spall response of mechanically processed 5083 aluminum (i.e., cold and hot rolled, extruded, etc.) has been previously studied by several researchers [1–4]. Results from the work of Boteler and Dandekar [1] show no spall strength dependency on peak shock stress ranging from 1.58 to 2.78 GPa for 5083-H131 aluminum. Appleby-Thomas and Hazell [2] were able to show that 5083-H32 armor grade aluminum exhibited no strengthening effects as a function of peak shock stress. From microstructural analyses conducted on shock recovered samples, they determined that spall failure in 5083-H32 aluminum initiated and propagated from one inclusion to another [2]. Whelchel et al. [3] studied the spall behavior of 5083H116 aluminum and found that the Hugoniot Elastic Limit (HEL) in the transverse direction exhibited the highest value and the lowest HEL was observed along the rolling direction. In addition, they determined that the spall strength in the rolling direction was higher than that in the transverse direction and from mi
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