Influence of processing temperature on microhardness evolution, microstructure and superplastic behaviour in an Al–Mg alloy processed by high-pressure torsion

Flow behaviour and microstructural stability in an Al–3Mg-0.2Sc alloy processed by high-pressure torsion at different temperatures

“…The calculations based on the TEM images gave grain boundary spacings of ~140 and 150 nm for the alloy processed by HPT at RT and 450 K, respectively, whereas 𝐿 ̅ was estimated as ~170 nm from the EBSD maps for both HPT temperatures. These results are consistent with earlier investigations in which a grain size of ~150 nm was measured for Al-3Mg [25,29] and Al-3Mg-0.2Sc [25] alloys after 5-10 HPT turns at RT. Material.…”

“…The solution-treated Al-Mg-Sc discs were processed through quasi-constrained HPT [41,42] at either room temperature (~300 K) or at 450 ± 5 K. The high temperature was achieved by using a resistive heating element positioned around the anvils as described in earlier investigations [29,35,43]. First, the discs were compressed within the shallow depression of the anvils [44] using a nominal pressure of 6 GPa.…”

“…The flow behaviours of the Al-3Mg-0.2Sc alloy processed by up to 10 turns of HPT followed by annealing at different conditions were assessed through tensile testing using miniature specimens with gauge lengths and widths of ~1.1 and 1.0 mm, respectively. As in earlier reports [29,[45][46][47], two off-centre specimens were cut from each processed disc using electrical discharge machining. The surfaces of the tensile specimens were carefully flattened through grinding and polishing down to ~0.6 mm to remove any irregularities impressed by the anvils during processing.…”

“…These results have motivated several investigations which were designed to evaluate procedures for further improving the thermal stability of nanostructured materials. Some of these strategies include inducing the formation of nanosized particles and/or solute segregation at grain boundaries by applying the SPD procedure in alloys having second phase particles prior to processing [29][30][31][32][33][34] and the processing of alloys at higher temperatures [26,[35][36][37]. It was shown that the Al-3Mg-0.2Sc alloy achieves an elongation to failure of ~1020 % during testing at 523 K and at 10 -3 s -1 after HPT at 450 K [26].…”