Al–Mg–Cu based alloys and pure Al processed by high pressure torsion: The influence of alloying additions on strengthening

Abstract

The influence of alloying additions on strengthening of high pressure torsion (HPT) processed alloys was investigated using commercially pure Al (Al-1050 alloy) and five Al-(1-3)Mg-(0-4)Cu alloys (in wt%). Microhardness was measured on cross sections. For Al-1050 the microhardness reaches a peak at an effective strain of about 3 and subsequently decreases. The microhardness of Al-Mg-Cu alloys increases strongly and continuously with increasing equivalent strain. This workhardening rate is enhanced by increasing Mg content over the entire range of strain. Furthermore, the workhardening rates were higher in Cu-free and low Cu-containing (≤ 0.4%) Al-Mg alloys as compared to high Cucontaining Al-Mg alloy at strains less than 3. The results indicate that dislocation-solute and dislocation-cluster interactions play an important role in strengthening.

Microstructural heterogeneity in hexagonal close-packed pure Ti processed by high-pressure torsion

“…6 Microhardness distribution in CP Ti before HPT and after HPT in the LP and TP a more homogeneous distribution is obtained after 5 turns which is consistent with earlier results for pure Ti after HPT [8]. Third, the microhardness near the disk center increases with increasing HPT turns as predicted by the accumulation of geometrically-necessary dislocations due to the large strain gradient induced by HPT [22] and by strain gradient plasticity modeling [23]. Fourth, the hardness after 5 turns is reasonably homogeneous at radial positions [1 mm implying that grain refinement has reached an essentially saturated condition.…”

Microstructure development and hardening during high pressure torsion of commercially pure aluminium: Strain reversal experiments and a dislocation based model

“…The predicted grain sizes in Fig. 10a are in line with those seen in TEM work [24] and our SEM work (Fig. 8) on m-HPT processed 1050.…”

“…On further changing the straining direction and deforming the grain to the strain gradient + dγ 2 /dr -dγ 2 /dr + dγ 2 /dr, the density of GNDs increases again GNDs and small grain sizes at the centre (e.g. see [24]), leading to higher hardness. During the application of the single reversal strain, the density of GNDs is initially reduced to a very low level (situation Sr) and subsequently increases again with further increasing the strain gradient.…”

“…Thus the study of HPT processing affords the possibility of studying these GNDs in conjunction with very high strains (>5) that are produced in a controlled manner. To date, very limited work referring to GNDs during HPT are available (see [22,23,24]), and there are no models that predict hardening due to HPT that incorporate GNDs.…”

High‐Pressure Torsion: Experiments and Modeling

“…Therefore, the thickness reduction is not evident during HPT. Normally, the constrained HPT is a more common method since this designing is conducted with a more effective back-pressure to the samples [7][8][9]. However, it is generally difficult to achieve an idealized constrained condition.…”