On the homogeneity of deformation by high pressure torsion

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

“…This is different from many other alloys (e.g. austenitic steel and a titanium [9,45]), where saturation occurred near the periphery of disks processed for at least 2 turns. The optical microscopy of Al-1Mg-4Cu (Fig.…”

“…Among these techniques, considerable interest has developed in high pressure torsion (HPT) due to the advantage of refining the grain sizes of pure metals and alloys by introducing a continuous and rapid accumulation of high strain without interruption of straining. The microhardness and microstructural evolution occurring during HPT have been investigated extensively, and most attention has been paid to pure and commercially pure metals [4,5,6,7,8,9,10]. Some investigations focused on pure or high purity metals such as pure Cu [4], commercially pure Ti [5] and pure Ni [6,7].…”

Microstructural evolution in commercial purity aluminum during high-pressure torsion

“…The results support earlier observations on pure Ni [7] and an Al alloy [5] but they are not consistent with microhardness data reported recently when processing an austenitic steel using HPT [11]. This difference may reflect the greater difficulty in reaching homogeneity in a material, such as steel, where the microstructure is complex.…”

“…These observations suggest that the microstructure becomes reasonably homogeneous at high total strains although it should be noted this homogeneity is inferred indirectly from the consistency in microhardness measurements taken across the specimen diameters and there may remain some microstructural inhomogeneities when detailed observations are made using transmission electron microscopy (TEM). By contrast, a very recent report described the development of inhomogeneities in an austenitic steel when microhardness measurements were taken after HPT processing although the microhardness measurements were not supported by corresponding observations using TEM [11].…”

“…Both constrained and unconstrained HPT have been used in prior experiments. Thus, the earlier investigation of pure Ni was conducted using unconstrained HPT [7], whereas the experiments on austenitic steel used constrained HPT although it was noted there was some limited outward flow of material between the two anvils on application of the load [11]. In the present investigation, the HPT processing was conducted using a constrained facility as shown in Fig.…”