Influence of severe plastic deformation on the precipitation hardening of a FeSiTi steel

The combined strengthening effects of grain refinement and high precipitated volume fraction (~6at.%) on the mechanical properties of FeSiTi alloy subjected to SPD processing prior to aging treatment were investigated by atom probe tomography and scanning transmission electron microscopy. It was shown that the refinement of the microstructure affects the precipitation kinetics and the spatial distribution of the secondary hardening intermetallic phase, which was observed to nucleate heterogeneously on dislocations and sub-grain boundaries. It was revealed that alloys successively subjected to these two strengthening mechanisms exhibit a lower increase in mechanical strength than a simple estimation based on the summation of the two individual strengthening mechanisms

Severe plastic deformation processes for thin samples

Among the known severe plastic deformation (SPD) techniques, one particular group can be defined as SPD processing of thin samples. Their distinctive feature is that one of the sample dimensions, namely the thickness, is much smaller than the other two dimensions. Examples include High Pressure Torsion and two recently developed techniques: the Cone-Cone Method and the High Pressure Tube Twisting. The mentioned group of SPD processes involve frictional forces acting on the large surfaces and a high hydrostatic pressure within the deformation zone. These techniques are particularly suited for microforming of metals. In this article, we outline the commonalities between these three techniques. The microstructure of copper samples deformed by all the three processes is presented and compared with those obtained by equal-channel angular pressing as a reference bulk forming SPD technique

Asymmetric rolling of interstitial-free steel using one idle roll

The effect of additional shear on the asymmetric rolling (ASR) of an interstitial-free (IF) steel was studied by modeling and experiments. The asymmetry was introduced by making one roll idle. A 66 pct of total thickness reduction was performed in 6 passes with less than 16 pct reduction per pass. ASR was performed in two ways: monotonically and by rotating the sheet between passes by 180 deg around the rolling direction (RD). Better grain fragmentation was obtained in the near surface layers. The results of monotonic asymmetric rolling are similar to symmetric rolling in terms of misorientation and cell size with the difference that the volume fraction of grains containing shear bands (SB) is larger for monotonic ASR. ASR with the sheet rotated 180 deg around the RD direction between passes showed the most promising results in terms of grain refinement, depth of the highly deformed layer, texture, and properties. The grain fragmentation process was also simulated with a recent grain refinement polycrystal model for strain hardening, texture development, grain size distribution, and grain misorientation distribution. The obtained simulation results showed strong agreement with the experiments