Effect of hot working on dynamic recrystallisation study of as-cast austenitic stainless steel

Effect of Twinning on Microstructural Evolution During Dynamic Recrystallisation of Hot Deformed As-Cast Austenitic Stainless Steel

“…The dependence of the recrystallised grain size as a power law function of Z is shown in Figure 3(c). The grain sizes obtained in the present investigation have been compared with the observations of Manshadi and Hodgson [13] and Mandal et al [6] in this figure. Manshadi's work [13] dealt with samples of homogeneous initial grain size of 35 and 8 lm.…”

“…[2,3] The second is associated with the nucleation and growth of new grains whose large misorientations with respect to the deformed surrounding matrix originate from continuous subgrain rotation or discontinuous subgrain growth and coalescence processes near the grain boundaries. [4][5][6] Third, it is multiple (annealing) twinning: nuclei are basically subgrains, which create high mobility boundaries by repeated annealing twinning. [7] The DRX grain size has traditionally been thought to depend only on the Zener-Hollomon parameter, Z, and not on the initial grain size.…”

“…The details of casting and details of PSC tests have been reported elsewhere. [6] Small pieces of dimensions 10 mm 9 5 mm were cut from the PSC tested samples for subsequent microstructural investigation using electron back-scattered diffraction (EBSD). Microhardness testing was conducted with the recrystallised specimens at the centre region of each polished specimen along the width direction.…”

“…This is mainly because during these tests, although the specimens were heated to the deformation temperature, the tools were at 1273 K (1000°C) due to the load limitation of the tooling material. [6] For the strain rate of 5 s À1 (Z value: 6.29 9 10 15 s À1 ), the total duration of the deformation was about 0.2 second. Observation of the temperature profile shows that the specimen temperature first quickly reached 1140°from 1358 K (1085°C), and then gradually decreased to 1408 K (1135°C) at the end of the deformation.…”

“…Some of these EBSD micrographs also reveal the presence of some fraction of martensite in the structure. [6] The area fraction of recrystallisation was calculated manually from basic principles of quantitative metallography as given by Rossi and Sellars [20] i.e., using the point counting method. About 400 grains were considered for the analysis and Figure 3(a) shows that with a decrease in Z (increasing temperature), the fraction of recrystallised grains increases.…”