Microstructural evolution and precipitation behavior of the 0.1C-18Cr-1Al-1Si ferritic heat-resistant stainless steel during hot deformation

Abstract

The 0.1C-18Cr-1Al-1Si ferritic heat-resistant stainless steel has attracted considerable attention to high-temperature applications due to its favorable combination of creep and oxidation resistance. In this paper, the microstructural evolution and precipitation behavior of the 0.1C-18Cr-1Al-1Si ferritic heat-resistant stainless steel is studied from the compression deformation data in the temperature range of 850°C-1050°C and the strain rate range of 0.01-1 s −1 . Experimental results demonstrate that higher temperatures and lower strain rates enhance the dynamic recrystallization (DRX) process with remarkable effectiveness. The main precipitates are proved as the AlN phases and the (Cr,Fe) 23 C 6 carbides during hot deformation. With an increase in the deformation temperature, the size of (Cr,Fe) 23 C 6 and AlN gradually increases, and volume fraction gradually decreases. When the strain rate decreases, the average size and volume fraction of (Cr,Fe) 23 C 6 and AlN gradually increase. At the lower temperatures, the occurrence of dynamic recrystallization (DRX) is strongly influenced by (Cr,Fe) 23 C 6 formed on the grain boundaries, mainly because it causes a pinning effect, which hinders the movement of dislocations and delays the occurrence of the DRX.

Microstructure evolution and texture formation of 16 % chromium ferritic stainless steel following simulated batch annealing treatments in mass production

“…Moreover, energy dispersive spectroscopy results indicated that the precipitates were composed of ferrum, chromium, carbon and silicon. Combined with the above-mentioned analysis and the previous literature information, it could be deduced that the fine precipitates were most likely the ðCr; FeÞ 23 C 6 [19]. The precipitates in the sample batch annealed at 850 °C for 10 hours and then cold-rolled annealed at 900 °C were analyzed with energy dispersive spectroscopy, Figure 7.…”

“…For samples annealed for 10 hours at 700 °C, 750 °C and 800 °C, the deformed microstructures were al-most identical with that from the hot-rolled sheet (not recrystallized), Figure 2b-d. That is because the softening mechanism at a lower temperature was mainly the dynamic recovery and low annealing temperature could not result in significant structural changes associated with recrystallization [19]. When increasing the annealing temperature to 850 °C, it was found that the microstructures were partially recrystallized, a few recrystallization nuclei and new grains were discerned, but a large number of elongated/deformed grains still presented along the rolling direction.…”

“…With different annealing treatment, it was found that annealing temperature was the significant factor affecting chemical composition, size, distribution and shape of carbide precipitates. The difference in size of precipitates mostly could be attributed to the fact that the diffusion rate and growth rate were relatively low at lower temperatures, which was not conducive to the growth of M 23 C 6 carbide [19]. The boundaries and dislocations were the channels for rapid diffusion of atoms (ions) and easily caused the segregation of impurity atoms (ions) [23].…”

Hot Deformation Characteristic and Optimization of Processing Parameters for 0.1C–18Cr–1Al–1Si Ferritic Heat Resistant Stainless Steel

“…The reason may be due either to machine compliance or to a high rate of data acquisition. 26) 3.2 Microstructure evolution and precipitation behavior Figure 3 shows the microstructure before hot deformation. It can be seen that the distribution of ferrite grains are relatively uniform and the average grain size is 127.3 µm.…”

The size effect of precipitates on microstructure evolution during high-temperature deformation

“…Precipitation pinning on the boundary retards recrystallization. Zhang et al [7] found that Cr23C6 on the boundary effectively prevents DRX during the high temperature deformation process of 0.1C-18Cr-1Al-1Si ferritic stainless steel. In a study by Liu et al [8] on 19Cr2Mo ferritic stainless steel, the addition of W reduced the size of the Laves phase and increased the amount of precipitation, and the smaller and more precipitation on the boundary effectively prevented DRX.…”