Abstract
The feasibility of establishing thermomechanical conditions to promote {100}//ND fiber texture via strain-induced boundary migration (SIBM) recrystallization mechanism in a non-grain oriented (NGO) electrical steel was investigated. Single-hit uniaxial compression at various temperatures and strains has been applied on Fe-6 wt pct Si to establish the relationship between stored energy and the softening mechanisms. Recovery only and recrystallization by SIBM or by subgrain growth (SGG) have been observed depending on the stored energy level. A strong {100}//ND fiber recrystallization texture, i.e., 45 pct area fraction, was seen in the sample which was deformed to 0.2 strain at 650 °C and then annealed at 1000 °C for 15 minutes, whereas only 13 pct {100}//ND fiber component was observed after 0.4 strain at 500 °C followed by the same annealing treatment. By examining the same microstructural region before and after annealing via EBSD, it has been shown that {100}//ND textured recrystallized grains were formed adjacent to the {100}// ND textured deformed matrix. Low stored energy has been shown to favor the formation of {100}//ND texture recrystallized grains via SIBM recrystallization mechanism attributed to its slow recrystallization nucleation rate. The results from the deformation studies have been used to suggest a processing window map concept to define the recovery, SIBM, and SGG regions for the starting as-cast columnar microstructure.
Highlights
TEXTURE significantly affects the final magnetic properties of electrical steel. {100}//ND texture is desirable for non-grain oriented (NGO) electrical steels
Liu et al and Wen et al suggested that deformation can reduce the degree of ordering in these phases giving a decrease in the flow stress with this effect being most significant at the transition temperature for the ordered phase formation, which for Fe-6 wt pct Si steel is around 550 °C.[11,12]
{100}//ND texture was promoted via the Strain-induced boundary recrystallization migration (SIBM) recrystallization mechanism at optimum deformation conditions, 650 °C, 0.2 to 0.3 strains
Summary
TEXTURE significantly affects the final magnetic properties of electrical steel. {100}//ND texture is desirable for non-grain oriented (NGO) electrical steels. The recovery and recrystallization behavior in Fe-6 wt pct Si steel with a starting columnar {100}//ND texture at various strains and deformation temperatures have been considered, and the concept of a processing map to promote SIBM mechanism has been established. Fang et al and Wang et al observed that both {111}// ND texture fraction and recrystallized grain size decreased with increasing heating rate ranging from 50 °C to 300 °C/s.[7] Jiao et al reported that the {110}//RD texture was strengthened by increasing annealing temperature from 900 °C to 1200 °C.[8] He et al observed that cube texture formed when annealing temperature increased from 600 °C to 750 °C after cross-rolling.[9] These parameters will not be discussed in this paper, with a constant reheating and annealing temperature used, as the main focus in this study is to establish the effect of deformation temperature and strain on the recrystallization texture. The condition chosen is to represent a twin-roll cast strip that could be processed warm rolling
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