Abstract
The effect of the deformation route on the microstructure, and the mechanical and electrochemical properties of low CN Fe-20%Cr alloy by equal channel angular pressing, have been investigated focusing on the anisotropy of the microstructure. This alloy was pressed at 423 K from one, two and four passes via routes A, Bc and C, and the microstructure was observed in three orthogonal planes. As has been acknowledged, overall grain fragmentation proceeded most effectively in route Bc. However, the degree of anisotropy of microstructural development was different among the three deformation routes. The fractions of the high angle grain boundary and mean grain boundary misorientation were high and nearly isotropic in route Bc, whereas they were consi- derably low in one direction and highly anisotropic in routes A and C. Most importantly, those two parameters were the highest in route C if limited to the transverse direction (Y-plane), i.e. normal to both the insert and extruding directions. This result contrasted with FCC materials, which was reported by most papers having the highest fraction of high angle grain boundary (HAGB) in route Bc. Ultrafine grained structure with the highest HAGB on Y-plane in route C exhibited the most stabilized corrosion behavior.
Highlights
Severe plastic deformation (SPD) as a processing of fabricating ultrafine grained (UFG) material to the sub micrometer level has been acknowledged for twenty five years in the field of materials science and engineering [1]
Low angle grain boundaries (LAGB) are predominant with little fraction of high angle grain boundary (HAGB) before and after 2 passes by Equal channel angular pressing (ECAP) (Figures 3(b)-(d)), but the fraction of HAGB increased after 4 passes replacing some LAGB (Figures 3(e)-(g))
The isotropic hardening in route Bc reflected the isotropic configuration of HAGB
Summary
Severe plastic deformation (SPD) as a processing of fabricating ultrafine grained (UFG) material to the sub micrometer level has been acknowledged for twenty five years in the field of materials science and engineering [1]. Several parameters of ECAP process that influenced on microstructural evolution and mechanical properties were die angle, pressing speed, die temperature and deformation route. Studies on the effect of the deformation route have been recommended for explaining its effect on microstructure and mechanical properties, especially in FCC material. These studies found that material processed by route Bc is the most efficient method to produce isotropic microstructure and high angle grain boundary (HAGB) due to the 90 ̊ crossing shear planes in every pass [8]-[10]. The effects of the pass number and deformation route on the microstructure, mechanical and electrochemical properties considering the degree of anisotropy will be discussed in detail in this study
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