Kinetics of Arsenic Surface Segregation in Scrap-Based Silicon Electrical Steel

Darja Steiner Petrovič

doi:10.3390/met11010001

Abstract

The segregation kinetics of surface-active, residual elements are investigated in an in situ study of annealing scrap-based silicon electrical steel sheet where the arsenic (As) surface segregation is highlighted. During annealing in the temperature range of 300–950 °C, different kinds of interactions between the segregated residual elements were observed. Attractive interactions between the segregands produced co-segregation, e.g., between Sn and Sb, whereas repulsive interactions resulted in site competition, e.g., between Sn and As. These competing interactions are strongly time dependent. In spite of there being twice as much Sn compared to As in the bulk material, the As prevailed in the surface enrichments of the polycrystalline silicon steel at 950 °C. The intensity of the As surface segregation in the temperature range 800–950 °C is proportional to the calculated amount of γ-austenite phase in the (α + γ) steel matrix. The detected phenomenon of the As versus Sn site competition could be valuable for the texture design and surface engineering of silicon steels with a thermodynamically stable two-phase (α + γ) region.

Highlights

The segregation kinetics of surface-active, residual elements are investigated in an in situ study of annealing scrap-based silicon electrical steel sheet where the arsenic (As) surface segregation is highlighted
Recent studies reveal that a properly controlled phase transformation from γ-austenite to α-ferrite provides a promising method to optimize the crystallographic texture of silicon steels [5,6]
The segregation kinetics of surface-active, residual elements was investigated in an in situ study of annealing scrap-based, silicon electrical steel sheet

Summary

Introduction

There is an increasing need for highly power-efficient electrical machines for a wide range of applications in which silicon electrical steel is the core material. For an optimal design of the electromagnetic properties, the chemical composition, and the recrystallization annealing of the steel are the most important influencing parameters [1,2,3,4]. Recent studies reveal that a properly controlled phase transformation from γ-austenite to α-ferrite provides a promising method to optimize the crystallographic texture of silicon steels [5,6]. It is well known that the phase transformations in an alloy system are set by the laws of thermodynamics. In Fe–Si alloys that are to be further processed into grain-oriented and non-oriented electrical steel sheets and coils, the metallurgy is relatively complex.

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