Annealing Behavior of Surface-Locally Cold-Deformed Low-Carbon Steel with a Large Strain Gradient

Xianguang Zhang,Munekazu Ohno,Kiyotaka Matsuura

doi:10.3390/met8110976

Xianguang Zhang, Munekazu Ohno + Show 1 more

Open Access

https://doi.org/10.3390/met8110976

Copy DOI

Abstract

The annealing behavior of surface-locally cold-deformed 0.2 mass% carbon steel with a large strain gradient was investigated, with special attention paid to the change in grain size. The surface local deformation was introduced by a ball-dropping (BD) model experiment. The local plastic strain profile evaluated from pure iron was used to confirm the occurrence of surface local deformation. It was found that the BD test led to severe local deformation near the surface, with a large strain gradient. Both the ferrite and as-transformed austenite exhibited a gradual change in grain size along the depth direction after annealing. The increased nucleation density of austenite in the deformed surface layer is not attributed to the increase in the density of the recrystallized ferrite–ferrite grain boundaries, but rather to the broken and dispersed cementite particles introduced by the deformation. The gradual change in ferrite and austenite grain size should be attributed to be the gradual change in the deformation degree of ferrite and perlite.

Highlights

Material failures such as fatigue, fretting, damage, and wear, usually originate from the exterior layers of the work piece
Surface local plastic deformation (SLPD) processes, such as ball milling [1,2] and high-energy shot peening [3], which are characterized by high strain rates, have been widely utilized in industrial processes
In the authors’ previous study [4], it was found that high strain rates lead to large strain gradients and severe plastic deformation near the surface

Summary

Introduction

Material failures such as fatigue, fretting, damage, and wear, usually originate from the exterior layers of the work piece. These phenomena are extremely sensitive to the structure and properties of the material surface. Surface local plastic deformation (SLPD) processes, such as ball milling [1,2] and high-energy shot peening [3], which are characterized by high strain rates, have been widely utilized in industrial processes. The cold-worked specimen tends to transform to states of lower energies through a sequence of recovery, recrystallization, and grain growth processes with microstructural changes [5]. The degree of local plastic deformation may strongly influence the development of grain structure in recrystallization, and the ferrite-to-austenite transformation kinetics during heat treatment processes. It is important to understand the annealing behavior of the steels with strain gradient

Objectives

Methods

Results

Conclusion