Journal Published Online: 16 June 2021
Volume 11, Issue 2

Formation of Ultrafine Single-Variant Martensite from Prior Ferrite + Cementite Microstructure and Its Mechanical Properties

CODEN: MPCACD

Abstract

In the present investigation, changes in the single-variant martensite structure of 0.1%C-2%Si-5%Mn steel with a decrease in the prior austenite grain size have been investigated. While prior austenite grain size in the range of 150 to 24 µm led to the formation of martensite with a multi-packet and multi-block structure, a single packet and multi-block martensite structure formed from the prior austenite grain size of about 7 µm. Furthermore, the prior austenite grain size of about 2 µm led to the formation of a single-variant (single-block) martensite structure. This microstructural analysis indicates that the critical prior austenite grain size to form martensite with a single-variant structure is about 2 µm. The tensile strength (TS, 1,490 MPa), uniform elongation (UEL, 7.1 %), and total elongation (TEL, 14.2 %) of the single-variant martensite was found to be higher than that of the multi-packet multi-block martensite (TS = 1,270 MPa, UEL = 6.2 %, and TEL = 13.6 %). The improvement in the mechanical properties of the single-variant martensite was attributed to enhancement in its strain-hardening rate as a result of change in the structure from the multivariant to the single variant.

Author Information

Torizuka, Shiro
Department of Materials and Synchrotron Radiation Engineering, The Graduate School of Engineering, University of Hyogo, Himeji, Hyogo, Japan
Oya, Ryusuke
Department of Materials and Synchrotron Radiation Engineering, The Graduate School of Engineering, University of Hyogo, Himeji, Hyogo, Japan
Prasad, Kartik
Department of Materials and Synchrotron Radiation Engineering, The Graduate School of Engineering, University of Hyogo, Himeji, Hyogo, Japan
Ito, Atsushi
Department of Materials and Synchrotron Radiation Engineering, The Graduate School of Engineering, University of Hyogo, Himeji, Hyogo, Japan
Pages: 17
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Stock #: MPC20200187
ISSN: 2379-1365
DOI: 10.1520/MPC20200187