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Structure-properties relationship in TRIP type bainitic ferrite steel austempered at different temperatures

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Abstract
Background: Attractive properties of TRIP-type bainitic ferrite (TBF) steel ascribe to its unique microstructure of lath
structure bainitic ferrite matrix and interlath retained austenite films. This work is concerned with obtaining ultra
high-strength hot forged TBF steel with high elongation and excellent strength-elongation balance.
Methods: The effect of austempering temperature on the microstructure along with its retained austenite
characteristics and tensile properties of a hot forged TBF steel was studied. A detailed investigation correlating the
steel structure and its tensile properties was carried out.
Results: Tensile strength ranging from 1058 to 1552 MPa was achieved when the hot forged steel was
austempered at (325 - 475 °C).
Conclusions: Ultra high tensile strength of 1058 MPa, large total elongation of 29% and excellent strengthelongation
balance of 30 GPa % were attained when the steel was austempered at 425 °C. The large total
elongation of this steel is mainly due to the uniform fine lath structure matrix and the pronounced TRIP effect of a
large amount of retained austenite films which prevents a rapid decrease of strain hardening rate at low strain and
leads to a relatively high strain hardening at high strain level. Rapid transformation of blocky retained austenite at
low strain in the hot forged TBF steel austempered at higher temperatures results in a rapid increase of initial strain
hardening. In addition, the coarse microstructure that contains large blocks of retained austenite / martensite and
the insufficient numbers of bainitic ferrite lathes and retained austenite films deteriorate the total elongation and
the strength-elongation balance of the TBF austempered at 475 °C.

Keywords: Ultrahigh-strength steels, TRIP-aided steels, Austempering heat treatments, Microstructure, Retained
austenite characteristics, Tensile properties

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Informasi Detail

Judul Seri

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No. Panggil

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Penerbit

: Springer Singapore., 2017

Deskripsi Fisik

International Journal of Mechanical and Materials Engineering

Bahasa

English

ISBN/ISSN

2198-2791

Klasifikasi

NONE

Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

Volume 12, Issue 1, December 2017

Subjek

TEKNIK MESIN

Info Detail Spesifik

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Pernyataan Tanggungjawab

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