TY - JOUR
T1 - Microstructural mechanisms controlling the mechanical behaviour of ultrafine grained martensite/austenite microstructures in a metastable stainless steel
AU - Celada-Casero, C.
AU - Huang, B.M.
AU - Yang, J.-R.
AU - San-Martin, D.
PY - 2019
Y1 - 2019
N2 - This study unravels the microstructural mechanisms controlling the mechanical behaviour and austenite mechanical stability in ultrafine grained austenite/martensite (α′/γ) microstructures, created varying the austenitisation heating rate (0.1–10 °C/s) and temperature within the start-finish austenite formation temperatures (AS − AF) in a cold-rolled semi-austenitic stainless steel. A wide spectrum of strength-ductility combinations; i.e. strengths of 900–2100 MPa and elongations up to 25%, were characterised by sub-size tensile testing. The nanoprecipitation of Ni3(Ti,Al) in martensite during heating to low austenitisation temperatures rises the strength, while the martensite recovery, enhanced at low heating rates, improves the work-hardening. The high strength of martensite partially suppresses the formation of mechanically-induced martensite during loading, which is enabled with the increase of austenite volume fraction and contributes positively to the work-hardening. The heating rate barely affects the mechanical properties of microstructures austenitised close to AF. The austenite ultrafine grain size controls the yield strength, while the decrease in austenite mechanical stability and the α′/γ composite effect increase remarkably the work-hardening with respect to dual (α′/γ) microstructures with larger martensite volume fractions and fully austenitised microstructures. These results will enable the design of microstructures with controlled mechanical behaviour for a wider spread use of similar steel grades.
AB - This study unravels the microstructural mechanisms controlling the mechanical behaviour and austenite mechanical stability in ultrafine grained austenite/martensite (α′/γ) microstructures, created varying the austenitisation heating rate (0.1–10 °C/s) and temperature within the start-finish austenite formation temperatures (AS − AF) in a cold-rolled semi-austenitic stainless steel. A wide spectrum of strength-ductility combinations; i.e. strengths of 900–2100 MPa and elongations up to 25%, were characterised by sub-size tensile testing. The nanoprecipitation of Ni3(Ti,Al) in martensite during heating to low austenitisation temperatures rises the strength, while the martensite recovery, enhanced at low heating rates, improves the work-hardening. The high strength of martensite partially suppresses the formation of mechanically-induced martensite during loading, which is enabled with the increase of austenite volume fraction and contributes positively to the work-hardening. The heating rate barely affects the mechanical properties of microstructures austenitised close to AF. The austenite ultrafine grain size controls the yield strength, while the decrease in austenite mechanical stability and the α′/γ composite effect increase remarkably the work-hardening with respect to dual (α′/γ) microstructures with larger martensite volume fractions and fully austenitised microstructures. These results will enable the design of microstructures with controlled mechanical behaviour for a wider spread use of similar steel grades.
KW - Martensite/austenite microstructures
KW - Metastable stainless steel
KW - Nano-precipitation
KW - Strengthening mechanisms
KW - Transformation-induced plasticity
UR - http://www.scopus.com/inward/record.url?scp=85067507484&partnerID=8YFLogxK
U2 - 10.1016/j.matdes.2019.107922
DO - 10.1016/j.matdes.2019.107922
M3 - Article
AN - SCOPUS:85067507484
SN - 0264-1275
VL - 181
JO - Materials and Design
JF - Materials and Design
M1 - 107922
ER -