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R+D on new TWIP steels with improved properties

Total activity: 1
Type of activity
Competitive project
Acronym
DTWIP
Funding entity
MIN DE ECONOMIA Y COMPETITIVIDAD
Funding entity code
MAT2014-59419-C3-1-R
Amount
114.950,00 €
Start date
2015-01-01
End date
2018-06-30
Abstract
The interest on TWIP steels has steadily increased since they were first developed about a decade ago. The main characteristics of these
steels is their elevated ductility, above 50%, and a high strain hardening coefficient, which leads to ultimate tensile strengths above
1400MPa. According to these mechanical properties, TWIP steels are promising for applications in the automotive industry, allowing
weight reduction of the components, and thus lowering consumption and CO2 emissions, while their energy absorption capability will
increase the safety of the passengers in the event of a collision.
To reach their exceptional properties, TWIP steels are alloyed with 18-25%Mn, in addition to other elements such as C and/or Al-Si. The
objective of these compositions is the generation of austenitic microstructures at room temperature and the control of the stacking fault
energy of the alloy to assure that twinning is a likely deformation mechanism. In fact, twinning is the origin of the excellent combination of
high strength and ductility of TWIP steels.
However, the fabrication of TWIP steels implies some difficulties due to the high alloying degree, as well as the nature of the alloying
elements. TWIP steels are now produced as thin sheets following the continuous casting plus hot and cold rolling route. In terms of
processing, the main problems which exhibit TWIP steels are Mn losses during casting, big segregation during solidification, hot shortness,
elevated reheating temperatures and times prior to hot rolling and tendency to generate heterogeneous microstructures. From the point of
view of the mechanical properties, TWIP steels have some limitations, such as their low yield strength, delayed fracture after cold forming
operations and low corrosions resistance.
This project is a comprehensive evaluation of the different factors which could mitigate some of the problems previously described,
exploring the benefits of applying alternative processing routes. For this purpose, different compositions will be designed based on
thermodynamic calculation, a reference Fe-Mn-Al-Si-C TWIP steel and three other improved TWIP steels with improved based on their
composition (through microalloying and Cr additions). Theses steels will produced following the conventional route as well as other
alternative routes based on powder metallurgy, because segregation can be minimized and more homogeneous microstructures can be
obtained. In particular, MIM technology has been chosen and powders will be produced following different procedures: atomization,
mixture of ferroalloys and mechanical milling of previously atomized powders. Moreover, the severe plastic deformation route by ECAP will
also be explored to improve the properties trough the generation of ultra-fine grained microstructures. The subsequent evaluation of the
mechanical behavior of the steels subjected to the different processing routes will be used to establish new limits to the properties which
can be achieved for TWIP steels.
Scope
Adm. Estat
Plan
Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016
Call year
2015
Funcding program
Programa Estatal de I+D+i Orientada a los Retos de la Sociedad
Funding call
Retos de Investigación: Proyectos de I+D+i
Grant institution
Gobierno De España. Ministerio De Economía Y Competitividad, Mineco

Participants

Scientific and technological production

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