Abstract
A new Ti-Cr based alloy has been developed to reach a TWIP (TWinning Induced Plasticity) effect as the main deformation mechanism. This new composition, involving Fe addition, was derived from a classical TRIP/TWIP alloy Ti-8.5Cr-1.5Al (wt%) (TCA). The main objective is to achieve an optimized strength/hardenability combination by limiting the TRIP (TRansformation Induced Plasticity) effect whose critical resolved shear stress lowers the plasticity threshold. This new alloy Ti-7Cr-1Al-xFe (wt%) (TCAF) displays excellent mechanical properties, with an increased yield strength (with respect to TCA alloy), a very high work-hardening rate and an extremely high fracture strength (UTS=1415MPa), while maintaining an excellent ductility (ε=0.38 at fracture). Both mechanical (tensile tests) and microstructural characterization at different scales (EBSD, XRD) have been performed, evidencing a dense network of fine {332}<113> mechanical twins as well as the presence of stress-induced martensite plates at twins intersections, as a secondary mechanism.
Highlights
A new Ti-Cr based alloy has been developed to reach a TWIP (TWinning Induced Plas city) effect as the main deforma on mechanism
The difference of shape between TCA and TCAF tensile curves, in par cular the absence of plateau for TCAF, where the martensite is supposed to form in large amount, may indicate a difference of deforma on mechanisms for TCAF compared to usual TRIP/TWIP tanium alloys such as TCA
Martensite (α’’) is clearly detected for TCA but seems to provide much weaker diffracted intensi es for TCAF, which confirms the hypothesis made when looking at the shape of the tensile curves, namely that the absence of the plateau indicates that the TRIP effect is not the main deforma on mechanism for this alloy
Summary
A new Ti-Cr based alloy has been developed to reach a TWIP (TWinning Induced Plas city) effect as the main deforma on mechanism. This new alloy Ti-7Cr-1Al-xFe (wt%) (TCAF) displays excellent mechanical proper es, with an increased yield strength (with respect to TCA alloy), a very high work-hardening rate and an extremely high fracture strength (UTS=1415MPa), while maintaining an excellent duc lity (ε=0.38 at fracture).
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