Deformation mechanisms in a metastable beta titanium twinning induced plasticity alloy with high yield strength and high strain hardening rate

Abstract

SUMMARYAs predicted by the notion that sister chromatid cohesion is mediated by entrapment of sister DNAs inside cohesin rings, there is perfect correlation between co-entrapment of circular minichromosomes and sister chromatid cohesion. In most cells where cohesin loads without conferring cohesion, it does so by entrapment of individual DNAs. However, cohesin with a hinge domain whose positively charged lumen is neutralized loads and moves along chromatin despite failing to entrap DNAs. Thus, cohesin engages chromatin in non-topological, as well as topological, manners. Since hinge mutations, but not Smc-kleisin fusions, abolish entrapment, DNAs may enter cohesin rings through hinge opening. Mutation of three highly conserved lysine residues inside the Smc1 moiety of Smc1/3 hinges abolishes all loading without affecting cohesin's recruitment to CEN loading sites or its ability to hydrolyze ATP. We suggest that loading and translocation are mediated by conformational changes in cohesin's hinge driven by cycles of ATP hydrolysis.

Strong and ductile beta Ti–18Zr–13Mo alloy with multimodal twinning

“…The invariant and undistorted twinning planes and shear (conjugate) directions between {5 8 11}T and β matrix were experimentally found to be K 1 = {5 8 11}, K 2 = {−1 0 1}, η 1 = {−5 −1 3} and η 2 = {1 1 1}, consistent to the theoretical prediction and the experimental observations in cubic Fe-Ni alloy [19,21]. Usually, SIM is the common mechanism to accommodate interface strain misfit [9,10,12] in TWIP/TRIP alloys. Here the SIM was completely suppressed despite the dense nano {112} < 111 > twinning (112T) intersecting 332T (discussed below).…”

“…Upon increasing the strain to 0.10 and to 0.15, the multiplication and growth of both variants are clearly noticed in Figure 2(b,c). It is worth noting that SIM transformation was not observed during the whole plastic deformation, indicating that the TRIP effects was fully suppressed due to the higher stability of this alloy when compared with the combined TWIP and/or TRIP modes Ti-alloys [7][8][9][10]13,17]. The role of the SIM-produced α is likely to relax the zones where strong stress concentration occurs (typically at the crossing zone of twins).…”

“…On the other hand, the {332} < 113 > twinning, which usually displays higher CRSS (critical resolved shearing stress) than SIM, leads to significant strain-hardening by dynamic Hall-Petch effect by reducing the mean free path of dislocation slip in BCC grains [6]. Recently, considerable efforts have been dedicated to developing a new family of β Tialloys [7][8][9][10][11] by combining twinning and SIM effects, i.e. the hybrid TWIP/TRIP effects (TWIP: twinninginduced plasticity, TRIP: transformation-induced plasticity), that generally display low yield strength (YS), large uniform elongation and high strain-hardening rate [9].…”

“…Recently, considerable efforts have been dedicated to developing a new family of β Tialloys [7][8][9][10][11] by combining twinning and SIM effects, i.e. the hybrid TWIP/TRIP effects (TWIP: twinninginduced plasticity, TRIP: transformation-induced plasticity), that generally display low yield strength (YS), large uniform elongation and high strain-hardening rate [9]. In hybrid TRIP/TWIP Ti-alloys [7,10], the stress plateau after the elastic limit is usually related to SIM, resulting in low YS but enhancing the uniform ductility.…”

Microstructural Evolution and Strain-Hardening in TWIP Ti Alloys

“…a long steady plateau in the intermediate stage (10% -20% strain) of deformation. In contrast with this, Ti alloys with combined TWIP/TRIP effects usually exhibit a much higher strain-hardening rate [31,33] , which increases from early stages and achieves a maximum value at intermediate strains. The increased strain-hardening rate in TWIP/TRIP alloys is caused by the simultaneous activation of mechanical twinning and martensitic transformation, where the primary α martensite may produce extra barriers to obstruct dis- location motions [33] .…”