Exceptionally high strain-hardening and ductility due to transformation induced plasticity effect in Ti-rich high-entropy alloys

Abstract

Their experimental observations confirmed the Bo-Md approach could be useful in terms of designing new Ti-rich BCC-HEAs. It should be noted however, the relevance and validity of these predictions based on this controlled alloy strategy for other alloys is not yet fully explored. The primary objective of the present study is to investigate deformation mechanisms of new Ti-rich BCC-HEAs designed using the Bo-Md approach. Given the vast compositional space of HEAs, appropriate alloying elements must be chosen in order to exploit the required properties in terms of designing new HEAs. Here, we designed two new Ti-rich HEAs having chemical compositions Ti 38 Zr 25 Hf 25 Ta 7 Sn 5 , Ti 38 Zr 25 Hf 25 Ta 10 Sn 2 to compare them with the Ti 35 Zr 27.5 Hf 27.5 Nb 5 Ta 5 alloy. It is known that an addition of Sn increases β stability of Ti-alloys 14-16. Furthermore, the combination of Ta and Sn alloying elements were previously reported to have advantages in terms of tuning the martensite formation temperature 15. Therefore, in the present study, first we chose the Ti 35 Zr 27.5 Hf 27.5 Nb 5 Ta 5 alloy 13 as a base reference and replaced Nb with Sn, and adjusted the overall chemical compositions as Ti 38 Zr 25 Hf 25 Ta 10 Sn 2 , and Ti 38 Zr 25 Hf 25 Ta 7 Sn 5 to make sure the alloys positions are maintained along or near the M s ~ RT domain, on the Bo-Md diagram. Latter, the obtained alloys were characterized and their deformation mechanisms were systematically investigated.

TiCoCrFeMn (BCC + C14) High-Entropy Alloy Multiphase Structure Analysis Based on the Theory of Molecular Orbitals

“…On the other hand, the Laves phase with a C14 structure are forming above 1.40 values of Md Ti . The analysis Bo–Md diagrams from [ 29 , 30 , 31 , 32 , 33 , 34 ] allows us to state that a Ti-based BCC structure occurs with Md values much higher, even above 2.5, which is evidently dependent of Bo values. Sheikh et al [ 35 ] suggest that border the Md parameter that characterizes precipitations in Fe-M or Cr-M can be used in HEA with dominant Ti content; however, the alloy composition should include iron and chromium.…”

“…The correctness of this method for the analysis of the martensitic transformation in titanium alloys was also confirmed in numerous studies analyzing phase transformations in conventional titanium alloys [ 24 , 29 , 30 , 31 ]. This concept was also used for the analysis of the phase transformation-induced plasticity (TRIP) occurring in high-entropy alloys with dominant titanium content [ 32 , 33 , 34 ]. It should be noted, however, that these works concern the changes that occurred in the conventional alloys with a solid solution structure without the precipitation of other phases, such as the Laves phase.…”

Deformation induced twinning in hcp/bcc Al10Hf25Nb5Sc10Ti25Zr25 high entropy alloy – microstructure and mechanical properties

“…Apart from the prognostication of deformation features of β alloys, the Bo-Md diagram also delineates the regions with the α and α+β structures. Several recent studies showed reasonable applicability of the Bo-Md diagram for Ti-containing HEAs demonstrating TRIP or MBIP effects [67][68][69][70]. Therefore, we reconstructed the Bo-Md diagram, collected numerous Ti-containing HEAs with either TRIP or MBIP effect, and several Ti alloys (Fig.…”

Evolution of microstructure and mechanical properties during annealing of heavily rolled AlCoCrFeNi2.1 eutectic high-entropy alloy

“…Studies of HEAs initially focused on as-cast single-phase alloys, for many of which it appeared difficult to reach a good balance of strength and ductility, as desired for industrial applications. Therefore, research has broadened to multiphase HEAs to explore precipitation strengthening [6][7][8][9][10][11], transformation-induced plasticity (TRIP) [12][13][14][15][16][17] and eutectic/eutectoid systems [18][19][20]. In particular, a combination of a comparatively high strength and high ductility was observed in ingots of an AlCoCr-FeNi 2.1 eutectic high-entropy alloy (EHEA) [20][21][22][23].…”