Design and development of a dual-phase TRIP-TWIP alloy for enhanced mechanical properties

Abstract

Triggering transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) mechanisms in metastable β titanium alloys (bcc, body centered cubic) have helped reaching unprecedented mechanical properties for Ti-alloys, including high ductility and work-hardening. Yet the yield strength of such alloys generally remains rather low. So far, mostly single-phase metastable bcc alloys have been developed. In this study, a dual phase TRIP/TWIP alloy is designed and investigated. While the β-matrix is expected to display TRIP/TWIP deformation mechanisms, the addition of a second phase, α in the present study, aims at increasing the yield strength. The composition was designed in the Ti-Cr-Sn system, based on Calphad prediction and on the semi-empirical d-electron alloy design approach. Results were compared to the published full β Ti – 8.5Cr – 1.5Sn (wt%) TRIP/TWIP alloy. The dual-phase alloy was prepared and processed to reach the desired microstructure containing about 20% α. It displays remarkable mechanical properties such as a ductility of 29%, an ultimate tensile strength of 1200 MPa and a yield strength of 760 MPa, 200MPa higher than the Reference single-phase β alloy. Analysis of the mechanical properties and deformation microstructures confirm the TRIP and TWIP effects, validating the proposed approach.

Trifunctional nanoprecipitates ductilize and toughen a strong laminated metastable titanium alloy

“…Figure 3c plots σ y vs. ε U of our β-Ti alloys and the reported metastable β-Ti alloys 9,10,13,14,20,[35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] . Compared with reported metastable β-Ti alloys by far, the HLS-0.34 β-Ti alloys show the highest σ y , while the HLS-0.43 β-Ti alloys show a desired combination of σ y ~890 MPa and ε U ~23%, comparable to the Ti-4Mo-3Cr-1Fe alloy 53 (with σ y ~870 MPa and σ UTS ~1092 MPa) deformed via the activation of both {332} β <113> β and {112} β <111> β twinning systems.…”

“…It implies that our HLS β-Ti alloys (except the HLS-0.34 sample), utilizing the size-dependent deformation mechanism to trigger SIM (after ODP) at very high stresses, unite ultrafinegrain strength with coarse-grain ductility. uniform elongation of our β-Ti alloys with reported metastable β-Ti alloys, including TRIP/TWIP Ti alloys: Ti-12Mo 9,54 , Ti-10Mo-5Nb 43 , Ti-10V-4Cr-1Al 10 , Ti-15Nb-0.2Ta-1.2Zr 20 , Ti-9Mo-6W 26 , Ti-8.5Cr-1.5Sn 37 , (Ti-4Al-2Fe-1Mn, Ti-4Al-2Fe-2Mn and Ti-4Al-2Fe-3Mn) 38 , Ti-15Nb-5Zr-4Sn-1Fe 39 , Ti-6Mo-4Zr 51 , (Ti-12V-2Fe-1Al and Ti-14V-2Fe-1Al) 44 , and Ti-12Mo-3Zr; 50 Dual-phase TRIP/TWIP Ti alloys: Ti-10V-2Fe-3Al 13 , Ti-3Mo-3Cr-2Fe-2Al 42 , Ti-8.5Cr-1.2Sn; 14 Twin+slip Ti alloys: Ti-3Al-5Mo-7V-3Cr 35 , (Ti-15Mo-5Zr, Ti-10Mo-2Fe, Ti-10Mo-1Fe and Ti-15Mo) 36 , Ti-10Mo, (Ti-14Mo-5Sn and Ti-11Mo-5Sn-5Nb) 43 , Ti-16V-1Fe 44 , Ti-20V-2Nb-2Zr 45 , (Ti-11.5Mo-5Zr-4.5Sn, Ti-20V-3Sn and Ti-20V) 46 , Ti-6Cr-4Mo-2Al-2Sn-1Zr 47 , Ti-18Zr-13Mo 48 , (Ti-12Mo-10Zr and Ti-12Mo-6Zr) 50 , Ti-2.6Mo-0.9Fe-1.3Sn; 49 UFG TRIP/TWIP Ti alloys: Ti-7.5Nb-2.5Mo (with different β grain sizes); 41 Stress-induced ω Ti alloys: (Ti-10Cr, Ti-11Cr, and Ti-12Cr) 64 , (Ti-30Zr-4Cr, Ti-30Zr-1Cr-5Mo, Ti-30Zr-2Cr-4Mo and Ti-30Zr-3Cr-3Mo); 40 Double TWIP Ti alloys: Ti-7Mo-3Cr 52 and Ti-4Mo-3Cr-1Fe 53 alloys. Error bars indicate standard deviations for three tests.…”

“…At postuniform elongation with ε = 0.26, indeed the microcracks initiated at the α/β interfaces and were arrested by the adjacent intragranular α Grain nanoprecipitates, as marked white arrows in Fig. 5c3, and the including TRIP/TWIP Ti alloys: Ti-12Mo 9,54 , Ti-10Mo-5Nb 43 , Ti-10V-4Cr-1Al 10 , Ti-15Nb-0.2Ta-1.2Zr 20 , Ti-9Mo-6W 26 , Ti-8.5Cr-1.5Sn 37 , (Ti-4Al-2Fe-1Mn, Ti-4Al-2Fe-2Mn and Ti-4Al-2Fe-3Mn) 38 , Ti-15Nb-5Zr-4Sn-1Fe 39 , Ti-6Mo-4Zr 51 , (Ti-12V-2Fe-1Al and Ti-14V-2Fe-1Al) 44 , Ti-12Mo-3Zr 50 and Ti-6Cr-4Mo-2Al-2Sn-1Zr; 47 Dual-phase TRIP/TWIP Ti alloys: Ti-10V-2Fe-3Al 13 , Ti-3Mo-3Cr-2Fe-2Al 42 , Ti-8.5Cr-1.2Sn; 14 Twin+slip Ti alloys: Ti-3Al-5Mo-7V-3Cr 35 , (Ti-15Mo-5Zr, Ti-10Mo-2Fe, Ti-10Mo-1Fe and Ti-15Mo) 36 , Ti-10Mo, (Ti-14Mo-5Sn and Ti-11Mo-5Sn-5Nb) 43 , Ti-16V-1Fe 44 , Ti-20V-2Nb-2Zr 45 , (Ti-11.5Mo-5Zr-4.5Sn, Ti-20V-3Sn and Ti-20V) 46 , Ti-18Zr-13Mo 48 , (Ti-12Mo-10Zr and Ti-12Mo-6Zr) 50 , Ti-2.6Mo-0.9Fe-1.3Sn 49 , UFG TRIP/TWIP Ti alloys: Ti-7.5Nb-2.5Mo (with different β grain sizes); 41 Double TWIP Ti alloys: Ti-7Mo-3Cr 52 and Ti-4Mo-3Cr-1Fe 53 alloys. Error bars indicate standard deviations for three tests.…”

“…Materials possessing superior strength and excellent ductility simultaneously have always been in high demand; unfortunately, these properties are generally mutually exclusive, which is referred to as the strength-ductility trade-off dilemma [1][2][3][4][5][6][7][8] . Transformation/ twinning-induced plasticity (TRIP/TWIP) mechanisms confer these metastable alloys, such as conventional steels 6 and Ti alloys 7,[9][10][11][12][13][14] and recently emerging multicomponent alloys [15][16][17] , enhanced workhardening rates (θ > 2000 MPa) and good ductility to balance the conflict between strength and ductility, whereas they often manifest very low yield strength (σ y ). Given that the strength σ y is one of the most important characteristics of structural materials 18 , it is natural to inquire whether the TRIP/TWIP mechanisms, e.g., stress-induced martensite (SIM) can be replaced by the ordinary dislocation plasticity (ODP) that is usually activated at high stresses and subsequently TRIP/TWIP switches on to achieve large ductility (ɛ f ), particularly uniform elongation (ɛ U ), thus enhancing the fracture resistance of these alloys.…”