Microstructure, creep, and tensile behavior of a Ti–21Al–29Nb(at.%) orthorhombic+B2 alloy

The Microstructure, Creep, and Tensile Behavior for Ti-5Al-45Nb (Atomic Percent) Fully-β Alloy

“…Over the stress range of 34 to 75 MPa, the creep stress exponent transitioned to a value of 2.6, and a Q app value of 217 kJ/mol was measured at r = 75 MPa. The n values obtained within both stress regimes are in agreement with those previously reported for O + bcc Ti-Al-Nb alloys; [9][10][11][12][13][14]16,[24][25][26] however, the Q app values tended to be lower. The Q app values determined from creep experiments in the intermediate-stress and high-stress regime at 650°C for fully-O and O + bcc alloys fall in the range of 256 to 376 kJ/mol.…”

“…The fully-b Ti-5Al-45Nb alloy exhibited lower strength values and higher elongation-to-failure (e f ) values in comparison to both fully-O and two-phase O + bcc Ti25Al-25Nb, Ti-23Al-27Nb, Ti-21Al-29Nb, Ti-15Al-33Nb, and Ti-12Al-38Nb alloys. [6,16,25,28,29] The elastic modulus, 0.2 pct offset YS, UTS, and e f values were 86 GPa, 545 MPa, 559 MPa, and 25 pct, respectively. Figure 10 illustrates secondary electron SEM photomicrographs taken from the surface of a sample that was metallographically prepared prior to RT tensile testing.…”

“…For Ti-Al-Nb alloy compositions ranging from Ti-12Al-38Nb to Ti25Al-25Nb and lying on the Ti = 50 at pct tie-line, heat treatments at 650°C have resulted in two-phase O + bcc microstructures. [6,7,16,25] The DTA results presented in Figure 1 show that no phase transformations occurred over the temperature range of 600°C to 1100°C. Thus, O-phase formation above 600°C can be suppressed by significantly reducing the Al content in Ti-Al-Nb alloys containing 50 at.…”

“…Several studies have focused on constructing microstructure-creep relationships and determining creep deformation mechanisms [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] and constructing microstructure-tensile relationships of two-phase O + bcc Ti-Al-Nb alloys. [6,8,16,[18][19][20][21][22][23]25,[27][28][29][30][31][32][33] To some extent, the tensile and creep properties of fully-O microstructures and the tensile properties of fully-bcc microstructures have been characterized.…”

“…[6,8,16,[18][19][20][21][22][23]25,[27][28][29][30][31][32][33] To some extent, the tensile and creep properties of fully-O microstructures and the tensile properties of fully-bcc microstructures have been characterized. [12,[15][16][17]29,[34][35][36] In particular, the creep behavior of fully-O microstructures under tensile and compressive loadings at temperatures greater than or equal to 650°C has been characterized.…”