Temperature-dependent mechanical properties and fracture behavior of directionally solidified Ti47Al2Cr2Nb alloy

Abstract

The influence of temperature on mechanical properties and fracture behavior of directionally solidified (DS) Ti47Al2Cr2Nb alloy was investigated in detail. Tensile tests and single-edge notched bending tests were performed in the temperature range of room temperature (≈25 °C) to 900 °C. The results revealed that both the yield strength and tensile strength of DS alloy specimens were insensitive to temperature until 850 °C. The yield strength and tensile strength at room temperature were found to be 500 MPa and 610 MPa, respectively, which were close to those at 850 °C (i.e., 534 MPa and 575 MPa). The ductility increased with the increase in temperature and the ductile-brittle transition (elongation >5%) occurred in the temperature range of 700–800 °C. Furthermore, the fracture toughness initially increased with the increase in temperature and reached the maximum value of 45 MPa m1/2 at 850 °C, followed by a decrease. It is worth emphasizing that the DS Ti47Al2Cr2Nb alloy exhibited a brittle trans-lamellar fracture at room temperature, which was similar to cleavage fracture. On the other hand, the fracture at high temperatures was influenced by the propagation and coalescence of microcracks at the lamellar interface, similar to micro-void accumulation fracture.

Keywords

• Directional solidification
• TiAl alloy
• Mechanical properties
• Fracture behavior