Achieving exceptionally high strength across a wide temperature range in a near-eutectic L12/B2 composite alloy via nano-sized η phase

Abstract

Excellent temperature-bearing capacity over a wide temperature rasnge is critical for elevated-temperature application. In this study, via a unique nano-particle precipitation hardening strategy, a novel near-eutectic Ni-19Al-15Ti alloy multi-composited with L1₂ and nano-sized η phase strengthened B2 intermetallics is developed, to improve the yield strength (YS) and ductility at room-medium temperature as well as to combine the superior microstructural stability and castability. The nano-sized η particles densely precipitated in the B2 phase can effectively strengthen the multi-fold composite structure, leading to the high hardness of 650 HV and super-high YS of about 1900 MPa at room-temperature. The samples also exhibit superior mechanic properties at high temperature, e.g., high YS of 790 MPa at 800 °C and compressive strain larger than 50 %. The superior mechanical properties can be attributed to the solution and precipitation strengthening effects as well as the synergistic deformation of composite structure. These results provide a paradigm for developing alloys with an excellent synergy of mechanic properties, temperature-bearing capability and castability.