The invention discloses a high-temperature high-strength TiAl-Nb monocrystal and a preparation method thereof. Based on the atomic percent, the high-temperature high-strength TiAl-Nb monocrystal comprises the
alloy components: Ti-(43-47) Al-(6-10)Nb-(0.1-1)(C, Si), and the balance of Ti. The preparation method comprises the following steps:
smelting TiAl-Nb button-shaped master
alloy ingot casting by using an electro-magnetic induction suspension method; preparing a cylindrical rod-shaped sample by means of
differential pressure suction
casting or gravity
casting; directionally condensing the cylindrical bar by using an optical float-zone
crystal growth
system to guarantee that the
heating power is between 65% and 70%, the
growth velocity is 5-30mm / h, the relative rotation speed is 20-40r / min and the
argon flow protection is carried out for 3-5L / min; finally obtaining a TiAl-Nb monocrystal test bar; and performing desegregation heat treatment on the TiAl-Nb monocrystal bar to finally obtain the monocrystal
test sample. By adopting the TiAl-Nb monocrystal
alloy material prepared by using preparation method disclosed by the invention, the alloy
pollution caused by a traditional Bridgman directional condensation method can be effectively avoided, a
solid-
liquid interface shape during condensation is controlled by regulating the
heating power so as to quickly obtain the TiAl-Nb monocrystal, and after the desegregation of the TiAl-Nb monocrystal, the high-strength TiAl-Nb monocrystal alloy of which the yield strength is 637MPa at a temperature of 900 DEG C, the elongation percentage is 8.1% and the ductile-brittle
transition temperature is not lower than 900 DEG C can be obtained.