Monotonic and cyclic properties of TiAl alloys Monotic and cyclic properties of TiAl alloys doped with Nb, Mo and C

Abstract

Six grades of TiAl alloys doped with 7 at.% Nb and variable content of C and/or Mo were studied. The as-received microstructure and phase composition of the alloys was characterized using neutron diffraction experiments and electron microscopy. They are substantially different in individual alloys. In Mo containing alloys, ordered beta0 phase is present while carbon suppresses the occurrence of this phase. Alternating lamellae of gamma and alpha2 phases are characteristic for all specimens. The specimens have been subjected to monotonic testing (tensile and compression) and to low cycle fatigue testing at ambient and at elevated temperatures. The differences in microstructure result in scatter of mechanical behaviour of the alloys, e.g. the yield stress at 750C varies from 445 to 626 MPa. The mechanical properties of the materials are discussed in relation to the initial microstructure and phase composition.

Bylo studováno šest typů TiAl slitin legovaných 7 at.% Nb a různým množstvím C a/nebo Mo. Charakterizace mikrostruktury „as-received“ stavu a složení fází byla provedena pomocí neutronové difrakce a elektronové mikroskopie. Vzorky byly podrobeny monotónním testům (tah a tlak) a také nízkocylkové únavě jak za pokojových tak za zvýšených teplot. Rozdíly v mikrostruktuře vedou k různým mechanickým vlastnostem jednotlivých typů slitin.