A comparative study of microstructure and high temperature mechanical properties of a β-stabilized TiAl alloy modified by lanthanum and erbium

The effect of rare earth (RE) elements addition on the microstructure and high temperature mechanical properties of a β-stabilized TiAl alloy was investigated by scanning electron microscopy (SEM) and high temperature compression tests. SEM and EDS results showed that RE-added alloys contained dispersed particles. Most particles were rich in RE-elements and oxygen, thereby suggesting that solute oxygen atoms in the matrix of alloys were scavenged by RE-elements. However, less than 10% of particles contained oxide phase in proximity to aluminide phase. With increasing RE-content, mean size of particles was increased; however, the number of particles reached to the maximum values at 0.2% RE, corresponding to minimum interparticle spacing. Afterwards, as a result of increasing growth rate, the number of particles was declined to the lower values. Fine and closely spaced particles in the microstructure of TNM+0.2La and TNM+0.2Er alloys led to retarding dynamic recrystallization and higher peak flow stresses at 900 and 1000 °C. Also, the results showed that Er-containing alloys possessed a higher flow stress, particularly at 1000 °C, since the particle size of Er-containing alloys was less than that of La-containing alloys.