Deformation behavior of ,-TiA1 composites in the solid and mushy states

The deformation behavior of a two phase (y+ a2) lamellar TiAl alloy reinforced with various amounts of AITi~C carbide platelets has been examined by determining Vickers hardness at room temperature and in the temperature range 900-1300 °C. The compression flow behavior of these materials has also been examined in the semi-solid state. The hardness values for all materials dropped from about 4 GPa at room temperature to 120 MPa at 1300 °C. The composites exhibited limited increase in hardness with respect to the base material over most of the temperature range investigated. At 900 °C, however, the 13% A1Ti2C reinforced composite showed an increase in hardness of about 1.2 GPa over that of the base material. The composites exhibited interfacial as well as transgranular cracks induced by indentations, while the matrix material did not exhibit cracking during the hardness tests. Forgeability of semi-solid Ti-48AI reinforced with 13% AITi2C composite was studied by performing compression tests at 1470 °C and strain rates ranging from 0.33 to 2.00 s1. Stress-strain curves exhibited a peak stress which is associated with breakdown of the carbide platelets. The size of the carbide platelets decreased and their reorientation took place with increasing strain. At strains higher than 0.9, reagglomeration of the carbide platelets was observed.