Microstructure control in two-phase Al-21Ti-23Cr alloy

To improve the mechanical properties of the Al-21Ti-23Cr two-phase alloy co nsisting of L1(2) matrix and 20 vol% Cr2Al as a second phase, microstructur e control was conducted through the aging treatment as a thermal process an d the addition of V and Zr as conventional alloying. It was found that TiAl Cr was precipitated as a third phase in the L1(2) matrix by the aging treat ment at 800 and 1000 degrees C, and its size was smaller at 800 degrees C t han at 1000 degrees C. The yield strength of the aged alloy increased rapid ly only at 800 degrees C although the third phase was precipitated at both 800 and 1000 degrees C. In the V-added two-phase alloys, the yield strength and the strain increased simultaneously when V was added up to 3 at%, whic h is attributable to the improvement in the ductility of Cr2Al. Microstruct ure control conducted in this study suggests the possibility of improving t he mechanical properties of Lit (Al,Cr)(3)Ti-based two-phase alloy by preci pitating the fine third phase in the Lit matrix and enhancing the ductility of the second phase. (C) 2000 Elsevier Science Ltd. All rights reserved.