Progress in research on cold crucible directional solidiifcation of titanium based alloys

摘要

Cold crucible directional solidification (CCDS) is a newly developed technique, which combines the advantages of the cold crucible and continuous melting. It can be applied to directionaly solidify reactive, high purity and refractory materials. This paper describes the principle of CCDS and its characteristics; development of the measurement and numerical calculation of the magnetic ifeld, lfow ifeld and temperature ifeld in CCDS; and the CCDS of Ti based aloys. The paper also reviews original data obtained by some scholars, including the present authors, reported in separate publications in recent years. In Ti based aloys, Ti6Al4V, TiAl aloys and high Nb-containing TiAl aloys, have been directionaly solidiifed in different cold crucibles. The cross-sections of the cold crucibles include round, near rectangular and square with different sizes. Tensile testing results show that the elongation of directionaly solidiifed Ti6Al4V can be improved to 12.7% from as cast 5.4%. The strength and the elongation of the directionally solidified Ti47Al2Cr2Nb and Ti44Al6Nb1.0Cr2.0V are 650 MPa/3% and 602.5 MPa/1.20%, respectively. The ingots after CCDS can be used to prepare turbine or engine blades, and are candidates to replace Ni super-aloy at temperatures of 700 to 900 °C.