EFFECTS OF MANGANESE ON THE L1(2) COMPOUND FORMATION IN AL3TI-BASED ALLOYS

Sintering of elemental powders was carried out to form ternary L1(2) c ompounds based on Al3Ti containing Mn. In the Al-Ti-Mn system, the L1( 2) phase field and equilibrium phases surrounding the L1(2) phase at 1 423 K have been established, and the vertical section of the Al-25 at% Ti-Mn alloys has been determined experimentally. Button ingots of som e ternary L1(2) compounds were prepared by are-melting to investigate their microstructure (especially second phases and porosity), microhar dness and bend ductility. In general, homogenization of as arc-melted alloys substantially reduces the amount of second phases but introduce s extensive porosity. However, no residual porosity was observed in al loys of higher Mn content. The formation of the porosity was closely a ssociated with the nature of the L1(2) matrix and solutionizing second phases. For Ti25Mn14Al61, Ti27Mn14Al59 and Ti29Mn14Al57 alloys with n early no porosity, a bend ductility of up to about 0 . 4% was achieved at ambient temperature. Copyright (C) 1996 Elsevier Science Ltd.