Microstructural studies on phase evolution sequence in rapidly solidified Zr3Al based binary and ternary alloys

Transformation sequences in the alloys Zr3Al, Zr3Al-Nb-3 and Zr3Al-10Nb des cribed and rationalized in terms of some basic tendencies such as phase sep aration and chemical ordering in the beta phase and displacive omega and be ta --> alpha (h.c.p.) transformations. These alloys were melt-spun and aged at different temperatures to study the evolution of different phases. The rapidly solidified Zr3Al alloy showed the presence of an amorphous phase or of a spinodally decomposed microstructure e depending upon the severity of quenching, whereas the microstructure of the Zr3Al-Nb-3 and the Zr3Al-10Nb alloys exhibited a distribution of cuboidal particles (D8(8) phase in the p matrix. Ageing of these alloys showed the formation of several metastable phases prior to the formation of equilibrium phase.. The transformation se quence was found to involve a gradual filling of the open structure into a close packed configuration without reconstruction of the lattice. (C) 2001 Elsevier Science B.V. All rights reserved.