Solidification structures in rapidly quenched Cu-Ti-Zr alloys
- PDF / 1,243,017 Bytes
- 8 Pages / 594 x 774 pts Page_size
- 40 Downloads / 214 Views
I.
INTRODUCTION
BOTHthe Cu-Ti [J'2] and Cu-Zr [3] systems are well established as providing wide ranges of metallic glass formation. While in each individual case the exact range depends on the nature of the quenching technique used, in both systems the glass-forming range extends over a number of equilibrium intermediate phases present in the phase diagram as well as the eutectic regions between them. Therefore, the above two systems provide an example of glass formation not only in composition regions where crystallization should be difficult and easily suppressible (eutectic regions), but also in composition regions involving congruently melting compounds where crystallization from the melt should be easy and glass formation difficult. Recent work on Cu-Ti alloys has also shown that both the amount of the amorphous phase actually obtained and the amount and structure of the crystalline phase with which glass formation competes strongly depend on the experimental technique used. IL4j Surprisingly, more metallic glass was present in wheelquenched ribbons produced at a cooling rate of about 106 K / s than in the same alloys irradiated with a pulsed laser where the cooling rate was estimated to be 10 ~~K/s. Evidently, the crystallization of the competing phase is more easily suppressed on a copper wheel, where the cooling surface may be partly oxidized or contaminated, than on a self-substrate in the case of pulsed laser-quenching, where the interface between liquid and solid may be very clean. In both systems the glass transition temperatures (TB) have been found to vary more or less monotonically with composition, with only a small maximum in the middle of each glass-forming range. Recently, the most probable phase relationships in the ternary system Cu-Ti-Zr have been established for an isothermal section at 703 ~ This work, together with additional work on the surface of primary separation (the liquidus surface), has revealed that the ternary system itself resembles the binary systems; a congruently melting ternary phase dominates the phase relationships in the central portion of T.B. MASSALSKI is Professor, Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University, Pittsburgh, PA 15213. C.G. WOYCHIK is Staff Engineer, Systems Technology Division, IBM Corporation, 1701 North Street, Endicott, NY 13760. J. DUTKIEW1CZ is Staff Research Member, Polish Academy of Sciences, Institute for Metal Research, ul. Reymonta 25. 30-059 Krakow, Poland. Manuscript submitted August 21, 1987.
METALLURGICALTRANSACTIONS A
the ternary phase diagram. Around the ternary phase a number of ternary eutectic points have been discovered which might be expected to provide regions of enhanced glass formation. In the present paper we report the glass formation ranges in the ternary system determined mainly with the wheelquenching technique. Several sets of alloys have been cast deliberately along lines joining the binary eutectic compositions in order to study the trends of the glass transition temperature
Data Loading...
