Preferred Orientation in Splat-Quenched Materials
- PDF / 265,502 Bytes
- 5 Pages / 420.48 x 639 pts Page_size
- 73 Downloads / 204 Views
PREFERRED ORIENTATION IN SPLAT-QUENCHED MATERIALS
N.W. BLAKE, F.A. RAMES AND R.W. SMITH Department of Metallurgical Engineering Queen's University, Kingston, Canada
ABSTRACT High purity, splat-quenched metal ribbons, produced by the melt spinning technique, were examined for preferred orientation using x-ray diffraction. Of the materials tested (Zn, Cd, Ag, Bi, Pb, Sb, Mg, Sn) all except Sn exhibited some degree of preferred orientation in the plane of the metal ribbon. the hcp metals Zn and Cd showed an extreme degree of preferred orientation with the 002 plane being closely parallel to the ribbon plane. The Zn ribbon was analysed more closely with a view to its use as a crystal monochromator for x-ray diffraction. The high purity Zn was found to have some instability of preferred orientation with increase in time and temperature. The orientation was found to be effectively stabilized by the intentional addition of impurities, or by the use of lower purity (99.99%) Zn. In this form, the Zn ribbon could be used as a crystal analyser for x-ray diffraction with both intensity and resolution comparable to that of the 1011 plane in Quartz.
INTRODUCTION A general study of the properties of rapidly frozen liquids is in progress in this laboratory. When, as part of this study a number of high purity, low melting point metals were splat-quenched to form continuous or semi-continuous ribbon via the melt-spinning technique, it was found that some of them solidified with a strong preferred orientation. The preferred orientation was found to be in the plane of the surface which had been in contact with the revolving copper drum. Initially only high purity metals were examined but then a number of different solutes were added to determine their effect on both the degree of preferred orientation and upon the thermal stability of the resulting ribbons. It is known that in castings, the directional solidification which produces columnar grains may sometimes result in a preferred orientation of the fibre axis of the grains. This fibre axis is different for the various metal crystal structures and is related to the fast growth directions. It was presumed that the results observed in the ribbons could be explained on this basis. EXPERIMENTAL The materials used for the pure metal and alloy tapes were high purity (at least 99.999%) unless specified otherwise. The materials were quenched from the liquid state using a conventional melt-spinning technique (1)(2) The metals were melted in a silica tube, under a helium atmosphere, in a small platinum-wound resistance furnace. The furnace conditions 0 were adjusted to give about 50 C superheat for each metal tested, as determined earlier by placing a thermocouple in test melts before splatting.
363
364 Then First the conditions to give acceptable tapes were investigated. the metals were splatted in air under standardised conditions of about 6 kPa helium ejection pressure through a 0.4 mm orifice onto a 10 cm diameter copper drum revolving at 2000 r.p.m. This produced ribbons of Before
Data Loading...
