Measurement of melting point and radiance temperature (at melting point and at 653 nm) of hafnium-3 (wt %) zirconium by a pulse heating method

Abstract

A subsecond duration pulse heating mcthod is used to measure the melting point and radiance temperature (at G.'i3 nm) at the melting point of hafnium containing 3.12 weight percent zirconium. The results yield a value of 2471 K for the melting point on the International Practical Temperature Scale of 1968. The radiance temperature (at G!)3 nm) of this material at its melting point iH 2236 K, and the corresponding normal spectral em ittance is 0.39. Estimated inaccuraci es arc: 10 K in the melting point and in the radiance temperature, and 5 percent in the normal spectral emittance.Key "'ords: Hafnium; high-~peed measurement; high temperature; melting puint; pyrometry; radiance temperature. . IntroductionA subsecond-duration pulse heating technique was used earlier to measure the melting point and the radiance temperature 1 at the melLing point of several refractory metals [1 -7] .2 In the present study, the same technique is used foJ' similar meaSUlements on hafnium containing 3.12 weight percent zirconium.The method is based on rapid resistive self-heating of the specimen from loom temperature to high temperatures (above 1500 K) in less than one second by the passage of an electrical current pulse through it; and on measuring, with millisecond resolution, such experimental quantities as current through the specimen, potential drop across the specimen, and the specimen temperature. Temperature is measured with a high-speed photoelectric pyrometer [8], which permits 1200 evaluations of specimen temperature per second. Details regarding the construction and operation of the measurement system, the methods of measuring experimental quantities, and other pertinent information, such as the formulation of relations for properties, elTor analysis, etc. are given in earlier publications [9,10]. MeasurementsThe material used in this study was a hafnium 'This work was supported in part by tho U.S. Air Force Office of Scientific Research.I Radiance temperature (sometimes referred to as brightness temperature) is the apparent temperature of the specimen surface correspo nding to the effeclive wavelength of the measuring pyrometer.2 Figures in brackets indicate tho literature references at the ('11(1 of this paprl'. alloy containing 3.12 (wt. %) zirconium 3 (referred to in this paper as hafnium-3 (wt. %) zirconium. The alloy specimens were 99.97 percent pure and contained, according to the manufacturer's analysis, the following impurities in ppm by weight: C, 15; 0,10; N, 10; Al, 20; Ca, 10; Cu, 10; Fe, < 50; Mn, 20; Mo, 10; Nb, 30; Si, 20; Ta, 30; Ti, 10; W, 10. The total amount of all other detected clements was less than 70 ppm, each element being below 10 ppm limit. Measuremen ts were performed on two specimens in the form of tubes and nine specimens in the form of strips. The tubes, used to determine the ~elting point, were fabricated from rods by removmg the center portion using an electro-erosion technique. A small rectangular hole (1 x 0.5 mm) was fabricated in the wall at the middle of the specimen to approximate b...

Radiance temperatures (in the wavelength range 523?907 nm) of group IVB transition metals titanium, zirconium, and hafnium at their melting points by a pulse-heating technique

“…The radiance temperature data obtained near 650 nm by Cezairliyan and McClure [13] is approximately 5 K lower than the present results, a difference that is within the experimental uncertainty. As in the case of Zr, radiance temperatures based on the wavelength-independent emissivity (~:N~=0.391 and T,, obtained by Hiernaut et al [17] for Hf show a different trend with changing wavelength than the present results.…”

“…Also given in Table l] are the corresponding values for normal spectral emissivity of these metals at their respective melting points that were calculated by means of Planck's law, on the basis of the present results for radiance temperature and literature values for the rnelting temperatures (T m) of titanium [11]. zirconium [12], and hafnium [13]. [10]. '…”

Heat capacity of liquid hafnium from the melting point to the boiling point at atmospheric pressure

“…As to the melting temperature of pure hafnium, the data available from the reference books give values from 2248 to 2506 K. According to the data of Cezairliyan and McClure [10], the melting temperature of pure hafnium is 2471 K. Because the most recent publication made in 2003 [1] gives the melting temperature of hafnium of 2504±20 K, we use this value in our study. In this case, the temperature of the beginning of solid-phase transition of hafnium in our experiment (taking T = 2504 K as the calibration of the pyrometer signal at the beginning of the plateau of melting) must be taken to be 2220 K. According to the data of Fast [11], the temperature of the beginning of solid-phase transition (for 94 at.% of hafnium) likewise has different values, i.e., 2173 K and 1583 K; our data are closer to the former value.…”

Ab initio inspection of thermophysical experiments for zirconium near melting

“…Optical properties of solid zirconium were studied in multiple experiments [103-105, 118, 119]. Most of the experimen- tal data for the liquid phase are close to the melting temperature [79,109,110,116,117]. Discussing the optical properties, we will focus on normal spectral emissivity.…”

“…Wavelength, nm Zr Figure 6: Normal spectral emissivity of liquid Zr at different wavelengths. Data obtained in this work is shown as red line; black circles are experiment [110], black line is its linear approximation; black square is experiment [116], black triangle is experiment [117], black diamond is experiment [109], down triangles with line is experiment [111].…”