Purification of Ti-Al Alloy by Cold-Crucible Induction Melting in Ultrahigh Vacuum

Abstract

In order to investigate the effect of ultrahigh vacuum melting on the purification of Ti-Al alloy, a 1 kg ultrahigh-purity Ti-45 mol% Al alloy ingot of more than 99.9940 mass% purity after analysis of 40 elements was prepared by cold-crucible induction melting (CCIM) in argon and in ultrahigh vacuum. High-purity aluminium of 99.9986 mass% purity and high-purity titanium of 99.985 mass% purity were used as starting materials. The impurity analysis was done using quadrupole residualgas analysis, chemical analysis, and glow-discharge mass spectrometry (GDMS) analysis. The concentration of gaseous impurities in the ingot was 51 mass ppm (O ¼ 35, N ¼ 11, C ¼ 5, S < 0.5). As a result of GDMS analysis of 36 metallic elements in the ingot, the total amount of metallic impurities was below 8.7 mass ppm, exclusive of 23 elements below their detection limits. The cold-crucible induction melting in UHV is effective in preparing an ultrahigh-purity Ti-Al alloy ingot containing low concentrations of gaseous and metallic impurities.

Neutron Activation Analysis of Ultrahigh-Purity Ti-Al Alloys in Comparison with Glow-Discharge Mass Spectrometry

“…High purity Ti-Al ingots of about 0.8 and 1 kg were prepared by melting the high-purity Ti and Al twice or three times in a copper-crucible induction-heating furnace. 6,7) The starting materials were first melted in Ar gas atmosphere to alloy them homogeneously. The ingots were then melted in ultrahigh vacuum to remove the gaseous impurities.…”

“…Recent efforts on purification of Ti-Al alloys succeeded in reducing gaseous impurities (C, N, O and S) from several hundreds mass ppm to several tens mass ppm by melting under ultrahigh vacuum con-ditions. [5][6][7] It is interesting to analyze other impurities such as metallic and metalloide impurities in the ultrahigh-purity Ti-Al alloys. By analyzing 35 impurity elements in the Ti-Al alloys, we compare NAA and GDMS to examine the validity of analytical results of the two methods.…”

Columnar Crystal Growth of Ti46Al0.5W0.5Si Alloys Directional Solidified by Rectangular Cold Crucible

“…The application of EMCC (electromagnetic cold crucible) technology provides a satisfactory way to solve this tough problem [7][8][9]. EMPF (electromagnetic push force) causes incomplete contact between melt and the crucible cold inner wall, and solidified shell forms simultaneously, which can avoid unacceptable impurities of melt during solidified process.…”