Liquid titanium solute diffusion measured by pulsed ion-beam melting

Abstract

The diffusivities of Sn, Mo, Zr, and Hf in liquid Ti were determined by pulsed ion-beam melting of thin liquid layers. Time-resolved optical reflectance and one-dimensional heat-flow simulations were employed to determine the melt duration. The broadening of nearly Gaussian solute concentration-depth profiles was determined ex situ using Rutherford backscattering spectrometry. Solute diffusivities in the range of 5 to 9 x 10 -5 cm 2 /s were determined at temperatures in the range of 2200 to 2500 K. Calculations of buoyancy and Marangoni convection indicate that convective contamination is unlikely.

Diffusion models for evaporation losses during electron-beam melting of alpha/beta-titanium alloys

“…The differences between the predicted values of at the surface were greatest at short times and were probably associated with the slow convergence of the series solution represented by Eq. [13]. In particular, the first three or four terms in Eq.…”

“…The concentration at the melt surface (x ϭ d) from Eq. [12] is [13] The integral for the flux is thus readily found to be the following: [14] A plot of the infinite series in Eq. [14] is given in Figure 1.…”

“…This value is comparable to the solute diffusion coefficients measured by Sanders et al (i.e., 0.5 to 1 ϫ 10 Ϫ8 m 2 /s) for tin, molybdenum, zirconium, and hafnium in liquid titanium. [13] Thus, the self-and solute diffusion coefficients (at the liquidus temperature) for the alloying elements in Ti-6Al-4V were assumed to be equal to 10 Ϫ8 m 2 /s. The corresponding interdiffusion coefficient for aluminum in liquid titanium would thus have an identical value.…”

“…In particular, the first three or four terms in Eq. [13] were sufficient to give a result to four significant figures at long times (t Ն 500 s), but use of even 10 terms at short times (of the order of 20 seconds) still had not produced convergence. Hence, the analytical (semi-infinite) solution provides the more accurate results for short times.…”

Solute diffusion in liquid nickel measured by pulsed ion beam melting

“…[4,5,6] By inducing uniform melting in a shallow surface layer over a short duration, convection is effectively eliminated. Reactive contamination is also eliminated because the molten pool is contained by identical solid, while reactivity at the free surface is limited by the brief melt duration.…”