Prakt. Met. Sonderband 30 (1999) 205 
EDS (Energy Dispersive Spectroscopy) 
EDS was performed in a scanning electron microscope JEOL JSM 840A equipped with a Pentafet® 
detector from Link Analytical. In the window-less mode we use EDS to determine qualitatively the 
presence of boron in phases occurring in the investigated alloys. Since the boron K peak lies close 
to the noise peak, it can be resolved only if the investigated surface is very clean (after polishing 
and ultrasonic cleaning) because eventual etching products or oxide layer on the surface can absorb 
most of the boron characteristic X-rays. Diboride particles were generally large enough to perform 
the reliable quantitative analysis of titanium and aluminium. We used titanium and aluminium 
standard spectra obtained from pure titanium and aluminium as well as from pure diborides AB, 
(large AlB; particles in binary Al-B alloy) and TiB; (from pure arc melted TiB,). We also applied a 
correction for the background shape at low energies between 1 and 2 keV. Therefore, we prepared a 
spectrum from pure spectrographic carbon that gives a peak-free spectrum and included this in the 
fit to the specimen spectrum. Composition of the diboride particles was determined using a ZAF-4 
58 layered FLS program provided by Link Analytical. 
ayers (b) 
X-ray diffraction (XRD) 
The phase composition of alloys was determined with an X-ray powder diffractometer Philips PW 
1710. The general recording curves were recorded at a scanning rate of 0.025 deg/s with 2@ (Bragg 
angle) scan range from 5 to 70° and the detailed recording curves with 0.025 deg/10 s with 20 scan 
son of Ti range from 33.5° to 35° (around the (100) diboride peak). 
Details of 
nto smal The results of X-ray diffraction were primarily used for the determination of the diboride lattice 
in a high parameters. It was found out that lattice parameters a and c of the diboride phase can be calculated 
60 °Clmin reliably if positions of at least five diffraction peaks can be determined. In some cases only (100) 
peak were well defined. In this case only the value of a-axis could be calculated. 
ai The composition of the diboride phase — the atomic fraction of aluminium on the metallic sublattice 
A of diboride ("1 — was estimated on the basis of two criteria: 
! the deviation of the lattice parameter a from that of pure TiB; (2) 
CE 100 [%] (1) 
_ Arp, — Ay. 
Rp the deviation of the axis ratio c/a from that of pure TiB, (3) 
—(c/ } 
Cy = _ daze, 100 [%]. 2) 
(c/a) yp, — (c/a) py, 
allographic 
ne N Results and Discussion 
| The compositions of Al-Ti-B alloys were chosen so that the diboride phase should exist in the 
equilibrium with the liquid phase at the annealing temperature (1600 °C). During heating of 
ached I Al-Ti-B alloys, all other phases present initially (e.g. Al3Ti, 0t-AlB;, AlB;) are melted completely, 
on (30 only the titanium rich diboride remain partly unmelted. To estimate the quantity of unmelted TiB, 
Pe we used the solubility product proposed by Sigworth (11): 
ul” N 
log[wt. % Ti][wt. % BJ? = 8.526 — 16,043/T 
(7 
(3)