Amorphouslike Diffraction Pattern in Solid Metallic Titanium

Amorphouslike diffraction patterns of solid elemental titanium have been detected under high pressure and high temperature using in situ energy-dispersive x-ray diffraction and a multianvil press. The onset pressure and the temperature of formation of amorphous titanium is found to be close to the $\alpha \mathrm{\text{−}}\beta \mathrm{\text{−}}\omega$ triple point in the $P\mathrm{\text{−}}T$ phase diagram. Amorphous Ti has been found to be thermally stable up to 1250 °C for at least 3 min at some pressures. By analyzing the conditions for producing amorphous elemental Zr and Ti, we observed a multi-phase-point amorphization phenomenon for preparing single-element bulk amorphous metals. The results reported may open a new way to preparing single-element bulk amorphous metals with a high thermal stability.

Figure 1

Schematic map of the sample assembly for high-pressure and high-temperature x-ray powder diffraction studies. (1) Pyrophyllite disk. (2) Boron-epoxy cube. (3) BN disk. (4) BN container. (5) NaCl. (6) Copper ring. (7) Graphite disk. (8) Graphite heater. (9) Ti rod. (10) Thermocouple.

Figure 2

In situ energy-dispersive x-ray powder diffraction patterns recorded at various temperatures for Ti rod at 6.3 GPa ($2\theta =10°$) together with patterns using $2\theta =8.6°$ at 1000 °C and various sample positions (along rod longitudinal $Z$ axis and transversal $X$ axis). The escaped peaks and a few Bragg peaks from BN were marked. The patterns for the sample at various positions were recorded for short times.

Figure 3

In situ energy-dispersive x-ray powder diffraction patterns recorded for Ti rod under (a) 6.3 GPa ($2\theta =10°$) and (b) 7.2 GPa ($2\theta =10°$ and $2\theta =9.2°$) and at various temperatures together with patterns recorded for quenched samples. The escaped peaks and a few Bragg peaks from BN were marked. The patterns at 1250 °C were recorded for about 3 min to avoid gasket explosion.

Figure 4

Phase diagram of Ti, obtained in compression and heating mode. Circle symbols are obtained from present work. Filled circles denote amorphous phase, and partially filled circles are a mixture of amorphous and crystalline phases. Solid lines, broken lines, and dotted lines are from data in Refs. 15, 21, 24, respectively. $\alpha =\mathrm{\text{close-packed hexagonal structure}}$, $\beta =\mathrm{\text{body-centered cubic structure}}$, and $\omega =\mathrm{\text{hexagonal structure with space group}}$ $P6/mmm$.