XAFS and XRD studies on local and long-range structures of mechanically alloyed AlxTi1-x solid solutions

Local and long-range structures of mechanically alloyed AlxTi1-x alloys milled for 360 ks have been studied by XAFS and XRD. The XAFS results clearly show that there are similar radial distribution functions for Al0.10Ti0.90 and Al0.50Ti0.50 alloys. The Ti-Ti coordination number is 10.0 and 8.5 for Al0.10Ti0.90 and Al0.50Ti0.50 alloys, respectively. The Ti atoms in the Al0.50Ti0.50 alloy favor to be coordinated by Ti atoms in the first shell. The XRD results suggest that after milled for 360 ks the AlxTi1-x alloys form mixed phases of amorphous state and hcp Ti(Al)(ss) solid solution for x = 0.10 and 0.50, and a single phase of fee Al(Ti)(ss) solid solution for x = 0.75. The XRD result is in good agreement with that from XAFS. We propose that the mechanical alloying with a low power can drive the first nearest neighbor coordination around Ti atoms to produce a large defect, and extend AlxTi1-x amorphous alloy range to a lower Al concentration x = 0.10.