The Al metal is observed to melt at the same temperature in all the samples independent of grain size and without a change in the shape of the sample. The results here confirm previous thermal measurements which show that the Al metal melts without apparent grain growth in these materials. On the other hand, the temperature for the onset of rapid atomic diffusion, as estimated from NMR line widths, shows a significant sample dependence.
Heated samples exhibit a factor of five increase in hardness and yet remain electrically conducting.