Why Aluminium is not BCC or HCP?

Alpha-iron and tungsten have the bcc form. The fcc lattice is both cubic and closely packed and forms more ductile materials. Gamma-iron, silver, gold, and lead have fcc structures. Finally, HCP lattices are closely packed, but not cubic. HCP metals like cobalt and zinc are not as ductile as the fcc metals. Thank you . read more

Thus to summarize, BCC dislocations' movement is thermally activated while (relatively) FCC dislocations' movement needs significantly smaller activation. This leads to BCC materials becoming brittle at low temperatures while FCC staying ductile irrespective of temperature - but probably not at 0 Kelvin since an atom still has to be moved. read more

Alpha-iron and tungsten have the bcc form. The fcc lattice is both cubic and closely packed and forms more ductile materials. Gamma-iron, silver, gold, and lead have fcc structures. Finally, HCP lattices are closely packed, but not cubic. HCP metals like cobalt and zinc are not as ductile as the fcc metals. read more