Abstract
Nanometric particles of a new chromium structure were produced by mechanical alloying of
Cr
3
P
2
under low nitrogen pressure. X-ray diffraction study has shown that the particles have an ordinary
bcc
structure of chromium
(α-Cr)
up to 1 h of milling but they have a new
cubic
chromium
A15-type
structure
(δ-Cr),
up to 2 h of milling, with a lattice parameter equal to 0.4703 ± 0.001 nm. The new structure has a
Pm-3
space group with eight atoms distributed within the unit cell: 2
Cr
atoms with occupancy equal to 1 in positions:
1a: 000
and
1 b: ½½½
in addition to 6 others
Cr
atoms with occupancy equal to 0.25 in positions:
6f: ¼ 0 ½; 6f: ½ ¼ 0; 6f: 0 ½ ¼; 6f: ¾ 0 ½; 6f: ½ ¾ 0; 6f: 0 ½ ¾
. As well as the new
δ-Cr A15-type
phase two chromium phosphides are formed in the nanometric
Cr
3
P
2
alloy: an orthorhombic
CrP
and the monoclinic
CrP
2
after 1 and 2 h of milling, respectively. Therefore, the formed phosphide records the highest density of dislocations and the lowest stacking fault probability after 2 h of milling. The mechanical properties show that the
P
and
CrP
are auxetic strong reentrant cellular structures with negative Poisson's ratio which makes them specifically resistant.