1. V10Cr10Co30Fe40Ni10 Intensity V10Cr10Co30Fe45Ni5 V10Cr10Co30Fe50
2 theta (degree)
FCC
BCC
VFCC : 100%, as-annealed
VFCC : 100%, tensioned at 77K
VFCC : 100%, tensioned at 298K
VFCC : 5%, tensioned at 77K
VFCC : 99%, tensioned at 298K
VFCC : 66%, as-annealed
VFCC : 0%, tensioned at 77K
VFCC : 0%, tensioned at 298K
V10Cr10Co30Fe40Ni10
V10Cr10Co30Fe45Ni5
V10Cr10Co30Fe50
Supplementary Fig 1.
XRD profiles of the V10Cr10Co30Fe50-xNix (x=0, 5, and 10 at%) high-entropy alloys for the states of as-annealed, tensioned at 298K, and tensioned at 77K.

2. <110>FCC // <111>BCC
K-S Relation
{111}FCC // {110}BCC
<110>FCC // <111>BCC
(b)
(c)
2 μm
(a)
FCC
BCC2
BCC1
{111}FCC <110>FCC
{110}BCC1 <111>BCC1
{110}BCC2 <111>BCC2
111
001
101
BCC
(d)
(e)
(f)
Athermal martensite
Deformation-induced martensite
Supplementary Fig 2.
Orientation relationship between FCC matrix and BCC martensite showing the Kurdjumov-Sachs (K-S) relation. EBSD (a) phase map, (b) IPF map of an enlarged area of Fig. 4c (e=0), and (c) pole figures of FCC and BCC phases. The athermal martensite has the K-S relation with the FCC matrix. EBSD (d) phase map, (e) IPF map of an enlarged area of Fig. 4c (e=0.05), and (f) pole figures of FCC and BCC phases. The deformation-induced martensite also shows a K-S relation with the FCC matrix.