TY - JOUR
T1 - Formation of fully equiaxed grain microstructure in additively manufactured AlCoCrFeNiTi0.5 high entropy alloy
AU - Guan, S.
AU - Solberg, K.
AU - Wan, D.
AU - Berto, F.
AU - Welo, T.
AU - Yue, T. M.
AU - Chan, K. C.
PY - 2019/12/15
Y1 - 2019/12/15
N2 - In this work, the non-equiatomic high entropy alloy AlCoCrFeNiTi0.5 was additively manufactured via the laser engineered net shaping (LENS™) process. Contrary to the columnar grain microstructure commonly observed in previously reported alloys, the as-deposited AlCoCrFeNiTi0.5 specimens exhibit a fully equiaxed grain microstructure in a wide range of temperature gradients G (85 to 1005 K/mm) and solidification velocities V (5 to 20 mm/s). The main microstructural characteristics were found to be B2-structured proeutectic dendrites delineated by lamellar or rod-like B2/A2 eutectic structures. The formation of this microstructural feature can be discussed with the aid of Scheil's solidification model. The proeutectic B2-structured dendrites were frequently found to be fragmented, which may provide profuse effective nucleation sites, and hence promote equiaxed grain formation. Furthermore, we estimated the volume fraction ϕ values of equiaxed crystals at solidification front for various G - V combinations established in this paper, which can provide a theoretical basis for our experimental findings. The current work provides guidelines for producing fully equiaxed alloys by the additive manufacturing (AM) process.
AB - In this work, the non-equiatomic high entropy alloy AlCoCrFeNiTi0.5 was additively manufactured via the laser engineered net shaping (LENS™) process. Contrary to the columnar grain microstructure commonly observed in previously reported alloys, the as-deposited AlCoCrFeNiTi0.5 specimens exhibit a fully equiaxed grain microstructure in a wide range of temperature gradients G (85 to 1005 K/mm) and solidification velocities V (5 to 20 mm/s). The main microstructural characteristics were found to be B2-structured proeutectic dendrites delineated by lamellar or rod-like B2/A2 eutectic structures. The formation of this microstructural feature can be discussed with the aid of Scheil's solidification model. The proeutectic B2-structured dendrites were frequently found to be fragmented, which may provide profuse effective nucleation sites, and hence promote equiaxed grain formation. Furthermore, we estimated the volume fraction ϕ values of equiaxed crystals at solidification front for various G - V combinations established in this paper, which can provide a theoretical basis for our experimental findings. The current work provides guidelines for producing fully equiaxed alloys by the additive manufacturing (AM) process.
KW - Additive manufacturing
KW - AlCoCrFeNiTi high entropy alloy
KW - Dendrite fragmentation
KW - Equiaxed grain formation
KW - Eutectic reaction
KW - Nucleation
UR - http://www.scopus.com/inward/record.url?scp=85073072160&partnerID=8YFLogxK
U2 - 10.1016/j.matdes.2019.108202
DO - 10.1016/j.matdes.2019.108202
M3 - Journal article
AN - SCOPUS:85073072160
VL - 184
JO - International Journal of Materials in Engineering Applications
JF - International Journal of Materials in Engineering Applications
SN - 0264-1275
M1 - 108202
ER -