Effects of ultrastrong gravitational field on the crystalline state of a Bi-Sb alloy

Huang, X.*; Mashimo, Tsutomu; Ono, Masao  ; Tomita, Takeshi; Sawai, Tomotsugu; Osakabe, Toyotaka  ; Mori, Nobuo*

Mega-gravity field experiments were performed on the BiSb(atomic percent) alloy and pure Bi below their melting points, to investigate the change in crystalline state. For the alloy centrifuged at 191-205 C, no change in composition was observed, and the grain sizes of the crystals decreased from several mm to tens of m, while no distinct change in grain size was observed for the centrifuged pure Bi. The alloy centrifuged at 220-240 C consisted of two regions with different morphologies-fine-grained crystals with grain sizes around tens of m in the low gravity region, and large crystals with grain sizes several mm long and hundreds of m wide along the direction of gravity in the high gravity region, where sedimentation of atoms was confirmed. The large crystals with hexagonal structures were formed by preferential crystal growth roughly along the c axes, and a large strain that increased as the gravitational field increased existed inside these crystals. Formation of this anomalous crystal state might be correlated with the sedimentation of atoms.