Formation and stability of icosahedral phase in Al₆₅Ga₅Pd₁₇Mn₁₃alloy

Abstract

In this work, we present the formation and characterization of a quaternary (pseudo ternary) icosahedral quasicrystal in Al 65 Ga 5 Pd 17 Mn 13 alloy. The Xray diffraction and transmission electron microscopy confirmed the formation of icosahedral, B2 type and ξ' crystalline (orthorhombic structure with unit cell a = 23.5Å, b= 16.6Å and c = 12.4 Å) phases in as cast alloy.The icosahedral phase gets formed after annealing at 800 °C for 60 hours.The formation of icosahedral phase in Al-Ga-Pd-Mn quaternary alloy by present technique has been studied for the first time. The Energy dispersive X-ray analysis investigations suggest the presence of Ga (~ 5 at %) in the alloy. It is interesting to note that pseudo twelve fold pattern in the as cast alloy has been observed. Icosahedral Al-Ga-Pd-Mn provides a new opportunity to investigate the various characteristics including surface characteristics. Attempts will be made to discuss the micromechanisms for the formation of quasicrystalline phase in Al-Ga-Pd-Mn alloys.

Nanoindentation characteristics of Zr69.5Al7.5−xGaxCu12Ni11 glasses and their nanocomposites

“…It indicates that the decrease in between the icosahedral quasicrystalline nuclei and the liquid with increasing Ga content contributes to the increase in the nucleation rate. The relevant interfacial energy per unit area of Ga (∼0.6 J/m 2 ) is reported to be lower than that of Al (∼1.2 J/m 2 ) [9,28]. Thus Ga substitution may be reducing the interfacial energy between quasicrystal and remaining amorphous phase, thereby increasing the nucleation rate of the crystalline/quasicrystalline phases.…”