Formations of amorphous and quasicrystal phases in Ti-Zr-Ni-Cu alloys

The structure of melt-spun Ti45Zr35Ni20-xCux (x=0, 1, 3, 5 and 7) alloys and a cast Ti45Zr35Ni17Cu3 bulk alloy have been studied. The melt-spun alloys have different structures depending on the thickness of the melt-spun ribbons. When the thickness is 86±5 μm, icosahedral quasicrystal (I) and Laves (L) phases are formed for x=0 and 7, and a single I phase is formed for x=1, 3 and 5. When the thickness decreases to 20±2 μm, I and amorphous phases are formed for x=0 and 1, and a single amorphous phase is formed for x=3, 5 and 7. The thickness of 15±1 μm for x=0 and 1 also causes the formation of a single amorphous phase. The cast alloy also has different structures depending on the size of the bulk samples. The structure of the cast rod sample with a diameter (D) of 1 mm consists mainly of I and amorphous phases. The I phase is homogenously distributed and its particle size is less than 5 μm. I and C14 L phases are formed in the cast rod sample with D of 2 mm. The particle size of the I phase is less than 10 μm. The volume fraction (Vf) of the I phase is about 67% for D of 1 mm rod and 55% for D of 2 mm rod. Three phases of I phase, C14 L and β-(Ti,Zr) are formed in the cast rod sample with D of 3 mm. EDS measurement indicates that the I phase has an approximate composition of Ti49Zr36Ni13Cu2