Synthesis and Indentation Behavior of Amorphous and Nanocrystalline Phases in Rapidly Quenched Cu–Ga–Mg–Ti and Cu–Al–Mg–Ti Alloys

Abstract

Rapidly solidified ribbons of Cu–Ga–Mg–Ti and Cu–Al–Mg–Ti alloys show the formation of γ-brass type phase, which is an approximant of quasicrystals. The Cu–Ga–Mg–Ti alloy displays ordered γ-brass structure, whereas Cu–Al–Mg–Ti leads to the formation of amorphous and nanocrystalline disordered bcc γ-brass phase. The hardness values of as-synthesized ribbons of Cu–Ga–Mg–Ti and Cu–Al–Mg–Ti alloys are ~7.36 and ~9.01 GPa, respectively. The high hardness value of the Cu–Al–Mg–Ti alloy can be attributed to the combined effects of amorphous and nanocrystalline phases. The absence of cracks around the indentation up to 100 g of load of this alloy suggests better toughness in comparison with Cu–Ga–Mg–Ti alloy. The formation of shear bands is more prominent in case of Cu–Al–Mg–Ti alloy. The value of yield strength and Meyer exponent of the material has been estimated. It has been found that the indentation parameter seems to be sensitive to structural and microstructural variations.