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

摘要

Rapidly solidified ribbons of Cu-Ga-Mg-Ti and Cu-Al-Mg-Ti alloys show the formation of y-brass type phase, which is an approximant of quasicrystals. The Cu-Ga-Mg-Ti alloy displays ordered y-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 micro-structural variations.