The effect of Hf substitution for Zr on glass formability in the Zr65Al7.5Ni10Cu17.5 and Zr55Al10Ni5Cu30 systems

The effect of the progressive substitution of Zr by Hf on glass formation and thermal characterisation, using chill-block melt spinning and copper die suction casting, has been studied for the Zr55−xHfxAl10Ni5Cu30 (0≤x≤55 at.%) and Zr65−xHfxAl7.5Ni10Cu17.5 (0≤x≤65 at.%) alloy series. For both series, Hf induced a decrease in glass forming ability (GFA), with the formation of amorphous cast rods limited to low Hf content. For melt spun ribbon, the former series was fully amorphous at all Zr:Hf ratios while beyond x≥45 crystalline phases in a glassy matrix were observed. For both series increased Hf concentration gave an increase in glass transition temperature (Tg) and liquidus temperature (Tl) and a decrease in magnitude of the supercooled liquid region (ΔTx). The effect of Hf substitution on reduced glass transition temperature (Trg= Tg/Tl) was dependent on the series, the latter and former exhibiting an increase and decrease, respectively.