The effects of tantalum addition on the glass forming ability, thermal stability, and mechanical properties of Ni-Co-W-B bulk metallic glasses

The effects of Ta substitution for Ni and Co on the glass forming ability (GFA), thermal stability, and mechanical properties of (Ni0.592Co0.408)(61.3-x)TaxW23.7B15 (x=0-10) bulk metallic glasses were studied by differential thermal calorimetry (DSC), X-ray diffractometry (XRD), microhardness and compressive tests. Tantalum additions up to 8 at.% increases the GFA. The alloy containing 8 at.% Ta has the highest GFA and its critical thickness was determined to be 1.5 mm. It is also determined that the thermal and mechanical properties of the alloys improve with tantalum additions. The glass transition temperature increases from 854 K in (Ni0.592Co0.408)(61.3)W23.7B15 alloy to 971 K in (Ni0.592Co0.408)(51.3)Ta10W23.7B15 alloy. Also, microhardness increases from 1151 Hv for (Ni0.592Co0.408)(61.3)W23.7B15 alloy to 1262 Hv for (Ni0.592Co0.408)(51.3)Ta10W23.7B15 alloy. The compressive strength and elastic modulus of 8 at.% Ta containing alloy are 4.2 GPa and 204 GPa, respectively.