The Effect Of Elements Addition On Properties Of Co-based Bulk Metallic Glasses

Bulk metallic glasses(BMGs)have attracted great attention due to their extremely high fracture strength,great elasticity,excellent magnetic properties and corrosion resistance.Among the BMGs,Co-based BMGs arouse more interests due to their ultrahigh fracture strength and unique magnetic performance and show great potential as structural and functional materials.However,they also have some shortcomings such as low glass forming ability(GFA),poor plasticity,etc.The method of element addition has been widely used in exploring new metallic glass systems as well as improving their properties.In the present work,we attempt to develop new Co-based BMGs systems through the element addition,and explore the effect of the added elements on their properties.The present work includes the following two parts:(1)The effect of Mo addition on properties of Co₈₀P₁₄C₆MG.By adding Mo element,a new series of quaternary Co_80-xMo_xP₁₄C₆(x=8,9,and 10 at.%)bulky glassy rods have been prepared by the combination of fluxing treatment and J-quenching technique,and the influence of Mo addition on GFA,thermal,magnetic and mechanical properties of the as-prepared bulky glassy rods have been explored.The results show that when x=9,the glass forming ability of the BMGs is the best and the critical diameter for glass formation reaches the maximum value of 1.5 mm.The Differential Scanning Calorimetry(DSC)curves of the present Co Mo PC BMGs show a multistage crystallization process but no pronounced glass transition,and their onset crystallization temperatures(T_x)move to high temperature region with the adding of more Mo content.The saturation magnetization of the present Co Mo PC BMGs gradually decreases from 0.35 T(39 emu/g)to 0.17 T(19 emu/g)as the addition Mo content from 8 at%to 10 at%.The compression test results display that the present Co Mo PC BMGs show fracture strength of 2.13-2.32 GPa and nearly zero plasticity.(2)A new series of Co_71-xFe_xMo₉P₁₄B₆(x=0,18,35.5,53 and 71 at.%)BMGs have been prepared by combining fluxing treatment and J-quenching technique,and the effects of Co/Fe content on GFA and properties of this Co Fe based BMGs have been investigated.The critical diameter for fully glass formation of the present Co Fe Mo PB BMGs shows a complicated change with composition,and reaches the largest value of 4.5 mm for the Fe-free alloy.The present Co Fe Mo PB BMGs exhibit good soft magnetic properties with the saturation magnetization of 0.18-0.71 T.The compression test shows that the present Co Fe Mo PB BMGs have relatively high fracture strength of 2.77-2.96 GPa,the Co-rich alloys(x=0-35.5)in the series of the present Co Fe Mo PB BMGs have nearly zero plasticity while the Fe-rich alloys(x=53-71)exhibit significant plasticity of 9.8%-15.4%.