Preparation And Properties Of (Fe,Co)-Ln-nb-b Bulk Metallic Glasses

Due to the high strength, strong corrosion resistance and good soft-magnetic properties, Fe-based bulk metallic glasses (BMG) have great potential for application in functional and structural materials so that widespread interests and attentions from researchers are being aroused in the field of materials both at home and abroad. But for the lower glass-forming ability (GFA), its application is vastly limited. At present, elemental addition is an important method to improve the thermal stability, GFA, magnetic and mechanical properties of BMG. It’s also an effective way to find new amorphous systems.In the present work, we prepared a series of amorphous ribbons by spin quenching. Firstly, the influence of elemental addition with different rare earth elements (La,Ce,Pr,Nd,Gd,Tb,Dy,Ho,Er,Y) on the thermal stability and GFA of (Feo.5Coo.5)67.5Ln3.5Nb4B25glassy alloys was investigated by using XRD, DSC, DTA et al. The experimental results show that the thermal stability and GFA of alloys can be improved with different degrees by adding the rare earth elements. When Ln=Y, the alloy has the widest supper cooled liquid region (△Tx=96K), with the best thermal stability. When Ln=Dy, the value of Trg and γ both reach the maximum, respectively0.604and0.418, with the best GFA.Furthermore, we also study the effects of B and Nb concentration on the thermal stability and GFA of (Fe,Co)-Gd-Nb-B Glassy Alloys. Meanwhile, the crystallization behavior and mechanism are discussed by using the isothermal and thermal crystallization. The results as follow:(1) Owing to B addition, the two-stage glass transition existing in (Fe0.5Co0.5)92.5-xGd3.5Nb4Bx(x=22.5-30) glassy alloys is weakened and finally eliminated. When x=25, the alloy has the maximum value of△Tx, Trg and γ (△Tx=96K, Trg=0.592, γ=0.413).(2) the thermal stability and GFA of (Fe0.5Co0.5)69-xGd3.5NbxB27.5(x=3-6) and (Fe0.5Co0.5)66.5-xGd3.5NbxB30(x=4-7) glassy alloys are greatly increased with increasing the B concentration.(Fe0.5Co0.5)59.5Gd3.5Nb7B30glassy alloy has the maximum value of△Tx, Trg and γ (△Tx=128K,Trg=0.614,γ=0.435). So far,(Fe0.5Co0.5)59.5Gd3.5Nb7B3o glassy alloy is characteristic of the widest supper cooled liquid region in Fe-based BMG systems. (3) The crystallization process of (Fe,Co)-Ln-Nb-B glassy alloys exhibits a phenomenon that many phases precipitate simultaneously, and their final crystallization products are all (Fe,Co)2B,(Fe,Co)23B6,(Fe,Co)2Nb,(Fe,Co)2GdB6, and α-Fe.