Effects Of W And Vacuum Condition On Preparation And Properties Of Fe-based Amorphous Alloys

As new-style structural and functional materials, the Fe-based amorphous alloys not only have high strength, wear resistance and corrosion resistance, but also exhibit excellent magnetic properties, which make the Fe-based amorphous alloys have broad application prospects. In this paper, we considered the Fe-Co-Zr-Mo-W-B amorphous alloys as the research object, and focused on the glass forming ability (GFA), mechanical properties, microstructure, thermal stability, crystallization behaviors, etc. of the Fe-based amorphous alloys, together with the effect of vacuum and tungsten content on the performance.The Fe61Co9-xZrgMo5WxB17 (x= 0 and 2) amorphous ribbons and rods were prepared by single roller melt spinning and copper mold casting, respectively, in different vacuum conditions. We analyzed the microstructure of the specimen using XRD, SEM, TEM and other experimental methods; measured the hardness of the samples using micro-hardness tester; studied the thermal properties such as the thermal stability, the crystallization behavior of the primary crystallization, the thermal expansion behavior of the specimen using DSC and DIL equipments; studied the crystallization kinetics of the samples through analyzing and calculating the isochronal and isothermal DSC data; obtained the activation energy for nucleation and growth through a new calculation method.By analyzing the rods with the diameter of 2mm, we can find that:SEM and XRD show the GFA of Fe61Co9-xZr8Mo5WxB17 (x= 0 and 2) alloys is dependent on the tungsten content and vacuum conditions, which can be described by a pseudo-ternary phase diagram; under low and high vacuum conditions, tungsten can improve the viscosity and hardness and decrease the fragility of the Fe-based alloys; the dilatometric measurement shows the higher GFA, the higher Aa, which can be explained by the free volume model.By analyzing the ribbons prepared in the high vacuum condition, we can find that:adding tungsten can improve the GFA of the Fe-Co-Zr-Mo-B alloys. Based on Kissinger equation, comparing the calculated activation energy ElK for the first crystallization of the ribbons, we can find that it can improve the thermal stability of the ribbons by adding tungsten; based on KJMA equation, analyzing the isothermal DSC data, we can find that the crystallization mode of ribbons is 1 dimension parabolic growth at very earlier stage and 3 dimension parabolic growth afterwards, and tungsten can restrain the nucleation of the primary crystallization and enhance the growth of the primary and secondary crystallization products in the isothermal crystallization process.