Fabrication and characterizations of new glassy Co71Ti24B5 alloy powders and subsequent hot pressing into a fully dense bulk glass

Abstract

A single glassy phase of Co 71 Ti 24 B 5 alloy has been synthesized by high-energy ball milling the elemental powders at room temperature, using the mechanical alloying method. The synthetic glassy powder obtained after 130 ks of ball milling exhibits good soft magnetic properties with a polarization magnetization and coercivity values of 1.01 T and 2.86 kA/m, respectively. This ternary glassy alloy in which its glass transition temperature (T g ) lies at a rather high temperature (805 K) crystallizes at 868 K through a single sharp exothermic peak with an enthalpy change of crystallization (⌬H x ) of Ϫ3.28 kJ/mol. The supercooled liquid region before crystallization, ⌬T x of the synthesized glassy powders shows a large value (63 K) for a ternary system. The reduced glass transition temperature (ratio between T g and liquidus temperatures, T l (T g /T l )) was found to be 0.55. The end product of the glassy powder (130 ks) was compacted in an argon gas atmosphere at 835 K with a pressure of 780 MPa, using the hot-pressing technique. The consolidated sample is fully dense (ϳ99.5 pct) and maintains its chemically homogeneous glassy structure. The measured polarization magnetization and coercivity values of as-consolidated powders are measured and found to be 0.96 T and 2.92 kA/m, respectively. The Vickers microhardness of the bulk glassy Co 71 Ti 24 B 5 sample is measured and found to be in the range between 7.32 and 7.46 GPa.

Characterization and amorphous phase formation of mechanically alloyed Co60Fe5Ni5Ti25B5 powders

“…However, the decrease in Ms after 1.5 h of milling could be due to the transformation of the crystalline phases to amorphous phases. Towards the end of the milling process, the Ms remained nearly constant because of the completion of the mechanically induced solid-state reaction [4,22,24]. As reported in Refs.…”

“…El-Eskandarany et al [3] reported that a single amorphous phase of Co 75 Ti 25 alloy powders was obtained after a short MA time (11 ks). They also reported the formation of a single glassy phase of Co 71 Ti 24 B 5 alloy powders after 130 ks of milling [4]. Wu et al [5,6] developed the ferromagnetic Co-based amorphous alloys by replacing some of the Co with (Fe, Nb) or (Zr, Ti) elements, and found that the substitution reduces the thermal stability of the amorphous powders.…”

“…These properties make them as an ideal candidate for some applications like magnetic sensors, memories, and power devices [1][2][3][4][5][6][7][8][9]. It is known that various Co-based amorphous alloys can be obtained by several methods: electro-deposition, gas condensation, rapid solidification and mechanical alloying.…”

Mechanical Properties and Crystallization Behaviors of Microstructured Co-Fe-P Amorphous Alloys

“…Although the mechanical strength is lower than that (the compressive strength) of Fe-or (Fe, Co)-based bulk amorphous alloys, it is larger than that of large amorphous alloys prepared by the consolidation method. [11] The inset of Figure 5 shows the fracture surface of the sample. Crack is observed to propagate along the boundaries of the amorphous grains, but fracture occurs in the amorphous grain as well since there are vein patterns at the fracture surface.…”

Microstructure/Phase Evolution in Mechanical Alloying/Milling of Stainless Steel and Aluminum Powder Blends

“…[1][2][3][4][5] Among other devices, MA is routinely carried out in planetary ball mills. The process involves high strain rate plastic deformation of a given powder charge within a confined volume that induces concomitant deformation, cold welding, fragmentation, interdiffusion, and dynamic recrystallization.…”