Hongbo Fan

Exceptionally high glass-forming ability of an FeCoCrMoCBY alloy

It has been well documented that the maximum thickness of as-cast glassy samples attainable through conventional metallurgical routes is the decisive criteria for measuring the glass-forming ability (GFA) of bulk metallic glasses (BMGs). Here we report the exceptionally high GFA of an FeCoCrMoCBY alloy which can be fabricated in the form of glassy rods with a maximum sample thickness of at least 16mm. It is demonstrated that, by substituting Fe with a proper amount of Co in a previously reported Fe-based BMG alloy, the glass formation of the resultant new alloy can be extensively favored both thermodynamically and kinetically. The new ferrous BMG alloy also exhibits a high fracture strength of 3500MPa and Vickers hardness of 1253kgmm−2.It has been well documented that the maximum thickness of as-cast glassy samples attainable through conventional metallurgical routes is the decisive criteria for measuring the glass-forming ability (GFA) of bulk metallic glasses (BMGs). Here we report the exceptionally high GFA of an FeCoCrMoCBY alloy which can be fabricated in the form of glassy rods with a maximum sample thickness of at least 16mm. It is demonstrated that, by substituting Fe with a proper amount of Co in a previously reported Fe-based BMG alloy, the glass formation of the resultant new alloy can be extensively favored both thermodynamically and kinetically. The new ferrous BMG alloy also exhibits a high fracture strength of 3500MPa and Vickers hardness of 1253kgmm−2.

Liquid-solid joining of bulk metallic glasses

Here, we successfully welded two bulk metallic glass (BMG) materials, Zr51Ti5Ni10Cu25Al9 and Zr50.7Cu28Ni9Al12.3 (at. %), using a liquid-solid joining process. An atomic-scale metallurgical bonding between two BMGs can be achieved. The interface has a transition layer of ~50 μm thick. The liquid-solid joining of BMGs can shed more insights on overcoming their size limitation resulting from their limited glass-forming ability and then promoting their applications in structural components.

Crystallization of a Ti-based Bulk Metallic Glass Induced by Electropulsing Treatment

The effect of electropulsing treatment (EPT) on the microstructure of a Ti-based bulk metallic glass (BMG) has been studied. The maximum current density applied during EPT can exert a crucial role on tuning the microstructure of the BMG. When the maximum current density is no more than 2720 A/mm2 the samples retains amorphous nature, whereas, beyond that, crystalline phases precipitate from the glassy matrix. During EPT, the maximum temperature within the samples EPTed at the maximum current densities larger than 2 720 A/mm2 is higher than the crystallization temperature of the BMG, leading to the crystallization event.

EFFECT OF HOT ISOSTATIC PRESSING ON MECHANICAL PROPERTIES OF Fe41Cr15Mo14C15B6Y2Co7 BMG

Fe-based bulk amorphous rods of 3 mm in diameter and a composition of Fe41Cr15Mo14C15B6Y2Co7 were produced by copper mold casting. The as-cast amorphous rods contain a small (2%) fraction of pores. To close the pores, samples cut from the amorphous rods were hot isostatically pressed (hipped) at 863 K, which is in the supercooled liquid temperature range between the glass transition temperature and the crystallization temperature of the amorphous phase, and under a pressure of 200 Mpa. Microstructure examination of the hipped samples shows that hipping results in an increase of the density of the samples from 7.9 g/cm3 to 8.0 g/cm3, and a decrease of the porosity level from 2% to 1%, and that a very small fraction of unknown crystalline phase form. As a result of these microstructure change caused by hipping, the average room temperature compressive fracture strength of the bulk metallic glass (BMG) decrease from 3500 Mpa to 3000 MPa, while the strain to fracture changes little from 1.5% to 1.4%. The mech...

Understanding the structure-Poisson’s ratio relation in bulk metallic glass

AbstractnHere, we employ isothermal annealing on a ZrCuNiAl bulk metallic glass (BMG) to obtain different structural states. The nanohardness of the studied Zr-based BMG shows a clear transition from heterogeneous to homogeneous distribution and the Poisson’s ratio gradually decreases with prolonging the isothermal annealing time. Then, the structural change is analyzed using high-resolution transmission electron microscope. The structure–Poisson’s ratio relation can be quantitatively illustrated by a rule of mixture. These findings have implications for better understanding the structure–property relation from atomic level and thus exploring high-performance BMGs of excellent strength and ductility.n