Bulk amorphous Al85Ni10Ce5 composite fabricated by cold hydro-mechanical pressing of partially amorphous powders

Abstract

Gas atomized Al 85 Ni 10 Ce 5 partially amorphous alloy powders were successfully consolidated into bulk alloy specimens with high relative density at room temperature by cold hydromechanical pressing. The consolidated specimens have a high fracture strength of up to 1.1 GPa. Two densification mechanisms are proposed to explain the consolidation process. The viscous flow of the amorphous phase because of local heating facilities the elimination of residual pores. Over the last few decades Al-based amorphous alloys with high Al concentrations have received considerable attention because of their high strength combined with excellent bending ductility [1][2][3]. Although Al-based amorphous alloys exhibit remarkable mechanical properties compared to their crystalline counterparts, most of the as-quenched Al-based amorphous alloys can only be obtained by melt spinning in the shape of thin ribbons or by gas atomization in the form of powders. The glass forming ability (GFA) of Al-based amorphous alloys is relatively lower than that of other alloy systems. Only recently, Al-rich bulk metallic glasses with a diameter of 1 mm have been obtained by copper mould casting [4][5][6][7][8]. The size limitation has seriously restricted the practical application of Al-based amorphous alloys. The fabrication of bulk amorphous alloys by consolidating glassy powders has been shown to be an effective way to overcome the size limitation [9-12]. To consolidate amorphous alloy powders with a low GFA and thermal stability into bulk and full dense specimens without compromising their amorphous structure is a difficult task.The inhomogeneous deformation of an amorphous alloy at room temperature is mainly localized within a few shear bands leading to catastrophic failure. With an increase in temperature to the supercooled liquid region, which is defined by the temperature range between the glass transition temperature T g and the crystallization temperature T x , the amorphous alloy exhibits homogeneous deformation and viscous flow [13][14][15][16]. Consequently, the amorphous powders are always consolidated in the supercooled liquid region using their viscous flow characteristics by a conventional consolidation method such as vacuum hot pressing [17] and spark plasma sintering (SPS) [18]. Because of the relatively low crystallization temperature of Al-based amorphous alloys, exposure at high temperature usually leads to crystallization. On the other hand, high temperature is necessary to obtain tight powder particle bonding. However, the temperature fluctuation and temperature gradient, which are difficult to control precisely in a conventional consolidation process, may cause crystallization and deteriorate the material's properties [19][20][21]. To reduce the influence of temperature control precision, amorphous alloys with a wide supercooled liquid region are always used as

Amorphous alloys — A kind of promising high-performance materials

“…The result is a delightful one. We have 17 papers collected in this special issue, which cover broad areas of amorphous alloys, including atomic packing and clusters formation in amorphous alloys [1-3], fragility in glass-forming liquid [4], effects of alloying elements on the glass forming ability of different alloys [5][6][7], deformation behavior and improved mechanical property of amorphous alloys [8][9][10][11], glass-based composites [12,13], high strength metallic glass [14] and functional properties of metallic glasses [15][16][17].…”