Deformation-induced crystallization in amorphous Al85Ni10La5 alloy

Vierke, Jens; Schumacher, G.; Pilyugin, V. P.; Denks, Ingwer A.; Zizak, Ivo; Wolf, Christian; Wanderka, N.; Wollgarten, Markus; Banhart, John

doi:10.1016/j.jallcom.2009.12.191

Cited by 20 publications

(16 citation statements)

References 42 publications

(63 reference statements)

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“…These maxima are assigned to the 2 2 0 and 3 1 1 reflections of the fcc-Al phase. This is in qualitative agreement with the results obtained after high pressure torsion of the same powder where fcc nanocrystals have been detected by means of energy dispersive diffraction of X-rays [9]. The size of the Al-nanocrystals was determined by fitting a Gaussian to the 1 1 1-and 2 0 0-reflections and by the use of Scherrer's equation taking into account the intrinsic line width.…”

Section: Resultssupporting

confidence: 88%

“…For Al-RE-TM type amorphous alloys (RE: rare earth elements, TM: transition metals) with amorphous/nanocrystalline composite microstructure the strength was shown to increase up to 1560 MPa [5]. The nanocrystals can be produced either by heat treatment [6] or by plastic deformation [7][8][9][10][11][12][13], e.g., cold rolling [7], nanoindentation [8], high pressure torsion [9], equal channel angular pressing [10], ball-milling [11] and extreme bending [12,13]. It is yet unclear whether the underlying mechanism for stress-induced crystallization is thermal or athermal.…”

Section: Introductionmentioning

confidence: 99%

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Devitrification of glassy Al85Ni10La5 powder by thermal treatment and ball-milling

Liu

Schumacher

Zimmermann

et al. 2011

Journal of Alloys and Compounds

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Section: Resultssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Devitrification of glassy Al85Ni10La5 powder by thermal treatment and ball-milling

Liu

Schumacher

Zimmermann

et al. 2011

Journal of Alloys and Compounds

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“…The temperature increase for the whole consolidated Al-Ni-Ce specimen was estimated to be 40° and thus the temperature at the particle boundaries may exceed T g . A temperature increase has also been reported for a high pressure torsion (HPT) process [26]. Local heating is mainly caused by inter-particle friction forces.…”

Section: Discussionmentioning

confidence: 84%

“…Recently, high pressure technology has been shown to be promising for the consolidation of nanocrystalline and amorphous alloy powders into a bulk specimen with relatively high density [22][23][24][25][26]. Very recently, a cold hydromechanical pressing (CHMP) consolidation method that combines the triaxial compression principle and high pressure technology has been proposed [27].…”

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confidence: 99%

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

et al. 2011

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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

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“…Alternatively to these methods, severe plastic deformation techniques such as equal channel angular pressing (ECAP) and high pressure torsion (HPT) can be used for powder consolidation at temperatures below T x (T x : crystallization temperature in the as-atomized state) in order to avoid uncontrolled crystallization [6,15,16]. While powder consolidation by HPT yields splats only with lateral dimension of centimeters and thickness in the order of 0.1 mm [15,17], ECAP allows for powder consolidation of larger samples. In addition, ECAP can be performed continuously [18], which makes it an interesting candidate process for use in industry.…”

Section: Introductionmentioning

confidence: 99%