High pressure torsion of amorphous Cu60Zr30Ti10 alloy

Abstract

High pressure torsion was applied to produce a disk-shaped specimen of Cu60Zr30Ti10 composition. The dependence of the morphology, microstructure, and thermal behavior on the applied shear strain was monitored by scanning and transmission electron microscopies, synchrotron x-ray diffraction, and calorimetry. The disk consists of a gradient microstructure ranging from large homogeneous blocks (about 20 μm) to finely dispersed nanocrystals (about 20 nm) of two stable hexagonal phases and continuously decreasing amorphous content with increasing strain. The evolution of such microstructure was interpreted by using a model based on heat conduction generated by the extensive shear deformation.

Structural changes in Zr-based bulk metallic glasses deformed by high pressure torsion

“…This kind of deformation induced softening is a consequence of extreme shear localization [4]. Recent numerical simulations suggest that the temperature can increase significantly during torsional straining, especially out of the center of the disk [16], which can homogenize the plastic deformation. This homogeneous shear is responsible for the observed bond length change which is hardly detectable for the areas with extreme shear localization.…”

Estimation of heat production during high pressure torsion of Cu-based metallic glass

“…3 and 4) compared to crystalline materials (20-140 K [21,22]) is related to the significantly higher yield stress [12]. In order to demonstrate the effect of the calculated shear dependent temperature rise, the deformation dependence of the morphology, microstructure and thermal behavior of a Cu 60 Zr 30 Ti 10 HPT-deformed amorphous alloy was investigated thoroughly in a recent paper [17]. In the following only the main points will be highlighted.…”

“…In the calculations the following material parameters were used which are typical for a Cu-based metallic glass i.e. k = 7.7 W m −1 K −1 , c = 420 J kg −1 K −1 , = 6125 kg m −3 [11], T g = 700 K [17], T vf = 610 K. The constants Á 0 and B were chosen (Á 0 = 591 Pa, B = 1.1) so: yield = 1.2 GPa at T g , characteristic value for metallic glasses [18]. The initial temperature in the calculation was 300 K.…”

High-Pressure Torsion of Machining Chips and Bulk Discs of Amorphous Zr<SUB>50</SUB>Cu<SUB>30</SUB>Al<SUB>10</SUB>Ni<SUB>10</SUB>

“…[3][4][5][6][7][8][9][10][11][12][13][14][15] The application includes the consolidation of metallic powders, [3][4][5] composites, [6][7][8][9][10][11][12] ball-milled powders, 13,14) amorphous powders, 15) amorphous ribbons, 16) and very recently machining chips. 17,18) Strain-induced amorphization was reported for some compounds, 19,20) whereas crystallization is detected in amorphous materials such as Cu 50 [21][22][23][24][25][26][27][28][29][30][31] It is well established that bulk amorphous materials have high strengths and high hardness [32][33][34][35] and it is known that processing through HPT leads to an increase in the strength of metallic materials. 1,<...>…”

“…17,18) Strain-induced amorphization was reported for some compounds, 19,20) whereas crystallization is detected in amorphous materials such as Cu 50 [21][22][23][24][25][26][27][28][29][30][31] It is well established that bulk amorphous materials have high strengths and high hardness [32][33][34][35] and it is known that processing through HPT leads to an increase in the strength of metallic materials. 1,2) In spite of many publications regarding the HPT processing of amorphous materials, [21][22][23][24][25][26][27][28][29][30][31] little attention has been paid to the strength of amorphous materials after processing by HPT.…”