Conchoidal Fracture of Zr- and Mg-Based Amorphous Glass

2017 ◽  
Vol 891 ◽  
pp. 504-508
Author(s):  
Jozef Miškuf ◽  
Kornel Csach ◽  
Alena Juríková ◽  
Mária Huráková ◽  
Martin Miškuf ◽  
...  
Keyword(s):  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Shear Bands ◽  
High Strength ◽  
Fracture Surfaces ◽  
Conchoidal Fracture ◽  
Final Failure ◽  
Complex Shear ◽  
Amorphous Glass ◽  
Surface Morphologies

In metallic glasses plastic deformation occurs via the creation and the propagation of a softened region in the shear bands. Some of the high strength metallic glasses (as Zr-based metallic alloys) exhibit complex shear band topography and the final failure respects the allocation of the shear bands. We studied the differences in the fracture surfaces of Zr-and Mg-based amorphous alloys. Ductile behaviour of the shear bands in Zr-based amorphous alloy tends to the dimple creation during the failure. On the fracture surfaces the vein pattern morphology manifestations were present. Conchoidal fracture was typical for Mg-based amorphous glass. Two different surface morphologies, plumes and rib marks ornament the fracture surfaces.

scholarly journals Specific Features of Structure Transformation and Properties of Amorphous-Nanocrystalline Alloys

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 358 ◽  
Author(s):  
Alexandr Aronin ◽  
Galina Abrosimova
Keyword(s):  
Amorphous Phase ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Structural Changes ◽  
Shear Bands ◽  
Component Composition ◽  
Amorphous Structure ◽  
Structure Evolution ◽  
Current State ◽  
Heterogeneous Phase

This work is devoted to a brief overview of the structure and properties of amorphous-nanocrystalline metallic alloys. It presents the current state of studies of the structure evolution of amorphous alloys and the formation of nanoglasses and nanocrystals in metallic glasses. Structural changes occurring during heating and deformation are considered. The transformation of a homogeneous amorphous phase into a heterogeneous phase, the dependence of the scale of inhomogeneities on the component composition, and the conditions of external influences are considered. The crystallization processes of the amorphous phase, such as the homogeneous and heterogeneous nucleation of crystals, are considered. Particular attention is paid to a volume mismatch compensation on the crystallization processes. The effect of changes in the amorphous structure on the forming crystalline structure is shown. The mechanical properties in the structure in and around shear bands are discussed. The possibility of controlling the structure of fully or partially crystallized samples is analyzed for creating new materials with the required physical properties.

Bulk Metallic Glasses

2008 ◽  
Vol 604-605 ◽  
pp. 229-238
Author(s):  
Marcello Baricco ◽  
Tanya A. Başer ◽  
Gianluca Fiore ◽  
Rafael Piccin ◽  
Marta Satta ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Shear Bands ◽  
Bulk Metallic Glasses ◽  
Rapid Quenching ◽  
Second Phase ◽  
Research Activity ◽  
Long Time ◽  
Geometrical Constraints

Rapid quenching techniques have been successfully applied since long time for the preparation of metallic glasses in ribbon form. Only in the recent years, the research activity addressed towards the synthesis of bulk metallic glasses (BMG), in form of ingots with a few millimetres in thickness. These materials can be obtained by casting techniques only for selected alloy compositions, characterised by a particularly high glass-forming tendency. Bulk amorphous alloys are characterised by a low modulus of elasticity and high yielding stress. The usual idea is that amorphous alloys undergo work softening and that deformation is concentrated in shear bands, which might be subjected to geometrical constraints, resulting in a substantial increase in hardness and wear resistance. The mechanical properties can be further improved by crystallisation. In fact, shear bands movement can be contrasted by incorporating a second phase in the material, which may be produced directly by controlled crystallisation. Soft magnetic properties have been obtained in Fe-based systems and they are strongly related to small variations in the microstructure, ranging from a fully amorphous phase to nanocrystalline phases with different crystal size. The high thermal stability of bulk metallic glasses makes possible the compression and shaping processes in the temperature range between glass transition and crystallisation. Aim of this paper is to present recent results on glass formation and properties of bulk metallic glasses with various compositions. Examples will be reported on Zr, Fe, Mg and Pd-based materials, focussing on mechanical and magnetic properties.

BULK AMORPHOUS AND NANOSTRUCTURED MATERIALS BY HIGH ENERGY BALL MILLING

2008 ◽  
Vol 22 (18n19) ◽  
pp. 2905-2913 ◽  
Author(s):  
CONSTANTIN POLITIS
Keyword(s):  
Ball Milling ◽  
Nanostructured Materials ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Glassy State ◽  
High Strength ◽  
Supercooled Liquid ◽  
High Energy ◽  
High Energy Ball Milling ◽  
Energy Ball

Mechanical alloying by high energy ball milling is a promising method for the production of bulk metallic glasses, amorphous alloys and nanostructured materials. Amorphous alloys reinforced by nanocrystals represent a big step in the optimization of new ultra high strength materials. Nano-scale W-Y solid solutions were synthesized by high energy ball milling. Only 1 at. % oxygen can stabilize the bulk metallic glassy state of Zr 54 Cu 19 Ni 8 Al 8 Si 5 Ti 5 O 1 to higher T x and to large supercooled liquid range Δ T xg .

Dynamic indentation response of ZrHf-based bulk metallic glasses

2007 ◽  
Vol 22 (2) ◽  
pp. 478-485 ◽  
Author(s):  
Ghatu Subhash ◽  
Hongwen Zhang
Keyword(s):  
Shear Band ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Shear Bands ◽  
Indentation Hardness ◽  
Strain Rates ◽  
Dynamic Indentation ◽  
Confinement Pressure ◽  
Static Indentation ◽  
Deformation Features

Static and dynamic Vickers indentations were performed on ZrHf-based bulk amorphous alloys. A decrease in indentation hardness was observed at higher strain rates compared with static indentation hardness. For equivalent loads, dynamic indentations produced more severe deformation features on the loading surface than static indentations. Using bonded interface technique, the induced shear band patterns beneath the indentations were studied. In static indentations, the majority of the deformation was primarily accommodated by closely spaced semicircular shear bands surrounding the indentation. In dynamic indentations two sets of widely spaced semicircular shear bands with two different curvatures were observed. The observed shear band patterns and softening in hardness were rationalized based on the variations in the confinement pressure, strain rate, and temperature within the indentation region during dynamic indentations. It is also proposed that free volume migration and formation of nano-voids leading to cracking are favored due to adiabatic heating and consequently cause the observed softening at high strain rates.

Mg–Ca–Zn Bulk Metallic Glasses with High Strength and Significant Ductility

2005 ◽  
Vol 20 (8) ◽  
pp. 1935-1938 ◽  
Author(s):  
X. Gu ◽  
G.J. Shiflet ◽  
F.Q. Guo ◽  
S.J. Poon
Keyword(s):  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Mass Density ◽  
High Strength ◽  
Light Metal ◽  
Glass Forming Ability ◽  
Bulk Glass ◽  
Bulk Amorphous Alloys ◽  
Specific Strength ◽  
Glass Forming

The development of Mg–Ca–Zn metallic glasses with improved bulk glass forming ability, high strength, and significant ductility is reported. A typical size of at least 3–4 mm amorphous samples can be prepared using conventional casting techniques. By varying the composition, the mass density of these light metal based bulk amorphous alloys ranges from 2.0 to 3.0 g/cm3. The typical measured microhardness is 2.16 GPa, corresponding to a fracture strength of about 700 MPa and specific strength of around 250–300 MPa cm3/g. Unlike other Mg- or Ca-based metallic glasses, the present Mg–Ca–Zn amorphous alloys show significant ductility.

Bulk Glass Formation in an Fe-Based Fe–Y–Zr–M (M = Cr, Co, Al)–Mo–B System

2004 ◽  
Vol 19 (3) ◽  
pp. 921-929 ◽  
Author(s):  
Z.P. Lu ◽  
C.T. Liu ◽  
C.A. Carmichael ◽  
W.D. Porter ◽  
S.C. Deevi
Keyword(s):  
Metallic Glasses ◽  
Glass Formation ◽  
Amorphous Alloys ◽  
High Strength ◽  
Supercooled Liquid ◽  
Glass Forming Ability ◽  
Bulk Glass ◽  
Bulk Amorphous Alloys ◽  
Glass Forming ◽  
Hardness Values

Several new bulk metallic glasses based on Fe–Y–Zr–(Co, Cr, Al)–Mo–B, which have a glass-forming ability superior to the best composition Fe61Zr10Co7Mo5W2B15 reported recently, have been successfully developed. The as-cast bulk amorphous alloys showed a distinctly high thermal stability with glass-transition temperatures above 900 K, supercooled liquid regions above 60 K, and high strength with Vickers hardness values larger than HV 1200. The suppression of the growth of primary phases in the molten liquids and the resultant low liquidus temperatures were found to be responsible for the superior glass-forming ability in these new alloys. It was found that the addition of 2% Y not only facilitated bulk glass formation, but the neutralizing effect of Y with oxygen in the molten liquids also improved the manufacturability of these amorphous alloys.

Scanning tunneling microscope observations of metallic glass fracture surfaces

1993 ◽  
Vol 8 (10) ◽  
pp. 2543-2553 ◽  
Author(s):  
D.M. Kulawansa ◽  
J.T. Dickinson ◽  
S.C. Langford ◽  
Yoshihisa Watanabe
Keyword(s):  
Fracture Surface ◽  
Metallic Glass ◽  
Metallic Glasses ◽  
Scanning Tunneling Microscope ◽  
Shear Bands ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Fracture Surfaces ◽  
Glass Fracture ◽  
Shear Instabilities

We report scanning tunneling microscope observations of fracture surfaces formed during catastrophic crack growth in three metallic glasses: Ni56Cr18Si22B4, Co69Fe4Ni1Mo2B12Si12, and Fe78B13Si9. Macroscopically, the first two glasses fail along a slip band formed during loading and display a characteristic, μm-scale pattern of vein-like ridges; in contrast, Fe78B13Si9 displays little slip prior to fracture, and its fracture surface shows a μm-scale chevron pattern of steps. STM observations of fracture surfaces of all three materials show nm-scale grooves. The grooves in Co69Fe4Ni1Mo2B12Si12 are especially prominent and display stepped edges which we attribute to the intersection of shear bands with the surface. STM observations of the vein-like features on Ni56Cr18Si22B4 also show stepped edges. We attribute the vein features to the interaction of adjacent crack fingers in which the material between adjacent fingers fails in plane stress. The origin of the grooves is uncertain, but may be due to other shear instabilities along crack fingers.

Fracture Toughness Study on Zr-based Bulk Metallic Glasses

2007 ◽  
Vol 1048 ◽  
Author(s):  
Jin-yoo Suh ◽  
Mary Laura Lind ◽  
C. Paul Kim ◽  
R. Dale Conner ◽  
William L Johnson
Keyword(s):  
Electron Microscopy ◽  
Fracture Toughness ◽  
Metallic Glasses ◽  
Shear Bands ◽  
Bulk Metallic Glasses ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Fracture Surfaces ◽  
Linear Elastic ◽  
Elastic Fracture

AbstractThe fracture toughness of Zr-based bulk metallic glasses of various compositions was studied in the as-cast and annealed condition. Properties were characterized using x-ray and differential scanning calorimetry (DSC) and fracture surfaces were examined using electron microscopy (SEM). Quaternary Zr-Ti-Cu-Be alloys consistently had linear elastic fracture toughness values greater than 80 MPa·m1/2, while Vitreloy 1, a Zr-Ti-Cu-Ni-Be alloy, had an average fracture toughness of 48.5 MPa·m1/2 with a large amount of scatter. The addition of iron to Vitreloy 1 reduced the fracture toughness to 25 MPa·m1/2. Fracture surfaces were carefully analyzed using electron microscopy. Some samples had highly jagged patterns at the beginning stage of crack propagation, and the roughness of this jagged pattern correlated well with the measured fracture toughness values. These jagged patterns, the main source of energy dissipation in the sample, were attributed to the formation of shear bands inside the sample. The Zr-Ti-Cu-Be alloy, having KQ=85 MPa·m1/2 as cast, was annealed at various time/temperature combinations. When the alloy was annealed 50°C below Tg, the fracture toughness dropped to 6 MPa·m1/2, while DSC and X-ray showed the alloy to still be amorphous. The roughness of the fracture surfaces on relaxed samples also compared well with the relative fracture toughness.

scholarly journals Formation and Mechanical Properties of Pd-Si Binary Bulk Metallic Glasses

2014 ◽  
Vol 2014 ◽  
pp. 1-5
Author(s):  
Na Chen ◽  
Hongxia Zhang ◽  
Ke-Fu Yao
Keyword(s):  
Mechanical Properties ◽  
Metallic Glasses ◽  
Shear Bands ◽  
Bulk Metallic Glasses ◽  
High Strength ◽  
Side Surface ◽  
Alloy System ◽  
Structural Inhomogeneity ◽  
Micrometer Scale ◽  
Scale Shear

Glassy spherical samples in the diameters up to 10 mm were produced in a binary Pd-Si alloy system. These Pd-Si bulk metallic glasses (BMGs) combine high strength of about 1600 MPa and superplasticity of over 70% together. In addition to abundant micrometer-scale shear bands, 10–20 nanometer-sized shear bands were also observed on the side surface of the deformed sample. The excellent ductility shown by the Pd-Si BMGs is suggested to arise from the nanoscale structural inhomogeneity.

scholarly journals The influence of rolling and high-pressure torsion in the Bridgman chamber on the quantitative characteristics of shear bands in an amorphous Zr-based alloy

2021 ◽  
pp. 67-74
Author(s):  
I. A. Khriplivets ◽  
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
High Pressure Torsion ◽  
Shear Bands ◽  
Quantitative Description ◽  
Polished Surface ◽  
Deformation Method ◽  
Quantitative Characteristics

Amorphous alloys based on metal components demonstrate a unique ability to realize plastic deformation under the influence of external mechanical stresses. Influenced by substantial degrees of plastic deformation in alloys, one can observe shear bands (SB) in the form of rough lines on the polished surface of the sample. The concept of shear band formation in amorphous metallic glasses varies greatly from plastic deformation processes in crystalline metals and alloys. Unlike crystalline metals, amorphous metallic glasses can exist in a spectrum of structural states with accompanying mechanical, thermodynamic, and physical properties of materials. The formation and evolution of shear bands control the fluidity and plasticity of almost all metallic glasses at room temperature, and in many cases, the formation of dominant shear bands rapidly leads to failure. The literature does not contain any rigorous quantitative description of SB main parameters, which could adequately describe in the analytical form the process of plastic deformation of amorphous alloys, similar to the dislocation and disclination theories of plastic deformation of crystals. An open question remains how the transition from macroscopic deformation to severe plastic deformations of amorphous alloys affects the key SB characteristics. In this work, using the method of optical profilometry, the author studied in detail the quantitative characteristics of the steps formed by shear bands on the surface of deformed samples of the massive amorphous alloy Zr60Ti2Nb2Cu18.5Ni7.5Al10 after high-pressure torsion (HPT) and after rolling. The study identified that the design of shear bands depends on the deformation method and showed that the magnitude of deformation had the controlling effect on the shear bands thickness (the height of the steps). The transition from deformation by rolling (e=0.4) to plastic deformation during HPT (e=2.6) leads to the threefold increase in the power of shear bands and the average distance between them.

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