A Unified Approach to Solid-State Amorphization and Melting

Lam, Nghi Q.; Okamoto, P.R.

doi:10.1557/s0883769400047540

Cited by 65 publications

(27 citation statements)

References 27 publications

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“…Several lattice instability models have been proposed for SSA. They include vibrational [4], elastic [5], topological [6], entropical [7] and Lindeman melting criterion [8]. From a thermodynamic aspect, elemental mixing or accumulation of lattice imperfections (point defects, dislocations, grain boundaries (GBs), chemical disorder, etc.)…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic model for solid-state amorphization of pure elements by mechanical-milling

Zhao

2006

Journal of Non-Crystalline Solids

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Section: Introductionmentioning

confidence: 99%

Thermodynamic model for solid-state amorphization of pure elements by mechanical-milling

Zhao

2006

Journal of Non-Crystalline Solids

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“…It is known that the softening of the transverse phonon is a common phenomenon in glasses. 17 The anomalous result can be understood from the microstructure of the BMG. Figure 4 exhibits an HRTEM image of the as-cast Nd 60 Al 10 Fe 20 Co 10 BMG.…”

mentioning

confidence: 99%

Structural evolution and property changes in Nd60Al10Fe20Co10 bulk metallic glass during crystallization

Zhang

Xia

Wang

et al. 2002

Applied Physics Letters

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The structural evolution and property changes in Nd 60 Al 10 Fe 20 Co 10 bulk metallic glass ͑BMG͒ upon crystallization are investigated by the ultrasonic method, x-ray diffraction, density measurement, and differential scanning calorimetry. The elastic constants and Debye temperature of the BMG are obtained as a function of annealing temperature. Anomalous changes in ultrasonic velocities, elastic constants, and density are observed between 600-750 K, corresponding to the formation of metastable phases as an intermediate product in the crystallization process. The changes in acoustic velocities, elastic constants, density, and Debye temperature of the BMG relative to its fully crystallized state are much smaller, compared with those of other known BMGs, the differences being attributed to the microstructural feature of the BMG. Recently, many glass forming alloys were discovered. 1,2Previous studies show that the crystallization in various bulk metallic glasses ͑BMGs͒ is characterized by the appearance of intermediate metastable phases. The formation of icosahedral phases as an intermediate product of the crystallization process in BMGs indicates that there is a structural relationship between the BMGs and quasicrystalline.3,4 The Ndbased BMGs have also evoked intensive interests due to their unique magnetic properties and anomalous crystallization behavior. 1,[5][6][7] It is found that the microstructural change induced by relaxation and crystallization has a very sensitive effect on the thermal and magnetic properties of the BMGs. This implies that the hard magnetic property of the BMGs may be related to the formed intermediate phases prior to the crystallization. In this letter, the microstructural and property changes in the Nd 60 Al 10 Fe 20 Co 10 BMG upon crystallization are investigated by using ultrasonic method and density measurement, which are effective and sensitive tools for studying the structural and vibrational characteristics of BMGs. 8-11The structural and property features, prior to and in the crystallization process, are connected.Nd 60 Al 10 Fe 20 Co 10 BMG was prepared by the die casting method. 6 The BMG rod was cut to a length of about 10 mm and its ends were polished flat and parallel. Afterward, the sample was stepwise isothermally annealed at various temperatures for 1.0 h in a vacuum of 10 Ϫ3 Pa, respectively. After each annealing, the rod was cooled to room temperature, and the acoustic velocities and density were measured. The acoustic velocities were measured by a pulse echo overlap method using a MATEC 6600 ultrasonic system with a 10 MHz frequency. 8,9 The density was measured by the Archimedean technique and the accuracy is 0.1%. Elastic constants ͑e.g., Young's modulus E, shear modulus G, bulk modulus K, and Poisson's ratio ͒ and Debye temperature ⌰ D of the BMG were derived from the acoustic velocities and densities. 12 The structure of the samples was characterized by x-ray diffraction ͑XRD͒ using a MAC M03 diffractometer with Cu K␣ radiation. Differential scanning calorimet...

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“…[19][20][21][22] The melting criteria are often involved (e.g., the Lindemann criterion for the critical thermal displacement of atoms 2o , 22 and the Egami-Waseda criterion for the critical elastic strain caused by the atomic-size mismatch 23 ).…”

Section: Atomistic Modelsmentioning

confidence: 99%

Modeling mechanical alloying: Advances and challenges

Хина¹,

Froes

1996

JOM

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While mechanical alloying is a commercial entity for oxide-dispersion-strengthened superalloys, its application to other systems has run into a number of scientific and commercial barriers. In part, this is due to the inadequate scientific underpinning. This article reviews the status of the modeling of the mechanical alloying processes and suggests an approach to improving current knowledge of the process. INTRODUCTIONMechanical alloying (MA) presents a unique means for producing a wide variety of far-from-equilibrium structures and phases possessing unusual mechanical and physical properties. The attributes ofMA include the production of a fine dispersion of second-phase particles, the extension of solubility limits, the refinement of the matrix microstructure down to the nanometer range, the synthesis of novel crystalline phases, the development of amorphous phases, and the possibility of alloying difficult-toalloy elements.The demand for further progress in MA necessitates the development of mathematical models of transformations in particles undergoing repetitive plastic deformation/cold welding. A brief overview of existing models is presented here, and the difficulties arising from the far-from-equilibrium attributes of the MA process are outlined. Further development of the macrokinetic description of solid-state diffusion and phase transformations under the conditions of continuous-defect generation due to plastic strain will bring together the mechanistic and atomistic approaches and permit modeling of metastable phase formation phenomena observed in MA (e.g., solid-solubility extension, nanograins, amorphous phases, etc.). STATUS OF MA MODELINGSince the first experimental results were reported, 1 and especially after the discovery of metastable phase formation in the course of ball milling,2-4 MA has attracted considerable attention from materials scientists, not only due to the unique properties of the products and promising commercial applications but also because of the unusual physical phenomena involved. An increasing demand for the adjustment of the properties of novel materials produced by 36 MA to particular applications and the improvement of the MA regimes and apparatus designs for commercial scaling necessitates the development of mathematical models of MA. Modeling and computer simulation are based on theoretical concepts and a formal mathematical description of the process. However, theoretical works in this area are not as abundant as experimental research (see reviews by Johnson,s Weeber and Bakker,6 Koch/ Ma and Atzmon 8 and others).Three typical mechanisms of metastable phase formation during MA have been observed: 6 • The gradual disordering of crystal lattice and eventual amorphization. A similar mechanism (but without the crystal-to-amorphous transition) can occur in immiscible systems (e.g., Fe-Cu), resulting in the formation of supersaturated solid solutions during MA.8 • A coexistence of crystalline and amorphous phases and the gradual growth of the latter. This implies the exist...

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A Unified Approach to Solid-State Amorphization and Melting

Cited by 65 publications

References 27 publications

Thermodynamic model for solid-state amorphization of pure elements by mechanical-milling

Thermodynamic model for solid-state amorphization of pure elements by mechanical-milling

Structural evolution and property changes in Nd60Al10Fe20Co10 bulk metallic glass during crystallization

Modeling mechanical alloying: Advances and challenges

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