Mechanical alloying (MA) is a solid-state powder processng technique involving repeated welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Originally developed to produce oxide-dispersion strengthened (ODS) nickel- and iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from blended elemental or prealloyed powders. The non-equilibrium phases synthesized include supersaturated solid solutions, metastable crystalline and quasicrystalline phases, nanostructures, and amorphous alloys. Recent advances in these areas and also on disordering of ordered intermetallics and mechanochemical synthesis of materials have been critically reviewed after discussing the process and process variables involved in MA. The often vexing problem of powder contamination has been analyzed and methods have been suggested to avoid/minimize it. The present understanding of the modeling of the MA process has also been discussed. The present and potential applications of MA are described. Wherever possible, comparisons have been made on the product phases obtained by MA with those of rapid solidification processing, another non-equilibrium processing technique.

Mechanical Alloying And Milling

Amorphous alloys were first developed over 40 years ago and found applications as magnetic core or reinforcement added to other materials. The scope of applications is limited due to the small thickness in the region of only tens of microns. The research effort in the past two decades, mainly pioneered by a Japanese- and a US-group of scientists, has substantially relaxed this size constrain. Some bulk metallic glasses can have tensile strength up to 3000 MPa with good corrosion resistance, reasonable toughness, low internal friction and good processability. Bulk metallic glasses are now being used in consumer electronic industries, sporting goods industries, etc. In this paper, the authors reviewed the recent development of new alloy systems of bulk metallic glasses. The properties and processing technologies relevant to the industrial applications of these alloys are also discussed here. The behaviors of bulk metallic glasses under extreme conditions such as high pressure and low temperature are especially addressed in this review. In order that the scope of applications can be broadened, the understanding of the glass-forming criteria is important for the design of new alloy systems and also the processing techniques.

https://www.tcd.ie/Physics/people/Graham.Cross/SF%20Poster%202011/Shek-MaterSciEng04-Bulk%20Metallic%20Glasses.pdf

Bulk metallic glasses

We report on the properties of one example of a new family of metallic alloys which exhibit excellent glass forming ability. The critical cooling rate to retain the glassy phase is of the order of 10 K/s or less. Large samples in the form of rods ranging up to 14 mm in diameter have been prepared by casting in silica containers. The undercooled liquid alloy has been studied over a wide range of temperatures between the glass transition temperature and the thermodynamic melting point of the equilibrium crystalline alloy using scanning calorimetry. Crystallization of the material has been studied. Some characteristic properties of the new material are presented. The origins of exceptional glass forming ability of these new alloys are discussed.

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A highly processable metallic glass: Zr41.2Ti13.8Cu12.5Ni10.0Be22.5

The following article is based on the MRS Medal talk presented by William L. Johnson at the 1998 MRS Fall Meeting on December 2, 1998. The MRS Medal is awarded for a specific outstanding recent discovery or advancement that has a major impact on the progress of a materials-related field. Johnson received the honor for his development of bulk metallic glass-forming alloys, the fundamental understanding of the thermodynamics and kinetics that control glass formation and crystallization of glass-forming liquids, and the application of these materials in engineering.The development of bulk glass-forming metallic alloys has led to interesting advances in the science of liquid metals. This article begins with brief remarks about the history and background of the field, then follows with a discussion of multicomponent glass-forming alloys and deep eutectics, the chemical constitution of these new alloys, and how they differ from metallic glasses of a decade ago or earlier. Recent studies of deeply undercooled liquid alloys and the insights made possible by their exceptional stability with respect to crystallization will then be discussed. Advances in this area will be illustrated by several examples. The article then describes some of the physical and specific mechanical properties of bulk metallic glasses (BMGs), and concludes with some interesting potential applications.The first liquid-metal alloy vitrified by cooling from the molten state to the glass transition was Au-Si, as reported by Duwez at Caltech in 1960. Duwez made this discovery as a result of developing rapid quenching techniques for chilling metallic liquids at very high rates of 105–106 K/s.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0883769400053252

Bulk Glass-Forming Metallic Alloys: Science and Technology

The factors of the atomic size difference Delta and the enthalpy of mixing ΔH mιx of the multi-component alloys were summarized from the literatures. The formation zones of solid-solution phases, intermediate phases, and bulk metallic glasses were determined and the validity was verified by experimental results. For forming the solid solution, the alloys should have high entropy of mixing, lower Delta, and not too negative and positive enthalpy of mixing.

Solid‐Solution Phase Formation Rules for Multi‐component Alloys

A low pressure casting of Mg-Cu-Y melts into copper molds was found to cause amorphous bulks in a cylindrical form. The maximum diameter of the amorphous cylinder (D c ) shows a significantcompositional dependence and reaches a maximum value of 4.0 mm for Mg 65 Cu 25 Y 10 . The compositional dependence of the D c is similar to that for the temperature span of the supercooled liquid region, ΔT x (=T x -T g )

/pdf/mg-cu-y-amorphous-alloys-with-high-mechanical-strengths-1a7r3uyhro.pdf

Mg–Cu–Y Amorphous Alloys with High Mechanical Strengths Produced by a Metallic Mold Casting Method

Bulky amorphous alloys in a cylindrical shape with diameters up to 16 mm were found to form by water quenching a Zr 65 Al 75 Ni 10 Cu 175 melt in a quartz tube The amorphous phase of this alloy has the widest temperature interval of supercooled liquid region before crystallization The glass transition temperature, crystallization temperature and Vickers hardness for the bulky amorphous alloy with a diameter of 16 mm are 625 K, 750 K and 465, respectively, being nearly the same as those for the corresponding melt-spun ribbon with a thickness of 30 μm The extremely large glass-forming ability is presumably due to a combination of significantly different atomic size ratios among the constituent elements and the necessity of redistribution of Al for the progress of crystallization

Preparation of 16 mm Diameter Rod of Amorphous Zr65Al7.5Ni10Cu17.5 Alloy

Amorphous Mg-Cu-Y alloys with diameters (or thicknesses) ranging from 1 to 7mm were formed in cylinder and sheet forms by using a high-pressure die casting process. The maximum diameter (or thickness) for formation of an amorphous phase was strongly dependent on composition and the largest value was obtained for Mg 65 Cu 25 Y 10 . There is a tendency for the maximum diameter to increase with an increase in the supercooled liquid region. The glass transition temperature, crystallization temperature and heat of crystallization are independent of sample diameter in the range below 7 mm while the heat of relaxation decreases with increasing sample diameter, indicative of the formation of a more relaxed atomic configuration in the thicker samples

Mg–Cu–Y Bulk Amorphous Alloys with High Tensile Strength Produced by a High-Pressure Die Casting Method

The application of a high-pressure die casting technique to La-Al-TM (TM=Co, Ni, Cu) alloys was found to produce bulk amorphous alloys in cylinder and sheet forms. The maximum sample diameter (d,) for formation of an amorphous phase is 3 mm for La 55 Al 25 (Ni or Cu) 20 , 7 mm for La 55 Al 25 Ni 10 Cu 10 and above 9 mm for La 55 Al 25 Cu 10 Ni 5 Co 5 . There is a clear tendency for d, to increase with an increase in the temperature interval of a supercooled liquid region. The glass transition temperature (T g ), the crystallization temperature (T x ) and the heat of crystallization (ΔH x ) remain unchanged in the thickness range of 1 to 7 mm for the La 55 Al 25 Cu 10 Ni 10 alloy

Takeshi Masumoto

Papers

Mg–Cu–Y Amorphous Alloys with High Mechanical Strengths Produced by a Metallic Mold Casting Method

Preparation of 16 mm Diameter Rod of Amorphous Zr65Al7.5Ni10Cu17.5 Alloy

Mg–Cu–Y Bulk Amorphous Alloys with High Tensile Strength Produced by a High-Pressure Die Casting Method

Bulky La–Al–TM (TM=Transition Metal) Amorphous Alloys with High Tensile Strength Produced by a High-Pressure Die Casting Method

Stable Icosahedral Al–Pd–Mn and Al–Pd–Re Alloys