https://www.tcd.ie/Physics/people/Graham.Cross/SF%20Poster%202011/Inoue-ActaMater00-Stabilization%20of%20metallic%20supercooled%20liquid%20and%20bulk%20amorphous%20alloys.pdf

Stabilization of metallic supercooled liquid and bulk amorphous alloys

https://dc.engconfintl.org/cgi/viewcontent.cgi?article=1032&context=superalloys_ii

A critical review of high entropy alloys and related concepts

Microstructures and properties of high-entropy alloys

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

Bulk metallic glasses (BMGs) have been classified according to the atomic size difference, heat of mixing (� H mix ) and period of the constituent elements in the periodic table. The BMGs discovered to date are classified into seven groups on the basis of a previous result by Inoue. The seven groups are as follows: (G-I) ETM/Ln-LTM/BM-Al/Ga, (G-II) ETM/Ln-LTM/BM-Metalloid, (G-III) Al/Ga-LTM/BMMetalloid, (G-IV) IIA-ETM/Ln-LTM/BM, (G-V) LTM/BM-Metalloid, (G-VI) ETM/Ln-LTM/BM and (G-VII) IIA-LTM/BM, where ETM, Ln, LTM, BM and IIA refer to early transition, lanthanide, late transition, group IIIB–IVB and group IIA-group metals, respectively. The main alloying element of ternary G-I, G-V and G-VII, ternary G-II and G-IV, and ternary G-VI BMGs is the largest, intermediate and smallest atomic radius compared to the other alloying elements, respectively. The main alloying element of ternary BMGs belonging to G-I, G-V, G-VI and G

Classification of Bulk Metallic Glasses by Atomic Size Difference, Heat of Mixing and Period of Constituent Elements and Its Application to Characterization of the Main Alloying Element

An amorphous phase in Ln-Fe-Al (Ln=Nd and Pr) systems is formed in wide composition ranges of 0 to 90 at% Fe and 0 to 93 at% Al by melt spinning. Ferromagnetic Ln/sub 90-x/Fe/sub x/Al/sub 10/ bulk amorphous alloys with high coercive force (/sub i/H/sub c/) at room temperature are obtained by copper mold casting. The maximum diameter of the cylindrical amorphous samples is 12 mm for the Nd-30%Fe-Al alloy and 3 mm for the Pr-30%Fe-Al alloys and decreases with deviating Fe content. The extremely high T/sub x//T/sub m/ and small /spl Delta/T/sub m/(=T/sub m/-T/sub x/), which are evaluated by the crystallization temperature (T/sub x/) and melting temperature (T/sub m/), are the reason for the achievement of large glass-forming ability in these systems. The bulk amorphous Ln/sub 60/Fe/sub 30/Al/sub 10/ alloys are ferromagnetic with the Curie temperature of 515 to 600 K which are higher than those for Nd-Fe and Pr-Fe binary amorphous ribbons. The remanence and /sub i/H/sub c/ are 0.089 to 0.122 T and 277 to 321 kA/m, respectively and the crystallization to Ln+Al/sub 2/Ln+/spl delta/ causes a ferromagnetic-to-paramagnetic transition. Thus, the hard magnetic properties are achieved only in the amorphous state.

Hard Magnetic Bulk Amorphous Alloys

Dual HCP structures formed in senary ScYLaTiZrHf multi-principal-element alloy

When an amorphous Fe 90 Nd 7 B 3 alloy subjected to annealing for 60 to 180 s at temperatures between 923 and 1023 K consists of a mixed structure of bcc-Fe, Fe 3 B, Fe 14 Nd 2 B and remaining amorphous phases, the (BH) max and remanence were found to have maximum values of 113 kJ/m 3 and 1.17 T, respectively. Their crystallites which precipitated through the process of Am→Am'+bcc-Fe→Am''+bcc-Fe+Fe 3 B→Am'''+bcc-Fe+Fe 3 B+Fe 14 Nd 2 B have the particle sizes of 20 to 60 nm and the thickness of the intergranular amorphous layer is 5 to 30 nm. The Fe 14 Nd 2 B phase is surrounded by the bcc-Fe and remaining amorphous phase in the optimally annealed state because it precipitates from the remaining amorphous phase which surrounds the bcc-Fe particles. The further increase in annealing temperature and annealing time causes the increase in particle size of their precipitates as well as the disappearance of the residual amorphous phase, leading to the significant decrease in (BH) max . The existence of the residual amorphous phase was also recognized for all other Fe-Nd-B alloys with maximum (BH) max values obtained by annealing the amorphous phase. The intergranular amorphous phase as well as the bcc-Fe phase is presumed to act as an effective magnetic exchange-coupled medium. This information is extremely important for the subsequent development of permanent magnet materials by the utilization of magnetic exchange-coupled state as well as for the interpretation of the appearance of hard magnetism in the use of the rapidly solidified Fe-rich amorphous phase as a precursor.

Hard Magnetic Properties of Nanocrystalline Fe–Nd–B Alloys Containing α-Fe and Intergranular Amorphous Phase

Septenary Zr–Hf–Ti–Al–Co–Ni–Cu high-entropy bulk metallic glasses with centimeter-scale glass-forming ability

An Al0.5TiZrPdCuNi high-entropy (H-E) alloy with a bcc single phase was found through a Ti20Zr20Pd20Cu20Ni20 H-E glassy alloy designed based on equi-atomicity inherent to H-E alloys. The constituent elements and the composition of the Ti20Zr20Pd20Cu20Ni20 alloy were determined by regarding a binary Cu64Zr36 bulk metallic glass as Cu60Zr40 alloy and subsequent replacements of the Cu and Zr atoms with other late- and early-transition metals, respectively. The Ti20Zr20Pd20Cu20Ni20 alloy in a ribbon shape forms into a glassy single phase. The addition of 0.5Al to the Ti20Zr20Pd20Cu20Ni20 H-E glassy alloy resulted in forming a bcc single phase for a rod specimen with a diameter of 1.5mm. The analysis revealed that the Al0.5TiZrPdCuNi H-E alloy is characterized by mixing enthalpy of ¹46.7kJ·mol ¹1 and Delta parameter of 8.8, which are considerably larger and negative for the former and larger for the latter against the conventional H-E alloys. [doi:10.2320/matertrans.M2012370]

Akira Takeuchi

Papers

Hard Magnetic Bulk Amorphous Alloys

Dual HCP structures formed in senary ScYLaTiZrHf multi-principal-element alloy

Hard Magnetic Properties of Nanocrystalline Fe–Nd–B Alloys Containing α-Fe and Intergranular Amorphous Phase

Septenary Zr–Hf–Ti–Al–Co–Ni–Cu high-entropy bulk metallic glasses with centimeter-scale glass-forming ability

Al0.5TiZrPdCuNi High-Entropy (H-E) Alloy Developed through Ti20Zr20Pd20Cu20Ni20 H-E Glassy Alloy Comprising Inter-Transition Metals