Nanocrystallization of Cu-Based Bulk Glassy Alloys upon Annealing

Pengjun, Cao,Dong, Jiling,Haidong, Wu,Peigeng, Fan,Anruo, Zhou Korean Society of Microscopy 2016 Applied microscopy Vol.46 No.1

The Cu-based bulk glassy alloys in Cu-Zr-Ti-Ni systems were prepared by means of copper mold casting. The Cu-based bulk glassy alloys samples were tested by X-ray diffractomer (XRD), differential scanning calorimeter, scanning electron microscopy (SEM), Instron testing machine and Vickers hardness instruments. The result indicated that the prepared Cu-Zr-Ti-Ni alloys were bulk glassy alloys. The temperature interval of supercooled liquid region (${\Delta}T_x$) was about 45.48 to 70.98 K for the Cu-Zr-Ti-Ni alloy. The Vickers hardness was up to 565 HV for the $Cu_{50}Zr_{25}Ti_{15}Ni_{10}$ bulk glassy alloy. The $Cu_{50}Zr_{25}Ti_{15}Ni_{10}$ bulk glassy alloys were annealed in order to obtain nanocrystals. The results showed that the Vickers hardness was raise up to 630 HV from 565 HV. As shown in XRD results, the amorphous alloys changed to nanocrystals, which were $Cu_8Zr_3$, $Cu_3Ti_2$ and CuZr, improved the hardness. The SEM analysis showed that the compression fractured morphology of amorphous alloys was brittle fracture, and the fracture morphology after annealing was ductile fracture. This proved that annealing of amorphous to nanocrystals can improve the plasticity and toughness of amorphous alloys.

Crystallization-induced plasticity of Cu–Zr containing bulk amorphous alloys

Lee, Seok-Woo,Huh, Moo-Young,Fleury, Eric,Lee, Jae-Chul Elsevier 2006 ACTA MATERIALIA Vol.54 No.2

<P><B>Abstract</B></P><P>This study examined the parameter governing the plasticity observed in various Cu–Zr containing monolithic amorphous alloys. All the alloys were fully amorphous in their as-cast condition but exhibited different plastic strains. Microscopic observations of the quasi-statically compressed alloys showed abundant nanocrystallites in the amorphous matrices in the alloys that exhibited pronounced plasticity. On the other hand, insignificant changes in the microstructure were observed in the alloy that did not show plasticity. The mechanism for the formation of these deformation-induced nanocrystallites was examined from the viewpoints of thermodynamics and kinetics. The role of the deformation-induced nanocrystallites on the plasticity of the amorphous alloy was examined using high-resolution transmission electron microscopy. The results demonstrate that compressive loading facilitates nanocrystallization in monolithic Cu–Zr containing amorphous alloys, resulting in plasticity. The parameter governing the plasticity in these monolithic Cu–Zr containing amorphous alloys lies in the activation energy for the overall crystallization process.</P>

Spark Plasma Sintering으로 제조된 Cu계 벌크 비정질 합금의 미세조직과 기계적 성질

김창규,이성학,신승용,김도향 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.3

Cu-based bulk amorphous powders were consolidated by a spark plasma sintering (SPS) process. Consolidation conditions such as consolidation temperature, consolidation pressure, and holding time were established to obtain good microstructures and compressive properties. Cu-based amorphous powders were produced by a gas atomization process. Amorphous alloys having a few micropores and nanocrystalline phases could be obtained with a consolidation pressure of 80 MPa, and were fractured in an intergranular mode along prior powder boundaries. Microstructures and compressive properties of the amorphous alloys consolidated with a pressure of 300 MPa were significantly modified as prior amorphous powders were sufficiently bonded without micropores. Fractographic investigation of these alloys indicated that vein patterns appeared on fracture surfaces as amorphous powders were strongly bonded during the high-pressure consolidation. These findings suggested that the high-pressure consolidation was effective in suppressing the crystallization of amorphous phases and in strongly bonding amorphous powders to consolidate good quality amorphous alloys. (Received December 6, 2004)

분말야금방법으로 제조된 Cu계 벌크 비정질 합금 빌레트의 미세조직과 기계적 성질

김창규,이한상,신승용,이재철,김도향,이성학 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.12

Cu-based bulk amorphous alloy billets fabricated by a powder metallurgy route were studied, focusing on the effect of consolidation temperature on the microstructural and compressive properties. Rapidly solidified amorphous powders were produced by commercial atomization method. In order to consolidate amorphous alloy billets, a spark plasma sintering (SPS) equipment was set up, and variables for hot consolidation were investigated. Using the consolidation temperature of 480℃ under the pressure of 80 MPa, a good quality amorphous alloy billet having very few micropores or crystalline phase particles was obtained. Compressive strength of the billet was 1.8 GPa, which was about 6% lower than that of the cast amorphous alloy. This reduction was associated with the existence of few micropores, crystalline phase particles, and oxide layers of prior powder boundaries in the billet. Amorphous matrix composite billets containing Cu particles homogeneously distributed in the amorphous matrix were successfully fabricated by the SPS consolidation. These composite billet showed a considerable amount of plastic strain, although their compressive strength was reduced. (Received June 7, 2004)

Design of high performance structural alloys using second phases

Elsevier 2007 Materials science & engineering. properties, micro Vol.449 No.-

<P><B>Abstract</B></P><P>Development of high performance structural alloys is not an easy task since the improvement in one property (e.g., strength) often results in the degradation of other properties (e.g., ductility, toughness). One of the ways of overcoming the obstacle is to utilize the beneficial effects of second phases. This paper presents some examples to show how such approach has enabled us to develop structural alloys for specified properties. Examples are drawn from our research programs on high-temperature Mg alloys, and wrought Mg alloys, and bulk amorphous alloys.</P>

Bulk nanocrystalline Al₈₅Ni₁₀La₅ alloy fabricated by spark plasma sintering of atomized amorphous powders

Sasaki, T.T.,Hono, K.,Vierke, J.,Wollgarten, M.,Banhart, J. Elsevier Sequoia 2008 Materials science & engineering. properties, micro Vol.490 No.1

Amorphous Al<SUB>85</SUB>Ni<SUB>10</SUB>La<SUB>5</SUB> powders were consolidated to cylindrical samples by spark plasma sintering (SPS), and their microstructures and mechanical properties were investigated. When the powders were consolidated below the crystallization temperature, an amorphous phase was retained in the consolidated sample. Sintering above the crystallization temperature caused full crystallization. The Vickers hardness of the amorphous-containing sample was about 350HV in the as-sintered state and increased up to 450HV by a subsequent heat treatment just below the crystallization temperature. The highest hardness was achieved in a nanocrystalline microstructure. Compression tests revealed the brittle nature of the consolidated samples although the fracture and yield strength was higher than 1GPa. The brittleness is due to the low relative density of the amorphous-containing samples and the presence of a large amount of intermetallic compounds in the fully crystallized sample.

Zr-Al-Cu-Ni계 합금의 비정질형성능에 미치는 Pd과 Ag 복합첨가의 영향

김미혜 ( Kim Mi Hye ),이병우 ( Lee Byeong U ),김성규 ( Kim Seong Gyu ),배차헌 ( Bae Cha Heon ),정해용 ( Jeong Hae Yong ) 한국주조공학회 2004 한국주조공학회지 Vol.24 No.1

N/A The intluence of Pd and Ag additions on the thermal stability, the glass forming ability (GFA) and mechanical property of Zr_(55)Al_(30)Cu_(20)Ni_(10)Pd_(15)_(10)Ag_(5) (x = 0-5at%) alloys obtained by melt spun and injection casting method have been investigated by using of X-ray diffraction, thermal analysis (DTA. DSC) and micro-Vickers hardness(Hv) testing. The thermal properties of melt-spun Zr_(55)Al_(30)Cu_(20)Ni_(10)Pd_(15)_(10)Ag_(5) (x = 0-5at%) alloys exhibit a supercooled liquid region(AT,) exceeding 91 K betore crystallization. The largest AT, reaches as large as 126 K for the Zr_(55)Al_(30)Cu_(20)Ni_(10)Pd_(15)_(10)Ag_(5) alloy. The reduced glass transition temperature, TrF increased with increasing Ag content. The largest T,, is obtained for the Zr_(55)Al_(30)Cu_(20)Ni_(10)Pd_(15)_(10)Ag_(5) alloy. The Zr_(55)Al_(30)Cu_(20)Ni_(10)Pd_(15)_(10)Ag_(5) bulk amorphous alloy rod with 3 mm in diameter was fabricated by injection casting. Hv increased with increasing Ag content and the largest value was obtained for the Zr_(55)Al_(30)Cu_(20)Ni_(10)Pd_(15)_(10)Ag_(5) bulk amorphous alloy.

Micro-Forming Characteristics of a Zr-Based Amorphous Alloy with a Gear-Like Mold

( Kyu Yeol Park ),( Young Sang Na ),( Seon Cheon Son ),( Jong Hoon Lee ),( Van Bon Nguyen ) 대한금속재료학회 ( 구 대한금속학회 ) 2007 METALS AND MATERIALS International Vol.13 No.5

The amorphous alloy Zr62Cu17Ni13Al8 exhibits a supercooled liquid state over a wide temperature range under high temperatures. In this present paper, the authors studied the micro-forming ability of the alloy by compressing specimens under a miniature pattern mold with a micro-gear shape. Micro-compressive formation is a formation method in which the surface of specimens of the Zr62Cu17Ni13Al8 amorphous alloy is compressed under conditions of dead loads and high temperatures and maintained for a given period for the fabrication of miniature patterns with a micro-gear shape. All the experiments were carried out under a vacuum environment to prevent the specimens from suffering deleterious effects, such as air traps in the miniature patterns and oxidation at the surface of the Zr62Cu17Ni13Al8 amorphous alloy. The characteristics of micro-compressive formation were investigated at temperatures higher than the glass transition temperature with different experimental parameters of loads and times. In addition, the micro-forming characteristics of the gear-like shape were investigated by means of scanning electron microscopes and a 3-D surface profiler system.

Effects of Metalloid Elements on the Mechanical Properties of Fe-Based Bulk Amorphous Alloys

Kim, Yongchan,Hwang, Byoungchul Materials Research Society of Korea 2016 한국재료학회지 Vol.26 No.12

In this study, the glass-forming ability and mechanical properties of newly developed Fe-Mn-Cr-Mo-B-C-P-Si-Al bulk amorphous alloys were investigated, and metalloid elements such as B, C, and P were found to have a strong influence on the properties of the Fe-based amorphous alloys. When the total metalloid content (B, C, and P) is less than 5 %, only the crystal phase is formed, but the addition of more than 10 % metalloid elements enhances the glass forming ability. In particular, the alloys with 10 % metalloid content exhibit the best combination of very high compressive strength (~2.8 GPa) and superior fracture elongation (~30 %) because they consist of crystal/amorphous composite phases.

벌크형 비정질 Zr계 합금의 결정화 열처리에 따른 동적변형 거동

장재준,이병주,황진일,박익민,조경목,조영래,Chang J. J,Lee B. J,Hwang J. I,Park I. M,Cho K. M,Cho Y. R 한국재료학회 2004 한국재료학회지 Vol.14 No.3

The mechanical properties of a bulk amorphous alloy ($Zr_{41.2}$ $Ti_{13.8}$ /$Cu_{10}$ $Ni_{10}$ $Be_{22.5}$ /at.%) before and after an annealing treatment were investigated. For the bulk amorphous alloy, the compressive strength was about 2.0 GPa, irrespective of the strain rates in the range of $10^{-4}$ to $10^3$$ sec^{-1}$ . Fine-sized nanocrystalline particles (10~100 nm) were precipitated homogeneously in the bulk amorphous matrix after the annealing treatments. Compared to the bulk amorphous materials, these composite materials, composed of the nanocrystalline phases and a bulk amorphous matrix had much different mechanical properties. The strength and strain of coposite materials measured by a compressive test showed a peak-maximum values at 7 vol.% of the nanocrystalline phases. The values in higher volume fraction of the crystalline phases in the amorphous matrix were decreased, as measured by both quasi-static and high strain rate. The decrease in fracture strength is due to presence of the dispersed large-crystalline phases in the amorphous matrix.