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)

Effect of Ce/La addition on the soft magnetic properties in Fe-Si-B-P amorphous alloys

Young-Sin Choi,Min-Woo Lee,Do-Hun Kwon,Eun-Ji Cha,Jong-Ryoul Kim,Hwi-Jun Kim 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1

Fe based amorphous alloys include metalloid elements in Fe matrix because they improve amorphous forming ability (AFA) leading to low coercivity and excellent core loss. However, Fe content is relatively decreased with increasing the content of metalloid elements, thereby lowering the saturation magnetic flux density. Several results have reported that the addition of Rare-earth (RE) metals can enhance magnetization in amorphous alloys. In this study, the optimal addition amount of lanthanide elements such as Ce, La in Fe-Si-B-P amorphous alloys was investigated to increase the magnetization while maintaining the coercivity below 35 A/m. The large atomic radius of Ce and La causes lattice distortion and lager heat of mixing value of ∆H, which enhances AFA according to Miedema’s model for atomic pairs. We estimated effect of Ce/La addition on the soft magnetic properties of Fe-based amorphous ribbons. The content of Ce and La additives changed from 0 to 2.5 at. % in Fe_81-(x+y)(SiBP)₁₉(Ce_xLa_y) alloys. The magnetic and thermal properties of amorphous alloys were measured by vibrating sample magnetometer (VSM) and Differential scanning calorimetry (DSC), respectively. Also, amorphous forming ability was measured with changing ribbon thickness by varying the wheel speed during melt spinning process. Furthermore, the phase analysis was performed using X-ray diffraction (XRD) analysis.

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.

비정질 합금-페라이트-에폭시 복합재의 전자파 흡수 특성

임경묵,김문철,이기안,박찬경 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.3

The electromagnetic wave absorption properties of various amorphous alloy-ferrite-epoxy composites have been investigated in a frequency range from 1 to 5 GH_Z. The fraction of amorphous alloy in the composites was varied from 0 to 50 vol.% at a fixed 50 vol.% fraction of epoxy resin polymer. The complex permeability(μ) and permittivity (ε) of the composites were measured by reflection/transmission technique. Both the matching frequency and thickness for maximizing reflection loss of the composites were theoritically determined by plotting the measured μ and ε on an impedance matching solution map. The increase of amorphous alloy fraction in amorphous alloy-ferrite-epoxy composites improved electromagnetic wave absorption properites, i.e, a larger matching frequency and thinner thickness compared with the ferrite-epoxy composite. On the basis of these results, a new thinner wave absorber is proposed by the optimization of amorphous alloy fraction and thickness in amorphous alloy-ferrite-epoxy composites.

비정질 합금이 나타내는 소성의 원천

이석우,이창면,채수원,김유찬,이재철 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.5

Various Cu-Zr bearing monolithic amorphous alloys, exhibiting different stress-strain behaviors, were prepared to investigate the nature of the plasticity shown by theses alloys. Microscopic observation of the quasi-statically compressed Cu_(50)Zr_(43)A1_(7) specimen revealed abundant precipitation of nanocrystallites, while insignificant changes in the microstructure were observed from the Cu_(64)Zr_(36) alloy. Finite element analysis was conducted in order to better understand the role of nanocrystallites in an amorphous matrix on the plasticity of the amorphous alloy. The activation energies for crystallization of the amorphous alloys were measured and correlated with the plasticity of the amorphous alloys. Herein, we report for the first time that the origin of the plasticity of monolithic amorphous alloys lies in the activation energy for crystallization. (Received February 14, 2005)

Effect of synthesis methods on magnetocaloric properties of Co-based Heusler-type alloys

Lee, A.Y.,Kim, S.Y.,Oh, H.R.,Kim, H.A.,Kim, Y.D.,Lee, M.H. Elsevier 2018 Materials science & engineering. B, Advanced funct Vol.231 No.-

<P><B>Abstract</B></P> <P>We evaluated the effect of fabrication methods such as arc melting, suction casting, spark plasma sintering and melt spinning on the magnetocaloric properties, i.e., magnetization, magnetic entropy change, and relative cooling power, of Co-based Heusler-type alloys having a high Curie temperature (>700 K). We also investigated entropy changes caused by phase transformation. Magnetic entropy change in the amorphous ribbon synthesized by melt spinning is much larger than that in the crystal sample within the high-temperature range. Moreover, unlike crystalline samples, both direct and inverse magnetocaloric effects were observed in the amorphous ribbons. Magnetocaloric properties of amorphous ribbon samples were superior to those of the other samples at temperatures above 745 K. The amorphous ribbon of the Co<SUB>85.5</SUB>Sn<SUB>4.5</SUB>Zr<SUB>10</SUB> alloy showed about 1.5 times stronger MCE that of the amorphous Co<SUB>85.5</SUB>Sn<SUB>4.5</SUB>Hf<SUB>10</SUB> alloy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Co-based Heusler alloys with high Curie temperature were produced by various methods. </LI> <LI> The Zr including amorphous ribbon was improved the magnetocaloric property. </LI> <LI> The amorphous ribbons were indicated not only inverse but also typical phase transition. </LI> <LI> The controlling of production methods and selection of optimized composition are important. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>We investigated the effect of synthesis methods on the magnetic entropy change and magnetocaloric property. The amorphous ribbons were observed not only inverse but also typical phase transition contrary to the crystalline samples. Also, the magnetic entropy change of Zr including amorphous ribbon was nine times higher than that of crystalline samples. Therefore, controlling of production methods and selection of optimized composition are important to obtain enhanced magnetocaloric materials.</P> <P>[DISPLAY OMISSION]</P>

벌크 비정질 합금의 초저온 소성

윤규상 ( Kyeu Sang Yoon ),이미림 ( Mi Rim Lee ),이재철 ( Jae Chul Lee ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 대한금속·재료학회지 Vol.48 No.8

We investigated the cryogenic temperature plasticity of a bulk amorphous alloy. Experiments showed that as temperature decreases, the plasticity of the alloy increases, such that the alloy exhibited ~20% of plastic strain when tested at -196℃. This enhancement in the plasticity at cryogenic temperatures was associated with the formation of abundant shear bands distributed uniformly over the entire surface of the sample. Nonetheless, the serrations, the characteristic feature of the plastic deformation of amorphous alloys, were unclear at -196℃. In this study, both the enhanced plasticity and the unclear serrations exhibited by the amorphous alloy at cryogenic temperatures were clarified by exploring shear banding behaviors in the context of the velocity and the viscosity of a propagating shear band.

비정질 합금의 소성에 미치는 조성분리 원소의 역할 : 실험 및 전산모사 연구

박경원,이창면,사인영,이병주,이재철,Park, Kyoung-Won,Lee, Chang-Myeon,Sa, In-Young,Lee, Byeong-Joo,Lee, Jae-Chul 한국재료학회 2009 한국재료학회지 Vol.19 No.2

A series of experiments demonstrated that an addition of Ag into $(Cu_{0.5}Zr_{0.5})_{100-x}Ag_{x}$ amorphous alloys alters the plasticity of the alloys in a systematic manner. Energy dispersive x-ray spectroscopy (EDS) conducted on the $(Cu_{0.5}Zr_{0.5})_{100-x}Ag_{x}$ alloys exhibited the presence of compositional modulation, indicating that compositional separation had occurred. The presence of compositional modulation was also validated using a combined technique of molecular dynamics and Monte Carlo simulation. In this study, the effect of Ag on the compositional separation in $(Cu_{0.5}Zr_{0.5})_{100-x}Ag_{x}$ bulk amorphous alloys was investigated to understand the role played by the phase-separating element on the plasticity of the amorphous alloys.

액체급냉법에 의한 비정질 Ti-Cu-Ni 합금들의 전기화학적 부식특성

김현구,장희진 한국물리학회 2015 새물리 Vol.65 No.9

This study was undertaken to examine the electrochemical corrosion properties of amorphous Ti50Cu30Ni20, Ti70Cu10Ni20, and Ti75Cu15Ni10 alloys prepared with various alloy composition by using the melt-spinning method. The potentiodynamic polarization showed that the corrosion potential (Ecorr) and the corrosion rate (icorr) of the Ti50Cu30Ni20 and Ti70Cu10Ni20 alloys were -0.078 and -0.082 VSCE and about 2.19 × 10−5 and 1.00 × 10−7 A/cm2, respectively, in a pH 2 solution. The corrosion rate of the Ti70Cu10Ni20 alloy was lower than that of the Ti50Cu30Ni20 alloy. This is explained by the fact that the corrosion resistance of the Ti70Cu10Ni20 alloy is primarily dominated by Ti. Also, the Ecorr and the icorr of the Ti70Cu10Ni20 and the Ti75Cu15Ni10 alloys were -0.082 and -0.248 VSCE and about 1.00 × 10−7 and 1.21 × 10−6 A/cm2, respectively. The corrosion resistance of Ti70Cu10Ni20 alloy was better than that of the Ti75Cu15Ni10 alloy. pH가 2인 산성 수용액에서 비정질 Ti50Cu30Ni20, Ti70Cu10Ni20, 그리고 Ti75Cu15Ni10 합금들의 전기화학적 부식 특성을 조사하였다. Ti50Cu30Ni20과 Ti70Cu10Ni20 비정질 합금의 부식전위 (Ecorr)는 각각 약 -0.078 VSCE, -0.082 VSCE로 거의 비슷하게 측정되었으며, 부식속도 (icorr)는 약 2.19 × 10-5 A/cm2과 1.00 × 10-7 A/cm2으로 Ti70Cu10Ni20 합금의 icorr가 Ti50Cu30Ni20 합금의 icorr보다 더 낮게 측정되어 Ni 함량이 일정할 경우 합금의 내식성은 Ti 함량이 높을수록 더 우수할 것으로 생각되었다. 또한 비정질 Ti70Cu10Ni20 합금과 Ti75Cu15Ni10 합금의 Ecorr는 각각 약 -0.082 VSCE와 -0.248 VSCE로 Ti70Cu10Ni20 합금이 더 높게 측정되었으며, icorr는 약 1.00 × 10-7 A/cm2과 1.21 × 10-6 A/cm2 으로 Ti70Cu10Ni20 합금의 icorr가 Ti75Cu15Ni10합금의 icorr보다 더 낮아 부식 저항성이 더 우수할 것으로 생각되었다.