Atomic-level structures and physical properties of magnetic CoSiB metallic glasses Guangcun Shan a , , , Ji Liang Zhang a , Jiong Li b , Shuo Zhang b , Zheng Jiang b , Yuying Huang b , Chan-Hung Shek a , , a Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tong, Hong Kong, China b Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Shanghai 200624, China Highlights • The atomic structure and the origins of the magnetic properties of two ternary CoBSi metallic glasses were revealed. • The atomic structures were elucidated by state-of-the-art extended X-ray absorption fine structure spectroscopy (EXAFS) combining with ab initio molecular-dynamics (AIMD) techniques. • The experimental spectra were in good agreement with the predictions of ab initio full multiple scattering theory using the FEFF8.4 code. • The origin of these magnetic behaviors was discussed in view of the EXAFS results and atomic structures of the metallic glasses. • These two metallic glasses consist of different clusters, and hence different magnetic properties, which are dominated by short-range orders (SROs). Abstract Two CoSiB metallic glasses of low Co contents, which consist of different clusters, have recently been developed by addition of solute atoms. In this work, the atomic structure and the magnetic properties of the two CoBSi metallic glasses were elucidated by state-of-the-art extended X-ray absorption fine structure spectroscopy (EXAFS) combining with ab initio molecular-dynamics (AIMD) computational techniques. Besides, the origin of these magnetic behaviors was discussed in view of the EXAFS results and atomic structures of the metallic glasses. Graphical abstract The atomic structure and the origins of the magnetic properties of two ternary CoBSi metallic glasses were elucidated by state-of-the-art extended X-ray absorption fine structure spectroscopy (EXAFS) combining with ab initio molecular-dynamics (AIMD) techniques. Figure options Keywords Metallic glass ; Extended X-ray absorption fine structure spectroscopy (EXAFS) ; Ab initio molecular-dynamics (AIMD)
Atmospheric RE-free Mg-based bulk metallic glass with high bio-corrosion resistance S.F. Guo a , b , e , , , K.C. Chan c , , , X.Q. Jiang a , e , H.J. Zhang d , D.F. Zhang d , J.F. Wang d , B. Jiang d , e , F.S. Pan d , e a School of Materials Science and Engineering, Southwest University, Chongqing 400715, China b State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China c Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hong Kong, China d College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China e Chongqing Research Center for Advanced Materials, Chongqing Academy of Science and Technology, Chongqing 401123, China Highlights A Mg 69 Zn 27 Ca 4 bulk metallic glass was successfully prepared in atmospheric air. This glassy alloy can be fabricated using recycled materials in atmospheric air. This glassy alloy possesses high fracture strength and good corrosion resistance. The findings are significant as a means of reducing the cost and manufacturability. Abstract In this work, a rare earth (RE) free Mg 69 Zn 27 Ca 4 bulk metallic glass (BMG) of diameter 1.5 mm was successfully fabricated by the injection casting method using recycled materials in atmospheric air. Without using high vacuum conditions, high purity starting materials and expensive rare earth materials, the findings of the work are of significance in reducing the cost and improving the manufacturability of BMGs. The results of the uniaxial compression tests further showed that there were no obvious differences between BMGs prepared under high vacuum or in atmospheric environment. The electrochemical polarization measurements in simulated physiological media revealed that the atmospheric Mg 69 Zn 27 Ca 4 BMG manifested much lower passive current densities, higher pitting potential and a wider passive region than those of ZK60 and pure Mg alloys. The findings not only present Mg 69 Zn 27 Ca 4 BMG as low cost material for potential biomedical applications, but also provide new insights into understanding of the effects of oxygen on glass formation. http://www.sciencedirect.com/science/article/pii/S0022309313004201
Effects of cooling rate on microstructure, mechanical and corrosion properties of Mg–Zn–Ca alloy Jing-feng WANG a , b , , , Song HUANG a , b , Sheng-feng GUO c , Yi-yun WEI a , b , Fu-sheng PAN a a National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China b College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China c School of Materials Science and Engineering, Southwest University, Chongqing 400715, China http://dx.doi.org/10.1016/S1003-6326(13)62679-5 , How to Cite or Link Using DOI Permissions Reprints Abstract Mg 69 Zn 27 Ca 4 alloys with diameters of 1.5, 2 and 3 mm were fabricated using copper mold injection casting method. Microstructural analysis reveals that the alloy with a diameter of 1.5 mm is almost completely composed of amorphous phase. However, with the cooling rate decline, a little α-Mg and MgZn dendrites can be found in the amorphous matrix. Based on the microstructural and tensile results, the ductile dendrites are conceived to be highly responsible for the enhanced compressive strain from 1.3% to 3.1% by increasing the sample diameter from 1.5 mm to 3 mm. In addition, the Mg 69 Zn 27 Ca 4 alloy with 1.5 mm diameter has the best corrosion properties. The current Mg-based alloys show much better corrosion resistance than the traditionally commercial wrought magnesium alloy ZK60 in simulated sea-water. Key words Mg–Zn–Ca alloy ; bulk metallic glasses ; cooling rate ; mechanical properties ; microstructure ; corrosion resistance http://www.sciencedirect.com/science/article/pii/S1003632613626795
Quaternary magnetic FeNiPC bulk metallic glasses with large plasticity Xiuhua Ma a , Xiaohui Yang a , Qiang Li a , , , Shengfeng Guo b , , a School of Physics Science and Technology, Xinjiang University, Urumqi, Xinjiang 830046, People’s Republic of China b School of Materials Science and Engineering, Southwest University, Chongqing 400715, People’s Republic of China http://dx.doi.org/10.1016/j.jallcom.2013.05.165 Abstract Magnetic Fe 80-x Ni x P 13 C 7 (x=0, 5, 10, 15, 20, 25, 30 at.%) bulk metallic glasses (BMGs) with the diameters up to 2.5 mm were prepared by the combination method of fluxing treatment and J-quenching technique. The effect of Ni substitution for Fe on the glass formation ability (GFA), thermal stability, mechanical properties and magnetic properties has been systematically investigated. It was found that the partial substitution of Ni for Fe can enhance the GFA of Fe 80 P 13 C 7 alloy, while excessive substitution will lead to the degradation of the GFA. The saturation magnetization of Fe 80-x Ni x P 13 C 7 (x=0, 5, 10, 15, 20, 25, 30 at.%) BMGs gradually decrease from 1.47 T to 1.15 T with increasing Ni content from x=0 to x=30, and the Curie temperature firstly increases with the Ni content and then deceases when x20. More importantly, the quaternary monolithic Fe 60 Ni 20 P 13 C 7 glassy alloy shows a significant plastic strain of more than 10%, which is the largest one reported to date for Fe-based BMGs. The potential beneficial effects of Ni in enhancing the GFA and the compressive plasticity of the FePC alloy system are discussed. http://www.sciencedirect.com/science/article/pii/S092583881301325X
Novel centimeter-sized Fe-based bulk metallic glass with high corrosion resistance in simulated acid rain and seawater S.F. Guo a , b , , , K.C. Chan b , , , S.H. Xie c , P. Yu d , Y.J. Huang e , H.J. Zhang f a School of Materials Science and Engineering, Southwest University, Chongqing 400715, China b Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hong Kong, China c Shenzhen Key laboratory of Special Functional Materials, Shenzhen University, Shenzhen 518060, China d College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 400047, China e School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China f College of Materials Science and Engineering, Chongqing University , Chongqing 400044, China Abstract In the present work, a novel Fe 43 Co 4.5 Cr 16.5 Mo 16.5 C 14 B 4 Y 1.5 (at.%) bulk metallic glass rod with 10 mm in diameter has been developed by Cu-mold suction casting using commercial grade raw materials. The thermal stability and corrosion behaviors of the centimeter-sized Fe-based alloys have been studied by differential scanning calorimeter and electrochemical measurements, respectively. The as-cast Fe-based alloy exhibits a high glass transition temperature of 820 K and a large super-cooled liquid region of 60 K, demonstrating an excellent thermal stability. Moreover, the Fe-based alloy developed appears to have corrosion resistance comparable to (or better than) that of 316L stainless steel, based on the measurements of breakdown potential and corrosion weight loss in simulated acid rain and seawater solution. The affluent of chromium and molybdenum elements included is conceived to be highly responsible for the high corrosion resistance in the current Fe-based bulk metallic glass, which may be good candidates to be used as low-cost, high-strength, and corrosion-resistant amorphous alloy. Journal of Non-Crystalline Solids Volume 369 , 1 June 2013, Pages 29–33 http://www.sciencedirect.com/science/article/pii/S0022309313001191
Effects of annealing on the hardness and elastic modulus of a Cu 36 Zr 48 Al 8 Ag 8 bulk metallic glass Ji Gu a , Min Song a , , , , Song Ni a , Shengfeng Guo b , Yuehui He a a State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China b School of Materials Science and Engineering, Southwest University, Chongqing 400715, China http://dx.doi.org/10.1016/j.matdes.2012.12.071 Abstract In this paper, the effects of isothermal annealing on the hardness and elastic modulus of a Cu 36 Zr 48 Al 8 Ag 8 bulk metallic glass (BMG) were investigated. It has been shown that the Vickers hardness increases from 481 Hv (as-cast state) to 518 Hv after annealed for 20 min. Nanoindentation tests also showed that the hardness and elastic modulus increase from 6.45 GPa and ㄢ13.0 GPa (as-cast state) to 7.27 GPa and ㄢ30.9 GPa after annealed for 20 min, respectively. The results indicated that the free volume of the BMG decreased and nanocrystals nucleated during annealing. The annihilation of the free volume decreased the nucleation ratio/sites of the shear bands, while the nucleation of nanocrystals inhibited the propagation of the shear bands. Both effects are responsible for the enhancement of the hardness and elastic modulus of the BMG. Highlights The free volume decreases and nanocrystals nucleate during annealing. Decrease of the free volume decreases the nucleation ratio of the shear bands. The nucleation of nanocrystals inhibits the propagation of the shear bands. Hardness and modulus depends on the evolution of free volume and nanocrystals. Keywords Bulk metallic glass ; Hardness ; Elastic modulus ; Shear bands
The effect of Mo on the glass forming ability, mechanical and magnetic properties of FePC ternary bulk metallic glasses Xiaohui Yang a , Xiuhua Ma a , Qiang Li a , Shengfeng Guo b a School of Physics Science and Technology, Xinjiang University, Urumqi, Xinjiang 830046, People’s Republic of China b School of Materials Science and Engineering, Southwest University, Chongqing 400715, People’s Republic of China http://dx.doi.org/10.1016/j.jallcom.2012.11.170 , How to Cite or Link Using DOI Permissions Reprints Abstract Bulk magnetic Fe 80-x Mo x P 13 C 7 (x=0, 3, 6, 9 and 12 at.%) glassy alloys were successfully prepared by the fluxing technique and J-quenching technique. The effect of Mo substitution for Fe on the glass formation ability (GFA), thermal stability, mechanical properties and magnetic properties has been studied systematically. It was found that the substitution of a small amount of Mo for Fe can dramatically enhance the GFA, which in turn, the critical maximum diameter for fully glass formation reached to 5.5 mm for x=3 and 6.0 mm for x=6, respectively. However, excessive substitution will promote the formation of Fe 2 Mo 3 competition crystalline phase leading to the degradation of the GFA. Furthermore, the substitution of propercontent of Mo for Fe can obviously enhance the mechanical properties of the present Fe-based alloys, which can be identified that the current FeMoPC bulk metallic glass possesses a high fracture strength (over 3000MPa) as well as a large room temperature plasticity (above 5%). In addition, the Mo doping FePC bulk metallic glasses exhibit good soft magnetic properties with a relatively high saturation magnetization of over 1.0 T at room temperature. Highlights Fe 80-x Mo x P 13 C 7 (x=0ㄢ2at.%) BMGs were prepared by fluxing and J-quenching techniques. substitution of a small amount of Mo for Fe can dramatically enhance the GFA. proper substitution of Mo for Fe can obviously enhance σ f and ε p of FeMoPC BMGs. FeMoPC BMGs exhibit good soft magnetic properties with relatively high M S .
Enhanced mechanical properties and corrosion resistance of a Mg–Zn–Ca bulk metallic glass composite by Fe particle addition Jingfeng Wang a , , , Song Huang a , Yiyun Wei a , Shengfeng Guo b , Pan Fusheng a a National Engineering Research Center for Magnesium Alloys, College of Materials Science and Engineering, Chongqing University, Chongqing 400044, PR China b School of Materials Science and Engineering, Southwest University, Chongqing 400715, PR China Abstract Mg 69 Zn 27 Ca 4 with a spot of Fe particle-reinforced alloys was synthesized by Cu-mold injection casting using industrial raw materials. The microstructure, mechanical properties and corrosion resistance of these Mg-based alloys were studied by X-ray diffraction, differential scanning calorimeter, compressive testing and electrochemical measurements, respectively. The Mg 69 Zn 27 Ca 4 alloy can be controlled to become fully amorphous using the industrial raw materials. With Fe particle addition, ductile α-Mg and Mg–Zn dendrites were embedded in the amorphous matrix, which enhanced the compressive strength and fracture strain. The Mg 69 Zn 27 Ca 4 glassy alloy and Mg 69 Zn 27 Ca 4 /Fe alloy remarkably improved the corrosion resistance in 3.5wt% NaCl solution compared with AZ31 and pure Mg. Therefore, Mg 69 Zn 27 Ca 4 and Mg 69 Zn 27 Ca 4 /Fe alloys have high potential as engineering materials. http://dx.doi.org/10.1016/j.matlet.2012.09.098
Corrosion resistances of amorphous and crystalline Zr-based alloys in simulated seawater S.F. Guo a , , , , H.J. Zhang b , Z. Liu c , W. Chen c , S.F. Xie d a School of Materials Science and Engineering, Southwest University, Chongqing 400715, China b National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China c Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hong Kong, China d Jiangxi Key Lab for Advanced Copper and Tungsten Materials, Jiangxi Academy of Sciences, Nanchang 330029, China http://dx.doi.org/10.1016/j.elecom.2012.08.006 Abstract It is well recognized that amorphous alloys usually offer much higher resistance to corrosion over their conventional counterparts in most aqueous solutions. Whereas, in this work, we reported an anomalous corrosion resistance of an arc melting Zr 62.3 Cu 22.5 Fe 4.9 Al 6.8 Ag 3.5 crystalline alloy, which was superior to that of the same composition in glassy state in simulated seawater. It was revealed that the easy formation of a highly protective Zr- and Al-enriched oxide layer at the surface of the crystalline alloy is responsible for the extremely high corrosion resistance. The current finding not only presents an excellent alloy candidate for potential application in seawater but provides a new insight into the understanding of corrosion behavior of amorphous/crystalline alloys in demanding corrosive media. Highlights corrosion properties of Zr-based glassy and crystalline alloys are investigated. Zr-based alloy ingot has much better corrosion resistance than the glassy one. corrosion resistance of Zr-based alloy is hundreds of times better than 304L. Zr-based alloy has an attractive prospect for use in a marine environment. http://www.sciencedirect.com/science/article/pii/S1388248112003372?v=s5
A plastic Ni-free Zr-based bulk metallic glass with high specific strength and good corrosion properties in simulated body fluid S.F. Guo a , b , , , , Z. Liu b , K.C. Chan b , W. Chen b , H.J. Zhang c , J.F. Wang c , P. Yu d a Southwest University, School of Materials Science and Engineering, No.2 Tiansheng Road, BeiBei District, Chongqing 400715, China b Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hong Kong, China c National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China d College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 400047, China Received 12 May 2012. Revised 4 June 2012. Accepted 16 June 2012. Available online 22 June 2012. http://dx.doi.org/10.1016/j.matlet.2012.06.057 Abstract The mechanical properties at room temperature and the corrosion behavior in simulated body fluid (PBS) at 37°C of a Ni-free Zr 62.3 Cu 22.5 Fe 4.9 Al 6.8 Ag 3.5 bulk metallic glass (BMG) were investigated. This BMG exhibits a good room temperature plasticity of 8%, a yield strain of 1.9% and a high fracture strength of about 1800MPa. Interestingly, the novel Zr-rich BMG possesses a specific strength (σ/ρ) of about 280MPa cm 3 /g higher than that of conventional biomedical Ti6Al4V alloy and 316L stainless steel. In addition, this alloy also has a high corrosion resistance with a low corrosion penetration rate in simulated body fluids (PBS). The present Ni-free Zr-rich BMG with a critical diameter above 1cm, together with the high specific strength, large plasticity and good corrosion resistance in PBS, has excellent potential in biomedical applications.
Plasticity enhancement of a Zr-based bulk metallic glass by an electroplated Cu/Ni bilayered coating W. Chen a , K.C. Chan a , , , S.H. Chen a , S.F. Guo b , W.H. Li a , c , G. Wang d a Advanced Manufacturing Technology Research Center, Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hong Kong b School of Materials Science and Engineering, Southwest University, Chongqing, People's Republic of China c School of Materials Science and Engineering, Anhui Institute of Technology, Ma’anshan, Anhui, People's Republic of China d Laboratory for Microstructures, Shanghai University, Shanghai, People's Republic of China Received 27 March 2012. Revised 3 May 2012. Accepted 5 May 2012. Available online 18 May 2012. http://dx.doi.org/10.1016/j.msea.2012.05.031 Abstract In this study, the effect of a Cu/Ni bilayered coating on the shear banding behavior and compressive plasticity of a Zr-based bulk metallic glass (BMG) was investigated. As compared to a mono-layered Cu or Ni coating, the Cu/Ni bilayered coating has provided a better geometric confinement effect. Through a detailed comparative analysis among coated BMG samples with different plasticity, the correlation between the macroscopic plastic deformation behavior and the serrated flow characteristics is studied from the potential energy landscape point of view. The comparatively longer hanging time and larger elastic energy density in the Cu/Ni coated BMG in the serrated plastic regime result in an increased global plastic strain of ㄢ1.2%. The enhanced plasticity is attributed to the thin soft Cu layer acting as a buffer zone for absorbing the elastic energy upon loading, and the strong outer Ni coating exerting a high confining stress upon loading, which impede the rapid propagation of the shear bands. In addition, the strong Cu-Ni interface is also believed to contribute to the enhanced plasticity. Keywords Bulk metallic glass; Electroplating; Cu/Ni bilayered coating; Mechanical properties; Shear bands Materials Science and Engineering: A http://www.sciencedirect.com/science/article/pii/S092150931200723X?v=s5
Bioactive calcium titanate coatings on a Zr-based bulk metallic glass by laser cladding Z. Liu a , K.C. Chan a , L. Liu b , S.F. Guo a , c , , , a Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hong Kong, China b The State Key Lab of Die and Mould Technology, Huazhong University of Science and Technology, 430074 Wuhan, China c School of Materials Science and Engineering, Southwest University, 400715 Chongqing, China Received 29 March 2012. Accepted 8 May 2012. Available online 12 May 2012. http://dx.doi.org/10.1016/j.matlet.2012.05.022 Abstract The bioactive calcium titanate coating was prepared by laser cladding on a (Zr 0.62 Cu 0.23 Fe 0.05 Al 0.1 ) 97 Ag 3 bulk metallic glass. The coating, which was mainly composed with dendrite calcium titanate and a little calcium pyrophosphate, formed a strong bonding with the substrate. The cladding process generated a crystallized heat-affected zone with a thickness of 300μm and other parts in the substrate remained amorphous structure after laser cladding. It was demonstrated that surfaces of Zr-based bulk metallic glasses can be made bioactive and that laser cladding techniques were useful methods in purpose of making Zr-based bulk metallic glass surface bioactive. http://www.sciencedirect.com/science/article/pii/S0167577X12006799?v=s5
Structure related hardness and elastic modulus of bulk metallic glass M. Song 1 , Y. Y. Sun 1 , Y. H. He 1 , and S. F. Guo 2 1 State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China 2 School of Materials Science and Engineering, Southwest University, Chongqing 400715, China In this paper, the structure (free volume) related hardness and elastic modulus of a typical Cu 36 Zr 48 Al 8 Ag 8 bulk metallic glass have been investigated. It is found that the cooling rate during sample preparation affects significantly the concentration of the free volume and thus the interatomic distance. The central region of the specimen has a much lower cooling rate and concentration of the free volume, which decreases the nucleation density of the shear bands, leading to higher hardness and elastic modulus. J. Appl. Phys. 111 , 053518 (2012); http://dx.doi.org/10.1063/1.3692568 ( 5 pages ) http://jap.aip.org/resource/1/japiau/v111/i5/p053518_s1
Enhanced plasticity of Fe-based bulk metallic glass by tailoring microstructure Abstract: The room temperature compressive plasticity of Fe 75 Mo 5 P 10 C 8.3 B 1.7 bulk metallic glass (BMG) was improved from 0.5% to 1.8% by increasing the sample diameter from 1.5 mm to 2.0 mm. With increasing the sample diameter to 2.0 mm, a heterogeneous microstructure with in-situ formed α-Fe dendrite sparsely distributed in the amorphous matrix can be attained. This heterogeneous microstructure is conceived to be highly responsible for the enhanced global plasticity in this marginal Fe-based BMG. Key words: bulk metallic glass; composite; rapid-solidification; mechanical property http://www.sciencedirect.com/science/article/pii/S1003632611611825 http://www.ysxbcn.com/Html_Article/En_16174.html
The structural evolution and mechanical properties of a Zr-based bulk metallic glass during superplastic gas pressure forming P. Yu a , , , S.F. Guo b , J.F. Wang c Abstract The structural evolution and mechanical properties of a Zr-based bulk metallic glass during superplastic gas pressure forming were investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and nanoindentation measurements at the optimum temperature of 676K under different stress states. It was found that the crystallized volume fraction of the deformed specimens with die aspect ratios of 1:1 and 3:2 are estimated to be 15% and 25%, respectively. The high resolution TEM results show that more particles at the nanometer level exist in the deformed specimen with the aspect ratio of 3:2. The nanoindentation tests further illustrate that the Young’s modulus and hardness of the deformed specimens have increased, and the deformed sample with the aspect of 1:1 shows slightly smaller modulus and hardness. The nano-scale crystalline structure induced by gas pressure forming process is considered to be the main reason for the change of the mechanical properties, and in addition to thermal and strain energy. In addition, the structural evolution is also affected by the stress state in the process of gas pressure forming. http://www.sciencedirect.com/science/article/pii/S0261306911008715
Enhancement of plasticity of Fe-based bulk metallic glass by Ni substitution for Fe S.F. Guo a , b , N. Li a , C. Zhang a and L. Liu a , , Abstract Bulk metallic glasses (BMGs) (Fe 1-x Ni x ) 71 Mo 5 P 12 C 10 B 2 ( x =0, 0.1 and 0.2) with a diameter of 3mm were synthesized by copper mold casting. The effect of Ni substitution for Fe on the structure, thermal and mechanical properties has been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and compressive testing. It was found that the substitution of Ni for Fe enhances the glass forming ability, and improves the plasticity of Fe 71 Mo 5 P 12 C 10 B 2 BMG as indicated by the increase in the plastic strain from 3.1% (x=0) to 5.2% (x=0.2). The improvement of the plasticity is discussed in term of the reduction of glass transition temperature and the supercooled liquid region due to the substitution of Ni for Fe. http://www.sciencedirect.com/science?_ob=ArticleURL_udi=B6TWY-4YDT3WH-N_user=2307902_coverDate=02%2F18%2F2010_rdoc=113_fmt=high_orig=browse_srch=doc-info(%23toc%235575%239999%23999999999%2399999%23FLA%23display%23Articles)_cdi=5575_sort=d_docanchor=view=c_ct=465_acct=C000056862_version=1_urlVersion=0_userid=2307902md5=f4dd08bc8d0ae2ce9d4d0db7a3ed3652
Fe-based bulk metallic glass matrix composite with large plasticity S. F. Guo 1, 3 , L. Liu 1, a) , N. Li 1 , and Y. Li 2, a) Abstract Through alloy design, an Fe 77 Mo 5 P 9 C 7.5 B 1.5 bulk metallic glass matrix composite reinforced by the in-situ formed ductile alpha;-Fe dendrite has been developed. In contrast to the monolithic Fe-based bulk metallic glasses that usually fail in brittle fracture, the resulting composite shows a significant plastic strain of more than 30% as well as a high fracture strength over 3.0 GPa. The in-situ formation of the ductile alpha;-Fe dendrites accounts for the significant enhancement of the plasticity. https://www.sciencedirect.com/science/article/pii/S1359646209006654
块体金属玻璃由于其独特的微观结构（原子排列长程无序、短程有序，无晶界、位错等传统意义的结构缺陷），赋予这类材料一系列优异的物理、力学、化学等性能。但是，在推进金属玻璃的实际应用过程中，最大的一个瓶颈是它在室温下极差的拉伸延性，其原因是金属玻璃在室温下的塑性变形高度局部化，极易形成纳米尺度的剪切带（见下图【Li et al., Philos Mag 2002】）。因此，对于金属玻璃中剪切带相关的研究就显得尤为重要。 关于金属玻璃中剪切带的形成机理或者物理起源，虽然经过几十年大量的探索，目前其清晰的物理图像仍然不清楚。一般认为，金属玻璃中某些不均匀处的粘度降低并进而导致塑性变形能力急剧下降是形成局部化剪切带的主要机制。但是，对于这种粘度降低的原因一直以来存在着两种截然不同的观点：自由体积软化和绝热软化。虽然，两种观点各自都有实验证据，但是有些现象它们单独仍然无法合理解释。 我们课题组在前面通过一系列的实验【Liu et al., MCP 2005; JNS 2005; JMR 2006】和理论分析【Dai et al., APL 87, 141916 ( 2005); Dai and Bai, IJIE 35, 704 (2008)】，初步揭示金属玻璃中剪切带形成是一种热力耦合的失稳过程，并不是某一因素（自由体积软化或者热软化）单独作用的结果。尤其是在高应力和高应变率条件下，应力驱动的自由体积产生和功热转变导致的温升都有可能发生，并且互相影响。这两个过程天然耦合在一起。最近发展的一些热力耦合模型能够很好地描述金属玻璃的（非）均匀塑性变形行为，但是对于在这种耦合过程中，自由体积和热的相互作用以及谁是剪切带的起源等关键问题没有给出明确的答案，仍然需要进一步的研究。 我们这个工作就是针对上述这个问题进行系统而深入的理论分析，重点关注在剪切带形成过程中，热和自由体积的相互作用图像；自由体积聚集、温升、体胀对于剪切带失稳的影响。相关工作已经发表在固体力学领域最有影响力的杂志 J. Mech. Phys. Solids 57 (2009) 1267-1292 On the origin of shear banding instability in metallic glasses M.Q. Jiang a , and L.H. Dai , a , a State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, PR China Received 20 October 2008; revised 13 April 2009; accepted 21 April 2009. Available online 4 May 2009. Abstract To uncover the physical origin of shear-banding instability in metallic glass (MG), a theoretical description of thermo-mechanical deformation of MG undergoing one-dimensional simple shearing is presented. The coupled thermo-mechanical model takes into account the momentum balance, the energy balance and the dynamics of free volume. The interplay between free-volume production and temperature increase being two potential causes for shear-banding instability is examined on the basis of the homogeneous solution. It is found that the free-volume production facilitates the sudden increase in the temperature before instability and vice versa. A rigorous linear perturbation analysis is used to examine the inhomogeneous deformation, during which the onset criteria and the internal length and time scales for three types of instabilities, namely free-volume softening, thermal softening and coupling softening, are clearly revealed. The shear-banding instability originating from sole free-volume softening takes place easier and faster than that due to sole thermal softening, and dominates in the coupling softening. Furthermore, the coupled thermo-mechanical shear-band analysis does show that an initial slight distribution of local free volume can incur significant strain localization, producing a shear band. During such a localization process, the local free-volume creation occurs indeed prior to the increase in local temperature, indicating that the former is the cause of shear localization, whereas the latter is its consequence. Finally, extension of the above model to include the shear-induced dilatation shows that such dilatation facilitates the shear instability in metallic glasses. Keywords: Metallic glasses; Free volume; Temperature increase; Shear-banding instability; Dilatation 全文下载： JMPS-2009
2007年12月25日我们关于金属玻璃在断裂过程中能量耗散机理的工作向英国《哲学杂志》，Philosophical Magazine，投稿。 两位审稿人给与非常高的评价，其中一位评价到 It may be an important step in understanding the failure mechanisms of BMGs, and also helpful improving the ductility and reliability of BMGs. The paper is very pleasant to read and is accessible to a broad readership. The work is of high quality with original results and deserves to be published in its present form in Philo. Mag. 另一位评价到 It tackles a very timely and highly interesting subject and will be of high value to the community for helping to get a better insight into the mechanical behavior of BMGs. 文章于2007年12月10日被接受发表，前后仅15天时间。 全文见 http://www.sciencenet.cn/m/user_content.aspx?id=22557 在文章中，我们提出了一种新的金属玻璃断裂能量耗散机制，即局部软化和局部准解理的固有竞争。在原子团簇尺度，局部软化的基本单元为经典的剪切转变区，即shear transformation zone-STZ。 对于准解理的基本单元，我们提出了一种新的原子团簇运动模式：拉伸转变区，即tension transformation zone-TTZ。应用提出的能量耗散机制， 能够解释目前在金属玻璃中观察到的所有断裂面形貌，并对纳米尺度的周期条痕的间距进行了定量预测。 最近该文章被《哲学杂志》和《哲学杂志快报》联合评为2008年度J.C. Maxwell young writer's prize第二名，获奖名单公布于 http://www.tandf.co.uk/journals/authors/tphm-tphl-prize.asp 获得500美元奖金以及该文章一年的open access的免费权。 并在2009年召开的美国物理协会APS三月会议上颁发证书（见下图）： 感谢导师Rrof. L.H. Dai对于本文的指导以及其他两位合作作者(Mr. J.X. Meng and Prof. Z. Ling)对于本文的重要贡献。 感谢美国橡树岭国家实验室Prof. Xiao代领证书以及邮寄给我。
标签: metallic
