High-temperature atomic defect properties and diffusion processes in intermetallic compounds

Data on thermal vacancy formation in intermetallic compounds obtained from positron lifetime spectroscopy yield high effective formation enthalpies H^F_V in close-packed structures and low values in bcc-type structures which can be well understood theoretically. The vacancy migration enthalpy H^M_V could be determined at high temperatures for B2-FeAl by studying the equilibration process after temperature changes. As demonstrated here in a comparative study on B2-FeAl the thermal formation and migration of defects can also be sensitively investigated by time-differential length-change studies after temperature changes in the vicinity of the equilibration temperatures. The present vacancy data can explain the wide variation of the transition metal self-diffusivities in intermetallic compounds. For B2-FeAl it is shown that the high-temperature mechanical properties are closely linked to the formation of thermal defects as evidenced by the temperature variation of the yield stress anomaly and its time dependence after fast heating.     

Nanomechanics of Mg-Al intermetallic compounds

Cold spraying of pure Al powder on a pure Mg substrate together with subsequent post-spray annealing treatment produced Mg₁₇Al₁₂ (β-phase) and Mg₂Al₃ (γ-phase) intermetallic layers on the surface of the substrate. These layers showed significantly better nanomechanical properties, including the reduced elastic modulus and nanohardness, which were determined using nanoindentation, than commercial purity Mg and AZ91 alloys. Combined with their improved corrosion resistance, it is believed that both the γ-phase and the β-phase layers can provide effective protection of Mg alloys from wear and corrosion. The effect of post-spray annealing process on the formation of thick, uniform and dense intermetallic layers on pure Mg substrate was also investigated.     

Gas-phase modification of rare-earth intermetallic compounds

Recent work concerning the interstitial modification of permanent magnet alloys based on rare-earth iron intermetallic compounds is reviewed. The crystal structure of the new materials is discussed, then the thermodynamic and statistical aspects of the low-temperature interstitial modification process are considered. Finally, reaction kinetics and thermal stability of the new compounds are discussed and future prospects assessed.     

Ti-Al系金属间化合物精密加工研究进展

稀有材料Ti-Al系金属间化合物的本征脆性在一定程度上限制了精密加工技术的选择和在航空航天、国防等领域的应用,为促进此类材料精密加工的适应性及获得高质量的表面,本文对Ti-Al系金属间化合物的精密加工技术进行综述.首先对此类材料的特性及精密加工技术进行总体概括;其次从材料的切削性能(材料去除机理、切削力、切削温度、切屑...     

Anelasticity of Fe3Al intermetallic compounds

Temperature dependent internal friction (TDIF) spectra in Fe–(25–26)at.%Al alloys were studied using different mechanical spectroscopy techniques in a wide range of vibrating frequencies from 0.1 Hz to 1 kHz. Four relaxation peaks are observed (D, S, X, Z peaks), at least two of them (D, X) have not been reported earlier in Fe₃Al intermetallic compounds. The nature of these peaks is discussed. Special emphasis is put in this paper on the instability of the Fe–Al structure with respect to heating during TDIF measurements.     

The thermodynamic properties of calcium intermetallic compounds

The thermodynamic properties of calcium alloys have been measured by emf (an original pin-point method) and calorimetry in recent years. A review of experimental results obtained for 15 binary (Ca,M) systems is presented (with M Ni, Pd, Pt, Cu, Ag, Au, Mg, Al, Ga, Si, Ge, Sn, Pb, Sb, Bi), and numerical optimization is performed for some of them. Application to the ternary (Ca,Sn,Pb) system of industrial interest, allowed calculation of the phase diagram for x(Ca) 0.25.     

Stability of intermetallic compounds under extreme actions

Conclusions  

Structural stability of intermetallic compounds of Mg-Al-Ca alloy

A first-principles plane-wave pseudopotential method based on the density functional theory was used to investigate the energetic and electronic structures of intermetallic compounds of Mg-Al-Ca alloy, such as Al2Ca, Al4Ca and Mg2Ca. The negative formation heat, the cohesive energies and Gibbs energies of these compounds were estimated from the electronic structure calculations, and their structural stability was also analyzed. The results show that Al2Ca phase has the strongest alloying ability as well as the highest structural stability, next Al4Ca, finally Mg2Ca. After comparing the density of states of Al2Ca, Al4Ca and Mg2Ca phases, it is found that the highest structural stability of Al2Ca is attributed to an increase in the bonding electron numbers in lower energy range below Fermi level, which mainly originates from the contribution of valence electron numbers of Ca（s） and Ca（p） orbits, while the lowest structural stability of Mg2Ca is resulted from the least bonding electron numbers near Fermi level.     

Exchange interactions and magnetic properties of intermetallic compounds

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｉｎｔｅｒｍｅｔａｌｌｉｃｃｏｍｐｏｕｎｄｓＲＭｎ2 Ｇｅ2 ｃｒｙｓｔａｌｌｉｚｅｉｎｔｈｅｂｏｄｙ ｃｅｎｔｅｒｅｄ ｔｅｔｒａｇｏｎａｌＴｈＣｒ2 Ｓｉ2 ｔｙｐｅｓｔｒｕｃｔｕｒｅ(ｓｐａｃｅｇｒｏｕｐｉｓＩ4 /ｍｍｍ) ,ｗｈｉｃｈｉｓｃｏｎｓｉｓｔｅｄｏｆＲ ,ＧｅａｎｄＭｎｌａｙｅｒｓ ,ｓｔａｃｋｅｄｉｎｔｈｅｓｅｑｕｅｎｃｅＲ Ｇｅ Ｍｎ Ｇｅ Ｒ ａｌｏｎｇｔｈｅｃ ａｘｉｓ[1] .Ｆｒｏｍｔｈｅｍａｇｎｅｔｉｃｐｏｉｎｔｏｆｖｉｅｗ ,ＲＭｎ2 Ｇｅ2 ｃｏｍｐｏｕｎｄｓｈ…     

AlTiB中间合金中的化合物形态

研究了原料与Ａｌ５Ｔｉ１Ｂ 中间合金组织形态之间的联系, 结果表明：在一定熔炼工艺条件下,用纯Ｔｉ 颗粒法可制备出含有颗粒状ＴｉＡｌ３（３ ～１５ μｍ） 和颗粒状ＴｉＢ２（０ ．１ ～１ ．２ μｍ） 的Ａｌ５Ｔｉ１Ｂ 中间合金; 用氟盐法可以制备出含有块状与片状形态ＴｉＡｌ３（１０ ～１００ μｍ） 和条状与颗粒状ＴｉＢ２（０ ．２ ～３ ．０ μｍ）的Ａｌ５Ｔｉ１Ｂ 中间合金。理论分析认为：原料对Ａｌ５Ｔｉ１Ｂ 中间合金化合物的影响是通过改变化学反应体系和熔体结构状态来实现的。     

Environmental corrosion resistance of porous TiAl intermetallic compounds

Porous TiAl intermetallic compound, as a novel substitute for current inorganic porous material, offsets the shortages of both ceramics and metals. The environmental corrosion resistance of porous TiAl intermetallic compound was investigated. The kinetic equation for the cyclic oxidation of porous TiAl alloy at 600 ℃ is determined to be Δm2=1.08×10-5t. After total oxidation of 140 h, porous TiAl intermetallic compound shows more stability of pore structure and the mass gain of TiAl alloy is 0.042 g/m2, which is only 10.6% that of porous 316L stainless steel. The kinetic equation for the cyclic corrosion behavior of porous TiAl alloy in hydrochloric acid with pH=2 at 90 ℃ is determined to be Δm2=5.41×10-5t-2.08×10-4. After 50 h exposure, the mass loss of TiAl alloy is 0.049 g/m2, which is only 14.8% and 5.57% that of porous Ti and stainless steel, respectively. The kinetic equation in hydrochloric acid with pH=3 is determined to be Δm2=2.63×10-6t-3.72×10-6.     

Al-Fe金属间化合物对复合板界面结合的影响(英文)

对固态铝和固态铁界面金属间化合物的生长及金属间化合物对界面结合的影响进行了研究。结果表明,固态铝和固态铁热处理后的界面主要包括Fe2Al5和FeAl3化合物层,金属间化合物恶化了界面结合强度。在拉剪测试中,断裂主要发生在Fe2Al5或FeAl3化合物层,断裂的位置主要取决于化合物层内部的缺陷,包括微裂纹和空洞。热膨胀系数不匹配产生的应力导致内部微裂纹产生,内部孔洞产生的原因是Kirkendall效应。该研究对铝和铁的焊接与连接,尤其是对铝钢复合板的制备,奠定了一定的基础。     

Zn-2Ni合金金属间化合物的细化

利用金相、扫描电镜观察及能谱分析研究了Ti、Al及Al-RE合金作为细化剂对Zn-2Ni合金中Zn-Ni金属间化合物的细化效果。结果表明:在Zn-2Ni合金中加入微量(≤0.20%)的Ti、Al及Al-RE均可对合金凝固组织中的金属间化合物粒子产生细化作用;以Ti为细化剂时,组织中会出现较大的Zn-Ni-Ti三元板条状粒子;以纯Al为细化剂时,出现-δNiZn8相依附-γNi2Zn5相生长的大粒子和以枝晶状NiAl相为核心较细小的-δNiZn8相粒子共存于凝固组织中;以Al-RE为细化剂时,将获得分布均匀且细化的-γNi2Zn5相粒子,且Al-RE合金细化效果明显优于Ti和Al,其最佳的加入浓度为0.05%~0.10%。     

无铅焊点金属间化合物的纳米压痕力学性能

研究Sn3.0Ag0.5Cu/Cu界面处的IMC在150℃下等温时效的生长情况,时效时间分别为100,300,500,1000 h.拟合出IMC的厚度与时效时间的关系,采用纳米压痕仪进行纳米压痕试验,发现Cu6 Sn5与Cu3 Sn的变形机制不同.Cu6Sn5为非连续性塑性变形,表现为压痕过程中的锯齿流变;Cu3 Sn的压痕曲线比较平滑.随Cu6Sn5厚度的增加,Cu6 Sn5的弹性模量和硬度没有太大变化.对时效100,500 h后的Sn3.0Ag0.5Cu/Cu界面处的过渡区进行纳米压痕试验,发现Cu,Cu3Sn,Cu6 Sn5和Sn3.0Ag0.5Cu的硬度大小顺序为Cu6 Sn5＞ Cu3 Sn＞ Cu＞ Sn3.0Ag0.5Cu.     

Reactivity and deuterium retention properties of titanium-beryllium intermetallic compounds

Beryllium intermetallic compounds (beryllides), such as Be₁₂Ti and Be₁₂V, are the most promising advanced neutron multipliers in demonstration (DEMO) fusion power reactors because of higher stability, lower retention, and swelling. The advanced neutron multipliers are being developed by Japan and the EU as a framework of Broader Approach (BA) activities, targeted at broadening the research fields to not only establish fabrication methods but also for their characterization. Our group has proposed a plasma sintering method for the synthesis of beryllides. When the mixed powder was plasma-sintered at the beginning of the experiment, consolidation of the target composition was so insufficient that single-phase beryllides could not be synthesized. In order to obtain single-phase beryllides, an additional homogenization treatment of the sintered beryllides at 1473 K was necessary, resulting in increased porosity. Using the homogenized powder as the starting material, single-phase Be₁₂Ti and Be₁₇Ti₂ intermetallic compounds were successfully synthesized. As experimental results, the hardness of the compounds was relatively low owing to low sintering density. In addition, the oxidation behavior of the beryllides, when exposed to 15% H₂O/Ar at high temperatures, were investigated and the results indicate the presence, gray colored Be oxide formed on the surface in Be₁₂Ti tested at above 1073 K and Be oxide with a small fraction of white colored Ti oxide even tested at 873 K in Be₁₇Ti₂ phase resulting in the bigger increase of the weight gain than Be₁₂Ti. In addition, this oxidation occurring at lower temperature can be reasoned by the assumption that the existence of BeO (=oxygen content) in Be₁₂Ti (1.95%) and Be₁₇Ti₂ (2.95%) may facilitate increased reactivity. Furthermore, thermal expansion of Be₁₇Ti₂ was found out to be bigger than that of Be₁₂Ti because Be₁₇Ti₂ has more complex crystal structure and higher melting temperature. In terms of deuterium desorption and retention properties, the maximum peaks are detected around 600 K in beryllides, while those in beryllium occur at 800 and 980 K. From the comparison of deuterium retention, it was obvious that Be₁₇Ti₂ has a lower retention than Be₁₂Ti, while Be has the highest value.     

Electrode materials based on titanium intermetallic compounds: Preparation and properties

The process of preparation of electrode materials based on Ti₃Al employing methods of powder metallurgy was studied. The possibility was shown to use wastes of titanium production—titanium chipping—with the aim to prepare a ternary Ti–Al–N system, a so-called MAX phase. The influence of the regimes of baking on the processes of formation of phases and structure, composition, and properties of ceramic and metal material was studied.     

键合界面金属间化合物对可靠性影响的研究现状

在微电子封装过程中,键合丝被广泛应用,而键合可靠性对于产品的应用性能有着极大的影响,受到人们的广泛关注。键合丝与常用的铝焊盘之间是异质材料,在应用和服役的过程中会在界面上产生金属间化合物(IMC),对器件可靠性产生影响,同时,键合强度也与键合丝和焊盘之间的界面反应联系密切,因此了解键合丝与铝焊盘之间金属间化合物的形成与演变对键合可靠性的影响是有必要的。本文综述了Au/Al、Ag/Al和Cu/Al三种键合界面上金属间化合物的形成与演变的研究现状,并根据目前的应用状况,展望了未来的应用发展前景。     

Types of mechanical relaxation by hydrogen in intermetallic compounds

Hydrogen in polycrystalline intermetallic compounds generally produces extremely broad damping spectra, indicating the presence of short-range as well as long-range relaxation mechanisms. These are discussed on the basis of vibrating-reed results on Zr₆₅Cu_27.5Al_7.5, Zr₆₅Cu_17.5Ni₁₀Al_7.5, and CuZr₂ alloys. A relaxation peak at 270 K observed in all three cases is interpreted as a Zener-type relaxation of hydrogen in the CuZr₂ lattice. The differences found at higher temperatures — a second relaxation peak in the ternary and quaternary alloys but an exponential increase of damping in CuZr₂ — are related to different grain sizes and can be attributed to an ‘intercrystalline Gorsky effect’ due to elastic anisotropy mismatch strains.