基于第一性原理计算的镍基单晶高温合金掺杂的机器学习研究

高温合金的成分设计对其力学性能有至关重要的影响。多种掺杂合金元素的占位构型数量巨大,第一性原理计算成本很高。利用机器学习可加速第一性原理计算对镍基单晶高温合金中掺杂元素占位的研究。使用支持向量回归(SVR)和随机森林(RF)方法构建机器学习模型,对γ相和γ′相中11种合金元素(M=Al,Co,Cr,Hf,Mo,Ni,Re,Ru,Ta,Ti,W)的单位点置换能(ESS)和局部平均键长变化(<Δd>)分别进行独立预测。结果显示:随机森林方法整体优于支持向量回归,对W、Co、Mo、Re、Cr和Hf等元素的置换能预测平均绝对误差小于300 meV,对Ni、Ta和Ru元素的预测误差在300~500 meV之间,对Ti和Al元素的预测误差大于500 meV;对<Δd>的预测误差均在10-3 量级。证明了基于第一性原理计算的机器学习模型可以对合金新掺杂元素的局部能量和结构变化进行预测,有助于指导多组元合金的成分设计。

B掺杂Si_(80)Ge_(20)合金的快速制备及热电性能

采用电弧熔炼、快速球磨结合放电等离子烧结快速制备了单相Si80Ge20Bx(x=0.5、1、1.5、2)热电材料,对烧结后试样进行了物相结构分析和热电性能表征。结果表明,B的引入导致样品载流子浓度增加,电导率随着B掺量增加而大幅增加,而Seebeck系数反之下降。B的固溶增加试样中点缺陷浓度而导致声子散射增加,热导率下降明显。当x=1时,样品在1000K获得最大ZT值0.78。

掺杂合金元素法抑制金属中氦脆的研究进展

聚变堆结构材料极易因α粒子和中子辐照引入大量的He原子而脆化,降低核设施的稳定性和安全性,因此必须提高材料的抗氦脆能力。添加合金元素法是一种有效抑制金属中氦脆的方法。然而,合金元素对金属中的氦脆抑制效果受到原子占位情况、原子尺寸大小、浓度、温度等因素影响。因此,掺杂合金元素时必须考虑合金元素的种类和含量,并辅以一定的热处理。回顾了掺杂合金元素法抑制金属中氦脆的研究进展,简要分析了影响合金元素在金属中氦行为角色的因素。

氮气流量对C、N共掺杂NiCr合金薄膜微观结构和电性能的影响

目的提高埋入式薄膜电阻材料的电性能,使其具有较大的方阻值、电阻率和较小的电阻温度系数。方法利用闭合磁场非平衡反应磁控溅射技术,制备C、N共掺杂NiCr合金埋入式薄膜电阻材料。以前期优化后的溅射参数作为基本实验条件,通过改变氮气流量,分别在铜箔基底和参照基底载玻片上,沉积C、N共掺杂NiCr合金埋入式薄膜电阻材料。用扫描电子显微镜(SEM)和白光干涉仪表征薄膜的表面形貌,用X射线衍射仪(XRD)表征薄膜的微观结构,用X射线光电子能谱仪(XPS)、X射线能量散射谱仪(EDS)测试薄膜的成分,用表面轮廓仪测膜厚,用拉曼光谱仪分析薄膜中的C元素,用四探针测量系统测试埋阻的方阻值和热稳定性。结果随着氮气流量的增加,薄膜的衍射峰减弱,非晶化程度增强;当氮气流量为15 mL/min时,薄膜能获得较小的电阻温度系数和较大电阻率,此时薄膜的电阻温度系数范围为0≤TCRNiCrCN≤1.663×10^-4K^-1,电阻率可达到2.2970×10^-3Ω·cm。结论反应溅射中产生的中间相Cr2N和CN对薄膜的电阻率和方阻值有影响,C、N共掺杂NiCr合金埋入式薄膜电阻材料的电性能优于NiCr合金薄膜和C掺杂NiCr合金薄膜电阻材料。

C掺杂型NiCr合金薄膜的电性能和微观结构

利用闭合磁场非平衡磁控溅射工艺制备出C掺杂型NiCr合金薄膜电阻材料,获得了电性能优于NiCr合金薄膜的NiCrC薄膜电阻材料.实验结果表明:NiCr薄膜中掺杂C元素后,薄膜的择优取向由Ni(011)变为Ni(111);薄膜的缺陷和应力得以减小;薄膜中C元素具有类石墨性质.

Mn掺杂浓度对γ-TiAl合金延性影响理论研究

采用基于密度泛函理论的第一性原理方法,利用Materials Studio 6.0中的CASTEP模块对不同浓度的过渡金属元素Mn替位掺杂γ-TiAl得到的8个合金体系的原子平均形成能、晶格参量及轴比、弹性模量和重叠布居数等进行了计算分析。原子平均形成能的计算结果表明,各掺杂体系的形成能均为负值,表明其均可稳定存在,同时Mn原子占据Al原子位置得到的掺杂体系原子平均形成能更低,说明Mn原子倾向于替代Al原子;对晶胞轴比和弹性模量的计算分析表明,Mn掺杂能够提高合金的延性,以Ti12Al11Mn体系效果最为明显;重叠布居数的计算结果表明,Mn原子的掺入减弱了体系内共价键的各向异性程度,从化学键的角度解释了掺杂体系延性得到改善的机理。

铝掺杂WC-Co基硬质合金的高温摩擦学性能、磨损机理及抗氧化性能研究

通过高能球磨和电火花等离子烧结,成功制备了(x Al-WC)-6Co(x=0.2,0.33)三元复合材料,并研究了铝掺杂WC-Co基硬质合金在空气环境中500、600和700℃下的摩擦学性能.所制备的铝掺杂WC-Co,基体由WC和Co耦合而成,Al在烧结过程中发生氧化,基体上弥散分布细小的Cr3C2和Al2O3增强相.(0.2Al-WC-6Co)的硬度与断裂韧性明显高于WC-6Co,(0.33Al-WC)-6Co的断裂韧性较低.脆性钨类氧化物的形成是Al-WC-Co硬质合金高温磨损的主要原因.随着Al元素加入量的提高,硬质合金的高温抗软化性能和抗氧化性能提高,磨损表面的剥落和破碎行为减弱,材料的高温耐磨性能提高.

ZrO_2掺杂Mo基合金的制备及强化机理分析

采用溶胶-凝胶法和两段氢还原工艺制得了ZrO2掺杂Mo粉,再通过粉末冶金法制得ZrO2掺杂Mo基合金,并通过SEM、TEM、XRD和EDS对ZrO2掺杂Mo粉和ZrO2掺杂Mo基合金进行表征,研究了ZrO2掺杂Mo基合金的强化机理。结果表明:所制备ZrO2掺杂Mo粉颗粒细小但大小不均,近乎圆球状,有轻微的团聚;所制备ZrO2掺杂Mo基合金中ZrO2以第二相的形式弥散分布于Mo基体晶界,通过Orowan强化、细晶强化提高了ZrO2掺杂Mo基合金的强度。

固-固掺杂钼镧合金板材性能研究

本文以平均粒度为4. 0μm钼粉和平均粒度为50 nm、0. 5μm和2μm 3种氧化镧粉为原料,采用固-固掺杂法制备了氧化镧含量为1%的3种不同钼镧合金板坯和轧制板材,研究了3种合金的烧结密度、金相、拉伸力学性能和不同热处理后的室温深冲性能。实验结果表明,固-固掺杂钼镧合金板材性能优异,且掺杂氧化镧粉平均粒度的变化对板材的烧结晶粒数、热轧板材的纵、横向显微组织、拉伸性能和深冲性能都有显著影响。

新型稀土钨合金的研究与发展

本文叙述了新型稀土钨合金的研究与发展动向,其中包括新型稀土合金电极,如氧化钐(Sm_2O_3)和氧化钆(Gd_2O_3)弥散的钨合金电极的新加工工艺、材料结构特征及可能产生的优良性能等,在分析研究基础上,提出了发展我国稀土钨合金电极的若干建议,其中包括新工艺、电极结构及其变化对应用寿命的影响等项建议.

添加合金元素对锡基电子材料电化学迁移影响的研究进展

锡基电子材料是电子元器件封装及焊接的核心材料之一,针对锡基电子材料服役过程中存在的电化学迁移失效问题,讨论了锡基电子材料的主要失效形式、电化学迁移的机理、研究方法、评价方法以及抑制方法,综述了掺杂不同合金元素对锡基电子材料电化学迁移行为的影响规律。

316L表面激光熔覆NiTi合金涂层的组织结构及元素占位

60NiTi(60wt%Ni-40wt%Ti)合金具有高硬度、高弹性模量及优异的耐磨和耐腐蚀性能,在许多领域有潜在的应用价值。本文对激光熔覆方法在316L不锈钢表面制备NiTi涂层的微观组织结构和物相组成进行了分析。结果表明:基材中主要成分Fe和Cr扩散到熔覆涂层中并显著地影响了镍钛涂层的组织结构和性能。熔覆涂层主要组成相为NiTi和Ni_(3)Ti,提高Ni含量可抑制NiTi_(2)析出。第一性原理计算结果显示,Fe和Cr元素易于固溶在B2结构的NiTi相中,并且都倾向于置换晶胞中的Ni原子。Ni_(3)Ti晶胞结构中的Ni和Ti原子各有2个不同的晶位,Fe原子倾向于置换晶胞中Ni-1晶位的Ni原子,而Cr原子倾向于置换晶胞中Ni-2晶位的Ni原子。根据涂层的成分分析结合模拟可知,镍钛合金涂层中NiTi和Ni_(3)Ti相的化学式分别为Ni_(5)Ti_(8)Fe_(2)Cr和Ni_(9)Ti_(4)Fe_(2)Cr。

碲化铋基热电半导体晶体研究

碲化铋基热电半导体是中低温区高性能热电转换材料,在微电子、计算机以及航天等领域广泛用于局部致冷与精确温控,在工业余废热回收温差发电等领域具有良好的应用前景。通过合金化和掺杂的方法,可以增强声子散射降低晶格热导率,优化载流子浓度提高电性能,从而提高碲化铋基材料的热电性能。在简述碲化铋晶体结构和能带结构基础上,综述了合金化和掺杂提高碲化铋基半导体的热电性能、碲化铋基半导体晶体生长的方法及空间微重力对碲化铋基晶体区熔生长的影响,并展望了利用天宫二号空间实验室开展碲化铋基晶体生长及其相关研究。

钾掺杂钨合金中气相热充氘的热脱附行为

钾(K)掺杂钨(W)合金已经表现了优异的高温力学性能,成为最有希望的PFMs备选材料之一。为评估氢同位素在W-K合金中的滞留情况,采用放电等离子烧结技术(SPS),制备了纯W及K含量82μg/g的W-K合金,通过气相热充法引入氘(D)元素,考察热脱附行为。研究表明,气相热充氘释放温区从600K延伸至1200K,掺杂K后,D脱附活化能从0.86 eV下降到0.68 eV;纯W样品D滞留量在1×10^(-6)(原子比)左右,掺杂K后有所提高,但依然大大优于商用ITER级纯W。

Effect of carbon on microstructures of Ti-45Al-3Fe-2Mo-xC alloy

The effect of carbon addition on the microstructures of TiAl-based alloy（Ti-45Al-3Fe-2Mo） was studied.The proportion of β/B2 phase reduces with the content of carbon increasing,while the colony size increases.With increasing the carbon content,the lamellar spacing first decreases from 267 nm（Ti-45Al-3Fe-2Mo） to 237 nm（Ti-45Al-3Fe-2Mo-0.3C） and 155 nm（Ti-45Al-3Fe-2Mo-0.5C）,but then increases to 230 nm（Ti-45Al-3Fe-2Mo-1.0C） with further increase in C level,which is affected by the inhibition of carbon atom and precipitation of carbides at the lamellar interface.Precipitation of carbides shows a response to aging time at 800 ℃.P-type carbides grow up at the boundaries and near the dislocation areas with the prolonging of aging time.And these carbides are projected different morphology in different beam directions（BD）.The effects of these microstructural modifications were examined and the observations were discussed.

蓝宝石的应用及单晶强韧化研究进展

蓝宝石具有硬度大、强度高、抗腐蚀性强及良好的光学和化学特性,已被广泛应用于众多高科技领域,其突出的光学透过性有望成为新一代电子产品屏幕的盖板材料。然而蓝宝石单晶的冲击韧性差是本征缺陷,这将限制其在电子消费产品上的应用。近年来,国内外对蓝宝石的功能开发与应用,以及蓝宝石单晶强韧化进行了大量的研究。首先,对蓝宝石的相关性能进行了详细的介绍,综述了蓝宝石在光学、半导体、激光等领域的应用;其次,总结了蓝宝石通过掺杂合金元素、掺杂石墨粉、粒子注入以及铁、钛共掺杂等方法进行强韧化的研究进展,这些方法均可不同程度地提高蓝宝石单晶的断裂强度和断裂韧性;最后,对未来蓝宝石功能材料的应用以及蓝宝石强韧化工作的发展趋势进行了分析和探讨。

First-principles investigation on stability and electronic structure of Sc-dopedθ′/Al interface in Al−Cu alloys

The properties of Sc-dopedθ′(Al_(2)Cu)/Al interface in Al−Cu alloys were investigated by first-principles calculations.Sc-doped semi-coherent and coherentθ′(Al_(2)Cu)/Al interfaces(Sc doped in Al slab(S1 site),Sc doped inθ′slab(S2 site))were modeled based on calculated results and reported experiments.Through the analysis of interfacial bonding strength,it is revealed that the doping of Sc at S1 site can significantly decrease the interface energy and increase the work of adhesion.In particular,the doped coherent interface with Sc at S1 site which is occupied by interstitial Cu atoms has very good bonding strength.The electronic structure shows the strong Al—Cu bonds at the interfaces with Sc at S1 site,and the Al—Al bonds at the interfaces with Sc at S2 site are formed.The formation of strong Al—Cu and Al—Al bonds plays an important role in the enhancement of doped interface strength.

Effects of doping route on microstructure and mechanical properties of W−1.0wt.%La2O3 alloys

A comparative study was conducted by using solution combustion synthesis with three different doping routes(liquid-liquid(WL10), liquid-solid(WLNO) and solid-solid(WLO)) to produce nanoscale powders and further fabricate the ultrafine-grained W-1.0 wt.%La2O3 alloys by pressureless sintering. Compared with pure tungsten, W-1.0 wt.%La2O3 alloys exhibit ultrafine grains and excellent mechanical properties. After sintering, the average grain size of the WLO sample is larger than that of WL10 and WLNO samples;the microhardness values of WL10 and WLNO samples are similar but larger than the value of WLO sample. The optimized La2O3 particles are obtained in the WL10 sample after sintering at 1500 ℃ with the minimum mean size by comparing with WLNO and WLO samples, which are uniformly distributed either at grain boundaries or in the grain interior with the sizes of(57±29.7) and(27±13.1) nm, respectively. This study exhibits ultrafine microstructure and outperforming mechanical properties of the W-1.0 wt.%La2O3 alloy via the liquid-liquid doping route, as compared with conventionally-manufactured tungsten materials.

Flow stress behavior of Al-Cu-Li-Zr alloy containing Sc during hot compression deformation

The flow stress behavior of Al-3.5Cu-1.5Li-0.25(Sc+Zr) alloy during hot compression deformation was studied by isothermal compression test using Gleeble-1500 thermal-mechanical simulator. Compression tests were preformed in the temperature range of 653-773 K and in the strain rate range of 0.001-10 s-1 up to a true plastic strain of 0.7. The results indicate that the flow stress of the alloy increases with increasing strain rate at a given temperature,and decreases with increasing temperature at a given imposed strain rate. The relationship between the flow stress and the strain rate and the temperature was derived by analyzing the experimental data. The flow stress is in a hyperbolic sine relationship with the strain rate,and in an Arrhenius relationship with the temperature,which imply that the process of plastic deformation at an elevated temperature for this material is thermally activated. The flow stress of the alloy during the elevated temperature deformation can be represented by a Zener-Hollomon parameter with the inclusion of the Arrhenius term. The values of n,α and A in the analytical expressions of flow stress σ are fitted to be 5.62,0.019 MPa-1 and 1.51×1016 s-1,respectively. The hot deformation activation energy is 240.85 kJ/mol.

Decomposition kinetics of carbon-doped FeCoCrNiMn high-entropy alloy at intermediate temperature

Phase decomposition kinetics and the corresponding mechanical properties of the severe cold-rolled(SCRed) carbon-doped(1.3 at.%) equimolar FeCoCrNiMn high-entropy alloy(HEA) after being annealed at 500 ℃ were investigated. This single face-centered cubic(FCC) solid-solution HEA decomposed to M23 C6+L10, B2, and σ in chronological order. The formation kinetics of the L10, B2, and σ phases followed the Johnson-Mehl-AvramiKolmogorov(JMAK) equation. The yield strength of the HEA was 1520 MPa and increased to 1920 MPa after being annealed at 500 ℃ for 1 h, as a result of the formation of nanosized M23 C6 and L10. Both strength and ductility decreased after 2 d of annealing due to the increase of volume fractions and the coarsening of the M23C6 and L10 precipitates. From 4 to 32 d, the hardness was found to increase, which is ascribed to the rapid formation of the B2 and σ phases. From 32 to 64 d, the hardness increased further to finally reach about HV 760, with the FCC matrix almost exhausted to form the M23 C6, L10, B2, and σ phases. The results of this work may serve as a guide for the heat-treatment of carbon-doped HEAs.