Simultaneous enhancement in strength and ductility of Fe_(50)Mn_(30)Co_(10)Cr_(10) high-entropy alloy via nitrogen alloying

The effect of nitrogen on microstructural evolution and tensile properties of transformation-induced plasticity(TRIP)Fe₅₀Mn₃₀Co₁₀Cr₁₀HEAs was investigated.Nitrogen was fully introduced in solid solution by pressure-induced melting technique.Nitrogen addition turned the TRIP alloy to a twinning-induced plasticity(TWIP)alloy,and simultaneously improved the strength and elongation.For the nitrogen-doped HEA,the high yield strength is mainly resulted from the friction stress via interstitial strengthening effect,and the high ductility is originated from retained high strain-hardening capability via the successive onset of dislocation accumulation and deformation twinning.The strain-hardening behavior and microstructural evolution at specified strains were revealed.     

熔盐法合成BaFe_（11）Co_（0．5）Ti_（0．5）O_（19）磁性粉体

采用熔盐法制备了六角晶系结构钡铁氧体ＢａＦｅ（１１）Ｃｏ（０．５）Ｔｉ（０．５）Ｏ（１９）。Ｘ射线衍射和热分析测量表明，合成反应过程在８５０℃下完成。粉料的磁性能测量和粉料的粒度及颗粒形态表明，熔盐法合成的粉料适合作为高性能磁记录材料。     

MlNi_4Co_(0.6)Al_(0.4)储H_2合金表面吸H_2的TDS研究

用热脱附谱 (TDS)对不同表面处理的富La混合储H2 合金MlNi4 Co0 6Al0 4 粉末样品进行H2 气吸附和脱附特性的比较和研究。未经表面处理的粉末样品 ,只测到一个H2 脱附峰 (α峰 ) ,脱附温度在 40 0K左右 ;经 6molKOH溶液 ,在 80℃下处理 6h的MlNi4 Co0 6Al0 4 粉末样品 ,有 2个H2 热脱附峰 (β峰和γ峰 ) ,脱附温度分别在 5 40和 6 30K处 ;而用 6molKOH 0 0 2molKBH4 溶液处理后 ,则有 3个H2 热脱附峰 (α峰 ,β峰和γ峰 ) ,脱附温度分别在 40 0 ,5 30和 6 40K处。TDS研究表明 ,热碱加还原的处理使材料表面对H2 气吸附的活性和容量提高 ,并使各个吸附态的扩散和转变更加容易。     

Grain size and temperature effect on the tensile behavior and deformation mechanisms of non-equiatomic Fe_(41)Mn_(25)Ni_(24)Co_8Cr_2high entropy alloy

The effect of the grain size on the tensile properties and deformation mechanisms of a nonequiatomic Fe_(41)Mn_(25)Ni_(24)Co_8 Cr_2 high-entropy alloy was studied in the temperature range between 298 and 1173 K by preparing the samples with three different grain sizes through severe plastic deformation and subsequent annealing:ultrafine(sub)grain size(≤0.5 μm),8.1 μm and 590.2 μm.In the temperature between 298 and773 K,the material with the large grain size of 590.2 μm exhibited the largest tensile ductility(57%-82%)due to its high strain hardening associated with mechanical twinning,but it exhibited the lowest strength due to its large grain size.The material with the ultrafine(sub)grain size exhibited the lowest tensile ductility(3%-7%) due to a greatly reduced strain hardening ability after severe plastic deformation,but it exhibited the highest strength due to the dislocation strengthening and grain refinement strengthening.At tensile testing at temperatures above 973 K,recrystallization occurred in the material with the ultrafine(sub)grains during the sample heating and holding stage,leading to the formation of fine and equiaxed grains with the sizes of 6.8-13.5 μm.The deformation behavior of the Fe_(41)Mn_(25)Ni_(24)Co_8 Cr_2 with different grain sizes in the high temperature range between 973 and 1173 K,where pseudosteady-state flow was attained in the stress-strain curves,could be explained by considering the simultaneous contribution of grain boundary sliding and dislocation-climb creep to total plastic flow.The activation energies for plastic flow for the materials with different grain sizes were similar as～199 kJ/mol.In predicting the deformation mechanism,it was important to consider the change in grain size by rapid grain growth or recrystallization during the sample heating and holding stage because grain boundary sliding is a grain-size-dependent deformation mechanism.The sample with the ultrafine(sub)grains exhibited the large tensile elongations of 30%-85% due to its high strain rate sensitivity,m(0.1-0.5) at temperatures of973-1173 K.The material with the large grain size of 590.2 μm exhibited the very small elongations of0.2%-8% due to its small m values(0.1-0.2) and occurrence of brittle intergranular fracture at the early stage of plastic deformation.     

Effects of Doped Element on Structure and Magnetic Performance of Nanocrystalline Sm_5Co_(19) Alloy

正In this study,permanent magnetic nanocrystalline Sm_5Co_(18.5)Ni_(0.5)、Sm_5Co_(18.5)Fe_(0.5) and Sm_5Co_(18.5)Nb_(0.5) alloys with high coercivity were prepared.The microstructure,crystal structure and magnetic properties of these alloys were studied.The results show that Ni,Fe and Nb doping do not lead to phase decomposition of the Ce_5Co_(19) type crystal structure,mean     

Thermal Stability Limit of Thin Palladium(II) Oxide Films

Inorganic Materials - X-ray diffraction and scanning electron microscopy data demonstrate that the thermal stability limit of thin PdO films in an oxygen atmosphere rises from 1083 ± 5 to 1133...     

热障涂层（TBC）稳定性的研究EI

将ＺｒＯ_２·８％Ｙ_２Ｏ_３用射频磁控溅射技术沉积在ＮｉＣｒＡｌＹ底涂层上，进行ｌｌ００℃→室温，１１００℃→冷水和９００℃→室温等热周期和熔盐作用的试验。随后进行Ｘ－射线衍射（ＸＲＤ）分析和扫描电镜（８ＥＭ）观察。结果表明，沉积态的氧化锆层主要为立方相和少量单斜相及四方相。热周期及熔盐Ｎａ_２ＳＯ_４－５％ＮａＣｌ与ＺｒＯ_２·８％Ｙ_２Ｏ_３的化学作用都促使立方相→单斜相的转变。熔盐对晶界和底涂层的化学和物理的作用是影响涂层稳定性的另一因素。     

TEM study of the FSW nugget in AA2195-T81

During friction stir welding (FSW) the material being joined is subjected to a thermal-mechanical process in which the temperature, strain and strain rates are not completely understood. To produce a defect free weld, process parameters for the weld and tool pin design must be chosen carefully. The ability to select the weld parameters based on the thermal processing requirements of the material, would allow optimization of mechanical properties in the weld region. In this study, an attempt is made to correlate the microstructure with the variation in thermal history the material experiences during the FSW process.     

Surface Layer of Ni_(68)P_(18)Cr_(14) Amorphous Alloy

In Ni_(68)P_(18)Cr_(14) amorphous alloy, the dominant component elements Ni and P were in lower contentin the surface layer, while Cr was enriched. There was a P enrichment region just below the surfaceoxide layer, which was supposed to enhance the surface segregation of Cr. Nickel was less oxidizedthan Cr.     

NiCrAlTi合金的晶界Cr_7 C_3和Cr_(23)C_6

采用断口的萃取碳复型技术,研究了 NiCrAlTi 合金晶界 Cr_7C_3和 Cr_(23)_C_6的形貌和分布特征,观察了 Cr_7C_3向 Cr_(23)C_6的转变,Cr_7C_3和 Cr_(23)C_6的溶解。某些结果在金相试样上观察不到,与一些工作者在金相试样上的研究结果存在一定差异。     

In Situ Detecting Thermal Stability of Solid Electrolyte Interphase (SEI)

Solid electrolyte interphase (SEI) plays an important role in regulating the interfacial ion transfer and safety of Lithium-ion batteries (LIBs). It is unstable and readily decomposed releasing much heat and gases and thus triggering thermal runaway. Herein, in situ heating X-ray photoelectron spectroscopy is applied to uncover the inherent thermal decomposition process of the SEI. The evolution of the composition, nanostructure, and the released gases are further probed by cryogenic transmission electron microscopy, and gas chromatography. The results show that the organic components of SEI are readily decomposed even at room temperature, releasing some flammable gases (e.g., H₂, CO, C₂H₄, etc.). The residual SEI after heat treatment is rich in inorganic components (e.g., Li₂O, LiF, and Li₂CO₃), provides a nanostructure model for a beneficial SEI with enhanced stability. This work deepens the understanding of SEI intrinsic thermal stability, reveals its underlying relationship with the thermal runaway of LIBs, and enlightens to enhance the safety of LIBs by achieving inorganics-rich SEI.     

热处理对Ba2Co0.6Zn1.0Cu0.4Fe12O22（Co2Y）铁氧体磁性能的影响

用化学共沉淀法制备均匀、细小、高活性的Y型平面六角铁氧体前躯体粉体,将前躯体在600-1050℃煅烧后在1000℃烧结,并对烧结样品进行表征,研究了热处理对Ba₂Co_0.6Zn_1.0Cu_0.4Fe₁₂O₂₂（Co₂Y）铁氧体性能的影响。结果表明,前躯体的颗粒粒度分布集中,粒径大小约为3μm。在较低温度（900℃）煅烧的样品能形成纯相Y型平面六角铁氧体;其比饱和磁化强度随着煅烧温度的升高而增大,对应磁环的起始磁导率先降低后增大;在900℃煅烧的样品σ_s≈17.262 A·m²·kg^-1、H_c≈5.146 kA·m^-1,频率为100 MHz,其μ_i≈3.7、Q≈13.4。     

湿法合成LiNi_(0.8)Co_(0.2)O_2及其性能表征

LiNi0.8Co0.2O2是极为看好的下一代锂离子电池正极材料,以湿法合成可得到成分均匀、颗粒尺寸一致的材料,有效提高电池性能,所以采用共沉法与微粒溶胶凝胶法(PSG)合成锂离子电池正极材料LiNi0.8Co0.2O2。共沉法先形成-β(Ni,Co)(OH2),然后与计量比的锂混匀,煅烧获得材料。PSG法在制得凝胶的同时发生酯化反应,将当中的镍与钴还原为金属,锂则以碳酸锂形态存在;随后煅烧得到LiNi0.8Co0.2O2。两种方法所得材料进行红外光谱、X射线衍射及XRD精修结构分析、电化学阻抗谱、循环性能等检测。其中X射线衍射鉴定出这两种方法合成物相结晶都良好,XRD精修结构分析、电化学阻抗谱、循环性能测试都表明PSG结构比较优良。     

Contents of volume 81 (1996)

Contents of volume 81 (1996)     

四元Heusler合金Co_2[Mn,Fe]Ge_(1-x)Ga_x的晶体结构、半金属稳定性和磁性

基于密度泛函理论的第一性原理研究了四元Heusler合金Co2MnGe1-xGax和Co2FeGe1-xGax的晶体结构、半金属稳定性和磁性,发现随着掺入Ga比例x的改变,其晶格常数遵循Vigard原理。对于Co2MnGa1-xGex系列的合金,其原胞磁矩很好地符合SP(Slater-Pauling)值和实验值;而对于Co2MnGe1-xGax系列合金,其原胞磁矩虽然与实验值一致,但却随x的减小而逐渐偏离SP值。态密度显示,Co2MnGe1-xGax系列合金在x=0～0.75的掺杂比例内都有0.4～0.6eV的自旋向下带带隙宽度,而Co2FeGe1-xGax虽然在费米面附近也存在较高的自旋极化,但几乎不存在显著的自旋向下带带隙。此外,四元合金Co2MnGe0.75Ga0.25的费米面居于最小自旋带隙的中部,将具有较好的半金属稳定性。     

Mi_（70）Mn_（25）Co_5触媒合金C－N－B三元共渗研究

研究了合成人造金刚石用Ｎｉ（７０）Ｍｎ（２５）Ｃｏ５触媒合金Ｃ、Ｎ、Ｂ三无共渗及其对合成人造金刚石质量和产量的影响，并与单独渗Ｃ、渗Ｎ、渗Ｂ合金进行了对比。结果表明，该合金三元共渗比单独渗合成的人造金刚石的性能更高。单产比渗Ｃ者低，比渗Ｎ、渗Ｂ者高，接近于原始合金。     

柔性衬底上Ni_(81)Fe_(19)/Ni_(50)Mn_(50)双层膜交换偏置效应研究

目的:探究制备在聚酰亚胺PI柔性衬底上的Ni_(81)Fe_(19/)Ni_(50)Mn_(50)双层膜的交换偏置效应。方法:采用直流磁控溅射技术分别在硅片和PI衬底上制备Ni_(81)Fe_(19)/Ni_(50)Mn_(50)双层膜,经相同温度退火处理后使用振动样品磁强计测试样品的磁滞回线。结果:柔性衬底上生长的双层膜的交换偏置场大小基本等于硅衬底上生长的,但其矫顽力始终比硅衬底上的大;薄膜的交换偏置场和矫顽力随着铁磁层厚度增大呈线性减小,随着反铁磁层厚度增大呈先增大后减小最后稳定的趋势,柔性衬底上薄膜的交换偏置场和矫顽力还会随着测量温度的升高而下降直至消失。结论:Ni_(81)Fe_(19/)Ni_(50)Mn_(50)双层膜的交换偏置场和矫顽力会受到铁磁层厚度、反铁磁层厚度和测量温度的影响,其中矫顽力还会受到衬底类型的影响。     

Investigations on Structural Characteristics,Thermal Stability,and Hygroscopicity of Sisal Fibers at Elevated Temperatures

An effort has been made to study the thermophysical properties of sisal plant fiber available in North-East India in the temperature range from 310 K to 760 K. The effect of heat on the structural characteristics of the fiber using X-ray diffraction and the chemical behavior by the infrared (IR) technique has been examined. Thermodynamic studies of the fiber have been carried out using thermogravimetric (TG), derivative TG (DTG), and differential scanning calorimetric methods. The hygroscopic properties of the fiber have been investigated in the temperature range from 310 K to 430 K at different relative air humidities using an ordinary gravimetric analysis. The interplanar spacings of the sample heated to 370 K remained same with respect to their normal values, but the degree of crystallinity and crystallite sizes increased slightly. The degree of crystallinity of the sample heated to 450 K is decreased by 10.32 % from its normal value, and the corresponding interplanar spacings and crystallite sizes are decreased by a small amount. A sample heated to 530 K shows transformation of the fiber’s crystalline structure to an amorphous state. The fiber shows thermal stability up to 500 K and follows two different closely related thermal decomposition processes in the temperature range of approximately 500 K to 630 K. Tests performed in oxygen can lead to combustion of the fibers in the temperature range of approximately 710 K to 720 K. The IR study of the sample heated at temperatures from 370 K to 600 K provides meaningful data to ascertain decomposition of the native structure of the fibers. The hygroscopicity of the fiber under heated conditions is less with respect to the value under ambient conditions. The saturation limit of moisture absorption of the fiber per gram varies and depends on the source as well as pretreatment of the sample.     

Magnetic Properties and Thermal Stability of Pr_(1-x)La_xCo_(5-y)Alloys

Pr1-xLaxCo5-y (x=0, 0.15. 0.25, 0.35,1.0, y=0.5, 0.7, 0.9, 1.0) alloys were investigated. The effect of the variation of x and y on magnetic properties and thermal stability of the alloys were studied. The magnetic properties for the Pr0.85La0.15Co4.3 and Pr0.75La0.25Co4.1 magnets are iHc=368 kA/m, Br=0.91 T, (BH)max=145.6 kJ/m3, αBr=-0.03%/℃ and iHc=568 kA/m,Br=0.8 T, (BH)max=127.2 kJ/m3,αBr,=-0.06%/℃, respectively The phase structures of as-cast alloys and magnets were investigated     

淀积磁场对NiO／Ni81Fe19双层膜特性的影响

用射频磁控溅射法在外磁场中淀积 Ｎｉ Ｏ／ Ｎｉ８１ Ｆｅ１９ 双层膜, 利用淀积磁场（ Ｈｄｅ） 诱导易轴并确定交换耦合场方向． 研究了淀积磁场对 Ｎｉ Ｏ／ Ｎｉ Ｆｅ 双层膜特性的影响, 结果表明, 淀积磁场改善了双层膜的磁滞回线的矩形度, 减小矫顽力, 增强交换耦合作用． 反铁磁性层 Ｎｉ Ｏ 和铁磁性层 Ｎｉ Ｆｅ 的厚度对矫顽力和交换耦合作用有很大的影响． 在５６ｋ Ａ／ｍ 的磁场中制备的 Ｎｉ Ｏ （５０ｎｍ） ／ Ｎｉ Ｆｅ （２５ｎｍ） 双层膜的易轴矫顽力 Ｈ Ｃ为１ ． ９ｋ Ａ／ｍ , 交换耦合场 Ｈ Ｅ Ｘ为２ ． ６ｋ Ａ／ｍ , 临界温度 Ｔｃ 为１５０ ℃, 截止温度 Ｔ Ｂ为２３０ ℃