Mn元素对纳米晶Fe_3Al材料的力学性能的影响

研究了合金元素Mn不同含量对铝热反应熔化法制备的块体纳米晶Fe3Al材料力学性能的影响,结果表明当Mn添加到纳米晶Fe3Al材料中,对其压缩屈服强度和抗弯强度影响显著。加Mn 10%时,纳米晶Fe3Al材料的力学性能得到很大提高,使材料由脆性材料向塑性材料转变,大幅度提高了其压缩屈服强度,而且提高了抗弯屈服强度。含Mn 10 wt%的材料具有最佳的力学性能是由于其具有最小的纳米晶粒尺寸。对含Mn 10 wt%的材料在不同加载速率下进行的压缩性能试验研究表明：材料的压缩屈服强度随加载速率的增大而降低。     

Y元素添加对CuZrAl块体金属玻璃的结构和力学性能的影响(英文)

研究添加Y元素对CuZrAl块体金属玻璃的结构和力学性能的影响。结果表明,添加Y元素提高CuZrAl体系的玻璃形成能力,而且由于添加Y元素可以降低该体系的结合能,从而降低其断裂强度。Cu45Zr48Al7块体金属玻璃的断裂表面主要呈脉状,而Cu46Zr42Al7Y5块体金属玻璃的断裂表面则很平滑。TEM观察表明,Cu45Zr48Al7的微观结构为非晶基体中含有纳米相,然而Cu46Zr42Al7Y5块体金属玻璃为全非晶结构。     

Mössbauer spectroscopy of the nanocrystalline materials

X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements were used to study the magnetic properties and the parameters of hyperfine interactions in the nanocrystalline (with a grain size less than 10 nm) and microcrystalline alloys Fe₉₀Ge₁₀, Fe₇₇Al₂₃ and pure α-Fe. It has been established that the nanocrystalline state does not affect the formation of the saturation magnetization, Curie temperature, isomeric shift, and hyperfine magnetic field. No additional sextets in the Mössbauer spectra and no additional features in the temperature dependences of dynamic magnetic susceptibility of the alloys investigated have been revealed. In the Mössbauer spectrum of pure nanocrystalline iron, a slight line broadening (～20%) is observed.     

Mn元素在7A99铝合金中微观组态分布的研究

通过半连续铸造方式向7A99铝合金中添加0.4％Mn(质量分数)元素,采用SEM、TEM、HRTEM与三维原子探针(3DAP)开展Mn元素在7A99铝合金铸锭、均匀化以及固溶时效过程中的微观组态分布的研究.结果表明,Mn元素在7A99铝合金铸锭中主要以晶界处鱼骨状的含AlZnMgCuMn的MgZn2型非平衡共晶化合物形...     

无氰电镀液中超声电沉积耐腐蚀纳米晶铜镀层

通过超声辅助电沉积法,在无氰络合电镀液中以高阴极电流密度在钕铁硼磁体上电沉积获得纳米晶铜防护镀层,研究了不同超声波频率下的镀层形貌、晶粒尺寸、显微硬度和耐腐蚀性能。结果表明,随着超声波频率的增加,络合电镀液体系的铜电沉积有效阴极电流密度显著增加,相应的阴极电流效率也提高,从而获得致密的纳米晶铜镀层。在阴极电流密度为4.0 A·dm^-2和超声波频率为40 kHz的条件下,能够获得平均晶粒尺寸为18.8 nm的铜镀层。超声辅助电沉积法还能促进烧结钕铁硼基体盲孔内的铜沉积,从而改善基体与镀层之间的结合力。在同样的镀层厚度下,烧结钕铁硼表面所沉积镀层的耐腐蚀性随超声波频率的提高而优化。     

Microstructure evolution and thermal stability of nanocrystalline Cu-Nb alloys during heat treatment

The microstructure evolution and high thermal stability of the mechanically-alloyed supersaturated nanocrystalline Cu-10%Nb alloy during subsequent heat treatment were investigated by X-ray diffractometry and transmission electron microscopy (TEM). The results show that no significant change of the microstructure of the solid solution can be detected after annealing at 300-400 ℃. The pronounced phase separation can be detected at 700 ℃. After annealing for 30 min at 900 ℃, almost all the Nb atoms precipitate from the solid solution, and the average Cu grain size is about 37 nm. As the solute atoms hinder the migration of fcc phase, at Cu grain boundaries, no significant grain growth occurs before large amount of Nb atoms precipitates from Cu matrix, and the decrease of internal strain and density of dislocation is small. Furthermore, the nanosized Nb precipitates can also help to reduce the Cu grains growth through precipitating pinning effect. Therefore, the mechanically-alloyed nanocrystalline Cu-Nb alloys have a high thermal stability. And the contaminations brought into the Cu matrix by milling can influence the phase formation and the thermal stability of Cu-Nb alloys during heat treatment.     

Mössbauer studies of phase separation in nanocrystalline Fe0.55−xCr0.45Snx alloys prepared by mechanical alloying

Mössbauer spectrometry (⁵⁷Fe and ¹¹⁹Sn) was used to investigate phase separation in coarse-grained Fe_0.55Cr_0.45 and in mechanically-alloyed nanocrystalline Fe_0.55Cr_0.45, Fe_0.52Cr_0.45Sn_0.03 and Fe_0.49Cr_0.45Sn_0.06 alloys during isothermal annealing at 748 K. Phase separation occurs faster in nanocrystalline Fe–Cr than in cold-rolled coarse-grained alloys. The effect of the interconnected microstructure on room-temperature hyperfine magnetic field distributions of alloys aged for hundreds of hours is qualitatively discussed. Tin hinders grain growth of nanocrystalline alloys.     

添加Cu和Mn对Zr-4合金耐腐蚀性能的影响

在Zr-4合金中添加Cu和Mn,用非自耗真空电弧炉熔炼了成分不同的7种锆合金,用高压釜在360℃/18.6MPa/0.01 mol/L Li OH水溶液中和400℃/10.3 MPa过热蒸汽中进行长期腐蚀试验,与出厂退火态Zr-4样品和经过重熔加工的Zr-4样品的耐腐蚀性能进行了比较。结果表明:添加0.05%~0.18%的Cu或0.07%~0.35%的Mn,或同时添加0.08%Cu和0.09%Mn都可以明显改善合金在Li OH水溶液中的耐腐蚀性能,在腐蚀增重曲线上没有出现明显的转折,耐腐蚀性能明显优于Zr-4合金;但是添加Cu或Mn后却使合金在400℃过热蒸汽中的耐腐蚀性能变坏,影响的程度随着Cu或Mn含量的增加而增加,并且Mn的有害作用比Cu更明显。讨论了氧化膜生长各向异性特征与添加合金元素之间的关系,解释了添加Cu和Mn合金元素后对Zr-4合金耐腐蚀性能在不同腐蚀条件下产生不同影响的原因。     

金属纳米晶热稳定性和晶粒长大行为的研究

推导出了金属纳米晶界的基本热力学函数,模拟计算了金属纳米晶界的吉布斯自由能随晶界过剩体积和温度的变化规律。以铜纳米晶材料为例,应用纳米晶热力学模型预测了纳米晶组织的热稳定性及纳米晶粒长大行为。将纳米晶界的热力学函数引入元胞自动机仿真算法,利用计算机模拟研究了金属纳米晶的变温晶粒长大过程。实验证实铜纳米晶粒长大的动力学特征符合纳米晶热力学模型的计算预测结果。     

Magnetic properties of nanocrystalline FeMCuNbSiB alloys (M: Co,Ni)

The magnetic properties and microstructure of nanocrystalline FeMCuNbSiB alloys (M: Co, Ni) annealed under a transverse field have been studied. Large induced magnetic anisotropy and good properties in the high frequency range were obtained in Co-rich nanocrystalline FeCo(Cu)NbSiB alloys.     

Fe合金化对Cu36Zr48Ag8Al8非晶合金的组织和力学性能影响

选择Cu36Zr48Ag8Al8BMG作为基体合金,研究Fe元素合金化对组织和力学性能的影响,分析了相分离非晶结构和纳米晶对合金力学行为的作用机理,并利用维氏硬度计考察了 Fe的掺杂对合金各相的相对硬度、塑性和压痕形貌的影响规律。结果表明,TEM衬度的眀相为富Fe相,暗相为富Cu、Ag相,由于具有不同的模量和硬度的相分离两相结构的存在,非晶合金在外力加载时呈应变硬化,而晶粒尺寸<5 nm的纳米晶起到弥散强化作用,使合金的强度进一步提高。维氏压头作用下使准脆性的非晶合金发生显著的塑性变形,非晶相硬度较高,其维氏压痕的周围形成了少量半圆型剪切带,且在同样的塑性变形量,塑性越好,剪切带的数量较多、间距较小。晶相硬度较低,其压痕周围没有裂纹出现     

快淬态纳米晶Fe—Cu—Ta—Si—B软磁金属薄带的制备

Fe-Cu-Ta-Si-B纳米晶金属薄带可以通过快淬技术直接制备,而无需退火过程。对比Fe-Cu-Ta-Si-B快淬纳米晶薄带,发现相同Cu含量下,α-Fe（Si）更易在Fe-Cu—Nb-Si—B快淬态薄带中析出。在快淬态Fe-Cu-Ta-Si-B金属薄带中,适当高的Cu含量有利于α—Fe（Si）的成核;但过高的Cu含量反而弱化了纳米晶化,这是由于团簇效应粗化了Cu颗粒的尺寸,却减少了α—Fe（Si）的有效成核位置。     

Grain refinement and tensile strength of carbon nanotube-reinforced Cu matrix nanocomposites processed by high-pressure torsion

In recent years, the processing of metallic materials via severe plastic deformation has been widely applied to manufacture bulk specimens of ultrafine grained/nanocrystalline structures. In this study, bulk nanocomposites of carbon nanotube-reinforced Cu were manufactured by consolidation of mixtures of coarse grained Cu powders and CNTs of two volume fractions (5 vol% and 10 vol%) using high-pressure torsion, a typical SPD method. The effects of CNT reinforcements on the microstructural evolution of the Cu matrix were investigated using electron backscatter diffraction and scanning/transmission electron microscopy; the results showed that the Cu matrix grain size was reduced to ～114 nm, and the CNTs were well dispersed in the matrix. Due to the effect of the UFG Cu and CNTs, the tensile strength (350 MPa) of the nanocomposite was higher than that (190 MPa) of Cu processed by the powder HPT process without CNTs. However, the Cu-CNT 10 vol% indicated a decreased tensile strength due to an increased interface area between the matrix and CNTs at high volume fractions of CNTs.     

Synthesis and properties of nanocrystalline nonferrous metals prepared by flow-levitation-molding method

Nanocrystalline nonferrous metals （Cu, A1, and Ag） were synthesized by flow-levitation-molding method. The microstructure of the as-prepared nanocrystalline metals was characterized by XRD and FESEM. The microhardness and electrical resistivity were tested by the HMV-2 type Microhardness Tester and 6157 type Electrometer, respectively. The synthesis process was also studied. The results show that the spheriform particles in nanocrystalline metals have average grain size of 20-30 nm. The relative density of nanocrystalline Cu, A1, and Ag are 95.1%, 98.1% and 98.3%, respectively. The microhardness of nanocrystalline Cu, Al and Ag are 2.01, 2.11 and 1.26 GPa respectively, which are larger than those of their coarse-grained counterparts by the factor of 4.5, 14, and 2.5, respectively. The electrical resistivity of nanocrystalline Cu at room temperature is 1.5× 10^-7Ω.m, which is higher than coarse-grained Cu by a factor of 7.5. The pressure is the predominant factor influencing the density of the as-prepared nanocrystalline nonferrous metals.     

Influence of two-step cooling method on magnetic properties of Fe82Mo7B10Cu1 nanocrystalline alloy

Soft magnetic properties of Fe82Mo7B10Cu1 nanocrystalline alloy were studied as a function of cooling condition. The results show that higher permeability and relaxation frequency can be obtained by the two-step cooling method, and the pinning field of the sample obtained by this method is smaller than that of the fitrnace-cooled and water-quenched samples. This phenomenon was interpreted in terms of internal stress and the magnetic ordering of the residual amorphous phase. The two-step cooling treatment is an effective way to improve the soft magnetic properties of Fe82Mo7B10Cu1 nanocrystalline alloy.     

挤压铸造Al-Cu-Mn和Al-Zn-Mg-Cu合金耐腐蚀性能研究

采用酸性盐雾试验,对Al-4.5Cu-0.8Mn和Al-7.3Zn-2.9Mg-1.9Cu 2种挤压铸造合金的耐腐蚀性能进行了对比研究.结果表明,在盐雾腐蚀过程中,随着腐蚀时间的延长和压力的增大,两种合金的耐腐蚀性能都出现了一定程度的下降.前者的腐蚀是由分布于枝晶间和晶界处的T(Al12CuMn2)和θ(Al2Cu)相溶解引起的,后者的腐蚀是由合金中η相的优先溶解,以及沿晶界分布的S相边沿的(Al)基体溶解所致;前者的耐腐蚀性能明显优于后者.     

Strain Hardening Associated with Dislocation,Deformation Twinning,and Dynamic Strain Aging in Fe–20Mn–1.3C–(3Cu) TWIP Steels

The effects of Cu on stacking fault energy,dislocation slip,mechanical twinning,and strain hardening in Fe–20Mn–1.3C twinning-induced plasticity(TWIP) steels were systematically investigated.The stacking fault energy was raised with an average slope of 2 mJ/m2 per 1 wt% Cu.The Fe–20Mn–1.3C–3Cu steel exhibited superior tensile properties,with the ultimate tensile strength reached at 2.27 GPa and elongation up to 96.9% owing to the high strain hardening that occurred.To examine the mechanism of this high strain hardening,dislocation density determination by XRD was calculated.The dislocation density increased with the increasing strain,and the addition of Cu resulted in a decrease in the dislocation density.A comparison of the strain-hardening behavior of Fe–20Mn–1.3C and Fe–20Mn–1.3C–3Cu TWIP steels was made in terms of modified Crussard–Jaoul(C–J) analysis and microstructural observations.Especially at low strains,the contributions of all the relevant deformation mechanisms—slip,twinning,and dynamic strain aging—were quantitatively evaluated.The analysis revealed that the dislocation storage was the leading factor to the increase of the strain hardening,while dynamic strain aging was a minor contributor to strain hardening.Twinning,which interacted with the matrix,acted as an effective barrier to dislocation motion.     

Ni,Mn对Al—Si—Cu—Mg系合金磨损失效机制的影响

采用快速磨损试验机进行耐磨性试验,并通过微区成分分析,图像分析、光学显微镜及扫描电镜分析探讨了Ni,Mn对Al-Si-Cu-Mg系合金组织及二体磨损条件下磨损失效机制的影响,在二体干摩擦条件下,Al-Si-Cu-Mg系合金的磨损失效机制为犁削磨损和表层剥落磨损,添加合金元素Ni后,组织中出现Al34Cu28Ni38化合物,磨损失效以表层剥落为主;添加合金元素Mn后,组织又出现了Al50Si4Cu9Ni26Mn5化合物,磨损失效以犁削磨损为主。     

纳米晶体铜的制备及其结构表征

研究了纳米晶体铜材料的压制工艺条件对其相对密度和显微硬度的影响,并用正电子湮没寿命谱、扫描电镜和热重分析仪对其微观结构进行了表征。结果表明:压制压力越大,保压时间越长,样品的缺陷尺寸及数量减少,相对密度增加,显微硬度显著提高。随着压制压力的增大,缺陷类型的相对含量发生变化。而且纳米铜粉表面吸附的气体是纳米晶体铜样品内部缺陷的一个主要来源。     

Size-induced enhanced mechanical properties of nanocomposite copper/niobium wires: nanoindentation study

The effect of microstructure dimension δ on plasticity of high strength multifilamentary nanocomposite copper/niobium wires was studied by nanoindentation. Two structures were tested: a Cu matrix containing Nb filaments and a Cu matrix containing Nb tubes filled with Cu. For δ>10 μm, no size effect on the composite hardness is observed. In the 1–10 μm range, a strong increase in hardness indicates a change in plasticity mechanism, attributed to the classical Hall–Petch grain size strengthening. In the nanometre range, the hardness of the nanocomposite Cu/Nb regions exceeds that of nanocrystalline Cu or Nb, reaching 5.8 GPa for the finest conductors. The observed size effect on the plasticity of Cu/Nb nanostructures added to the dislocation barrier role of Cu/Nb interfaces confirms previous analyses based on the occurrence of a single dislocation regime at nanometre scale associated with impenetrable Cu/Nb interfaces.