Electron irradiation-enhanced core/shell organization of Al(Cr,Fe, Mn)Si dispersoids in Al–Mg–Si alloys

The age hardening 6061-T6 aluminium alloy has been chosen as structural material for the core vessel of the material testing Jules Horowitz nuclear reactor. The alloy contains incoherent Al(Cr, Fe, Mn)Si dispersoids whose characterization by energy-filtered transmission electron microscopy (EFTEM) analysis shows a core/shell organization tendency where the core is (Mn, Fe) rich, and the shell is Cr rich. The present work studies the stability of this organization under irradiation. TEM characterization on the same particles, before and after 1 MeV electron irradiation, reveals that the core/shell organization is enhanced after irradiation. It is proposed that the high level of point defects, created by irradiation, ensures a radiation-enhanced diffusion process favourable to the unmixing forces between (Fe, Mn) and Cr. Shell formation may result in the low-energy interface segregation of Cr atoms within the (Fe, Mn) system combined with the unmixing of Cr, Fe and Mn components.     

Tb doping induced enhancement of anomalous Hall effect in NiFe films

Tbx(Ni0.8Fe0.2)1-x films with x≤0.14 are fabricated and the anomalous Hall effect is studied.The intrinsic anomalous Hall conductivity and the extrinsic one from the impurity and phonon induced scattering both increase with increasing x.The enhancement of the intrinsic anomalous Hall conductivity is ascribed to both the weak spin–orbit coupling enhancement and the Fermi level shift.The enhancement of the extrinsic term comes from the changes of both Fermi level and impurity distribution.In contrast,the in-plane and the out-of-plane uniaxial anisotropies in the Tb Ni Fe films change little with x.The enhancement of the Hall angle by Tb doping is helpful for practical applications of the Hall devices.     

Theoretical study of the optical gain characteristics of a Ge1-xSnx alloy for a short-wave infrared laser

Optical gain characteristics of Ge_(1_x)Snμx are simulated systematically.With an injection carrier concentration of 5×10~(18)/cm~3 at room temperature,the maximal optical gain of Ge_(0.922)Sn_(0.078) alloy(with n-type doping concentration being 5×10~(18)/cm~3) reaches 500 cm~(-1).Moreover,considering the free-carrier absorption effect,we find that there is an optimal injection carrier density to achieve a maximal net optical gain.A double heterostructure Ge_(0.554)Si_(0.289)Sn_(0.157)/Ge_(0.922)Sn_(0.078)/Ge_(0.554)Si_(0.289)Sn_(0.157) short-wave infrared laser diode is designed to achieve a high injection efficiency and low threshold current density.The simulation values of the device threshold current density J_(th)are 6.47 kA/cm~2(temperature:200 K,and λ=2050 nm),10.75 kA/cm~2(temperature:200 K,and λ=2000 nm),and23.12 kA/cm~2(temperature:300 K,and λ=2100 nm),respectively.The results indicate the possibility to obtain a Si-based short-wave infrared Ge_(1-x)Sn_x laser.     

The study of phase,microstructure, and magnetocaloric properties in LaFe11.6*xSi1.4B0.1 alloys

The effect of Fe on the phase and magnetocaloric property of LaFe_11.6*xSi_1.4B_0.1 alloys with x = 1.0–1.4 have been studied. The results show that the excess of Fe will make the α-Fe phases increase, but the easy corrosion LaFeSi phase reduces in LaFe_11.6*xSi_1.4B_0.1 alloys. All LaFe_11.6*xSi_1.4B_0.1 alloys keep the first-order magnetic phase transition. The saturation magnetizations of LaFe_11.6*xSi_1.4B_0.1 alloys with x > 1 are much higher than LaFe_11.6Si_1.4B_0.1 alloy under 2T magnetic field. This results in the maximum isothermal magnetic entropy changes, and the relative cooling power of LaFe_11.6*xSi_1.4B_0.1 alloys is bigger than for LaFe_11.6Si_1.4B_0.1 alloys.     

溶胶凝胶自燃烧法合成金属与合金材料研究进展

本文综述了溶胶凝胶自燃烧法制备金属与合金材料的研究进展, 详细介绍了该方法的实验原理和技术路线, 通过实例介绍了该方法在制备金属和合金材料中的具体应用. 通过这一系列的工作介绍, 我们证实可以把传统的溶胶凝胶法制备氧化物材料的技术拓展到金属与合金材料的制备, 希望能够对材料研究的实验工作有所帮助.     

基于分数阶流变模型的铁基块体非晶合金黏弹性行为研究

采用分数阶黏弹单元替代经典模型中的黏壶, 结合非晶合金在外加载荷作用下的微观结构演化, 建立了以分数阶微积分表示的非晶合金黏弹性本构模型. 并根据Hertz弹性理论及分数阶黏弹性本构模型, 推导了块体非晶合金在纳米压痕球形压头下的位移与载荷及时间关系式. 基于推导的解析式, 对铁基块体非晶合金在表观弹性区的纳米压痕位移与载荷及时间曲线进行了非线性拟合分析. 相较于整数阶模型, 分数阶模型不仅具有较高的拟合精度, 其拟合参数能敏锐地反应加载速率对块体非晶合金黏弹性行为的影响, 且参数的变化规律与载荷作用下非晶合金微观结构演化呈现出较强的相关性.     

Development of Surface Nano-Crystallization in Alloys by Surface Mechanical Attrition Treatment (SMAT)

Nanometer-sized grain structures that exhibit a large number of grain boundaries on the surface of a bulk material demonstrate excellent properties relative to their coarse-grained (CG) equivalents. Surface modification using surface mechanical attrition treatment (SMAT) is an option that cab be used to tailor the corrosion, tribological, mechanical, and chemical reaction properties of a surface. SMAT is an effective route to create the nanostructured surface layer. The SMAT process has unique advantages compared with the other coating and deposition techniques for surface nanocrystallization. For example, SMAT does not alter the chemical composition of the nanocrystalline surface layer in the matrix. In addition, SMAT has been demonstrated to activate the material surface layer by surface modification and enhance the atomic diffusivity. This article presents a review of the advantages offered by the SMAT technique for the creation of high performance surface layers. The influence of the created nanocrystalline layer on mechanical, physical, and chemical properties is assessed. Developments and the current status of the surface nanolayer that are formed are evaluated from a physical approach. Finally, prospects for the future development of grain refinement on the surface of a material matrix and potential applications are presented.     

LY12CZ铝合金表面等离子浸没离子注入氮层的摩擦磨损性能研究

对LY12CZ(2024)铝合金进行了氮等离子体浸没离子注入(PIII)处理,分析比较了不同工艺参数下离子注入前后试样的化学组成、各元素的化学价态及其摩擦磨损性能.结果表明:铝合金表面改性层中形成了弥散强化的氮化铝(AlN)相;与基体相比,铝合金试样在不同条件下处理后的表面显微硬度均有所提高,最大增幅达1.4倍;铝合金的磨损质量损失减少了75%,摩擦系数显著降低,表面综合性能得到了显著改善.