含1.5%W的FeCrCoVTi永磁合金穆斯堡尔谱的研究

研究含1.5%W的FeCrCoVTi永磁合金穆斯堡尔谱.在室温下,该合金的穆斯堡尔谱可以分解为八套亚谱,其中7个铁磁性亚谱属于合金中脱溶的α1相,它的平均超精细磁场约为309 kOe;一套顺磁性亚谱对应于合金中基体的α2相.计算讨论合金中的磁矩平均取向度θ及其对该合金磁性能的影响.     

Mold-filling ability of semisolid alloy

The mold-filling ability of the semisolid alloy has very important effects on the quality and properties of the work pieces produced by the semisolid forming process. The factorial experiments show that all of the heating factors, such as mold temperature, heating temperature and the keeping time of billets, have some effects on the mold-filling ability of semisolid alloy. According to the analysis of influencing extent on the filling ability, it is found that the most important one of the factors is the mold temperature instead of the billets temperature, the next one is the heating temperature of the billet, and the keeping time rows on the third. It is also found that there is an interrelation between the billet heating temperature and the mold temperature. The effect of the interrelation on the mold-filling abilityis even stronger than the keeping time. The higher the mold temperature, heating temperature or the keeping time is, the better the mold-filling ability of the semisolid alloy is. The parameter to describe themold-filling ability, defined as the maximum filling height along theupright direction or the maximum filling length along the horizontal direction, can be theoretically determined according to the flowing theory of viscous fluid.     

强磁场对Al-12.6%Si合金变质效果影响

研究了强磁场对共晶铝硅合金变质效果的影响．对共晶Al—12．6％Si合金进行Na盐变质处理,发现施加强磁场的条件下,在变质剂反应温度下保温20min,共晶硅细化,并呈现一定程度的粒状化,其变质效果明显优于不施加强磁场．760℃下延长保温时间至40min,未施加强磁场条件下的试样出现严重的变质衰退现象,施加强磁场的试样变质衰退现象相对教轻．在施加强磁场条件下,即使保温40min,其变质效果也优于不施加强磁场时保温20min时的,即强磁场具有一定的延长变质有效时间的作用．分析认为强磁场抑制对流是其中的原因之一．     

工作电压对微弧氧化6061铝合金耐腐蚀性能的影响

【目的】为提高铝合金的耐腐蚀性能,采用交流恒压微弧氧化方法在6061铝合金表面制备金属陶瓷涂层并研究了工作电压对涂层性能的影响。【方法】采用XRD分析、SEM微观组织形貌观察、交流阻抗(EIS)测试和涂层厚度分析等方法,测试工作电压对涂层生长、物相组成、耐腐蚀性能等的影响,分析其影响机理。【结果】6061铝合金微弧氧化涂层表面为疏松多孔的"火山口喷射"形貌,当工作电压小于450V时,涂层的厚度随着工作电压的增加而增大,火山口状放电孔数增加,涂层主要相为β?Al2O3和少量α?Al2O3;工作电压大于450V后,火山口状放电孔数减少而孔径增大,并且工作电压增大到500V时涂层开始出现微裂纹,耐腐蚀性先增强后减弱。【结论】工作电压为450V时制备的涂层,疏松层放电微孔电阻Rp和基体金属腐蚀反应的电荷转移电阻Rct分别为2.875×106Ω·cm2和7.575×106Ω·cm2,比制备的其他涂层具有更好的耐腐蚀性能。     

皮秒Nd:YAG激光对生物金属纯Ti和Ti–13Nb–13Zr合金的表面改性

The effects of picosecond Nd:YAG laser irradiation on chemical and morphological surface characteristics of the commercially pure titanium and Ti–13Nb–13Zr alloy in air and argon atmospheres were studied under different laser output energy values. During the interaction of laser irradiation with the investigated materials, a part of the energy was absorbed on the target surface, influencing surface modifications. Laser beam interaction with the target surface resulted in various morphological alterations, resulting in crater formation and the presence of microcracks and hydrodynamic structures. Moreover, different chemical changes were induced on the target materials’ surfaces, resulting in the titanium oxide formation in the irradiation-affected area and consequently increasing the irradiation energy absorption. Given the high energy absorption at the site of interaction, the dimensions of the surface damaged area increased. Consequently, surface roughness increased. The appearance of surface oxides also led to the increased material hardness in the surface-modified area. Observed chemical and morphological changes were pronounced after laser irradiation of the Ti–13Nb–13Zr alloy surface.     

Hot deformation behaviors of WE71 alloy under plain strain compression at elevated temperature

Hot deformation behaviors of WE71 (Mg–7Y-1Nd-0.5Zr) alloy was investigated by plain strain compression tests conducted at temperatures ranging from 350 °C to 500 °C and strain rates varying from 0.01 s^-1 to 10 s^-1. Results show that the hot deformation of WE71 was accompanied by the precipitation of rich Zr phase with granular shape and block-shaped phase rich in element Y. When deformed at low temperature and high strain rate, the softening behavior of the alloy was synergically determined by shear bands propagation, adiabatic heating, twinning formation and dynamic recrystallization (DRX). For the conditions of high temperature and high strain rate, DRX was the major softening mechanism while the formation and annihilation of extension twinning resulted in a special flow curve characteristic at the strain of around 0.3. According to the microstructural observations, it can be concluded that the irregular flow curves of WE71 alloy during plain strain compression process are mainly ascribed to shear bands propagation, adiabatic heating, twinning formation and DRX.     

Microstructure and improved mechanical properties of ultrafine-grained Mo-12Si-8.5B (at.%) alloys with addition of ZrB2

Multi-hierarchical Mo-12Si-8.5B-x Zr B_2(x=0,0.5,1.0,1.5,2.5 wt%)alloys consisting of three ultrafine-grained(UFG,0.47–0.81μm)phases of Mo_5Si B_2(T2),Mo_3Si and Mo solid solution(α-Mo)were prepared by mechanical alloying following hot pressing.Microstructure observations showed that the intermetallic phases(Mo_3Si and T2)distributed dispersedly in the continuousα-Mo matrix associated with the homogeneously embedded nanoscaled particles(10–225 nm)in the grain interiors and at the grain boundaries.The Mo-12Si-8.5B-x Zr B_2alloys exhibited monotonically increasing compressive strength to 3.13 GPa with increasing content of Zr B_2,and the fracture toughness increased about 27%and reached at 11.5 MPa m~(1/2)at 1.0 wt%Zr B_2,rendering the Mo-12Si-8.5B-1.0 wt%Zr B_2alloy possessing the best combined mechanical properties of high strength and high toughness.The underlying reason for the superior mechanical properties of the Mo-12Si-8.5B-x Zr B_2alloys is that the dispersedly distributed nanosized particles in the UFG multi-phased-matrix can not only effectively block the dislocation motion to increase the strength but also store the dislocations to increase the strain hardening ability during mechanical deformation.     

如何快速制得大量甲烷

本文对教材中的甲烷制取演示实验,从改进装置着手,对温度、药品的配比及用量进行了研究,取得了较好的效果,可快速、大量地制取甲烷。     

石墨炉原子发射法测定饮料中的铝

石墨炉原子发射法(GFAES)是近年来发展起来的一种新的分析方法,该法对某些易激发元素(如K、Na、Ba、Al等)的测定灵敏度和稳定性皆优于石墨炉原子吸收法(GFAAS).本文在非火焰原子吸收装置上,对铝的GFAES法测定进行了较详细的研究,并通过测定不同包装的同类饮料中铝的含量,考察了方法的可靠性和精度,结果发现,该法完全可用于饮料中微量铝的测定.当被测溶液中铝的含量在0.00～0.25ppm时,铝的发射强度与浓度呈线性关系.加入回收试验表明,方法的回收率达96.0%～102.0%,对饮料中常见的各种成份进行干扰试验,发现100倍的K~+、Na~+、Ca~(++)、Mg~(++)、CO_3~-和50倍的柠檬酸,苯甲酸等不干扰铝的测定.     

石墨化阴极炭材料热物性测试研究(英文)

对经典的周期热流法测试原理进行深入分析,根据实验模型和石墨化阴极炭块材料性能的特点,设计开发了一套铝电解槽用阴极碳素材料瞬态热物性测试系统。采用两路热电偶来检测通过试样的正弦温度信号,根据信号在试样内传播时产生的振幅衰减和相位滞后,可以直接计算出导温系数,在已知密度和比热参数的情况下可以计算出导热系数。在20～300℃的范围内,测定装置操作方便,数据可靠。对计算方法和测试系统的研究,为获得可靠的热物性数据提供了有效的途径。