NdFeB永磁合金的晶粒结构缺陷模型及矫顽力机制

概述了ＮｄＦｅＢ类稀土永磁合金的晶粒结构及其缺陷模型。包括单变量连续变化模型，三变量突变模型和激活体积模型。介绍了基于不同结构缺陷模型的各种矫顽力理论，比较了他们的异同点，提出了统一结构缺陷模型的构想。     

Nd:YAGCW激光热传导焊Ⅰ.温度场三维解析计算

激光热导焊是激光焊接中一种重要的焊接模式 ,广泛应用于薄件的焊接中。焊接温度场以其为焊接过程最直接的外在表征而成为焊接过程研究的一种常用的研究手段。通过连续波激光热导焊温度场解析计算对激光热导焊进行了研究 ,建立了激光热导焊温度场的三维解析模型 ,并讨论了利用模型对焊缝熔合线进行计算。最后基于焊缝熔合线尺寸试验值和计算值的比较对温度场解析模型进行了验证 ,验证试验结果表明所建立的激光热导焊温度场三维解析模型能够较为准确地计算出焊缝熔合线的尺寸     

Improving corrosion properties of high-velocity oxy-fuel sprayed inconel 625 by using a high-power continuous wave neodymium-doped yttrium aluminum garnet laser

Thermal spray processes are widely used to protect materials and components against wear, corrosion and oxidation. Despite the use of the latest developments of thermal spraying, such as high-velocity oxy-fuel (HVOF) and plasma spraying, these coatings may in certain service conditions show inadequate performance,e.g., due to insufficient bond strength and/or mechanical properties and corrosion resistance inferior to those of corresponding bulk materials. The main cause for a low bond strength in thermalsprayed coatings is the low process temperature, which results only in mechanical bonding. Mechanical and corrosion properties typically inferior to wrought materials are caused by the chemical and structural inhomogeneity of the thermal-sprayed coating material. To overcome the drawbacks of sprayed structures and to markedly improve the coating properties, laser remelting of sprayed coatings was studied in the present work. The coating material was nickel-based superalloy Inconel 625, which contains chromium and molybdenum as the main alloying agents. The coating was prepared by HVOF spraying onto mild steel substrates. High-power continuous wave Nd:YAG laser equipped with large beam optics was used to remelt the HVOF sprayed coating using different levels of power and scanning speed. The coatings as-sprayed and after laser remelting were characterized by optical microscopy and scanning electron microscopy (SEM). Laser remelting resulted in homogenization of the sprayed structure. This strongly improved the performance of the laser-remelted coatings in adhesion, wet corrosion, and high-temperature oxidation testing. The properties of the laser-remelted coatings were compared directly with the properties of as-sprayed HVOF coatings and with plasma-transferred arc (PTA) overlay coatings and wrought Inconel 625 alloy.     

稀土Nd及热处理对Al2O3f/Mg-9Al复合材料组织和性能的影响

复合材料的硬度分别达到232HB、262HB.     

Sn合金化对Gd5Si2Ge2磁致冷材料结构和性能的影响

以商业纯Gd为原料,采用非自耗电弧炉氩气保护下熔炼了Gd5Si2Ge2-xSnx(x=0.2,0.5,1)和Gd5Si2-yGe2Sny(y=0.1,0.2,0.5)系列合金,研究Sn合金化对Gd5Si2Ge2晶体结构和磁热性能的影响.粉末XRD结果表明Sn代Ge样品具有正交Gd5Si4型结构;Sn少量代Si(y=0.1,0.2)的样品具有单斜Gd5Si2Ge2型结构;Gd5Si1.5Ge2Sn0.5则为单斜和正交的混合结构.用超导量子磁强计(SQUID)测定了样品的M-T和不同温度的M-H曲线,结果表明Gd5Si2Ge2-xSnx(x=0.2,0.5,1)不具有巨磁热效应;Gd5Si1 9Ge2Sn01合金的最大磁熵变达15.3 J/kg·K(0 T～5 T),具有巨磁热效应.     

Gd2O2S：Ti的长余辉性能研究及机理探讨

利用高温固相法合成了一种长余辉发光材料Gd2O2S：Ti，利用XRD测试了其结构并测试了其在紫外光激发下的发光特性；停止照射，有橙色的余辉，时间接近2h。分析该磷光体的发光和余辉产生细节，认为空穴和电子的复合导致Ti^3＋的^2E→^2T2的跃迁是产生发光和余辉的原因；并根据缺陷和空位对Gd2O2S：Ti的余辉机理进行探讨，提出了余辉机理模型。     

掺钕钨酸钆钾激光晶体生长及性能研究

采用顶部籽晶提拉法(TSSG)生长出Nd3+:KGd(WO4)2晶体,测得Nd3+实际掺杂浓度3.2at%。测得样品的吸收光谱及荧光光谱,计算得出808nm处吸收截面为0.6799×10-20cm2;荧光输出波长为1068nm和1351nm,测得荧光寿命为112μs。对不同尺寸的两样品进行了激光实验,当LD泵浦源输出功率为900mW时,分别获得326mW,305mW的1064nm激光输出,斜效率分别为62.7%和57.8%。水平和垂直两个方向上光束传输因子M2均小于1.2。经倍频获得532nm的绿光。用Cr:LuAG作为可饱和吸收体进行调Q实验,重复频率为15kHz时,脉冲宽为170ns。     

钕对铸造Al-Si-Cu-Mg合金力学性能的影响

微量合金元素Nd的添加延缓了Al-Si-Cu-Mg合金的时效过程,细化了强化相,提高了合金时效硬度。当加入0.30%Nd,合金的强度提高了18%,但加入量继续增加,强度下降。分析显示,Nd的加入延缓了亚稳相的析出。富Nd相化合物,少量稳定相和过剩硅相质点的均匀析出,对合金起到了第二相强化的作用。在这两类析出相的共同作用下,合金获得了高的峰时效强度,但当合金中的Nd的含量超过一定量时,会形成一些富Nd的多元相和纯Nd质点相,这些相的出现导致了合金力学性能的下降。     

Proton beam writing and electroplating for the fabrication of high aspect ratio Au microstructures

We present an approach to fabricate tall high aspect ratio Au microstructures by means of proton beam direct writing. Combining proton beam direct writing and electroplating, we successfully produced gold structures with sub-micrometer lateral dimensions, structure heights in excess of 11 μm, and aspect ratios over 28. Sidewall quality of the Au structures was improved by lowering the process temperature to 20 °C when developing PMMA patterns with GG developer. The application of such structures as X-ray masks for deep X-ray lithography with synchrotron radiation was demonstrated.