Sn晶须形态的研究

添加微量稀土可以有效地改善钎料的综合性能.然而当钎料中添加过量的稀土时,钎料内部会形成体积较大的稀土相.如果将稀土相暴露于空气中,其将发生氧化,氧化产生的压应力将加速稀土相表面Sn晶须的生长.研究了CeSn3与YSn3与ErSr3稀土相表面Sn晶须的生长情况.研究结果表明,稀土相表面出现了Sn晶须的快速生长现象,且试验中发现了一些特殊形态的Sn晶须.     

稀土Ce加速Sn晶须生长的研究

稀土被认为是金属中的"维他命",在钎料中添加微量的稀土Ce可以显著地改善钎料合金的综合性能.然而,当钎料中添加过量的稀土时,将会发现Sn晶须的快速生长现象.结果表明,如果将Sn3.8Ag0.7Cu1.0Ce钎料内部的稀土相暴露于空气中,稀土相将发生氧化而产生体积膨胀,钎料基体对体积膨胀的抑制作用将使稀土相内部产生巨大的压应力从而加速Sn晶须的生长.     

Sn-3.8Ag-0.7Cu-1.0Er无铅钎料中Sn晶须变截面生长现象

在Sn-3.8Ag-0.7Cu无铅钎料中添加质量分数为1%的稀土Er会在其内部形成尺寸较大的稀土相ErSna.暴露于空气中ErSn3将发生氧化,同时在其表面会出现Sn晶须的快速生长现象.室温时效条件下,在氧化的ErSn3表面会生长出少量的杆状Sn晶须,Sn晶须的截面尺寸会发生连续变化;高温时效条件下,在氧化的ErSn3表面会生长出大量的针状Sn晶须,Sn晶须的截面尺寸会发生阶梯式变化.提出了ErSn3氧化过程中体积应变能是一个变量的模型,可以解释观察到的现象.     

CROSS SECTION CHANGING GROWTH PHENOMENON OF Sn WHISKER IN Sn–3.8Ag–0.7Cu–1.0Er LEAD–FREE SOLDER

在Sn--3.8Ag--0.7Cu无铅钎料中添加质量分数为1%的稀土Er会在其内部形成尺寸较大的稀土相ErSn₃. 暴露于空气中ErSn₃将发生氧化, 同时在其表面会出现Sn晶须的快速生长现象. 室温时效条件下, 在氧化的ErSn₃表面会生长出少量的杆状Sn晶须, Sn晶须的截面尺寸会发生连续变化; 高温时效条件下, 在氧化的ErSn₃表面会生长出大量的针状Sn晶须, Sn晶须的截面尺寸会发生阶梯式变化. 提出了ErSn₃氧化过程中体积应变能是一个变量的模型, 可以解释观察到的现象.     

稀土相ErSn3表面Sn晶须的快速生长

将稀土相ErSn3分别暴露于空气与真空环境中,研究在时效处理过程中ErSn3表面Sn晶须的生长情况。结果表明：大气环境中,在稀土相ErSn3的表面出现了Sn晶须的生长现象,且室温条件下Sn晶须的分布不均,生长速度慢,而高温条件下Sn晶须的分布均匀,生长速度快;真空环境中,在稀土相ErSn3的表面未出现Sn晶须的生长现象。由于在大气环境中稀土相ErSn3发生了氧化,氧原子向ErSn3晶格内部的扩散引起的体积膨胀提供了Sn晶须生长的驱动力,因此,大气环境中在ErSn3的表面会出现Sn晶须的生长现象,而真空环境中则不会出现     

稀土相RE-Sn表面Sn晶须的生长规律

将稀土相CeSn3、LaSn3、(La0.4Ce0.6)Sn3及ErSn3暴露于空气中,研究在时效处理过程中其表面Sn晶须的生长规律。结果表明:室温时效过程中,在稀土相的表面均出现了Sn晶须的生长现象,且稀土相LaSn3的表面倾向于形成包状和扭结状的Sn晶须,稀土相CeSn3和(La0.4Ce0.6)Sn3的表面倾向于形成针状和扭结状的Sn晶须,而稀土相ErSn3的表面倾向于形成大尺寸的杆状和棒状Sn晶须。150℃时效过程中,稀土相CeSn3、LaSn3和(La0.4Ce0.6)Sn3的表面没有出现Sn晶须的生长现象,而稀土相ErSn3的表面出现了大量的小尺寸线状Sn晶须。综上所述,稀土相的氧化倾向决定了其表面Sn晶须的生长规律。     

Sn晶须的形态机制

将稀土相CeSn3与ErSn3暴露于空气中,研究在时效处理过程中稀土相表面Sn晶须的形态机制.结果表明:时效过程中在稀土相表面出现的绝大多数Sn晶须均是具有恒定截面的规则Sn晶须;同时也发现少数特殊形态的不规则Sn晶须,如卷曲状的Sn晶须、变截面的Sn晶须、分枝及搭接的Sn晶须等;由于稀土相的氧化所产生的体积膨胀提供Sn晶须生长的驱动力,而稀土相的氧化极不均匀,因此,认为Sn晶须在生长过程中其根部受力状态的改变是导致特殊形态Sn晶须出现的根本原因.     

稀土相表面特殊形态锡晶须生长现象

在Sn3.8Ag0.7Cu钎料中添加过量的稀土Ce和Er元素会在其内部形成尺寸较大的稀土相CeSn3和ErSn3.将钎料合金Sn3.8Ag0.7Cu1.0Ce/Er的铺展试样沿中心剖开,利用金相水砂纸及专用抛光液抛光后,将制备好的试样在空气中分别进行室温与150℃时效处理.分析了时效处理过程中稀土相CeSn3及ErSn3表面锡晶须的生长行为.结果表明,在稀土相的表面出现了大量规则的针状及线状锡晶须,它们在生长过程中始终保持了恒定的截面.试验中还发现了一些特殊形态的锡晶须,如锡晶须的分枝、合并以及锡晶须的搭接现象.     

Sn晶须生长的双应力区模型

利用FIB(Focused Ion Beam)将发生氧化的稀土相ErSn3剖开,研究其表面Sn晶须的生长机制。结果表明:时效过程中稀土相ErSn3发生了不均匀氧化,在其内部形成了大量的"快速氧化通道"及"氧化区"。由于在Sn晶须的根部及附近同时存在两个"氧化区",且它们通过"快速氧化通道"相连。因此,提出了Sn晶须生长的"双压应力区"模型,即Sn晶须的生长需要形成两个压应力区,其根部的"低压应力区"将为Sn晶须的形成提供驱动力,而"高压应力区"将为Sn晶须的生长提供Sn原子。     

氧化对含稀土无铅钎料表面锡须生长的影响

通过环境试验(室温、湿热和"无氧"试验)和扫描电镜组织分析对比研究了相同时效时间(30天)、三种不同氧化条件下锡须在Sn-Zn-Ga-Pr无铅钎料表面的生长行为.发现在室温环境下,锡须呈典型的针状生长;在湿热条件下,锡须呈丘状生长;而在氮气氛围的近似无氧条件下仅发现有少量锡粒在稀土相PrSn3表面产生.基于稀土相氧化驱动锡须生长理论,分析认为三种环境条件下锡须生长行为的不同是由于稀土相氧化程度不同造成的.湿热条件下稀土相快速氧化和腐蚀,从而比在室温和"无氧"条件下产生更多的压应力和活性Sn原子,为丘状锡须的生长提供了条件;而在氮气氛围下,稀土相氧化非常缓慢,驱动力和锡源都较少,因而只有少量短锡须和锡粒生长.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Rheology Feature of Simple Metal Melt

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.     

Microstructures and Mechanical Properties of a Newly Developed Austenitic Heat Resistant Steel

The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results show that the main phases in the alloy after solution treatment are γ and primary MX. Subsequent aging treatment causes the precipitation of M_(23)C_6 carbides along the grain boundaries and a small number of nanoscale MX inside the grains. In addition, with increasing the aging temperature and time, the morphology of M_(23)C_6 carbides changes from semi-continuous chain to continuous network.Compared with a commercial HR3C alloy, T8 alloy has comparable tensile strength, but higher stress rupture strength. The dominant cracking mechanism of the alloy during tensile test at room temperature is transgranular, while at high temperature, intergranular cracking becomes the main cracking mode, which may be caused by the precipitation of continuous M_(23)C_6 carbides along the grain boundaries. Typical intergranular cracking is the dominant cracking mode of the alloy at all stress rupture tests.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

The 15th Global Foundry Sourcing Conference 2014held in Qingdao China

Organized by Suppliers China Co., Ltd and co-organized by the National Technical Committee 54 on Foundry of Standardization Administration of China, the 15th Global Foundry Sourcing Conference 2014 （hereinafter referred to as FSC 2014） was successfully held on Sep. 23rd in Grand Regency Hotel, Qingdao. More than 500 delegates from home and abroad attended this conference, including over 130 purchasers from 20 countries and 380 domestic and foreign suppliers.     

Secondary Recrystallization Behaviors of Grain-Oriented 6.5 wt% Silicon Steel Sheets Produced by Rolling and Nitriding Processes

By rolling and nitriding processes, 0.23- to 0.3-mm-thick grain-oriented 6.5 wt% silicon steel sheets were produced. The core losses of grain-oriented 6.5 wt% silicon steel at frequencies ranging from 400 Hz to 20 k Hz were lower than that of the grain-oriented 3 wt% silicon steel with the same thickness by 16.6–35.8%. The secondary recrystallization behavior was investigated by scanning electron microscopy, energy-dispersive spectroscopy, and electron backscattered diffraction. The results show that the secondary recrystallization in high-silicon steel sheets develops more completely as the nitrogen content increases after nitriding, secondary recrystallized grain sizes become larger, and the sharpness of Goss texture increases. Because more {110}116 grains in the subsurface and the central layer of the sheets have a lot of 20°–45° high-energy boundaries in addition to Goss grains, {110}116 can be the main component through selective growth during secondary recrystallization when the inhibitor quantity is not enough and inhibitor intensity is weaker. The increases in nitrogen content can increase the inhibitor intensity and hinder abnormal growth of a mount of {110}116 grains and therefore enhance the sharpness of Goss texture.     

Laser Cladded TiCN Coatings on the Surface of Titanium

Laser cladded coatings of TiCN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs (OM). The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TiCN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TiCN, TiC, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm / s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm - 2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TiCN, TiO2, and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80?滋m, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

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正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis