半固态法泡沫铝材料制备工艺研究

采用半固态法制备泡沫铝,并对制备工艺进行了初步探索。研究了熔体浇注温度、发泡剂TiH_2添加量对Al-Si合金熔体发泡孔隙率和平均孔径的影响。研究表明,利用Al-Si合金在半固态区的自增粘作用,可以得到孔隙率为20%~50%、孔径为2~4 mm的泡沫铝;浇注温度在650~670℃时,随浇注温度的升高,Al-Si合金泡沫铝试样孔隙率增加,更高的浇注温度使孔隙率减少;发泡剂TiH_2添加量在1%~3%时,随发泡剂添加量的增加,孔隙率和孔径均增加,发泡剂过多反而使孔隙率和孔径减小。浇注温度为670℃、TiH_2添加量3%时,Al-Si熔体发泡效果最优,孔隙率可达48%。     

小孔径泡沫铝的制备及压缩性能研究

在常规熔体发泡法基础上,采用添加0.5%Mg(质量分数,下同)以降低表面张力;发泡剂400 ℃,6 h+500℃,1 h氧化预处理以协调发泡剂分散均匀性与发泡过程关系;发泡搅拌60s以破碎初始气泡等措施,成功制备出了平均孔径1.3 mm、孔隙率70.5%、结构均匀的小孔径泡沫铝.泡沫铝及Al-9Si泡沫的压缩性能分析表明,随平均孔径减小,泡沫铝的屈服强度、致密化应变和能量吸收能力均明显提高,泡沫铝压缩性能随孔径减小而提高,与泡沫铝的孔结构因素及孔结构均匀性有关.     

通孔多孔铝的压缩性能研究

在采用复模铸造工艺制备孔径d=2.5~3.50 mm,孔隙率P=56.8%~86.1%通孔多孔铝的基础上,通过单轴压缩试验,研究了通孔多孔铝的压缩性能和吸能能力。通孔多孔铝单轴压缩应力-应变曲线,呈现线弹性变形、平缓塑性变形和压缩紧实3个阶段。通孔泡沫铝的压缩屈服强度、吸能能力随孔隙率增大而减小,采用Gibson-Ashby的模型拟合通孔多孔铝的压缩屈服强度。     

温度对PCM法制备大尺寸泡沫铝的影响

在对静态PCM法制备泡沫铝的研究基础上,设计出动态制备大尺寸泡沫铝的实验装置,通过调整温度来控制预制体的发泡。研究了两种不同牵引速度（0.496 mm/s、0.687 mm/s）下预制体的发泡过程,研究发现：所得大尺寸泡沫铝孔结构质量（通过孔隙率、当量圆直径来衡量）随着发泡温度升高而提高,当温度超过800℃（v=0.496 mm/s）、820℃（v=0.687 mm/s）时,泡沫铝孔结构质量反而会下降。同时对其影响机理进行了分析。当牵引速度为0.496 mm/s时,发泡温度在780℃～800℃时,可以获得孔隙率在70%以上,孔径在2.75 mm左右,孔结构圆形度在0.68以上的大尺寸泡沫铝;当牵引速度为0.687 mm/s时,发泡温度在800℃～820℃时,可以获得孔隙率在65%～70%,孔径在2.5 mm左右,孔结构圆形度在0.67以上的大尺寸泡沫铝。     

渗流法制备高孔隙率多孔铝

采用负压渗流铸造法,通过控制铝熔体浇铸量,制备了高孔隙率(70%～90%)、高通孔度(25%～50%)的多孔铝;研究了渗流驱动压力、铝熔体浇铸温度及模具预热温度对渗流过程的影响;测试了多孔铝的渗透系数,并分析了孔结构对渗透系数的影响.结果表明:通过正交实验选择渗流参数,可以降低多孔铝在渗流方向上的孔隙率梯度;多孔铝的渗透系数与其孔结构密切相关:对于相同孔径的多孔铝,渗透系数随孔隙率增大而提高;在孔隙率相同的条件下,随着孔径增大,表面积减小,摩擦阻力减小,渗透系数相应增大.     

塑性中孔隙率通孔多孔铝的压缩性能研究

在采用熔模铸造工艺制备孔径d=2.5~3.5mm和d=3.8~4.3mm,孔隙率P=56.8%~86.6%的通孔多孔铝基础上,通过单轴压缩试验,研究通孔多孔铝的压缩性能和吸能能力。通孔多孔铝单轴压缩应力应变曲线,呈现线弹性变形、塑性平台段、压缩紧实阶段3个阶段;通孔泡沫铝的压缩屈服强度、吸能能力随着孔隙率增大而减小,采用Gibson-Ashby的模型拟合通孔多孔铝的压缩屈服强度。     

采用新型发泡剂制备泡沫铝

研究了一种在泡沫铝制备过程中可替代TiH2及ZrH2类发泡剂的新型发泡粉末的热分解行为,探讨该新型发泡剂加入量及发泡温度等因素对泡沫铝孔隙率的影响。研究表明:该新型发泡材料具有分解温度范围宽及分解过程缓慢的特点。当采用该发泡剂时,泡沫铝制备过程无需额外加入金属Ca类增粘剂;随发泡温度的升高,泡沫铝的孔隙率先升高后下降;随发泡剂量的增多,发泡体中的无泡层逐渐减少,当发泡剂的加入量在1.40%以上时,发泡体中的无泡层消失;在发泡温度740℃、发泡剂加入量1.40%~2.20%、搅拌时间3min、保温发泡时间5min的条件下,可以制备出孔径2~5mm,孔隙率60%~80%,孔隙基本均匀且无实心体的泡沫铝。     

盐球渗透铸造法制备开孔泡沫铝的孔结构及压缩性能

使用圆盘造粒机制备近球形的NaCl颗粒,并将其用于渗透铸造制备开孔泡沫铝。盐球的平均抗压缩强度为3.9 MPa,在超声波清洗机中可在5 min内完全塌陷。通过控制热压烧结时间为0.5～2 h,热压温度700℃,可制备堆积密度在0.66～0.83 g/cm³的预制体。延长热压烧结时间会使开孔泡沫铝的孔径从0.48 mm增加到1.16 mm,孔隙率从64%增加到82%。压缩实验结果表明,不同孔隙结构下泡沫体的宏观变形特征基本相同,均表现出逐层塌陷的变形特征。此外,泡沫铝的致密化应变值、弹性模量、平台屈服应力和能量吸收能力均随着孔隙率的增加而降低。当孔隙率为64%时,能量吸收能力最大(15.0 MJ·m^-3)。     

CaCl2作为造孔剂制备泡沫青铜的结构和力学性能

以青铜粉为原料、CaCl_2为造孔剂,采用粉末烧结溶解法制备开孔泡沫青铜。通过改变造孔剂体积分数和粒径成功制备出孔隙率为70%~90%,孔径1~3mm的泡沫青铜试样。研究了孔隙率和造孔剂的关系以及孔隙率、孔径对泡沫试样力学性能的影响,并对其孔结构,相组成和微观形貌进行观察和分析。结果表明:泡沫青铜试样的塑性屈服平台应力随孔隙率增加而减小,当孔隙率为77%~89%时,对应塑性屈服平台应力为12.6~2.6MPa。当应变量为50%时,孔隙率为77%~89%的泡沫青铜单位体积能量吸收值(W)范围为6.21~0.91MJ/m~3。试样的理想吸能效率(I)都接近0.82,说明泡沫青铜可以作为一种理想的吸能材料。     

氢化锆熔体发泡法制备小孔径泡沫铝

以ZrH_2为发泡剂,采用熔体发泡法制备铝基小孔径泡沫铝,分析其制备过程及影响孔结构的因素;优化实验室制备泡沫铝的工艺条件;借助图形分析方法表征泡沫铝的孔径分布,并与TiH_2制备的泡沫铝进行了对比;采用改进座滴装置研究铝合金与氢化物的润湿行为.结果表明:ZrH_2较适合制备小孔径泡沫铝;优化工艺条件为:Al 650 g,增粘剂Ca 的加入量2.5%,发泡剂ZrH_2的加入量1.0%,发泡温度680 ℃,搅拌时间1.5 min,保温时间2.5 min;制备的泡沫铝孔径均匀,平均孔径小于1.5 mm;ZrH_2在铝合金中的润湿特点是导致泡沫铝孔径较小的主要原因.     

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