基于人工神经网络的高精度Ti6242s合金热变形本构模型

使用Gleeble-3800对锻态Ti6242s钛合金在温度950～1010℃、应变速率0.01～10 s-1的条件下进行了75%变形量的热压缩模拟试验。基于实验取得的真应力-真应变曲线,分别使用人工神经网络(ANN)和Arrhenius方程建立Ti6242s合金本构模型,研究其热变形行为。结果表明:流变应力在变形开始后迅速上升至峰值应力,随后硬化与软化达到动态平衡,在真应变达到0.6后加工硬化逐渐占据主导,硬化幅度随应变速率的增大而提高;人工神经网络本构模型预测值的平均相对误差(AARE)为2.25%,决定系数(R2)为0.999 06;Arrhenius方程本构模型预测值的AARE为14.40%,R~2为0.954 68,精度在参数范围内波动较大;ANN本构模型精度远高于Arrhenius本构模型,且在整个参数范围内具有一致的精度;ANN本构模型具有良好的泛化能力,在实验参数范围外预测流变应力仍具有较高的精度。     

基于GA-Arrhenius本构模型的EA4T钢高温变形行为北大核心CSCD

通过Gleeble-3800热模拟实验机,对EA4T车轴钢分别在变形温度为970、1070和1170℃及应变速率为0.01、0.1和1.0 s的条件下进行热压缩实验,压缩至最大真应变为0.8。以得到的真应力-真应变实验数据为基础,分别建立了考虑应变补偿的Arrhenius本构模型和经过遗传算法优化后的Arrhenius本构模型(GA-Arrhenius),用于预测真应力与真应变的关系。为了验证GA-Arrhenius本构模型在真应力预测中的优越性,使用相关系数R、平均绝对误差AARE和均方根误差RMSE来说明其预测精度。实验结果表明:采用Arrhenius本构模型时,R=0.9970、AARE=3.4232%、RMSE=2.8773 MPa;采用GA-Arrhenius本构模型时,R=0.9982、AARE=2.6577%、RMSE=2.2110 MPa。说明相较Arrhenius本构模型,GA-Arrhenius本构模型能够更好地预测EA4T钢热成形过程中的真应力与真应变的关系,可以实现更高精度的有限元数值模拟。     

铸态GH4169合金热变形行为及三种本构模型对比

在Gleeble-1500热力模拟机上对铸态GH4169合金进行热压缩试验,变形参数为:温度(1193～1373K)、应变速率(0.01～10s~(-1))、变形量50%。通过分析真应力真应变曲线,研究铸态GH4169合金的热变形行为;对比分析了Johnson-Cook(JC)、修正的Johnson-Cook(MJC)和应变补偿Arrhenius3种本构模型的相关系数(R)和平均相对误差(AARE)。结果表明:铸态GH4169合金的流变应力随变形温度的升高和应变速率的降低而减小。JC模型、MJC模型和应变补偿的Arrhenius本构模型的相关系数(R)分别为0.891、0.956和0.961,AARE依次为29.02%、11.16%和9.31%。因此,应变补偿的Arrhenius模型能够更为精确地描述铸态GH4169的热变形行为。     

基于修正J-C和BP神经网络模型的超细晶纯钛动态本构行为

为研究超细晶纯钛在高温、高应变速率加载下的复杂力学行为,建立能够准确描述其动态力学行为的模型,对超细晶纯钛在温度为300~450 ℃,应变速率为2000~3000 s-1下进行了动态冲击实验,获得真应力-真应变曲线。结果表明：在所研究的条件下,真应力-真应变曲线均表现为明显的“双应力峰”特征,晶界处的位错湮灭、重新排列及后续绝热剪切带的形成是两次应力减小的主要因素,流动应力均表现出正应变速率敏感性和负温度敏感性。综合考虑应变硬化、应变速率硬化和热软化效应,提出一种修正J-C本构模型和BP人工神经网络模型,并对两种模型进行了准确性分析。结果表明BP人工神经网络模型能够更好地预测超细晶纯钛的动态力学行为,相关系数可达0.97065,平均相对误差仅为4.63%。     

120°模具室温ECAP制备工业纯钛的压缩变形本构关系

在Gleeble-1500热模拟机上对120°模具室温Bc方式ECAP变形8道次制备的平均晶粒尺寸约为200 nm的工业纯钛进行等温变速压缩实验,研究超细晶工业纯钛在变形温度为298~673 K和应变速率为1×10-4~1×100s-1条件下的流变应力行为。结果表明:变形温度和应变速率均对流变应力具有显著影响,峰值应力随变形温度的升高和应变速率的降低而降低;流变应力在变形初期随应变的增加而增大,出现峰值后逐渐趋于平稳,呈现稳态流变特征。采用双曲正弦模型确定了超细晶工业纯钛的变形激活能Q=104.46 kJ/mol和应力指数n=23,建立了相应的变形本构关系。     

新型钛合金Ti-555热变形行为及热加工图研究

本文通过高温热压缩试验研究Ti-555钛合金热变形过程中变形温度、应变速率对流变应力的影响,采用Arrhenius双曲正弦函数模型推导出Ti-555本构方程,并依据动态材料模型建立了ε=0.6时的热加工图。结果表明,Ti-555钛合金流变应力对应变速率和变形温度较为敏感,热变形时随变形温度升高或应变速率降低,流变应力下降。根据热加工图确定了两个热加工安全区参数为(1)变形温度为850～950 ℃、应变速率为0.6～10 s_^-1;(2)变形温度为950～1150 ℃、应变速率为0.36～0.9 s_^-1。     

低成本Ti-Al-V-Fe-O钛合金热变形行为及热加工图

通过真空非自耗熔炼炉制备了低成本Ti-6Al-2.5V-1.5Fe-0.15O合金,利用Gleeble-1500D热模拟机,研究了其热加工参数为：变形温度875℃-1100℃、应变速率0.001s_-1-1s_-1,变形量为70%时的热变形行为,建立了Ti-6Al-2.5V-1.5Fe-0.15O合金考虑应变量的Arrhenius本构方程,基于动态材料模型建立热加工图。研究结果表明：变形温度升高,应变速率降低,流变应力降低。通过本构方程计算可得两相区平均热激活能为398.824KJ/mol,远大于纯钛自激活能,表明热变形软化机制与动态再结晶有关。单相区热激活能为210.93KJ/mol,略大于纯钛自激活能,以动态回复为主。通过热加工图确定两个失稳区,中等变形温度(950℃-1070℃)高应变速率(0.31-0.1s_-1)易发生绝热剪切,结合热加工图确定适合的加工区间：应变速率为0.001-0.01s_-1,变形温度为875℃-925℃。     

复合细化超细晶工业纯钛高周疲劳性能研究

室温下,超细晶工业纯钛光滑试样在加载频率f=25 Hz、应力比R=-1的条件下进行高周应力疲劳测试,拟合超细晶工业纯钛应力幅σ_a与疲劳断裂循环周次N_f之间的关系曲线,并对疲劳断口形貌进行观察分析。结果表明：200 ℃退火60 min超细晶工业纯钛的疲劳极限值σ_-1为376.5 MP,比未退火超细晶工业纯钛的疲劳极限值提高56.5 MPa。疲劳裂纹源萌生于超细晶工业纯钛的表面, 200 ℃退火60 min超细晶工业纯钛的疲劳辉纹间距较小,疲劳裂纹不易扩展,室温疲劳性能优良。     

高强韧Ti6246合金热变形行为及应变补偿型本构模型

在温度为1123~1423 K,应变速率为0.01~10 s-1条件下,对Ti-6Al-2Sn-4Zr-6Mo(Ti6246)合金进行高温热压缩试验。研究温度、应变速率和应变对Ti6246合金高温流变应力的影响规律,建立了该合金考虑应变补偿的Arrhenius本构模型,同时获得了热激活能Q和本构模型中材料参数对应变的响应规律。将模型计算结果与热压缩试验值进行对比发现,预测结果较为准确,其相关系数(R)及平均相对误差(AARE)分别为0.9984和1.71%,表明该合金热变形过程中的流变应力可用构建的应变补偿Arrhenius本构模型来描述。     

轻轨用55Q钢的高温流变应力本构模型

通过Gleeble-3800热模拟实验机,在应变速率为0.1～20 s^-1、变形温度为900～1200℃的条件下对轻轨用55Q钢进行轴向单道次压缩实验,得到55Q钢的真应力-真应变曲线,并分析研究了不同热加工条件对55Q钢高温流变应力的影响。实验结果表明：在相同变形温度下,低应变速率时的流变应力较低,在相同应变速率下,高温时的流变应力较低,说明低应变速率和高温有利于动态软化。对流变应力、应变速率和变形温度之间的关系进行线性拟合,建立了55Q钢的修正Johnson-Cook本构模型和基于应变补偿的Arrhenius本构模型,对比两种模型发现,基于应变补偿的Arrhenius本构模型的预测精度更高,能够较好地揭示55Q钢的热变形特性。     

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