超载发生频率对A537钢疲劳裂纹扩展的影响

拉伸超载叠加在常幅循环载荷上会导致疲劳裂纹减速扩展，出现超载阻滞效应．它是载荷交互作用研究中的一个基本内容，也是变幅载荷谱下工程构件寿命预测中不可回避的问题．近年来，人们在单次拉伸超载效应研究上开展了大量的工作，研究了超载比n“’、应力比R’“以及常幅应力强度因子AKb。se”’等力学因素对它的影响．但是，对有关间歇超载的系统研究报道较少，有限的工作都是在航空材料铝合金上进行卜’，而铝合金的延迟机制与钢相比有较大差别．单次拉伸超载裂纹扩展的阻滞效应是超载与常幅载荷之间作用的结果，而间歇超载除了超载与…     

超载对X52管线钢疲劳裂纹扩展速率的影响

用紧凑拉伸试样研究了不同应力比和超载比对X52管线钢疲劳裂纹扩展速率的影响,并对疲劳断口形貌进行SEM分析.结果表明,拉伸超载有阻滞X52钢疲劳裂纹扩展的作用,使疲劳裂纹扩展由超载扩展,减速扩展和恢复扩展三个阶段组成.在恒定的应力比下,超载比越大,裂纹扩展的阻滞效应也越明显.超载前后形貌差别越大;在恒定超载比下,低应力比的裂纹扩展阻滞现象更明显.     

3.5%NaCl中阴极极化下A537钢间歇超载疲劳断品分析

测量了Ａ５３７钢在３．５％ＮａＣｌ中阴极极化条件和不同间歇超载发生频率下疲劳裂纹扩展曲线,并利用扫描电子显微镜对腐蚀疲劳断口进行观察,结果表明：超载对裂纹扩展速度及断口特征的影响取超载发生频率。当超越发生频率ＯＣＲ＝１０＾－１,１０＾－２时,间歇超载加速裂纹扩展,腐蚀疲劳断口只存在解理、沿晶等一般脆性特征：当ＯＣＲ＝１０＾－３,２×１０＾－４,１０＾－４时,间歇超载对裂纹扩展存在阻滞效应,Ａ５３７     

3.5%NaCl中阴极极化下A537钢间歇超载疲劳断口分析

测量了A537钢在3．5％NaCl中阴极极化条件和不同间歇超载发生频率下的疲劳裂纹扩展曲线,并利用扫描电子显微镜对腐蚀疲劳断口进行了观察结果表明：超载对裂纹扩展速率及断口特征的影响取决于超载发生频率．当超载发生频率OCR＝10(-1),10(-2)时,间歇超载加速裂纹扩展,腐蚀疲劳断口只存在解理、沿晶等一般脆性特征;当OCR＝10(－3),2×10(－4),10(－4)时,间歇超载对裂纹扩展存在阻滞效应,A537钢断口上能观察到铁素体、珠光体两种组织,且阻滞效应越大,两种组织越清晰．分析表明,这种断口形态的形成是氢在组织界面附近大量富集而使界面强度降低,铁素体、珠光体以不同方式开裂的结果．     

300M钢腐蚀疲劳裂纹萌生的超载特性

本文对３００Ｍ钢在空气与３．５％ＮａＣｌ溶液中疲劳裂纹萌生的周期超载和单次超载特性进行了试验研究与理论分析。试验结果表明，３．５％ＮａＣｌ溶液中，单次超载所致腐蚀疲劳裂纹迟滞萌生的迟滞强度远小于周期超载的对应值。３．５％ＮａＣｌ溶液与空气中，超载迟滞强度均随超载比增大或等效应力幅水平的提高而增大，在腐蚀疲劳裂纹萌生寿命估算中，只考虑单次超载的迟滞规律，会得出大大保守的寿命估计，只有将单次超载和周期     

腐蚀疲劳过程中载荷间交互作用的研究

介绍了近年来进行了Ａ５３７钢在３．５％ＮａＣｌ水溶液中阴极溶解与阴极充氢条件 下腐蚀疲劳裂纺扩展中载荷交互作用方面的一些研究结果。其中包括恒△Ｋ控制下的单周超载延迟作用, 裂纹扩展率的波型响应以及小幅载荷的幅度与相对主载荷的位置对裂纹扩展的影响规律等。     

NaNO2对A537钢在盐水中腐蚀疲劳的缓蚀作用

利用平板及单边裂纹试样研究了１％ＮａＮＯ２对Ａ５３７钢在３．５％ＮａＣｌ水溶液中腐蚀疲劳寿命与裂纹扩展的缓蚀作用，并在不同应变速率与外加电位下研究了相应体系圆柱形应变电极的电化学响应规律．结果表明，ＮａＮＯ２对裂纹萌生过程具有抑制作用，从而提高腐蚀疲劳寿命．即使在阴极极化条件下，动态应变的一定阶段仍可有较大的阳极溶解电流密度，这显示了ＮａＮＯ２对裂纹扩展过程作用的复杂性．分析表明，ＮａＮＯ２存在的情况下，形变引起的附加阳极电流密度除受到形变速率与新表面再钝化速率控制外，还强烈地受到表面滑移状态的影响．     

腐蚀疲劳裂纹扩展的机理

针对高强度低合金钢、钛合金和镁合金进行了腐蚀疲劳裂纹的扩展FCG、外加电压对于腐蚀疲劳裂纹扩展速率的影响以及断裂表面的研究。在外加电压对于腐蚀疲劳裂纹扩展速率影响的研究过程中,在一段时间内发生极化,可以根据此期间内的开路电压记录裂纹扩展速率,并测量极化情况下的裂纹增长速率。由于裂纹扩展测量技术的进步,测量的时间很少超过300s,这使观测非独立模式阴极极化对于腐蚀疲劳裂纹扩展速率的影响成为可能。当最大应力强度（Kmax）超过给定材料--溶液组合的特定临界特征值时,阴极极化会加速裂纹的扩展。当Kmax低于临界值,而所有其他条件（试件、溶液、pH值、载荷频率、应力比率、温度等）不变时,同样的阴极极化会妨碍裂纹扩展,或者对于裂纹扩展无影响。断口显微分析结果显示,阴极极化下加速裂纹的扩展是由于氢致腐蚀(HIC)。因此,根据氢致腐蚀机理以及KHIC和△ KHIC的显示,Kmax的临界值,以及应力范围（△ K）是由相应的腐蚀疲劳裂纹扩展的症状所确定的。当Kmax > KHIC（△ K > △ KHIC）时,腐蚀疲劳裂纹扩展的主要机理是HIC。对于大多数的材料--溶液组合的研究表明,当Kmax < KHIC（△ K < KHIC）时,应力协助扩散在腐蚀疲劳裂纹扩展中起决定性作用。     

超载对压铸镁合金AZ91HP的疲芝裂纹扩展速率的影响

就镁合金压铸件在变载条件下的疲劳性能,研究了经过时效处理的压铸镁合金ＡＺ９１ＨＰ在不同超载情况下的疲劳裂纹扩展行为及裂纹扩展的机理。发现不同超载方式对裂纹扩展速率的影响不同,拉伸、拉伸－压缩超载可延缓裂纹扩展,压缩,压缩－拉伸超载可稍提高裂纹扩展速率或使裂纹扩展速率不变。     

波型与电位对A537钢疲劳裂纹扩展的影响

研究了A537钢在3.5%NaCl水溶液中阴极极化与阳极极化条件下加载波型对疲劳裂纹扩展速率的影响并研究了相应电位条件下应变电极的电化学响应规律,结果表明,在外加电位为-800mV(SCE)以上时阳极溶解机制起主导作用,在-800mV以下时氢脆机制起主导作用,在阳极极化条件下,持续应变型加载波型的影响主要体现于低△K范围,而在阴极极化条件下,其影响体现于高△K范围,持续应变导致了自腐蚀电位的下降与阳极溶解电流密度的大幅度提高     

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