表面涂层对奥贝球铁水脆化行为的影响

水附着拉伸试验中,试样表面附着的水在试样塑性变形时分解出氢使奥贝球铁(ADI)产生氢脆,抗拉强度和伸长率显著下降,发生明显的水脆化现象.试样表面镀锡使ADI的抗拉强度和伸长率下降,镀锡层不能有效防止ADI的水脆化.聚乙烯涂覆能降低ADI的水脆化程度,而环氧树脂和尼龙涂覆无防止ADI水脆化的效果.     

石墨直径对等温淬火球铁水脆化行为的影响

研究石墨直径对等温淬火球铁(ADI)水脆化的影响。水附着条件下不同石墨直径的ADI均发生抗拉强度和伸长率显著降低的脆化行为，但随石墨直径的减小，ADI的水脆化程度明显降低。ADI水脆化是由于水分解的氢使ADI基体组织中的应力诱变产生马氏体引起氢脆而导致的。细化石墨可减少共晶边界的未转变残余奥氏体量，减少拉伸变形时的应力诱变马氏体，从而抑制ADI的水脆化。     

等温淬火温度对奥贝球铁水脆化行为的影响

研究了等温淬火温度对奥贝球铁(ADI)水脆化行为的影响，水附着条件下不同等温淬火温度处理的ADI均发生水脆化行为，抗拉强度和伸长率显著降低；但随着等温淬火温度升高，ADI的水脆化程度降低。高强度的ADI、淬火回火球铁和珠光体球铁均发生水脆化行为，而铁素体含量高的铸态球铁和铁素体球铁无明显的水脆化行为。     

受腐蚀亚共析铀铌合金的力学性能研究

利用加速腐蚀实验方法研究了腐蚀对一种亚共析铀铌合金拉伸性能的影响,并用SEM和EDS对拉伸试样的组织结构、成分、表面形貌和断口形貌进行了分析.腐蚀实验表明:随着腐蚀时间的增加,拉伸试样表面的腐蚀程度加剧,经过约180 d的腐蚀后,试样表面形成了腐蚀斑,其大小为50μm左右;力学拉伸测试表明:在实验范围内,合金的屈服强度和抗拉强度无明显变化,而试样的延伸率及断面收缩率则有下降的趋势.断口形貌表明,合金在实验范围内腐蚀后,其断裂方式仍以韧性断裂为主.此外,对引起合金力学性能变化的主要因素也进行了探讨.     

水附着状态下奥贝球铁的拉伸性能及断裂机制

研究结果表明,水附着状态下,奥贝球铁的抗拉强度和伸长率显著降低,发生明显的脆化现象。特别是在工艺窗口内等温淬火处理的试样脆化更显著。经断口分析发现,这种脆化现象是水附着拉伸试样在塑性交形初期。表面附近产生了脆性断裂区域,作为试样破坏的起点,导致试样早期断裂而造成的。     

预形变及模拟压水堆一回路水中预浸泡对690合金拉伸性能的影响

研究了预充氢和模拟压水堆核电站一回路水中预浸泡对有、无经过20%轧制冷加工690合金拉伸性能的影响。室温下空气中拉伸试验结果表明,冷加工显著提升690合金的抗拉强度并降低延伸率和断面收缩率;预充氢显著降低有、无冷加工690合金的延伸率和断面收缩率,并且降低冷加工690合金的抗拉强度;高温水中预浸泡对未冷加工690合金的拉伸性能有一定影响。320℃高温水中测得的抗拉强度、延伸率和断面收缩率均低于室温时的值;高温水中预浸泡对抗拉强度和延伸率的影响不大,使断面收缩率略有增大。     

超细晶Cu-Cr-Zr合金的高温拉伸性能及断裂机制

研究了2种变形处理方式下的超细晶Cu-Cr-Zr合金从室温到600℃的拉伸性能、断口微观组织特征及其断裂机制.结果表明:经4道次等径弯曲通道挤压(ECAP)+时效+4道次ECAP变形处理的合金(No.1试样)的抗拉强度随拉伸温度的升高而降低,室温时,合金抗拉强度为577.17 MPa,延伸率为14.6%;在300℃开始发生动态再结晶软化,抗拉强度迅速减小,到600℃时抗拉强度仅为59.12 MPa.经过8道次ECAP+时效变形处理的合金(No.2试样),室温抗拉强度为636.71 MPa,延伸率为12.1%;从400℃开始析出相对晶界的钉扎作用开始逐渐减弱,抗拉强度大幅降低,600℃时的抗拉强度为65.20 MPa.No.2试样比No.1试样具有更好的室温性能和热稳定性.2种方式处理下合金延伸率随拉伸温度的升高而升高,在高温下都表现出超塑性.高温拉伸断口微观形貌为大量密集、深入的韧窝,其高温断裂机制为微孔聚集的韧性断裂.     

中国低活化马氏体钢在液态Pb-Bi中的脆化现象

为了评价反应堆候选结构材料与液态金属的相容性,针对低活化马氏体钢在液态Pb-Bi共晶中的拉伸脆化现象,采用2种拉伸速率的拉伸实验,研究了中国低活化马氏体钢(CLAM)在200~500℃范围内的Ar气和液态Pb-Bi共晶环境中的拉伸断裂行为。结果表明,在Ar气环境中拉伸时,CLAM钢均为韧性断裂;而在液态Pb-Bi共晶环境中拉伸时,在300~450℃下会出现脆性断裂现象。在300~450℃脆化温度区间内试样强度变化不大,但总延伸率显著降低,出现"韧谷"现象。然而拉伸温度在低于或高于脆化温度区间时,脆断现象消失,总延伸率回复到与对比试样相同水平。在更低的拉伸速率下,CLAM钢发生"韧谷"现象的温度区间明显扩大,表明拉伸速率对CLAM钢在液态Pb-Bi共晶中的脆化也有影响。经低温回火硬化后,CLAM钢在液态PbBi共晶中出现拉伸脆化现象是由于液态Pb-Bi接触裂纹尖端后造成表面能降低,进而降低临界解理应力而发生脆性断裂。     

L80钢在CO2/H2S腐蚀环境中的力学特性

目的：研究L80钢在CO2/H2S环境中的力学特性。方法利用微机控制慢应变速率拉伸试验机,对特定腐蚀条件下的L80钢试样进行拉伸实验,分析各因素对L80钢力学特性的影响变化规律。结果在CO2/H2S环境中,随着含水率的增加,L80钢的屈服强度、抗拉强度、延伸率均下降,L80钢拉伸曲线出现劣化。随预拉应力的增大,L80钢的屈服强度变化不明显,而抗拉强度和延伸率降低,当预拉应力超过0.8σs时,L80钢的腐蚀速率显著增加,表现出较强的应力腐蚀敏感性;随着H2S分压的增加, L80钢的力学性能发生劣化,表现出氢脆敏感性,而受CO2分压的影响不明显;温度升高导致L80钢的拉伸曲线出现了轻度劣化,延伸率和屈服区宽度小幅降低,但抗拉强度变化不大。结论 L80钢在CO2/H2S环境中的力学特性受温度、CO2分压影响程度小。含水率和预拉应力的增大降低了L80钢的力学韧性,预拉应力的存在使L80腐蚀速率加快,缩短了耐腐蚀寿命。L80钢的力学性能对于H2S分压较对CO2分压更为敏感,试样的断裂是机械拉力和应力腐蚀共同作用的结果。     

Effect of Friction Stir Processing on Microstructure and Mechanical Properties of Cast AZ31 Magnesium Alloy

对铸态AZ31镁合金进行单道次和双道次搅拌摩擦加工,对其微观组织和力学性能进行研究.结果表明:铸态AZ31镁合金搅拌摩擦加工后,共晶网状β-Mg17Al12相破碎并发生固溶,微观组织显著细化和均匀化.AZ31镁合金母材和单道次搅拌摩擦加工后的试样没有择优取向,而双道次搅拌摩擦加工后的试样存在择优取向,其(0002)基平面与试样表面平行.单道次和双道次搅拌摩擦加工后试样的抗拉强度分别提高了43和82MPa,延伸率提高了4.3％和11.9％.搅拌摩擦加工后试样的拉伸断口表现为韧性断裂特征.     

25钢在热带海洋环境下海水中的微生物腐蚀及其对力学性能的影响

通过对比25钢在热带海洋环境下自然海水和无菌海水中的平均腐蚀深度,研究微生物对碳钢腐蚀行为的影响。结果表明,海水中微生物的存在显著影响碳钢的平均腐蚀深度。浸泡时间为365 d时,在自然海水中的腐蚀深度为无菌海水中的2.6倍,产生了明显的局部腐蚀。无菌海水和自然海水腐蚀都会造成材料抗拉强度的下降,对比发现腐蚀时间较长时自然海水中材料抗拉强度下降更大,说明微生物腐蚀对材料抗拉强度有一定影响。微生物腐蚀对材料抗拉强度的影响作用,主要在于微生物的存在使材料的平均腐蚀深度增大,引起材料横截面积的减小。微生物腐蚀并不会降低退火25钢的延伸率和夏比冲击功,实验过程中未发现微生物作用下材料的氢脆现象。     

Potentialabhängigkeit der Schwingungsrißkorrosion von höherfestem Dalbenstahl in Salzwässern

Potential dependence of the corrosion fatigue of high strength sheet piling steel in salt water Cathodic protection of high strength steel, grade X 65, against corrosion fatigue (25 Hz) is not effective in seawater. An influence of hydrogen is assumed because hydrogen embrittlement occurs at slow strain-rates (not a constant load) under the condition of cathodic hydrogen evolution. The potential dependency of corrosion fatigue at 5 Hz was investigated with notched and smooth electropolished tensile specimens. The notched specimens showed a slight decrease of the number of cycles to failure with decreasing potential. The polished smooth specimens displayed cathodic protection. The results of the investigation can be explained by recent publications as an participation of hydrogen embrittlement, which happens only at critical strain rates and is dependent on the amount of straining, the frequency and the surface of the specimen.     

氢对铜的电化学行为和应力腐蚀的影响

纯铜充氢后并不改变组织结构和晶粒大小而且抗拉强度、伸长率和面缩率也不变化，这表明铜没有氢脆，在ＮａＮＯ＿２溶液中，氢使纯铜电位降低，使应力腐蚀开裂敏感性升高，但断口形貌不发生变化。     

Effect of Immersion Time on the Mechanical Properties of S135 Drill Pipe Immersed in H2S Solution

During drilling process, if oil and gas overflow containing H₂S enters drilling fluids, the performance of drill pipes will decline significantly within a short time. In this paper, S135 drill pipe specimen was immersed in the saturated solution of H₂S at room temperature for 6, 12, 18, and 24 h, respectively. The tensile properties and impact properties of S135 drill pipe were determined before and after immersion for comparison. In addition, the S135 specimens were immersed for 3 days at 80 °C to determine the changes in fatigue performance. The test results indicated that the yield strength of S135 material fluctuated with immersion time increasing and the tensile strength slightly varied with immersion time. But the plasticity index of S135 decreased significantly with the increase in immersion time. The impact energy of S135 steel also fluctuated with the increase in immersion time. After 3-day immersion at 80 °C, the fatigue properties of S135 steel decreased, and fatigue life showed the one order of magnitude difference under the same stress conditions. Moreover, fatigue strength was also decreased by about 10%. The study can guide security management of S135 drill pipe under the working conditions with oil and gas overflow containing H₂S, reduce drilling tool failures, and provide technical support for drilling safety.     

The Determination of the Porosity of Electro Deposits

Newly developed steels with tensile strength of up to 150 Ions p.s.i. are shown to fail by embrittlement under constant load, well below their nominal ultimate strength. This effect is usually attributed to hydrogen embrittlement. The paper describes a programme of tests on one specific type of ultra-high tensile steel. Small specimens (tensometer No. 12), notched in their centre, are subjected to constant stress in specially designed rigs. Various types of electrolytic or vapour-deposited coatings are applied to the specimens. The tests are conducted in non-corrosive or corrosive conditions. It is concluded that with stresses of the order of 80% of fracture strength, specimens electroplated with cadmium generally fail in 10–100 hr in the absence of corrosion, whilst zinc vapour-coated specimens do not appear to be sensitive to delayed fracture. Nickel-chromium plated specimens give inconsistent results, whilst nickel-plating usually behaves in much the same way as zinc vapour- coated specimens.

If a corrosive agent, such as 3% sodium chloride spray, is applied, rapid failure of uncoated and coated specimens takes place at stresses of approximately 70% of the notched fracture strength. Of the metal coatings, cadmium-plated specimens are most sensitive, nickel-plated specimens the most resistant; hard silicone lacquer show the best results. There is evidence that failure is related to the mechanism of corrosion reaction rather than to the extent of corrosion. Other corrosive agents, such as tap water or solutions of ammonium carbonate, do not cause this accelerated failure even if severe corrosion takes place.     

聚脲涂层的耐酸、碱、盐腐蚀试验及结果

采用海水浸泡、盐雾试验、硫酸浸泡和氢氧化钠浸泡腐蚀等方法,研究了聚脲涂层的耐腐蚀性能,并采用扫描电镜(SEM)观察了涂层老化后的表面形貌.结果表明,海水浸泡180天后,聚脲涂层的拉伸强度仅下降4%,断裂伸长率增加了1.2%.盐雾试验180天后涂层拉伸强度下降了25.7%,断裂伸长率增加了4.2%,涂层表面局部有孔洞,涂...