共查询到19条相似文献,搜索用时 154 毫秒
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晶粒尺寸对GH720Li镍基合金蠕变-疲劳寿命的影响 总被引:1,自引:0,他引:1
胡殿印 《稀有金属材料与工程》2018,47(8):2386-2391
为探明晶粒尺寸对涡轮盘材料—GH720Li镍基高温合金的蠕变-疲劳寿命的影响机理,开展了650℃下不同晶粒尺寸的GH720Li高温合金圆棒蠕变-疲劳试验研究。GH720Li高温合金的蠕变-疲劳寿命随着晶粒尺寸的减小而降低。而后,通过断口的SEM分析研究晶粒尺寸对GH720Li高温合金的蠕变-疲劳损伤影响机制。其失效机制主要为晶界的氧化起裂,而晶界长度随晶粒尺寸变小而增加。最后,对基于迟滞能量的损伤方程和机械功密度2种方法进行了修正,GH720Li合金的蠕变-疲劳寿命预测与试验结果吻合较好,验证了方法的准确性。 相似文献
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晶粒尺寸与保载载荷对Cu膜纳米压入蠕变性能的影响 总被引:1,自引:0,他引:1
利用纳米压入仪对Si片上的多晶Cu膜进行压入蠕变研究.实验结果显示晶粒尺寸大于200nm时,应力指数对晶粒尺寸不敏感.当晶粒尺寸小于200nm时,因压头底部更多的晶粒参与变形,应力指数随晶粒尺寸的降低而增大.认为薄膜材料存在一个对应力指数不敏感的最小If缶界晶粒尺寸ιc,Cu膜的应力指数随保载载荷增大而增大,其主要原因在于高载荷下位错强化机制使蠕变率降低。 相似文献
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钛镁合金的汽相淬火工艺 总被引:2,自引:0,他引:2
在总结超塑变形二维晶粒重排模型基础上,研究了超塑变形三维晶粒重排。金相观察表明:1号铝锂合金板状试样宽度方向边层微细晶粒填入了中心层大晶粒在拉伸方向产生的空洞而实现晶粒重排。通过扫描电镜观察了晶粒涌出及2号名锂合金中大Al3Zr相在变形时的转动情况。研究表明,微细晶粒是通过晶粒转动填入空洞的,该过程是一个能量降低的过程。宽度方向微细晶粒的运动解释了超塑变形的试样宽度尺寸的减小及试样板边缘局部颈缩迁 相似文献
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为研究纳米压痕过程中晶粒尺寸对γ-TiAl合金力学性能及变形行为的影响,利用Voronoi方法建立多晶γ-TiAl模型,采用分子动力学方法模拟压头压入不同晶粒尺寸模型的压痕过程,得到相应尺寸下的载荷-深度曲线,并计算了7种晶粒尺寸下γ-TiAl的硬度。结果表明:当晶粒尺寸小于9.9nm时,晶粒尺寸与硬度表现出反Hall-Petch关系,位错和晶界活动共同促使材料发生塑性变形,晶界活动起主导作用。当晶粒尺寸大于9.9nm时,晶粒尺寸与硬度符合Hall-Petch关系,晶界对材料变形影响较小,位错主导基体发生塑性变形。另外,分析了γ-TiAl在压痕过程中的应力传递和形变恢复过程,发现致密晶界网格结构能够有效抑制压痕缺陷及内应力向材料内部传递;晶粒尺寸越小,压头下方的内应力分布越均匀,沿压痕方向的弹性恢复比越小。 相似文献
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基于镍基单晶合金蠕变过程中的细、微观组织结构变化及损伤特点,本文建立了考虑材质劣化和空洞损伤的双参数蠕变损伤本构方程及寿命预测模型。利用DD3单晶材料〈001〉晶体取向的760,850和1000℃实验结果考核表明,所建模型可以比较准确地预测蠕变第二、第三阶段变形状态及破坏特征。第二阶段持续时间、第三阶段开始时间可以表示成蠕变应力的指数函数;随着温度的升高,材料劣化加剧,空洞损伤也增加。 相似文献
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结合多态相场(MSPF)模型与晶体畸变模型,获得变形镁合金初始变形晶粒组织以及合金内部的非均匀储存能分布,计算模拟不同退火温度条件下的再结晶形核和晶粒长大的微观演化过程,分析退火温度对再结晶晶粒长大和晶粒尺寸的影响,对比不同时刻的再结晶晶粒分布特征。结果表明:在相同的变形条件下,位错密度高的区域,如晶界附近,储存能较高,再结晶形核最先在高储存能区域出现,并通过合并与吞噬机制长大;而在变形晶粒内部,储存能较低且分布相对均匀,再结晶过程中形核长大较慢。不同退火温度下晶粒尺寸权重概率的分布表明:低温下会出现双峰结构和异常晶粒长大现象;高温下晶粒长大较快,晶粒尺寸分布向大尺寸方向变化且趋于均匀。 相似文献
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以云纹法和光学滤波技术为主,从细观尺寸对多晶体大晶粒的受力变形状态进行了测量,并观测到晶体的变形、晶界位错、滑移、晶粒之间的转移等现象.对位于三晶粒交界的裂纹尖端附近区域的微空洞萌生、长大和裂纹扩展的规律进行分析与研究.该实验结果为细观塑性理论的研究提供了重要的实验依据. 相似文献
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Yo Seob Lee Dae Whan Kim Dok Yol Lee Woo Seog Ryu 《Metals and Materials International》2001,7(2):107-114
The effect of grain size on creep properties of type 316LN stainless steel has been investigated at 600°C under different
stresses. The initial strain at the beginning of creep tests decreased with the decrease of grain size. This was confirmed
by the Hall-Petch relationship. The steady state creep rate decreased to a minimum value at the intermediate grain size (dm=80–130 μm) and then increased with the further increase of grain size. This result agreed with Garofalo's model stating that
grain boundaries act simultaneously as both dislocation sources and barriers to dislocation movement. The rupture elongation
at the intermediate grain size was minimal due to the cavity formed easily by carbide precipitates in the grain boundaries. 相似文献
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High-temperature creep properties of sintered uranium dioxide pellets with two grain sizes(9.0μm and 23.8μm)were studied.The results indicate that the creep rate becomes a little faster with the reduction of the uranium dioxide grain size at the same temperature and the same load.At the same temperature,the logarithmic value of the steady creep rate vs stress has linear relation, and with increasing load,the steady creep rate of the sintered uranium dioxide pellet increases.Under the same load,the steady cr... 相似文献
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Astroloy合金中弯曲晶界显著改善了材料的蠕变持久塑性和蠕变裂纹生长抗力。通过尖切口根处蠕变裂纹形成寿命分析与试验比较,证实蠕变J~*积分是控制尖切口(和裂纹)场的有效参量。据此由线性损伤模型和HRR奇异性结合,导出与直晶和弯晶试验结果吻合良好的蠕变裂纹扩展速率表达式: da/dt=Be~(k/n+1)D(x_0)J~(*kn/n+1) 从晶界孔洞形成角度讨论了弯曲晶界蠕变损伤的微观机制。 相似文献
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M. Chang A. K. Koul P. Au T. Terada 《Journal of Materials Engineering and Performance》1994,3(3):356-366
The influence of a modified heat treatment (MHT) and the standard heat treatment (SHT) on the damage tolerance of alloy 718
turbine disk material has been studied over a range of temperatures— from room temperature to 650 °. The influence of these
heat treatments on creep, low-cycle fatigue (LCF), notch sensitivity, cyclic stability, and fatigue crack growth rate (FCGR)
properties has been studied. The microstructure developed through the MHT sequence is shown to be damage tolerant over the
temperature range studied. Shot peening leads to a marked improvement in the LCF crack initiation life of the MHT material
relative to the SHT material at 650 °. Serrated grain boundaries formed through controlled precipitation of grain-boundary
5 phase are beneficial to elevated- temperature FCGRs. The S-phase precipitates formed at an angle to the grain boundaries
do not make the material notch sensitive. 相似文献
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E. Ahmad M. Sarwar Tanvir Manzoor N. Hussain 《Journal of Materials Engineering and Performance》2006,15(3):345-348
The phenomenon of grain refinement was studied in a steel containing 0.15% C, 0.32% Si, 1.4% Mn, and 0.43% V. Initial austenite
grain size was found to be 50 μm, determined by quenching the specimen in an iced brine solution from 1150 °C. Transformational
grain refinement (TGR) was applied to give a reasonable refinement in the grain size. A rolling reduction of about 67% was
given to specimens at 900 °C, which was followed by air cooling. Cold rolling and recrystallization of these specimens gave
refinement of grains down to 1 μm size was obtained. The electron backscattered diffraction (EBSD) technique was used to determine
low- and high-angle grain boundaries that are effectively used to determine the substructure contribution at various stages
of recrystallization. 相似文献
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WANG Fugang ZHU Suming ZHU Shijie REN Xiaomin TAN Yi ZHANG Junshan Dalian University of Technology Dalian China 《金属学报(英文版)》1992,5(1):48-51
Creep crack growth behavior of Fe-Cr15-Ni25 alloys with different grain boundary featureshas been studied.Cavities nucleate at triple junctions of grain boundaries for the single phasealloy and at grain boundary carbide for the alloy with grain boundary carbide.Grain bounda-ry carbide particles are obstacles to cavity growth and coalescence,and therefore increase thecreep crack growth resistance greatly. 相似文献
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The effect of grain refinement on the superplasticity of ingot-processed magnesium alloy was investigated. From the AZ61 material
with a linear intercept grain size of 5 μrn, which was obtained by the multi-rolling process at an elevated temperature, tensile
elongation over 400% could be achieved at 10-3s-1 at 400°C with a maximum value of 560% at 2x10-4s-1 at the same temperature. It was found that grain boundary diffusion controlled grain boundary sliding and pipe diffusion
controlled slip creep govern the plastic flow at low and high strain rate ranges, respectively. A deformation map for pure
magnesium was constructed to examine the effect of grain size and flow stress on deformation behavior at elevated temperature.
The superplastic formability of Mg alloys was demonstrated by forming an AZ61 sheet into a hemi-sphere. 相似文献
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ZHU Shijie Institute of Metal Research Academia Sinica Shenyang China ZHAO Jie Fushun Institute of Petrochemistry Fushun China WANG Fugang Dalian University of Technology Dalian China Institute of Metal Research Academia Sinica Shenyang 《金属学报(英文版)》1990,3(6):449-452
The influence of two different grain shapes and carbides in the HK40 alloy,the material foruse of furnace tube,on the rate of creep crack growth has been investigated.The resistance tocreep crack growth of the material with columnar grains is inferior than that with equiaxialgrains when the load line is perpendicular to the columnar grain axis.The influence of secon-dary carbide on the rate of creep crack propagation depends upon the Brain shape. 相似文献