LI Da-zhao
,
et al
钢铁研究学报(英文版)
The mechanical properties of the TWIP steel subjected to impact loading at various strain rates were analyzed by the Split Pressure Hopkinson Bar. Meanwhile the microstructure of the TWIP steel fore-and-after the dynamic deformation were characterized and analyzed by optical microscopy (OM), X-ray diffraction (XRD), and transmission electron microscope (TEM). The result shows that when the TWIP steel was deformed under dynamic station, the stress, microshardness and work hardening rate increase with the increment of strain and strain rate; there exist stress fluctuation and decline of work hardening rate for adiabatic temperature rising softening. There exist many pin-like deformation twins in the microstructure of the TWIP steel subjected to impact loading, the grain size after deformation is bigger than that before; the interaction of twins with dislocation and twins with twins, especial emergence of high order deformation twins are the main strengthening mechanisms of the TWIP steel. The nucleation mechanism of deformation twins will be “rebound mechanism”; the incomplete deformation twins can be observed when the strain rate is low; when strain rate raises, deformation twins unite together; furthermore, deformation twins become denser because the nucleation rating enhancing with strain rate increasing.
关键词:
TWIP;Split Pressure Hopkinson Bar;Deformation twins;Strain rate;Work hardening
LI Da-zhao
,
WEI Ying-hui
,
HOU Li-feng
,
LIN Wan-ming
钢铁研究学报(英文版)
A nanocrystalline layer was synthesized on the surface of TWIP steel samples by surface mechanical attrition treatment (SMAT) under varying durations. Microhardness variation was examined along the depth of the deformation layer. Microstructural characteristics of the surface at the TWIP steel SMATed for 90 min were observed and analyzed by optical microscope, X-ray diffraction, transmission and high-resolution electron microscope. The results show that the orientation of austenite grains weakens, and α-martensite transformation occurs during SMAT. During the process of SMAT, the deformation twins generate and divide the austenite grains firstly; then α-martensite transformation occurs beside and between the twin bundles; after that the martensite and austenite grains rotate to accommodate deformation, and the orientations of martensite and between martensite and residual austenite increase; lastly the randomly oriented and uniform-sized nanocrystalline layers are formed under continuous deformation.
关键词:
SMAT technology
,
twinning
,
stacking fault energy
,
deformation twin
余万华
,
高山
,
刘飞
,
刘力哲
,
孙理
,
刘澄
材料热处理学报
对80级帘线钢C82DA和90级帘线钢C92DA化学成分进行检测,分析化学成分中合金元素差异对其相变的影响.采用光学显微镜、扫描电镜(SEM)、热膨胀仪和显微硬度仪,对比研究C82DA和C92DA的相变规律;相同热处理条件下的相变点、显微组织、珠光体片层间距;以及通过等温转变实验得到的相变动力学方程,并对参数n值和k值关系进行对比.结果表明:C92DA钢中的C、Si、Cr含量要高于C82DA,因此C92DA的片层间距要比C82DA细密,C92DA的n值要比C82DA大.这些结果对制定生产工艺和构建在线质量预报模型提供了基础数据.
关键词:
帘线钢
,
高碳钢
,
冷速
,
显微组织
,
相变模型
Materials Transactions
Effects of phosphorus microalloying on the microstructure and mechanical properties of direct-aging DA761 alloy have been studied. The aim of this work is to find a new way to develop a higher performance of wrought superalloy. The optimum addition of phosphorus in DA761 alloy is determined by investigating effects of phosphorus and boron on the microstructure and properties of DA761 alloy, that are compared to GH761 alloy treated by standard heat treatment. The stability of microstructure and properties of fine-grain DA761 alloy with optimum content of phosphorus is proved by studying the evolution of microstructure and properties of the alloy after long-term high temperature ageing. The practicability of phosphorus microalloying in improving the mechanical properties of DA761 alloy is verified by smelting a 500 kg ingot and detecting the microstructure and properties of billet near the size of engine disk. The results verify the phosphorus microalloying and fine-grain direct aging treatment in improving commercial GH761 alloy. Mechanism of phosphorus microalloying is also discussed. [doi: 10.2320/matertrans.MF200908]
关键词:
phosphorus;GH761 alloy;fine-grain treatment;mechanical property;trace-elements
陈篪
金属学报
本文证明我们所建议的关系: (da/dN)-C[(△K)~2-K_2~2/K_1~2-(△K)~2]~p能够很好地表达R=(K_(min)/K_(max))=常数时(da/dN)随△K的全部变化,其中P值在1左右,C约在3×10~(-3)—10~(-2)毫米/周之间。
关键词:
材料科学技术（英文）
Lower content of carbon can further improve the stress rupture life of p-modified DA 718 alloy up to more than 270%. Meanwhile, the ductility of the alloy decreased a little. More boron atoms dissociate due to decreasing carbon content and interact with phosphorus which brings the longer stress rupture life of the alloy. Less carbon may induce more phosphorus segregating in the grain boundary and result in brittleness.
关键词:
DA 718 alloy;carbon;phosphorus;phosphorus;segregation;superalloy
李淑兰
,
杨玉芬
兵器材料科学与工程
doi:10.3969/j.issn.1004-244X.2008.03.016
在介绍40CrMnSiMoVA钢的力学性能和试验条件基础上,根据金属材料疲劳裂纹扩展的统计分析方法,求出Pa-N和P-da/dN-△k曲线,并对不同应力比条件下的试验数据进行可靠性分析和比较,探讨中值da/dN-△k曲线和99.9%可靠度dddN-△k曲线的变化规律.研究结果表明,P-da/dN-△k曲线与应力比有很强的相关性,随着应力比增强,裂纹扩展速率增加.当可靠度要求增加时,这种趋势更明显.根据研究结果,恰当地考虑40CrMnSiMoVA钢对于不同应力比的影响,便于进行概率断裂力学分析.
关键词:
断裂
,
40CrMnSiMOVA钢
,
P-da/dN-△k曲线
,
应力比
于艳
,
刘鹏涛
,
蹇锡高
,
刘程
,
张元红
,
洪定一
,
李扬
,
吕占霞
高分子材料科学与工程
由自制二胺1,2-二氢-2-(4-氨基苯基)-4-[4-(4-氨基苯氧基)-苯基]-二氮杂萘-1-酮(DHPZ-DA)、4,4'-二氨基二苯醚(DAPE)和对苯二胺(PPD)与2,6-萘二酸(NDA)进行共缩聚反应,改变不同二胺的配比,所得聚芳酰胺树脂特征粘度为0.24 dL/g～2.78 dL/g ;以FT-IR、1H-NMR手段分析了聚合物的结构;用DSC、TGA手段研究了聚合物的耐热性能.结果表明,该类聚合物具有较高的玻璃化转变温度(280 ℃以上);氮气气氛中5%热失重温度在450 ℃以上;当DHPZ-DA+DAPE在二胺中比例达70%时能溶于NMP中,当DHPZ-DA+DAPE含量达80%时能溶于DMAc、DMF等非质子极性溶剂中.
关键词:
聚芳酰胺
,
2,6-萘二酸
,
耐热性
,
可溶性
陈汉存
,
刘正义
,
庄育智
中国腐蚀与防护学报
水介质会延迟疲劳裂纹的扩展,此作用随介质中氧浓度的增加而增强,这是由于裂纹内的腐蚀产物以及粗糙的断口表面促使裂纹提早闭合。文中还用裂纹尖端氧浓度计算公式来解释水介质中da/dN的变化规律。
关键词:
