共查询到18条相似文献,搜索用时 46 毫秒
1.
本文研究了8090Al-Li合金穿透疲劳短裂纹的门槛值,测定了不同长度短裂纹的门槛值和裂纹闭合效应,探讨了该合金疲劳短裂纹门槛值、裂纹尾迹和裂尖屏蔽之间的关系,给出了该合金穿透疲劳短裂纹的上界值和理论最低门槛值。 相似文献
2.
3.
4.
本工作研究了2090和8090合金名义门槛值、本征门槛值和闭合效应对裂纹尾迹的响应关系。Al-Li合金具有优良的疲劳长裂纹门槛值和强的短裂纹效应,其物理本质是高的裂纹闭合效应和裂纹闭合效应的尾迹依赖性.2090合金微小裂纹的扩展抗力劣于7075合金,系因△Ki低;8090合金的△Ki与2024合金相当,其短裂纹扩展抗力相当或优于2024合金,微量稀土元素Ce可显著改善2090合金的本征门槛值,有益于裂纹闭合效应,较大幅度提高其疲劳长、短裂纹扩展抗力。Ce降低8090合金的本征门槛值,有损于其疲劳长、短裂纹扩展抗力。 相似文献
5.
6.
7.
8.
Al—Li—Zr合金的分级时效 总被引:1,自引:0,他引:1
用透射电镜研究了Al—2.31Wt%Li—0.34Wt%Zr合金的分级时效过程。通过控制Li含量、固溶温度和时效温度,探寻β′(Al_3Zr)和强化相δ′(Al_3Li)最佳弥散分布条件。Li的添加,在673K一级时效的初期,能促进β′相的析出并抑制过时效进程;在473K二级时效后,由于δ′(Al_3Li)相与β′(Al_3Zr)相形成复合析出组织,屈服应力达到280兆帕。分级日于效是提高Al—Li—Zr合金强度和韧性的新途径。 相似文献
9.
10.
11.
FATIGUE CRACK PROPAGATION IN Al-Li ALLOY 8090 总被引:1,自引:0,他引:1
WANG Zhongguang ZHANG Yun HU Zhuangqi State Key Laboratory for Fatigue Fracture of Materials 《金属学报(英文版)》1992,5(6):436-442
Fatigue crack growth rates of Al-Li alloy 8090 in air were found to be strongly dependent up-on the aging conditions.The naturally aged and underaged specimens showed the highest re-sistance to the fatigue crack propagation.The fatigue crack growth resistance of the overagedspecimen is the lowest and that of the peakaged specimen in between.As compared to air,3.5% NaCl solution does not change the effect of aging conditions on the fatigue crackgrowth,but causes a decrease of the resistance to the fatigue crack growth under the same ag-ing condition.Both short cracks from notch and physically short cracks showed much higherrates of fatigue crack propagation in comparison with long cracks under the same aging condi-tion and stress intensity level.The growth behavior of the short crack depends on its type.Thegrowth rate of short crack from notch decreases first to a minimum and then increases with in-creasing △K.However,the physically short crack grows at a progressively increasing rate.The effects of aging conditions are explained in terms of the slip planarity of dislocations andthe cyclic slip reversibility.The observed short crack behavior is considered to be dependent onthe crack closure and the local plasticity near the crack tip. 相似文献
12.
CHEN Zheng Northwestern Polytechnical University Xi′an China Lab.No. Northwestern Polytechnical University Xi′an 《金属学报(英文版)》1991,4(2):135-138
Threshold of fatigue for short through cracks for Al-Li alloy 8090 was evaluated to be lowerthan that of long cracks,and to decrease with the shortening of the crack length.The correla-tion among the threshold,crack wake,and crack tip shielding of the short fatigue cracks wasdiscussed.The super demarcation length and lowest theoretical threshold of short through fa-tigue cracks were presented. 相似文献
13.
14.
1.IntroductionAl-Liall0ysrepresentanewclass0flightweight,highmodulusandhighstrengtheconomica1structuralmaterials.Theref0re,theseall0ysareespeciallyattractivet0aero-nauticalandaer0spaceindustries.Tensilepr0pertiesandfracturet0ughnessinAl-Liall0ysaswellaseffectofprecipitates0nthemhavebeenextensivelyinvestigated[1w7].Fatiguefracture0fmaterialsacc0untsf0rthemaj0rity0fin-servicefailureinengineeringc0mpo-nents,andl0wcyclefatiguebehaviorisimportantforlifetimepredicti0ninpracticalalloys-Severalresea… 相似文献
15.
本文对1420Al-Li合金厚板采用紧凑拉伸、三点弯曲、电镜原位拉伸疲劳力等方法,不同取向的疲劳裂纹扩展行为。观测了长裂纹扩展路径形态,讨论了层状结构与材料疲劳性能之间的关系,结果表明,层片的界面对板材的疲劳性能具有重要影响,在裂纹扩展过程中,层片与裂纹尖端相互作用,通过不同的外化答独1420合金裂纹扩 阻力在不同取向出现显著差异,在L-T和T-S取向时,在△K为3-4和6-9MPa.m1/2范围 相似文献
16.
Al—Li合金的疲劳性能 总被引:2,自引:0,他引:2
研究了8090Al—Li合金在自然和人工时效状态下光滑样品的室温疲劳寿命,以及在100,150和200℃下的高温疲劳性能。结果表明:人工时效的8090合金的疲劳寿命高于自然时效的;在两种时效状态下,与传统的高强Al合金LC4和LY12相比较,Al—Li合金的疲劳寿命均高。人工时效的8090合金随实验温度的升高,疲劳寿命明显降低;自然时效的8090和LY12合金,高温疲劳寿命虽然略有降低,但在200和150℃时分别有所提高。断口观察表明:Al—Li合金的疲劳裂纹均在表面和亚表面的冶金缺陷处萌生;且层状断裂特征比传统的Al合金更加明显。 相似文献
17.
本文研究铁素体-马氏体复相钢中铁素体含量对裂纹萌生、扩展和裂纹尖端塑性变形的影响。在24.2—41.5%的铁素体含量范围内,以33.8%含量的复相钢裂纹萌生期N_0较长、门槛值ΔK_(th)高、并有低的扩展速率和较高的闭合应力强度因子K_(Cl)。三种铁素体含量复相钢的dα/dN-ΔK_(eff)一致的事实,表明裂纹闭合对低速扩展的重要作用,且闭合程度(K_(Cl)/K_(max))随裂纹尖端ΔK的降低而提高,在ΔK_(th)时达到最大。铁素体含量为33.8%的K_(Cl)/K_(max)值最高达0.7。 相似文献