Ni基高温合金单晶裂尖位错行为的动态研究——Ⅱ.界面对DFZ的影响

Ni 基高温合金中含有大量的γ′强化相,γ/γ′界面阻碍位错的运动,同时对裂尖无位错区(DFZ)的形成及尺寸都有很大的影响。可用以下表达式来描述两者间的关系:L(DFZ)=0.7X_(ob)~(1.07),其中 L(DFZ)为 DFZ 长度,X_(ob)为γ/γ′界面到裂尖距离。对实验结果进行了理论推算并同实验结果相吻合。     

碳化硅颗粒增强铝基复合材料中颗粒尺寸对材料断裂韧性的影响

通过对三种不同的碳化硅颗粒尺寸增强的铝基复合材料的断裂韧性的分析得到：复合材料的断裂韧性随增强剂颗粒尺寸的变化并不呈现单调变化规律。当颗粒尺寸很小时，断裂韧性随颗粒尺寸的增加而增加；但当颗粒尺寸本身很大时，复合材料的断裂韧性却随着颗粒的增加而减小。本文从实验和理论两方面证实了上述结论。此外，采用声发射装置及扫描电镜从微观结构上也都证实了上述结论的正确性。     

一种单晶高温合金的高周疲劳行为(英文)

本文对一种单晶高温合金在800℃经高周疲劳实验的断裂特征和微观变形机制进行了详细研究,发现该单晶合金存在两种断裂形貌,一种是定向解理断裂,一种是蜂窝状撕裂,这两种断裂方式分别与按确定取向的滑移变形机制和位错胞变形机制相联系。还观察到了小角晶界的变形机制,合金中存在的极微量 MC 碳化物仍然是重要的疲劳源,该单晶高温合金的高周疲劳强度极限较之相应的普通铸造 IN738合金和低偏析定向凝固 DE38G 合金大幅度提高。     

The Study of Dual-phase Steel after Cyclic Deformation at Various Strain Amplitudes

Low cycle fatigue tests under plastic straincontrol were carried out with a dual-phase steelcontaining 23 Vol.-％ martensite. Specimens hardenedrapidly at first few cycles followed by a slightsoftening to saturation stages when cycled athigher strain amplitudes, whereas at lower strainamplitudes the specimens presented continuallyhardening for a long time until saturation.TEM examination of the saturation dislocationstructures show that clusters, parallel wallsand cells were found at low, medium and highstrain amplitude, respectively. It also hasbeen found that the martensite/ferrite interfacesdid not affect the dislocation structures signi-ficantly when a specimen was fatigued at lowerstrain amplitude. However, the dislocation struc-ture adjacent to the two-phase boundary is dif-ferent to some extent from that in the remoteregions in the ferrite when a higher strainamplitude is applied.     

Acoustic Emission Monitoring the Fatigue Crack Growth in SM50B-Zc Steel

The acoustic emission(AE)characteristicsfrom the fatigue crack propagation in SM50B-Zcsteel were strongly affected by the environment me-dium.The AE feature from the fatigue process bothin air and in 3.5% NaCl aqueous solution mani-fested a periodicity which indicated the fatigue ex-tension was discontinuous.The fatigue striationand secondary cracking were the main AE sourcesduring the fatigue crack growth in air.In contrast,AE during the fatigue crack propagation in 3.5%NaCl solution was released from the intergranularfracture and quasicleavage cracking.     

表面等离子涂层对45钢疲劳性能的影响

本文通过对等离子表面喷涂试样的疲劳试验及断口金相分析,研究45钢经等离子喷涂后的疲劳行为,探索涂层厚度、结构、结合强度等因素与疲劳性能间的联系,为进一步改善喷涂件的疲劳强度提供依据。     

Laboratory of Fatigue and Fracture for Materials(LFFM)

This laboratory was designated as Na-tional Laboratory in 1988 and is subordi-nate to the Institute of Metal Research(IMR),Academia Sinica.It is nowwell-equipped after rebuilding under a spe-cial grant-in-aid program from the centralgovernment.According to the policy of“Opening,Flowing and Serving the WholeCountry”for the national laboratories,vis-iting research fellows at home and fromabroad are welcome to join common re-search projects in this lab.     

0Cr18Ni10Ti 不锈钢室温和高温表面疲劳裂纹扩展的研究

前言工程中使用的构件或压力管道,常常由于冶炼、加工、热处理和焊接工艺的影响,在未经使用的构件表面或内部就存在着各种形式的缺陷,而这些缺陷在以后的使用过程中,将以裂纹的方式不断扩大,最后致使构件发生突然     

晶界在塑性形变过程中的行为

本文简要地介绍了目前广泛采用的几种晶界结构理论,并以此为基础从宏观与微观相结合的角度阐述了不同结构的晶界在循环形变与单向形变中,与晶内滑移位错的交互作用。     

铝-锂合金平面应力断裂韧性的研究

一、前言 Al-Li合金因具有低密度、高弹性模量、高比强度等优点而引起宇航工业的广泛重视。但由于滑移局部化及无沉淀区的存在,导致Al-Li合金塑性较差。Sanders,Grig-son等人认为,共面滑移是导致Al-Li合金塑性较差的重要原因。加入某些合金元素如Cu、Mg、Zr等或改善热处理制度,形成非剪切沉淀相或促进均匀滑移可使合金的断裂韧性和塑性有较大提高,和Al-Li-Cu-Mg-Zr合金中存在的S’(Al_2CuMg),β’(Al_3Zr),T_1(Al_2LiCu)等析出相均可有效地提高合金的断裂韧性。所以,对Al-Li合金断裂韧性进行测试具有十分重要意义。通常能够反映材料本身属性的断裂韧性K_(IC)是对厚板的测试得到的,而实际应用的Al-Li合金多为薄板(厚为1～3mm),而通常情况下薄板的平面应力K_C估均高于厚板的平面应变K_(IC)值,因此,宇航工业的薄壁构件如用K_(IC)作依据则过于保守,于是Al-Li合金平面应力K_C值就显得更为重要,本文运用阻力曲线(R曲线)法对薄板8090Al-Li合金、LC4合金和LY12合金面应力K_C值进行测试。