Effects of Nd on microstructure and mechanical properties of as-cast Mg-12Gd-2Zn-xNd-0.4Zr alloys with stacking faults

In order to study the effects of Nd addition on microstructure and mechanical properties of Mg-Gd-Zn-Zr alloys,the microstruc-ture and mechanical properties of the as-cast Mg-12Gd-2Zn-xNd-0.4Zr(x=0,0.5wt%,and 1wt%)alloys were investigated by using optical microscope,scanning electron microscope,X-ray diffractometer,nano indentation tester,microhardness tester,and tensile testing machine.The results show that the microstructures mainly consist ofα-Mg matrix,eutectic phase,and stacking faults.The addition of Nd plays a significant role in grain refinement and uniform microstructure.The tensile yield strength and microhardness increase but the compression yield strength decreases with increasing Nd addition,leading to weakening tension-compression yield asymmetry in reverse of the Mg-12Gd-2Zn-xNd-0.4Zr alloys.The highest ultimate tensile strength(194 MPa)and ultimate compression strength(397 MPa)are obtained with 1wt%Nd addition of the alloy.

Evolution of microstructure and texture of cold-drawn polycrystalline Ag with low stacking fault energy

The evolution of microstructure and texture for drawn polycrystalline Ag was investigated by transmission electron microscopy and electron backscattering diffraction.The results show that there are deformation twins and some un-tangled discrete dislocations at low strains.When the strain is increased to 0.58,a lot of high density dislocation walls and microbands come into being.At the same time,some twins lose the twinning relationship of 60°<111>.At a strain of 0.94,both dislocation boundaries and twin boundaries will rotate to the axis direction of wires and the shear bands start to appear.When the strain is higher than 1.96,most of the boundaries are parallel to the drawn direction.Texture analysis indicates that with the strain increasing,the volume fraction of complex texture component decreases,but<111>and<100>texture components increase.However,the variation in the volume fraction of each texture component as strains is not evident when the strains are higher than 0.58.For polycrystalline Ag with low stacking fault energy,complex texture components are easily formed.

Microstructure evolution and mechanical properties of Mg-7Gd-3Y-1Nd-1Zn-0.5Zr alloy

X-ray diffraction （XRD）, optical microscopy （OM）, scanning electronic microscopy （SEM）, transmission electron microscopy （TEM） and tensile tests at room temperature （RT） were performed to investigate the effect of homogenization on microstructure evolution and mechanical properties of Mg-7Gd-3Y-1Nd-1Zn-0.5Zr （mass fraction,%） alloy. The results indicate that the microstructure of the as-cast alloy is composed of α-Mg, （Mg, Zn）3RE phase and stacking fault （SF）, the homogenization results in the disappearance of （Mg, Zn）3RE phase and stacking fault （SF） as well as the emergence of 14H-type long-period stacking ordered （LPSO） phase. The ultimate tensile strength （UTS）, yield strength （YS） and elongation of the as-cast alloy are 187 MPa, 143 MPa and 3.1%, and the UTS, YS and elongation of the as-homogenized alloy are 229 MPa, 132 MPa and 7.2%, respectively.

Selective laser melting of bulk immiscible alloy with enhanced strength:Heterogeneous microstructure and deformation mechanisms

To overcome the dimension limits of immiscible alloys produced by traditional techniques and enhance their mechanical properties,bulk Cu-Fe-based immiscible alloy with abundant nanotwins and stacking faults was successfully produced by selective laser melting(SLM).The SLM-produced bulk immiscible alloy displays a heterogeneous microstructure characterized by micro-scaledγ-Fe particles dispersed in fineε-Cu matrix with a high fraction(~92%)of high-angle grain boundaries.Interestingly,abundant nanotwins and stacking faults are generated in the interior of nano-scaledγ-Fe particles embedded withinε-Cu matrix.The heterogeneous interface of soft domains(ε-Cu)and hard domains(γ-Fe)not only induces the geometrically necessary dislocations(GNDs)but also affects the dislocation propagation during plastic deformation.Therefore,the bimodal heterogeneous interface,and the resistance of nanotwins and stacking faults to the propagation of partial dislocation make the bulk immiscible alloy exhibit an enhanced strength of~590 MPa and a good ductility of~8.9%.

Study on Active Faults in Quaternary Unconsolidated Sediments by Microstructural Method

Active faults in Quaternary unconsolidated sediments are important indicators to determine paleoearthquake events. They can be studied by macroscopic geological survey, but some problems have been encountered, such as invisible active faults. The authors found an approach to solve these problems by microstructural observation. Firstly, oriented original-state samples of Quaternary unconsolidated sediments in active fault zones are collected. Secondly, the samples are consolidated in laboratory. Thirdly, microstructural slides are ground in three-dimension coordinate system. Lastly, microstructures are observed in the microscopic field. By this method, the movement properties of active faults can be determined in lack of the support of macroscopic data. The invisible faults in Quaternary unconsolidated sediments can be found and described. The mechanisms of die-out faults can be also studied. Moreover, the boundaries between different unconsolidated sediments in engineering sites can be studied to judge whether they are active faults or not.

Microstructures and mechanical properties of high Mn and high Al steels

Super-ductile and high strength manganese TWIP steels have received much attention in recent years.In the present work,two high Mn high Al steels with different stacking fault energies were investigated, microstructures were examined and mechanical properties were measured.The results showed that Fe-26Mn-6Al- 1C steel（6Al steel） exhibits high tensile strength and Fe-26Mn-12Al-1C steel（12Al steel） possesses a very high strength.Both steels exhibit good ductility.For 6Al steel with a moderate stacking fault energy（60 mJ/m;）, twinning is the major deformation mechanism;while dislocation slip dominates the deformation process of 12Al steel with stacking fault energy of 90 mJ/m;.

基于孔隙结构和核磁测井建立火山岩储层分类标准——以松南断陷查干花气田为例

以松南断陷查干花气田火石岭组火山岩为例,平均孔隙度、渗透率分别为4.5%和0.08×10^(-3)μm^(2),储层致密且非均质性强,需要大套储层一起试气才能达标,储层分类标准难以确定。利用物性数据、高压压汞、核磁共振等实验进行火山岩储层微观结构分析,通过多参数对比建立了微观分类标准,采用核磁测井作为衔接,从微观参数推导到宏观参数,综合建立了火山岩储层分类评价标准,其中包括微观结构的孔喉半径、排驱压力、退汞饱和度等,以及核磁测井和实验的T2谱分布、离心饱和度,还有宏观参数孔隙度、渗透率、饱和度、声波时差、岩性密度、电阻率,将储层由好到坏划分为A、B和C类,该方法可操作性强,为新钻井的测试方案以及勘探、开发水平井的“甜点”层优选提供了可靠依据。研究方法与认识对开展火山岩储层的分类研究具有一定的参考意义。

泌阳凹陷井楼八区低序级断层识别及其应用

泌阳凹陷井楼八区发育较多低序级断层,常规技术难以识别,在地层精细对比的基础上,运用井间地震资料联合、地震等时切片及油藏动态分析等技术,精细刻画了20m以下低序级断层产状,为注采调整提供地质依据。

Geological Evidence and Characteristics of Activity of the Wuhe-Mingguang Section of Tancheng-Lujiang Fault Zone in Late Pleistocene

As the most influential strike-slip fault in East China,the Tancheng-Lujiang fault zone draws scholars attention for its strong seismic activity. Nevertheless,most research has been conducted along segments in Shandong Province and Bohai Bay where huge earthquakes occur frequently. Meanwhile,it is generally believed that segments lying to the south of Huaihe River have been inactive since the late Quaternary and thus it is incapable of generating moderate or strong earthquakes. However,these understandings about the Tancheng-Lujiang fault have been questioned by our recent work for part of the fault south to the Huaihe River. Based on interpretation of high-resolution satellite images,detailed field investigations near Wuhe county and Mingguang City in northern Anhui Province and elaborate microstructure analysis, we come to the conclusion that the Tancheng-Lujiang fault zone mainly consists of four branches and at least one should be active since the late Pleistocene for the Wuhe-Mingguang section. This segment is monopolized by dextral strike-slip motion in late Quaternary. Different from obvious faults in bed rocks or consolidated sediments,the latest activity trace in Quaternary loose sediment revealed by trench excavation is not obvious or even invisible to visual observation. According to our recent work and previous studies, we call for more attention to be paid to invisible faults in young sediment and also suggest that more research be conducted along this seemingly placid segment.

Microscopic Indicators of Stick-Slip and Creep-Slip in Deformation Products From the Daqingshan Piedmont Active Fault

Through the collection of oriented samples,consolidation of undisturbed samples,and systematic microscopy of thin sections,the deformation products from the Daqingshan piedmont active fault zone have been studied.The obtained results have been analyzed in combination with those of rock fracture experiments and macroscopic surveys.Based on the above,the present article summarizes the microscopic indicators of stick-slip and creep-slip,which reflect the characteristics of fault movement,and has given some suggestion on relevant problems.

Initiation Timing of the Jiamusi–Yitong Fault Zone in NE China

The NE-striking Jiamusi-Yitong fault zone(JYFZ) is the most important branch in the northern segment of the Tancheng-Lujiang fault zone. The precise shearing time of its large-scale sinistral strike-slip has yet to determined and must be constrained. Detailed field investigations and comprehensive analyses show that strike-slip faults or ductile shear belts exist as origination structures along the western region of Yitong Graben. The strike of the shear belts trend to the NE-SW with steep mylonitic foliation. The zircon U-Pb dating result for the granite was 264.1±1 Ma in the ductile shear belt of the JYFZ. The microstructural observation(rotated feldspar porphyroclasts, S-C fabrics, and quartz c-axis fabrics, etc.) demonstrated the sinistral shearing of the ductile shear zones. Moreover, the recrystallized quartz types show a transitional stage of the subgrain rotation toward the recrystallization of the grain boundary migration(SR-GBM). Therefore, we suggest that the metamorphic grade of the shear zone in the ductile shear zones should have reached high greenschist facies conditions, and the deformation temperatures should approximately 450-500°C, which is obviously higher than the blocking temperature of muscovite(300-400°C). Hence, the ^40Ar/^39Ar isochron age of muscovite from ductile shear zones should be a cooling age(162.7±1 Ma). We infer that the sinistral strike-slipping event at the JYFZ occurred in the late Jurassic period, and it was further inferred from the ages of the main geological events in this region that the second sinistral strike-slip age of the Tancheng-Lujiang fault zone occurred during the period of tectonic movements in the Circum-Pacific tectonic domain. This discovery also indicates the age of the Tancheng-Lujiang fault zone that stretches to northeastern China. The initiation of the JYFZ in the late Jurassic is related to the speed and direction of oblique subduction of the west Pacific Plate under the Eurasian continent and is responsible for collision during the Jurassic period.

Line Faults in Gd_5Si_2Ge_2-Type Phase

Gd5Si2Ge2.2 alloy was synthesized by arcmelting and its phase components, microstructure, and especially the line features were investigated by X- ray diffraction （XRD）, scanning-electron microscope （SEM）, energy-dispersive spectroscopy （EDS）, and transmission-electron microscope （TEM）. Gd5Si2Ge2.2 consists of Gd5Si2Ge2-type and GdGe-type phases and presents eutectic characteristics. There are many regular line features on the Gd5Si2Ge2-type phase according to SEM. EDS shows that the line feature is not the Gd5 （Si,Ge）3-type phase because Gd content decreases at the line features. Two types of line features are found in the fine microstructure of Gd5Si2Ge2-type phase by TEM. Selected area diffraction （SAD） confirms that both line features are not the secondary phase or twins. There is no changes observed in the microstructure of Gd5Si2Ge2 2 from room temperature to 1400 ℃ with in situ high temperature optical microscope, therefore, it is deduced that the line features observed by SEM are formed during the solidification.

渤海湾盆地廊固凹陷古近系沙河街组油藏单元精细表征

依据岩心相、测井相、岩屑分析化验等资料,利用点-线-面的油藏单元表征方法,对渤海湾盆地廊固凹陷古近系沙河街组的微构造、主力层油藏单元类型及油水连通关系进行了详细研究。研究结果表明:(1)廊固凹陷古近系沙河街组主要发育构造型油藏单元和“断砂配置”型油藏单元。安11井区Es_(4)^(上)-Ⅰ砂组1小层、2小层、3小层和4小层的油藏单元数量分别为6个、5个,3个和2个;安22井区Es3中-Ⅱ砂组3小层和7小层的油藏单元均为5个,其他小层油藏单元数量不等。(2)安11井区Es_(4)^(上)-Ⅰ砂组油藏单元砂体连通程度和流体连通程度均较高;安22井区Es_(3)^(中)油藏单元类型、空间分布特征均较为复杂,油藏单元砂体连通程度较高、流体连通程度相对较低。(3)在实施油藏单元作为开发单元后,安11井区和安22井区各小层的单井日产原油量均有增加。通过油藏单元的精细表征,不仅能发现勘探开发中的滚动评价目标,而且可为开发过程中动态储量及经济可采储量的标定提供准确的油层厚度、油藏边界及油藏分布范围等。

岩盐断层带黏滑及稳滑过程中声发射活动特征的初步分析

本文利用双轴摩擦实验对含水条件下岩盐断层带摩擦滑动性状进行了实验研究,观测和分析了摩擦滑动过程中的声发射活动,并利用扫描电镜分析了断层带的微观变形结构.结果表明,含水岩盐断层带在伴随黏滑的速度弱化域和伴随稳定滑动的速度强化域,摩擦过程中均产生了大量声发射事件;黏滑过程与稳滑过程中的小声发射事件存在共同之处,即两者均表现为能级低;但黏滑过程中的小声发射事件的优势频率既有低频(10 kHz左右)和中频(100 kHz左右),也有高频(370 kHz左右),而在稳定滑动过程中,小声发射事件的优势频率仅有低频和中频,缺少高频事件.这种差异与两者变形主导机制的不同密切相关.在断层黏滑循环中,接近摩擦峰值时声发射发生率明显增加,但高频事件减少、中频和低频事件增加;进入亚失稳阶段后,声发射只有低频和中频信号,几乎不再出现高频信号.这种差异与断层带变形方式的变化密切相关.

Fe-Mn-Al-C系低密度钢及其强韧化机制研究进展

汽车行业的迅速发展使得能源消耗、环境污染等问题日益严重,而开发高强度且轻量化的汽车用钢对节能减排具有重要意义。目前正在研发的第三代先进高强钢包括轻质(Lightweight)钢、Q&P(Quenching and partitioning)钢和中锰钢(Mn质量分数为5%~10%)。其中,Fe-Mn-Al-C系低密度高强钢由于Al元素的加入,在密度降低的同时保持着良好的力学性能,满足第三代汽车用钢对轻量化的要求。同时,由于大量Al、Mn和C元素的添加,Fe-Mn-Al-C系低密度钢的冶炼连铸、微观结构、变形机制、加工过程及应用性能与传统钢种大不相同。本文系统阐述了Fe-Mn-Al-C系低密度钢的成分设计及其中合金元素的作用,介绍了低密度钢的微观组织结构特征;重点讨论了单一铁素体钢、奥氏体基钢、奥氏体基双相钢和铁素体基双相钢的各种强韧化机制,包括固溶强化、细晶强化、沉淀强化及其独特的应变硬化机制,如相变诱导塑性(TRIP)、孪晶诱导塑性(TWIP)、微带诱导塑性(MBIP)、剪切带诱导塑性(SIP)和动态滑移带细化(DSBR)等;并就层错能(SFE)对奥氏体钢变形机制产生的影响进行了总结;最后,对Fe-Mn-Al-C系低密度钢的强韧化机制研究进行展望,为后续研究者的工作提供参考。

断层泥的再生显微结构特征及其地震地质意义

三轴剪切摩擦实验后的断层泥与天然断层泥的再生显微结构特征研究表明，断层泥的显微结构特征与断层滑动方式之间有一定的关系，稳滑使断层泥变形均匀，产生低角度剪切（＜１４°）、布丁构造和颗粒碎裂流动。粘滑使断层泥局部发生强烈变形、高角度剪切（＞１４°）和碎粒出现随机裂纹等。断层泥的再生显微结构特征可用作鉴别古地震的存在。

变形过程中纳米金属镍的微结构演变

利用透射电镜对冷轧变形所致纳米结构金属镍的微结构组织演变特征进行了研究.结果表明,经过轧制变形后,纳米晶的平均晶粒尺寸为50～70 mm,有少量位错结构,但没有发现位错堆积缠结;在晶界处及附近有台阶界面结构,以及与台阶形状相对应的应力场衬度.在变形后期,可以靠晶界发射不全位错从而促使层错生成,并依赖层错尺寸长大(即层错界面位错)的运动进行.而当层错尺寸长大时,其前沿局部变形应力逐渐变大,直至该应力大到一定值时,位错停止运动,层错尺寸也不再长大,并留下了台阶结构.

鲜水河断裂西北段的断层泥特征及其地震地质意义

对鲜水河断裂的断层泥样品进行原样的结构、构造和碎砾的显微构造、刻蚀形貌结构的观测统计，断层泥的粒度分析和分形研究，认为，断裂处于强烈的定向应力场作用之下，其运动方式是以粘滑运动为主，且晚更新世和全新世时期断裂仍有活动。从断层泥的粒度分布和分形分析可将断层分为：甘孜－格篓、格篓－恰叫、恰叫－乾宁３段，这与前人的地形变分析的分段结果相一致。

准噶尔盆地南缘霍-玛-吐断层活动特征及成藏过程

以准噶尔盆地南缘霍-玛-吐断层的野外观测为基础,对断层岩显微构造进行了观察。结果表明,该断层大致经历了3次构造运动。结合前人对该区断层岩以及三级河流阶地的年代学研究结果,确定了该断层3次活动的时间分别为早更新世晚期、中更新世晚期至晚更新世早期、晚更新世末期。根据断层岩中发育的包裹体的均一温度、断层带中方解石脉的碳氧同位素测定结果,确定了该断层的最小贯穿深度为6 500m,至少断至侏罗系的烃源岩。对准噶尔南缘油气成藏条件的分析结果表明,霍-玛-吐断层向下断至侏罗系烃源岩,并在侏罗系主力烃源岩大量生、排烃之后,经过3次启闭过程,对应了3次成藏过程。断层目前处于封闭状态,可对油气藏形成遮挡。对成藏过程进行的分析表明,霍尔果斯、玛纳斯、吐谷鲁构造的中部成藏系统成藏条件最为有利,是有利的勘探远景区。

广宁深层次推覆构造前缘陡倾带变形构造研究

河台含金韧性剪切带是广宁深层次推覆构造前缘的一个陡倾带，它又是继推覆剪切之后再行右旋走滑剪切的复合带。首先解析了河台带中推覆与走滑两期构造变形的存在，并研究了带中的变形特征和运动规律及估算了几个主要糜棱岩带的水平走滑距离。通过显微镜和透射电镜，还研究了糜棱岩的显微、超显微构造，估算了变形的差异应力和应变速率。