The Ductile to Brittle Transition Behavior of the Modified 9Cr-1Mo Steel and Its Laser Welds

The ductile to brittle transition temperature (DBTT) of the modified 9Cr-lMo steel and its laser welds was studied. The increase in grain size of the weld structure ascended the DBTT of the steel significantly. The transformation of retained austenite at martensite interlath boundaries into untempered and/or twinned martensite could also contribute to increased DBTTs of the steel and its welds tempered at 540℃.     

The Ductile to Brittle Transition Behavior of the Modified 9Cr-1Mo Steel and Its Laser Welds

The ductile to brittle transition temperature (DBTT) of the modified 9Cr-1Mo steel and its laser welds was studied. The increase in grain size of the weld structure ascended the DBTT of the steel significantly. The transformation of retained austenite at martensite interlath boundaries into untempered and/or twinned martensite could also contribute to increased DBTTs of the steel and its welds tempered at 540℃.     

NiAl-28Cr-5.94Mo-0.05Hf-0.01Ho定向共晶合金的高温氧化行为

在900-1150℃氧化的NiAl-28Cr-5.94Mo-0.05Hf-0.01Ho定向共晶合金,在其表面生成了连续的Al_2O_3氧化膜,具有良好的抗氧化性能。定向凝固工艺使合金的组织细化并提高了Cr(Mo)相中Al元素的含量,以及加入微量稀土元素Ho,都有利于生成Al_2O_3氧化膜。在NiAl-28Cr 5.94Mo-0.05Hf-0.01Ho定向共晶合金的氧化过程中表面氧化膜发生相变θ-Al_2O_3→α-Al_2O_3,导致其1000℃氧化质量增加出现反常。     

ZA73镁合金热变形行为研究

在应变速率为0.001s(-1)和0.1s(-1),温度为150-300℃的条件下,采用热模拟对ZA73镁合金的高温拉伸变形行为进行了研究,并结合显微组织观察和挤压试验,分析确定了适合该合金的热加工工艺.结果表明:变形温度和应变速率是影响ZA73合金流变应力和塑性的关键参数,应变速率一定时,流变应力随温度的增加而降低;...     

室温大气环境下过时效状态3J21合金拉伸性能

在万能拉伸试验机上对室温大气环境下过时效态3J21合金的拉伸性能进行研究,并采用金相显微镜对过时效态金相组织及物相进行分析,采用TEN对固溶态、过时效态试样及拉伸断口附近形变的显微组织进行分析,采用扫描电镜（SEN）对拉伸断口进行观察。结果表明室温大气环境下,过时效态3J21合金的抗拉强度和屈服强度较低,延伸率较大;过时效态合金的拉伸断口为韧窝断口,断口上滑移线之间的距离较大。文中对室温大气环境下过时效态对3J21合金拉伸性能的影响进行了讨论。     

铸态Ti40阻燃钛合金高温拉伸力学性能及断裂行为研究

研究了不同试验温度下铸态Ti40合金的高温拉伸力学性能变化规律,并采用光学显微镜和扫描电子显微镜对拉伸样断口形貌进行观测,确定其断裂机制。结果表明:合金的抗拉强度随着试验温度的升高而显著下降,而塑性则分别表现出两个塑性较优区和脆性区,即400℃以下低温和900~1000℃高温的较好塑性区以及500~800℃的热脆区和1000℃以上的高温脆性区。脆性区试样断口形貌均呈现为沿晶脆性断裂,这一断裂机制与合金粗大晶粒以及严重的氧化相关。高温塑性区断口形貌为穿晶韧性断裂,则合金具有较高的塑性和较低的变形抗力,可作为较好的热加工温度区间。     

TiAl—Sb—Mo合金的高温氧化行为和机理

研究了Ｔｉ－３４Ａｌ，Ｔｉ－３４Ａｌ－０．５Ｓｂ－０．０３Ｍｏ，Ｔｉ－３４Ａｌ－１．０Ｓｂ－０．０７Ｍｏ合金在９００℃的氧化行为和机理，发现在ＴｉＡｌ基合金中复合添加Ｓｂ和Ｍｏ以后，氧化增重量增加，主要是由于Ｍｏ氧化生成易挥发的ＭｏＯ３引起的，三种合金的氧化过程都遵循氧化剥循环，残余氧化膜的平均度随合金元素添加而下降，在基体中不产生大的元素富集，添加合金元素可以促进氧化膜的种类由第一阶段向第二阶段     

硬铝约束对纯铝韧脆转变的影响

本文通过四点弯曲试验以及数值模拟方法对爆炸焊接的LY12/Al/LY12层合材料中纯铝中间层在不同界面强度错配比条件下裂端应力场及韧脆转变行为进行了研究。结果表明:在双侧硬铝约束下,界面强度错配比增加对裂端应力三轴度及其分布具有显著影响,裂端前沿应力三轴度的提高对中间纯铝层韧脆转变起主导作用,在一定应力三轴度及最大主拉应力条件下,裂端前沿将发生脆性解理启裂。     

Mg-9Li-3Al-2.5Sr合金的热变形行为

使用Gleeble-1500D型热模拟试验机,对挤压态Mg-9Li-3A1-2.5Sr合金进行热力模拟实验(变形温度为200-350℃,应变速率为0.001-1 s^-1),分析了材料的流变应力与变形温度和应变速率的关系,建立了该合金热变形过程中的本构方程,计算了该合金的热加工图,并结合显微组织观察对加工图进行了分析.结果表明:材料的流变应力随着应变速率的增加而增加,随着温度的升高而下降;用双曲正弦函数关系式能很好地描述材料在热变形过程中的稳态流变应力;对热加工图的分析结果表明,在实验参数范围内材料的最佳理论热加工区为260-300℃和0.01-1 s^-1.材料的超塑性加工区为340-350℃和0.003-0.01 s^-1。     

1420合金的拉伸断裂行为

研究了１４０２合金在不同热处理状态的拉伸性能和拉伸断口，并考察了合金的显微组织，分析了断裂机制，结果表明，合金在各种热处理状态呈稳定的穿晶韧性断裂，原因是δ′粒子细小，晶内强度低，而且晶界没有析出平衡相和无折出带，晶界强度没有降低。     

Ni19Co9Mo5粉末件高温锰系磷化膜形成过程的研究

研究了Ni19Co9Mo5粉末冶金工件黑色高温锰系磷化膜的生长过程,用扫描电子显微镜(SEM)观察了不同磷化时间下磷化膜的形貌,用能谱分析仪(EDS)分析了磷化膜成分,测量了膜重随时间变化的曲线.结果表明:磷化膜晶粒不呈传统的块状,而为棒状或条状;磷化膜的生长分为基体腐蚀、成膜和膜重增加3个阶段;磷化完成大约需要15 min.     

钛合金双态组织高温拉伸行为的晶体塑性有限元研究

创建一个包含多变体结构特征的双态组织几何模型,提出一种变形协调性的评估方法,采用以率相关滑移为主的晶体塑性有限元本构关系,研究了具有不同组织特征的Ti-6Al-4V合金双态组织的高温拉伸行为。结果表明：在多晶变形过程中,α_p相承载了更多的应变;在变形后的样品中,出现了大致对称分布于拉伸方向两侧的高应变交叉条带;存在于α_p与β_T之间的包围结构特征,可加剧局域应变分配的差异;随着α_p相体积分数的升高应变量降低,整体应变协调性先较快降低而后平稳;随着α_s片层厚度的增加高应变条带特征弱化,整体应变协调系数升高;含双变体α_s片层团簇结构的β_T组织,其应变协调性低于含单变体和三变体的组织。     

SiC晶须增强AL—2.0wt%Li合金的拉伸变形行为

本文研究了通过压力铸造法引入体积分数为17％的SiC晶须后,对Al-2.0wt％Li合金在550℃固溶化和190℃时效条件下拉伸变形行为的影响。结果表明:17％SiCw/Al-2.0Li复合材料的起始塑变抗力主要受基体合金的时效状态所决定,而受SiC晶须的直接影响较小。SiC晶须的强化作用主要在于提高了加工硬化事。通过观察变形后位错组态的变化表明,SiC晶须的存在可以抑制位错切过δ′相而引起的共面滑移。     

Nondestructive Evaluation of Ductile to Brittle Transition Temperature for Martensitic Steels Based on Magnetic Measurements

Interest in magnetic nondestructive evaluation (NDE) methods for nuclear reactors materials to quantify material embrittlement and ensure reactor safety is increased. In this paper, ductile–brittle transition temperature (DBTT) and temperature dependence of the coercive field (\(H_{C})\) and magnetization (M) of martensitic steels (F82H, Eurofer97, SCRAM, T91 and cold rolled T91 steels) were investigated from 100 to 350 K to non-destructively evaluate their DBTT. Results show that a characteristic temperature in both ln(\(H_{C})\) and d(lnM)/d(1/T) vs temperature curves coincides well with the corresponding DBTT measured by Charpy impact test. The curves decrease linearly above and below DBTT respectively, the absolute slope above DBTT is larger than that below. The phenomenon is closely related to the different motion status and the pinning strength of dislocations and magnetic domain wall in the ductile and brittle regions. Results indicate the magnetic evaluation method could be a promising technique with good reproducibility and high sensitivity to evaluate DBTT of martensitic steels used in nuclear reactors.     

Ti-6Al-3Nb-2Zr-1Mo合金室温压缩蠕变行为及位错类型研究

研究Ti-6Al-3Nb-2Zr-1Mo合金在不同外加应力下的室温压缩蠕变行为,拟合了蠕变曲线,计算出蠕变发生第二阶段的临界值,并对不同应力水平压缩后的合金显微组织进行TEM观察,研究其位错滑移类型。结果表明：室温条件下,Ti-6Al-3Nb-2Zr-1Mo合金压缩蠕变-时间曲线符合时间强化指数模型,该合金发生蠕变第二阶段的临界值为518 MPa,这为深海装备的安全设计提供了依据。Ti-6Al-3Nb-2Zr-1Mo合金室温压缩蠕变机制主要是位错滑移,其中基面滑移最容易启动,其次是柱面滑移和锥面滑移。结合微观组织分析与蠕变曲线可以判断锥面滑移对蠕变有较大贡献。     

Al_2O_3弥散强化Cu基复合材料高温拉伸行为研究

Al2O3颗粒弥散强化铜基复合材料因具有高强度和高导电性而在电子行业和电阻焊行业有着广阔的应用前景,本文利用扫描电子显微镜和透射电子显微镜对内氧化法制备的Al2O3/Cu复合材料的显微组织进行了分析,并用高温电子拉伸试验机测试了其高温拉伸力学性能。结果表明,Cu 0.6%Al2O3复合材料的室温拉伸屈服强度为442MPa,600℃时屈服强度为154MPa;试验温度低于300℃,其断面收缩率为22.2%～62.0%,温度高于400℃,其断面收缩率为4.5%～9.1%,呈现出明显的高温脆性。对其拉伸断口形貌和断裂机理进行了初步分析。     

Effect of Nb on the Microstructure and Mechanical Properties of Cast NiAl-Cr（Mo） Eutectic Alloy

The microstructure and mechanical behaviors of NiAl-28Cr-5Mo-1Nb eutectic alloy were investigated by using scanning electron microscopy, X-ray diffraction, transmission electron microscopy and compression tests, respectively. The alloy is mainly composed of three phases, which are the gray lamellar Cr（Mo） plate, black NiAI matrix and semicontinuously distributed Cr2Nb-type Laves phase. Through Nb addition, NiAl-Cr（Mo）/Nb alloy exhibits a reasonable balance of high temperature strength and room temperature compression ductility and its mechanical behaviors are superior to the NiAl-28Cr-6Mo eutectic alloy at all temperature. The elevated temperature compression deformation behavior of NiAl-Cr（Mo）/Nb alloy can be properly described by power-law equation.the National High Technology Committee of China （No. 863-715-005-0030） for financial supports.     

Microstructure and Elevated Temperature Tensile Behavior of Directionally Solidified Ni-rich NiAl-Mo(Hf) Alloy

The microstructure, high strain rate superplasticity and tensile creep behavior of directionally solidified (DS) NiAl-Mo(Hf) alloy have been investigated. The alloy exhibits dendritic structure, where dendritic arm is NiAl phase, interdendritic region is Ni3Al phase, and Mo-rich phase distributes in the NiAl and Ni3Al phases. The alloy exhibits high strain rate superplastic deformation behavior, and the maximum elongation is 104.2% at 1373 K and strain rate of 1.04×10-2 s-1. The balance between strain hardening (by dislocation glide) and strain softening (by dynamic recovery and recrystallization) is responsible for the superplastic deformation. All the creep curves of the DS NiAl-Mo(Hf) alloy have similar shape of a short primary creep and dominant steady creep stages, and the creep strain is great. The possible creep deformation mechanism was also discussed. The creep fracture data follow the Monkman-Grant relationship.     

Tensile deformation behavior and mechanical properties of a bulk cast Al_(0.9) CoFeNi_2 eutectic high-entropy alloy

In this study,a new Al0.9CoFeNi2 eutectic high entropy alloy(EHEA) was designed,and the microstructures as well as the deformation behavior were investigated.The bulk cast Al0.9CoFeNi2 EHEA exhibited an order face-centered cubic FCC(L12) and an order body-centered cubic(B2) dual-phase lamellar eutectic microstructure.The volume fractions of FCC(L12) and B2 phases are measured to be 60 % and 40 %,respectively.The combination of the soft and ductile FCC(L12) phase together with the hard B2 phase resulted in superior strength of 1005 MPa and ductility as high as 6.2 % in tension at room temperature.The Al0.9CoFeNi2 EHEA exhibited obvious three-stage work hardening characteristics and high workhardening ability.The evolving dislocation substructure s during uniaxial tensile deformation found that planar slip dominates in both FCC(L12) and B2 phases,and the FCC(L12) phase is easier to deform than the B2 phase.The post-deformation transmission electron microscopy revealed that the sub-structural evolution of the FCC(L12) phase is from planar dislocations to bending dislocations,high-density dislocations,dislocation network,and then to dislocation walls,and Taylor lattices,while the sub-structural evolution of the B2 phase is from a very small number of short dislocations to a number of planar dislocations.Moreover,obvious ductile fracture in the FCC(L12) phase and a brittle-like fracture in the B2 phase were observed on the fracture surface of the Al0.9CoFeNi2 EHEA.The re search results provide some insight into the microstructure-property relationship.     

环境温度及外磁场对Fe-13Cr-2.5Mo合金阻尼性能的影响

在环境温度和外磁场变化的条件下用改进的倒扭摆内耗仪分析了Fe-13Cr-2.5Mo合金的阻尼性能,用扫描电子显微镜分析了阻尼合金的组织结构.结果表明,合金的阻尼值包括铁磁部分和非铁磁部分.前者在室温条件下占整个阻尼的80%～90%,后者占10%～20%.当环境温度从23℃升高到550℃,阻尼性能逐渐下降到原来的60%～70%.比较900℃水冷处理的试样,1100℃炉冷试样的阻尼峰值对应的扭转应变较低,这表明其因外界噪声产生阻尼的能力较强.组织中晶粒的大小,析出物的产生及快速冷却过程中产生的微观残余应力是900℃水冷试样扭转应变较高的主要原因.