TiAl金属间化合物的高温氧化与防护研究进展

ＴｉＡｌ金属间化合物在高温下形成Ａｌ２Ｏ３／ＴｉＯ２混合氧化膜，抗氧化能力较差，耐施加合适的防护涂层。本文综合评述ＴｉＡｌ金属间化合物的高温氧化机理，合金元素、表面处理及防护涂层对其抗氧化性能的影响。     

TiAI合金的结构特征与物理常数

ＴｉＡｌ金属间化合物的物理和力学性能与其本征电子结构、晶体结构及相关物理常数密切相关。较为系统地评述了ＴｉＡｌ与Ｔｉ３Ａｌ金属间化合物的价键特征和晶体学特征,并综述了弹性模量、Ｐｏｉｓｓｏｎ‘ｓ比、热学工用行为和界面能等物理常数。     

热轧态TiAl基金属间化合物超塑性研究

热轧态ＴｉＡｌ基金属间化合物在高温下拉伸时可以产生超塑性变形。材料在１１００℃、初始应变速率５×１０－４ｓ－１条件拉伸时，最大延伸率δＦ达到３４０％。本文研究了热轧态ＴｉＡｌ基金属间化合物在超塑性变形过程中组织的演变过程以及其与力学参数ｍ、γ之间的关系，并讨论了试验条件对材料超塑性性能的影响。     

热轧态TiAl基金属间化合物超塑性研究

热轧态ＴｉＡｌ基金属间化合物在高温下拉伸时可以产生超塑性变形。材料在１１０００℃，初始应变速率５＊１０＾－４ｓ＾－１条件拉伸时，最大延伸率δＦ达到３４０％。     

颗粒增强Ti－Al化合物基复合材料

本文在介绍Ｔｉ－Ａｌ金属间化合物基体及其颗粒增强剂的基础上，重点讨论了利用ＸＤ合成法、自蔓延高温合成法及真空热压法制造ＴｉＢ２、ＳｉＣ、Ａｌ２Ｏ３、ＴｉＮｂ等颗粒增强Ｔｉ－Ａｌ金属间化合物基复合材料的力学性能，同时还对颗粒增强Ｔｉ－Ａｌ金属间化合物基复合材料的其它制造方法，如反应热压烧结法、冲击波固结法、高能高速法的工艺、特点也进行了简要叙述。     

Fe—40Al及其含Mn或Ti合金的Mossbauer谱

用Ｍｏｓｓｂａｕｅｒ谱研究了Ｂ２结构金属间化合物Ｆｅ－４０Ａｌ及其加Ｍｎ或Ｔｉ量分别为１，５，１０ａｔ．－％的合金．在室温下，Ｆｅ－４０Ａｌ及其合金的Ｍｏｓｓｂａｕｅｒ谱均接近单峰谱线，Ｆｅ原子无明显磁矩对加入第三组元的Ｆｅ—４０Ａｌ合金的Ｍｏｓｓｂａｕｅｒ谱用最小二乘法拟合为两条洛仑兹曲线之和，认为Ｍｎ原子既占据Ｆｅ原子位置，也占据Ａｌ原子位置；而Ｔｉ原子优先占据Ｆｅ原子位置，超过５ａｔ．－％时，才有少量Ｔｉ原子占据Ａｌ原子位置．     

硼／铝复合材料管构件的界面特性EI

主要研究带钛合金连接头硼／铝复合材料管构件中Ｂ－Ａｌ－Ｔｉ间的界面结构与性质。研究表明，在复合工艺条件下，硼－铝界面附近没有检测到任何铝－硼化合物，而钛－铝间形成ＴｉＡｌ有序金属间化合物相。实验证明，硼／铝复合材料与铝合金端环之间采用的固结方法是有效的，且可按照受载类型随意调整斜面搭接长度，达到承受不同载荷的目的。     

钛合金的超塑性成型与扩散焊接

在超塑性成型／扩散焊接（ＳＰＦ／ＤＢ）联合工艺生产的零部件中，绝大多数是由Ｔｉ－６Ａｌ－４Ｖ制造的。这一材料的缺点是使用温度低且ＳＰＢ／ＤＢ温度高。具有较镐工作温度的近α钛合金及含钛－铝金属间化合物（ＴｉＡｌ或Ｔｉ３Ａｌ）的钛合金材料正肥到越来越广泛的重视。β相转变温度对钛合金的使用温度及ＳＰＦ／ＤＢ温度有很大影响。本文以Ｔｉ－６Ａｌ－４Ｖ为基础，比较了其它几种新型钛合金的ＳＰＦ／ＤＢ行为。其中包     

Fe—40La及其含Mn或Ti合金的Mossbauer谱

用Ｍｏｓｓｂａｕｅｒ谱研究了Ｂ２结构金属间化合物Ｆｅ－４０Ａｌ及其加Ｍｎ或Ｔｉ量分别为１，５，１０ａｔ．－％的合金，在室温下，Ｆｅ－４０Ａｌ及其合金的Ｍｏｓｓｂａｕｅｒ谱均接近单峰谱线，Ｆｅ原子无明显磁矩。对加入第三组元的Ｆｅ－４０Ａｌ合金的Ｍｏｓｓｂａｕｅｒ谱用最小二乘法拟合为两条洛仑兹曲线之和，认为Ｍｎ原子既占据Ｆ原子位置，也占据Ａｌ原子位置；而Ｔｉ原子优先占据了Ｆｅ原子位置，超过５ａｔ．－％     

TiAl系金属间化合物发动机零件

ＴｉＡｌ系金属间化合物发动机零件众所周知，ＴｉＡｌ系金属间化合物的高温比强度和刚性都比镍基高温合金和钛合金高，而且在１２７３Ｋ左右还具有优良的抗氧化性，是公认的密度小、重量轻、强度高的好材料（表１）。对于航空发动机来说，要达到更高性能的目的，无疑地必...     

Mechanical behaviour of a hot pressed aluminum nitride under uniaxial compression

Failure strength of a hot pressed aluminum nitride (AlN) is measured as a function of strain rate under uniaxial compression. At low strain rates (10-6–10-2s-1), the material is found to exhibit a weak strain rate sensitivity and at higher strain rates (102–103s-1), a strongly strain rate sensitive behaviour is observed. The quasi-static failure strength is found to be around 2.81 GPa and it increases to 5.25 GPa at a strain rate of 2200 s-1. During high strain rate testing, the specimen fractured into columnar fragments by axial splitting. Microscopic examination of the fractured surfaces revealed a typical brittle fracture with a combination of inter and intragranular failure modes. Based on the experimental results and microscopic observations, a micromechanical model has been developed to predict the constitutive behaviour of these ceramics under uniaxial compression. The model predictions of failure strength are shown to to be in agreement with the experimental observations. © 1998 Chapman & Hall     

DP980高强钢动态拉伸力学行为

对比分析DP980高强钢在应变速率10~(-3)~10~3s~(-1)范围内的动态拉伸实验结果,研究其力学行为以及断裂模式特点。结果表明:应变速率从准静态(10~(-3)s~(-1))增加至10~0s~(-1)过程中,强度基本保持不变,塑性下降了7.5%;应变速率从100s~(-1)增加至103s~(-1)过程中,强度不断增大,而塑性在10~0~10~2s~(-1)范围内上升14%,随后在10~2~103s~(-1)范围内下降了24.7%;应变速率敏感系数m始终随应变速率的增加而升高。变形过程中,位错增殖强化和加速阻力是强度上升的主要原因。塑性变形集中在铁素体中,微孔裂纹主要沿马氏体/铁素体交界扩展。试样沿厚度方向上的宏观断口,在应变速率小于101s~(-1)时呈"V"形杯锥状,在应变速率高于10~1s~(-1)时则是与拉伸方向成约45°的纯剪切型。     

Serrated Flow Behavior during Compression at Elevated Temperatures in Mg-3Al-1Zn-0.1RE Alloy

The deformation behaviour of an AZE(Mg-3Al-1Zn-0.1RE) alloy at temperature between 393 and 453 K was investigated by uniaxial compression tests carried out at initial strain rate values of 1×10-4,5×10-4 and 1×10-3 s-1 in air.The results show that serrated flow occurs at the strain rate of 10-4 s-1 under all test temperatures and 5×10-4 s-1 at 453 K.The mechanism of serrated flow was proposed,which is mainly attributed to the interaction of dislocations to the precipitates.     

Influence of strain rate and crystallographic orientation on dynamic recrystallization of pure Zn during room-temperature compression

This work investigates the strain rate dependence of dynamic recrystallization behaviour of high-purity zinc in room temperature compression under strain rates of 10-4 s-1,10-2 s-1 and 0.5 s-1.Results from electron backscatter diffraction provide insight into the deformation and dynamic recrystallization mech-anisms operative.Continuous dynamic recrystallization,twin-induced dynamic recrystallization,and discontinuous dynamic recrystallization are all active under compressive deformation at room temper-ature.Due to the high stacking fault energy of Zn,continuous dynamic recrystallization is the dominant mechanism while discontinuous dynamic recrystallization only operates in the early stages of compres-sion at 10-4 S-1.Dynamic recrystallization kinetics are enhanced at higher strain rates(10-2 s-1 and 0.5 s-1)due to an increased contribution from twin-induced dynamic recrystallization.The present study reveals that the controlling mechanisms for continuous dynamic recrystallization are basalslip and 2nd order pyramidalslip activity.Because the activation of slip systems is mainly deter-mined by crystallographic orientation,continuous dynamic recrystallization behaviour varies with grain orientation according to their propensity for basal and 2nd order pyramidal slip.     

应变率和温度对耐碱玻璃纤维织物增强水泥基复合材料弯曲力学行为的影响

为研究不同应变率和温度下耐碱玻璃织物增强水泥基复合材料的弯曲力学行为,采用美特斯(MTS)万能试验机和INSTRON落锤冲击系统对其试样分别进行室温(25℃)下准静态三点弯曲(应变率为3.33×10-5 s-1)和不同应变率(4、8、12、16和18s-1)及温度(-50、0、25、50和100℃)下的动态三点弯曲试验,静态和动态三点弯曲试验采用一套弯曲夹具。同时考虑了增强织物层数对其弯曲力学性能的影响。试验结果表明:室温下,随应变率的增加,弯曲强度提高,弯曲峰值应变和韧性先减小后增大,弯曲模量先增大后减小;应变率为12s-1时,随着温度的升高,弯曲强度、弯曲模量和韧性整体上减小,弯曲峰值应变变化不明显;纤维织物为六层时,对混凝土的增韧效果较明显。应变率、温度和织物层数均能对试样的弯曲性能产生较大影响。     

中等应变率下泡沫铝的吸能特性

进行了不同密度、高度和压缩方向下泡沫铝的准静态压缩试验和中等应变率下(＜100 s-1)的冲击试验,研究了具有不同密度的闭孔泡沫铝在准静态压缩和冲击工况下的吸能特性.结果表明,泡沫铝是一种近似的各向同性结构,具有较高的单位质量吸能特性,是一种较好的吸能材料.在准静态和中等应变率冲击条件下,泡沫铝对应变率不敏感,其应力应变关系与应变率关系不大.不同的泡沫铝,其平台应力与密度之间的关系不同,在研究其性能时,必须测量应力-应变关系.泡沫铝的致密区对其吸能特性有很大的影响.     

Effect of Strain Rate on the Ferrite Grain Refinement in a Low Carbon Nb-Ti Microalloyed Steel during Low Temperature Deformation

1. IntroductionThe thermomechanical controlled processing(TMCP) of microalloyed steels has been employed fosome times in the production of plates and sheet material to optimize mechanical properties. The centrafeature of thermomechanically processed steel is the ul-trafine grain size in the final product. Therefore, theferrite grain refinement of structural steels has attractedconsiderable interest from engineering scientists due toits unique role of increasing both strength and toughnessDem…     

Comparison of dynamic softening in 301, 304, 316 and 317 stainless steels

The mechanical torsion data in the form of flow curves and strain hardening rates from both as-cast and worked 300 series austenitic stainless steels, tested in the range 1200-900°C and 0.1 to 5.0 s-1, have been analysed to deepen understanding of dynamic softening mechanisms. The critical strain for dynamic recrystallization (DRX) is determined from the downward inflection of the strain hardening rate-stress curves, and completion of DRX is taken from the start of the steady-state regime. The rate of softening can be described by means of the Avrami equation with a mean k value of 1.27. These conclusions, based upon mechanical data, have been confirmed by optical metallographic methods. The peak strain (e _p) at which there is about 30% DRX is shown to be a function of the Zener-Hollomon parameter (Z) and the original grain size (D₀). The transition from multiple-peak grain coarsening to single-peak grain refinement behaviour has been determined. While the DRX grain size is a linear function of the steady-state flow stress with a power of -1.23, the subgrain diameter function has a power of -1. The stress and strain for subgrain formation were determined from changes in slope of the strain hardening-stress curves.     

10Ni8CrMoV钢热影响区的动态力学特征及其本构模型

使用热模拟试验机获得10Ni8CrMoV钢热影响区类似组织,通过霍普金森压杆试验对热影响区试样的动态力学行为进行表征,并观察其微观组织。结果表明:在高应变速率下,热影响区真实应力随着应变率的增加而增加,表现出明显的应变率强化效应;应变速率为2 000 s-1时,试样中出现大量的变形孪晶,应变速率为4 000 s-1时,试样被剪切破坏;基于Johnson Cook模型,得到10Ni8CrMoV钢热影响区动态本构模型。      

三种船用钢的动态力学性能

利用分离式霍普金森杆（SHPB）对三种合金钢A、B、C的动态压缩性能（应变率500 s-1～7 500 s-1）进行研究。结果表明：三种材料中A的压缩屈服强度最高,其次为C,B的强度最低;材料A、B在应变率500 s-1～6 000 s-1范围内均没有表现出明显的应变率效应,在应变率7 500 s-1下表现出较弱的应变率效应;这两种材料的压缩曲线形态相似,均表现出一定的应变硬化。C材料在整个应变率范围内均未表现出应变率效应,表现出一定的应变硬化。