Microstructure Characterization and Fracture Toughness of Laves Phase-Based Cr–Nb–Ti Alloys

Three Laves phase-based alloys with nominal compositions of Cr2Nb–x Ti(x = 20,30,40,in at%) have been prepared through vacuum non-consumable arc melting.The results show that the microstructures of Cr2Nb-(20,30) Ti alloys are composed of the primary Laves phase C15–Cr2(Nb,Ti) and bcc solid solution phase,while the microstructure of Cr2Nb–40Ti alloy is developed with the eutectic phases C15–Cr2(Nb,Ti)/bcc solid solution.The measured fracture toughness of ternary Laves phase C15–Cr2(Nb,Ti) is about 3.0 MPa m1/2,much larger than 1.4 MPa m1/2for binary Laves phase Cr2 Nb.Meanwhile,the fracture toughness of Cr2Nb–x Ti(x = 20,30,40) alloys increases with increasing Ti content and reaches 10.6 MPa m1/2in Cr2Nb–40Ti alloy.The eutectic microstructure and addition of Ti in Cr2 Nb are found to be effective in toughening Laves phase-based alloys.     

锆对X70钢焊缝微观组织及韧性的影响

通过在埋弧焊焊剂中添加铁锆合金粉末，以此向焊缝金属过渡锆元素，研究了金属锆对X70钢焊缝金属微观组织和性能的影响。结果表明，锆的加入增加了焊缝金属中针状铁素体的含量，改善了焊缝金属的微观组织。夏比冲击韧性试验显示，锆含量在0．006％时焊缝金属韧性最好。超过0．006％，焊缝金属中虽然也保持了较高的铁素体含量，但由于出现了小岛状的M-A组元，导致韧性降低。     

Effect of Active Gas on Weld Shape and Microstructure of Advanced A-TIG-Welded Stainless Steel

Advanced A-TIG method was conducted to increase the weld penetration and compared with the conventional TIG welding process.A two-pipeline setup was designed to apply Ar + CO_2 mixed gas as the outer layer,while pure argon was applied as the inner layer to prevent any consumption of the tungsten electrode.The results indicate that the presence of active gas in the molten pool led to the change in the temperature coefficient of surface tension so that the Marangoni convection turns inward and forms a deep weld zone.The increase in gas flow rate causes a decrease in the weld efficiency which is attributed to the increase in oxygen content in the weld pool and the formation o f a thicker oxide layer on the weld surface.Moreover,the stir and the temperature fluctuation,led by double shielding gas,create more homogeneous nucleation sites in the molten pool so that a fine grain micros true ture was obtained.     

X65管线钢焊缝金属断裂韧度的统计分布

基于焊接制造过程的影响，焊缝的断裂韧度具有本质的变异性。文中进行X65管线钢焊缝断裂韧度测定试验。建立确定断裂韧度统计分布模型，经多种数理统计检验，对断裂韧度指标δc的统计分布函数进行了统计拟合检验。统计结果表明威布尔分布函数是描述断裂韧度指标δc的最佳拟合分布函数。     

微合金非调质钢的断裂韧性与断裂机理分析

本文测试了两种微合金中碳钢35MnVN和40MnVTi的断裂韧性K_IC值及不同正火处理状态下35MnVN的J_R阻力曲线。对热加工条件及组织参数对K_IC值及J积分值的影响进行了分析。结果表明,采用降低了的始锻温度以及相应低的终锻温度可提高K_IC值。组织状态相似条件下,40MnVTi的断裂韧性值比35MnVN略高些。860～950℃正火处理对改善断裂韧性效果明显,温度过高则无效果。本文还对脆性断裂机制进行了讨论。     

Effect of Alloying on the Microstructure and Fracture Toughness of Nb-Mo-Si Alloys

It was found that typical Nbss /Nb5Si3 eutectic lamellar structure formed in the Nb-Mo-Si alloy. The interface between Nbss and Nb5Si3 phases was so strong that the alloy fractured mainly in the cleavage mode. In this paper, the fourth element was added with the aim of modifying interface structure. The microstructural characterization and the fracture toughness of Nb-17Si-10Mo ternary alloy doped with Ga, In, Zn and V, respectively, were investigated. It was revealed that the lamellar structure maintained ...     

Effect of Cr on Microstructure and Fracture Toughness of Nb-20Ti-16Si-xCr Alloys

The present paper reported the phase stability and microstructures evolution of Nb-20Ti-16Si-xCr (x = 0～20at.%) in-situ composites as function of Cr addition. It was suggested that with the addition of Cr less than 7%, the silicide phase in as-cast Nb-20Ti-16Si alloy was Nb3Si. The silicides changed to be α-Nb5Si3 by the addition of Cr above 7%. It was found that annealing of 1300 ℃ for 100 h could result in the decomposition of Nb3Si to NbSS and α-Nb5Si3 in Cr containing Nb-20Ti-16Si based alloys by means ...     

ADI的冲击韧度和断裂韧度

论述了ADI的冲击韧度和断裂韧度。室温有缺口和无缺口ADI的冲击韧度比铸钢,锻钢要略差,但约是普通珠光体球铁的3倍,ADI的冲击韧度虽随温度降低而降低,但在-40℃条件下仍保持大约室温冲击韧度的70%。断裂力学性能是更重要的安全设计和失效分析依据,无论哪一种断裂韧度,ADI的试验数据都好于普通球铁,相当于或好于强度相当的铸钢和锻钢。     

合金元素对堆焊焊缝硬度的影响

研究了堆焊焊缝的硬度及碳化物分布，分析了C、Nb、Ti、V对硬度的影响，优选了一种硬度高、碳化物分布均匀的堆焊焊缝。结果表明，V对提高硬度有明显作用，但其碳化物易沿晶界析出；Ti、Nb促进碳化物均匀分布，但含量过高会形成大量碳化物，反而降低焊缝硬度。     

厚板冲裁过程的模拟仿真及其参数优化

利用有限元模拟仿真软件Deform3D以及2D,对20Cr钢7mm厚板冲裁进行了模拟,采用NormalC&L断裂准则,分析了裂纹的产生和扩展机理,以及影响厚板冲裁质量的几个核心因素,得到了影响规律。通过进一步优化相关工艺参数,其结果为提高冲模寿命和冲压件质量提供了依据。     

稀土氧化物对堆焊金属冲击韧度及组织的影响

研究了稀土氧化物对堆焊金属冲击韧度及一次结晶组织的影响。结果表明 :稀土氧化物能提高堆焊金属在其工作温度下的韧性 ,并细化了一次结晶组织 ,使焊后结晶组织由柱状晶向等轴晶过渡。     

Torsional Fatigue Cracking and Fracture Behaviors of Cold-Drawn Copper:Effects of Microstructure and Axial Stress

The fatigue cracking and fracture behavior of cold-drawn copper subjected to cyclic torsional loading were investigated in this study.It was found that with increasing stress amplitude,the fracture mode of cold-drawn copper gradually changes from a shear fracture on transverse maximum shear stress plane to a mixed shear mode on both transverse and longitudinal shear planes and finally turns to the shear fracture on multiple longitudinal shear planes.Combining the cracking morphology and the relationship between torsional fatigue cracking and the grain boundaries,the fracture mechanism of cold-drawn copper under cyclic torsional loading was analyzed and proposed by considering the effects of the microstructure and axial stress caused by torsion.Because of the promotion of the grain boundary distribution on longitudinal crack propagation and the inhibition of axial stress on transverse crack grown,the tendency of crack propagation along the longitudinal direction increases with increasing stress levels.     

钢的动态断裂韧性及止裂韧性的研究现状

根据国内外关于动态断裂力学性能的研究文献，对动态断裂韧性KId(JId)及止裂韧性的研究现状进行了概括总结。     

2397铝锂合金显微组织、拉伸性能和断裂韧性研究

通过金相显微镜、透射电镜和扫描电镜观察以及X射线织构测量、拉伸试验和平面应变断裂韧性测试,研究了130 mm厚2397-T87铝锂合金不同厚度层及不同取向的微观组织、拉伸性能和断裂韧性。结果表明:厚度方向织构分布不均匀,表层织构以高斯织构为主,中心织构则主要由β取向轧制织构和少量立方织构组成,亚表层T/8处织构较弱,且从中心到亚表层,β取向织构和立方织构含量降低,剪切织构含量增加,T/8处剪切织构含量最大。L方向不同厚度层拉伸性能具有不均匀性,亚表层的抗拉强度(σb)和屈服强度(σ0.2)小于中心,LT方向拉伸性能差异相对较小;同一厚度处,合金强度和断裂韧性具有各向异性,σb、σ0.2的变化规律为:L方向﹥LT方向﹥SL方向,L-T取向的断裂韧性最好,T-L取向次之,S-L取向最差。     

显微组织对高碳钢韧性的影响

讨论了Ｔ１２Ａ钢制锉刀中碳化物粒子大小，形状及马氏体形态对锉刀使用寿命的影响。结果表明：适当粗化并尽量球化原始组织中的碳化物粒子，可增加淬火组织中板条马氏量与未溶碳化物的体积分数，从而显著提高锉刀韧性并延长其使用寿命。     

合金元素Al对Laves相NbCr2显微组织及断裂韧性的影响

采用机械合金化+热压烧结的工艺路线制备Laves相NbCr2合金,研究合金元素Al对其显微组织、力学性能,特别是韧化效果的影响.结果表明:合金元素Al主要占据了Laves相NbCr2金属间化合物中Cr原子的晶格位置.添加合金元素Al的Laves相NbCr2合金较未合金化的NbCr2硬度有所提高;当Al含量达到12at%时,断裂韧性要高于未合金化的NbCr2合金,达到了6.8 Mpa√m,远远高于熔铸合金的断裂韧性(1.2 Mpa√m).     

试样缺口组织对P92钢焊缝冲击功的影响

根据对P92钢进行焊接工艺评定时出现的焊缝冲击韧性问题,从标准V型冲击试样的缺口组织方面研究了P92钢焊缝冲击韧性.结果表明,P92钢焊缝冲击韧性随焊缝柱状晶与V型缺口角度的增加而增加,缺口尖端组织晶粒的大小对其焊缝冲击韧性有重要影响.     

Effects of V and Al on Microstructure and Room Temperature Fracture Toughness of Nb-Si In-situ Composites

The effect of alloying elements V and Al on microstructure and room temperature fracture toughness of an experimental Nb-Si in-situ composite was investigated. The Nb-Si alloys with different amount of V and Al were prepared by non-consumable arc-melting furnace. The experimental results showed that with the addition of V and Al, the microstructure of the Nb-Si materials transformed from Nbss+Nb3Si to Nbss+Nb5Si3 and the lattice parameters of Nbss phase decreased, and the alloying element V promoted the for...     

Microstructure and fracture toughness of Ti(C0.7N0.3)-WC-Ni cermets

Mo₂C is normally added to improve the wettability between Ti(C,N) and Ni in Ti(C,N)-based cermets. Due to the increasing price of Mo₂C, much attention has been paid to Ti(C,N)-based cermets with WC addition. In this paper, effect of WC content on the microstructure and properties of Ti(C_0.7N_0.3)-xWC-15wt.%Ni cermets free of Mo₂C was studied. The experimental results show that the microstructure is refined obviously with the increase of WC content. The fracture toughness decreases with the increase of WC content when WC content is 10-25 wt.%, and increases when WC content varies from 25 wt.% to 30 wt.%.