45钢表面超音速电弧喷涂Ti-Al涂层的组织与性能研究

采用自行开发研制的超音速电弧喷设备，在45钢表面制成了钛铝合金复合涂层。并利用金相显微镜、X射线衍射仪、扫描电镜、电子探针，对涂层的成分、相结构、显微组织及其结合强度、显微硬度进行了研究。结果表明，利用超音速电弧喷涂设备，可以在45钢表面形成 度高、孔隙率低，结合强度较好和硬度高的Ti-Al合金涂层。     

Amorphous diffusion bonding of steel pipe and its impact toughness

An iron-based amorphous foil (FeNiCrSiB) was used as an interlayer for the amorphous diffusion bonding of low carbon steel pipes under argon flux. The microstructure and mechanical properties of the joint were analyzed using an electron probe micro-analyzer (EPMA), tensile test, bending test and impact test. The results show that the joint microstructure resembles that of the base metal and no precipitates form at the joint. Melting point depressants (B, Si) diffuse far away from the joint and the base metal element is homogenous across the joint. The joint impact toughness is greater than the base metal toughness and the mechanical properties of the joint are similar around the pipe.     

Microstructures formed by spray freezing of food fats

The spray-freezing of two food fats, tripalmitin (PPP) and cocoa butter (CB) and mixtures thereof, has been modeled experimentally using a novel single droplet freezing apparatus configured so that temperature profiles or samples for microstructure analysis can be obtained. For 2 mm diameter droplets suspended in a cold air flow at temperatures around 2–15°C, initial cooling rates were on the order of 10 K s⁻¹ and the temperature profiles could be correlated directly to DSC data collected at 20 K min⁻¹, indicating that minimal supercooling of the materials occurred in the droplet form. Microstructure analysis confirmed that PPP crystallized preferentially in mixtures, and that the surface structure was very sensitive to storage conditions. The bulk structure was much less sensitive, and the internal microstructure of the PPP droplets revealed distinct nucleation sites, which were absent from the CB: These persisted in the mixtures up to 50 wt%. X-ray analysis indicated that the fats crystallized in their more stable forms, namely, β for PPP and Form V/V1 in CB.     

薄膜润滑研究的回顾与展望

薄膜润滑是20世纪90年代以来广泛研究的新型润滑状态。它是界于弹流润滑和边界润滑之间的一种过渡润滑状态，有着自己独特的润滑规律。文章回顾了薄膜润滑的研究历史，包括薄膜润滑概念的提出、测试技术的发展、薄膜润滑的膜厚特性、润滑机理探索以及计算理论等方面的研究成果与主要进展。     

Cr对低碳Si-Mn系TRIP钢组织与力学性能的影响

主要研究了Cr对低碳Si-Mn系TRIP钢组织与力学性能的影响。首先利用Formastor-F型膨胀仪测定了含Cr和不含Cr两种低碳钢的连续冷却转变(CCT)曲线,分析指出了Cr对连续退火工艺的潜在影响;然后采用Gleeble-3800热/力模拟试验机对两种钢的薄板试样进行了连续退火模拟实验,并通过拉伸试验测定了力学性能;最后采用金相、扫描电镜、X-射线衍射分析等技术考察分析了两种钢的显微组织。结果表明:含Cr的TRIP钢的组织比较细小,铁素体晶粒近似等轴分布;两种TRIP钢的残余奥氏体含量相近,但含Cr钢的残余奥氏体中的含碳量较高。分析认为这是由于含Cr钢在热轧阶段较易生成细小的组织,而在热处理阶段则抑制贝氏体的生成,最终获得稳定的残余奥氏体。     

Effects of Y and Ce on Microstructures and Properties of Nb-Si System Composites

The effects of yttrium and cerium on microstructures and properties of Nb-Si system composites were investigated by scanning electron microscopy( SEM), energy dispersive spectrum(EDS), X-ray diffraction(XRD) and high temperature oxidation experiments.It is found that the coarse primary silicide phase became finer and more homogeneous with Y and Ce addition.The results of high temperature oxidation experiments show that the oxidation rates of NbSi system composites with an appropriate amount of Y and Ce decrease compared with those of alloys without Y or Ce addition, and oxidation products mainly distribute along the phase boundaries between the Nb solid solution and silicide.     

Threshold and growth mechanism of fatigue cracks under mode II and III loadings

ABSTRACT The fatigue crack growth behaviour of 0.47% carbon steel was studied under mode II and III loadings. Mode II fatigue crack growth tests were carried out using specially designed double cantilever (DC) type specimens in order to measure the mode II threshold stress intensity factor range, ΔK_IIth. The relationship ΔK_IIth > ΔK_Ith caused crack branching from mode II to I after a crack reached the mode II threshold. Torsion fatigue tests on circumferentially cracked specimens were carried out to study the mechanisms of both mode III crack growth and of the formation of the factory‐roof crack surface morphology. A change in microstructure occurred at a crack tip during crack growth in both mode II and mode III shear cracks. It is presumed that the crack growth mechanisms in mode II and in mode III are essentially the same. Detailed fractographic investigation showed that factory‐roofs were formed by crack branching into mode I. Crack branching started from small semi‐elliptical cracks nucleated by shear at the tip of the original circumferential crack.     

热处理对Ti-25V-15Cr-2Al-2Mo-0.2C合金组织稳定性的影响

研究了热处理对Ti-25V-15Cr-2A1-2Mo-0.2C阻燃β钛合金组织稳定性的影响。结果表明，高温固溶并直接时效处理导致合金β基体上析出较多的α相沉淀，尤其在随后的热暴露组织中形成了恶化合金塑性的连续晶界α膜。然而，若在时效前再进行一次低温固溶处理则可明显减少α相的析出数量，合金的热稳定性因此而得到显著改善。     

Evolution of grain structure in thin film reactions

In this paper, we examine, both experimentally and theoretically, the kinetics of formation and microstructure of product phases in thin film reactions, using the Nb/Al and Ti/Al systems as our prototypes. The results of calorimetry and microscopy studies are interpreted using simple kinetic and morphology models. In particular, the kinetic models employed here focus on the nucleation and growth components of the phase formation process and the morphology models provide a starting point for the classification of product grain structures. An erratum to this article is available at .