渗硼层脆性判据K的物理本质

从实验和理论上对显微硬度压痕结合声发射测量渗硼层脆性的合理性及其脆性判据Ｋ的物理意义进行了讨论。Ｋ值可以反映渗硼层显微压痕裂纹长度随负荷增加的变化率，因而可以表征渗硼层的脆性。根据断裂力学可以导出入与Ｇ＿（ＩＣ）之间存在如下关系：Ｋ＝β（Ｇ＿Ｉ－Ｇ＿（ＩＣ））。Ｋ值间接反映了渗硼层的断裂韧性，可以作为定量评价渗硼层本质脆性的力学参量。     

Synergistic influence of alloy grain size and Si content on the oxidation behavior of 9Cr−1Mo steel

The synergistic influence of prior-austenite grain size and silicon content of 9Cr–1Mo steel on the resistance to scale spallation has been studied in air at 773 K (for 500 hr) and 973 K (12 hr). Two steels, irrespective of their grain size and Si content, did not show spallation during oxidation at 773 K. Spallation occurred at 973 K, and fine-grain steels exhibited less spallation resistance than coarse-grain ones (in low-as well as high-Si steels). Among the four possible combinations of grain size ans Si content, the steel with low Si and fine grains showed least resistance to spallation, while the steel with high Si and coarse grains showed the best resistance. Spallation was found to initiate in the areas adjoining the oxide ridges formed at the alloy grain boundaries. Oxide scales at the ridges and within the grains were analyzed by scanning electron microscopy (SEM/EDX) and secondary-ion mass spectrometry (SIMS). These analyses suggest depletion of silicon from the areas adjoining grain boundaries, resulting in thicker scaling that triggers spallation in such areas. For similar grain-size materials, the necessary thickness for spallation was attained earlier with low-Si steel rather than in high-Si steel.     

离子注入Y~ 对Ni30Cr定向凝固合金氧化膜界面缺陷与剥落机制的影响

用AE技术和SEM研究了离子注入Y＋(1×1017Y ／cm2)对Ni30Cr走向凝固合金1000℃形成的氧化膜在冷却过程中的破裂行为的影响结果表明：合金的横向和纵向虽具有不同的显微结构，但表面氧化膜的破裂行为相似．未注Y 合金氧化膜在冷却过程中发生了开裂和剥落，裂纹萌生于合金晶界及膜／合金界面的空洞处，以后扩展至膜内，导致膜发生剥落离子注入Y 显著改善了氧化膜的抗剥落性能．注入Y 明显减少了界面缺陷的数量及减小了缺陷的平均尺寸．     

计算机辅助声发射源检测定位系统

针对普通声发射（ＡＥ）检测仪缺乏源定位功能，开发了计算机辅助ＡＥ源检测定位系统，并详细论述了该系统的组成、接口、源定位算法和程序、剔除噪声等问题     

声光调Q Nd:YAG脉冲激光修锐树脂结合剂CBN砂轮

采用声光调Q Nd:YAG脉冲激光径向辐照，对树脂结合剂CBN砂轮进行修锐试验研究。研究了单脉冲激光辐照下，平均功率，脉冲频率和离焦量等参数对烧蚀凹坑深度的影响，由此可方便获得合适的激光修锐参数；分析了声光调Q YAG脉冲激光修锐树脂CBN砂轮的选择性去除机理，观察并比较了声光调Q脉冲激光，连续激光和机械法修锐后砂轮表面的地形地貌，试验表明声光调Q Nd:YAG脉冲激光径向辐照修锐树脂CBN砂轮，可获得更为良好的修锐效果。     

声发射技术在氧化膜破裂监测中的应用

在高温腐蚀领域,声发射技术是一种最有效且具有极高灵敏度的监测氧化膜破裂的技术.通过分析声发射计数,可以判断氧化膜首次发生破裂的时间及最后破裂的程度.如对声发射频谱进行分析,则可以判别氧化膜内发生塑性变形、开裂及剥落的过程.利用声发射技术还可以测量氧化膜/合金界面处预存物理缺陷大小及分布.此外,将声发射技术与其它技术结合,可建立全新的分析测试系统.综述了声发射技术用于监测氧化膜破裂的原理和方法,以及多种性能测试方面的应用与新发展.     

Preparation of flee-standing diamond films for high frequency SAW devices

Free-standing diamond films were prepared by hot filament chemical vapor deposition （HFCVD） method under different conditions. Inter-digital transducers （IDTs） were formed on the nucleation sides of free-standing diamond films by photolithography technique. Then piezoelectric ZnO films were deposited by radio-frequency（RF） reactive magnetron sputtering to obtain the ZnO/diamond film structures. Surface morphologies of the nucleation sides and the IDTs were characterized by means of scanning electron microscopy （SEM）, atomic force microscope （AFM） and optical microscopy. The results indicate that the surfaces of nucleation sides are very smooth and the IDTs are of high quality without discontinuity and short circuit phenomenon. Raman spectra show the sharp diamond feature peak at about 1 334 cmI and the small amount of non-diamond carbon in the nucleation side. X-ray diffraction （XRD） patterns of the structure of ZnO/diamond films show a strong diffraction peak of ZnO （002）, which indicates that as-sputtered ZnO films are highly c-axis oriented.     

EFFECT OF TOOL WEAR ON MICROSTRUCTURE, MECHANICAL PROPERTIES AND ACOUSTIC EMISSION OF FRICTION STIR WELDED 6061 Al ALLOY

Tool condition is one of the main concerns in friction stir welding （FSW）, because the geometrical condition of the tool pin including size and shape is strongly connected to the microstrueture and mechanical performance of the weld. Tool wear occurs during FSW, especially for welding metal matrix composites with large amounts of abrasive particles, and high melting point materials, which significantly expedite tool wear and deteriorate the mechanical performance of welds. Tools with different pin-wear levels are used to weld 6061 Al alloy, while acoustic emission （AE） sensing, metallographic sectioning, and tensile testing are employed to evaluate the weld quality in various tool wear conditions. Structural characterization shows that the tool wear interferes with the weld quality and accounts for the formation of voids in the nugget zone. Tensile test analysis of samples verifies that both the ultimate tensile strength and the yield strength are adversely affected by the formation of voids in the nugget due to the tool wear. The failure location during tensile test clearly depends on the state of the tool wear, which led to the analysis of the relationships between the structure of the nugget and tool wear. AE signatures recorded during welding reveal that the AE hits concentrate on the higher amplitudes with increasing tool wear. The results show that the AE sensing provides a potentially effective method for the on-line manitoring of tool wear.     

Fracture dynamics of sprayed and laser-glazed titania by an inverse processing of elastic waves

A new elastic wave (EW) or acoustic emission (AE) monitoring and signal processing system has been developed and used to elucidate the fracture behavior of sprayed and laser-glazed ceramic coatings. The system measures the minute surface displacements excited by the propagation of elastic waves. It enables elucidation of the fracture dynamics (fracture mode and kinetics) of stressed coatings. The surface displacement at the sensor position was computed by the convolution integral of an assumed source wave with the dynamic Green’s function until signals resembled the measured wave. This new signal processing method was used to determine the fracture strength and dynamics of microcracks in sprayed and laser-glazed titania subjected to four-point bending. It was found that mode II shear cracking along the interface between the coating and substrate occurred prior to mode I cleavage cracking. The fracture strength of laser-glazed titania was higher than that of as-sprayed titania in most cases; however, this depended on the coating structure. This article introduces the principle of source inversion processing of elastic waves, the monitoring system, laser glazing of sprayed titania, and experimental work on the fracture behavior of titania coatings.     

功率超声对Pb-Sn合金凝固行为的影响

研究了功率超声对铅锡合金凝固过程的影响,分析了其影响机制.结果表明,在功率超声作用下,声空化效应和声流效应使含铅5%的铅锡合金的凝固组织明显细化,并且经过功率600W的超声处理后,先析出相的析出温度升高3℃,凝固温度升高了5℃.随着超声功率的增加,合金组织的细化程度提高,但功率提高到一定程度时,细化作用减弱.