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951.
952.
This paper reports an experimental study of laser spot welding on stainless steel sheets. A pulsed Nd:YAG laser was used to weld the stainless steel specimen in the range of laser energy 0.6–1.2 J and incident angle 30–75° (the angle of the laser beam incident direction to the sheet surface). Metallography was applied to measure the cross-sectional size and shape of the welded spot. From the experimental results, it is found that as the laser energy increases, the penetration depth, bead length, and bead width of the welded spot increase. As the laser incident angle increases, the penetration depth and the bead width increase while the bead length decreases. The results illustrate that the shape and size of the welded spot depend not only on the laser energy, but also on the incident angle of laser beam. 相似文献
953.
954.
声光调Q Nd:YAG脉冲激光修锐树脂结合剂CBN砂轮 总被引:1,自引:0,他引:1
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。 相似文献
955.
挤压铸造ZA43合金组织及性能研究 总被引:2,自引:0,他引:2
研究了挤压铸造对ZA43合金组织性能的影响,分析了高压下凝固ZA43合金的组织形成过程。结果表明:挤压铸造可细化合金的铸态组织、减轻枝晶偏析,大幅度提高其力学性能;枝晶闸显微缩孔的消除是合金韧性显著改善的首要原因。 相似文献
956.
Two nano-composite coatings based on nc-TiC particles in an a-C:H matrix are deposited via closed-field unbalanced reactive magnetron sputtering. The compositions of the coatings are varied by changing the acetylene gas flow during the depositions. A Cr/Cr–Ti/Ti–TiC graded interlayer is introduced between substrate and coating. Electron probe micro-analyses (EPMA) show that the Ti content of the coatings varies between 31.7 and 11.5 at.%. The coatings exhibit a hardness (H) of 20.0 and 15.7 GPa, and a Young's modulus (E) of 229.4 and 136.6 GPa, respectively, as measured through nano-indentations. Cube corner indentations are performed to probe the fracture toughness of the coatings through the determination of critical indentation loads (Lr) at which radial cracks start to propagate. Transmission electron microscopy (TEM) observations and energy-filtered TEM are employed to characterize the coatings nanostructures. The variation in Ti content is accompanied by a variation in TiC particle size and volumetric fraction, as well as a change in the columnar structure of the coatings. A focus ion beam (FIB) slicing technique is employed to prepare samples from nano-indented locations of coated Silicon and stainless steel (SS) substrates. TEM inspection of the FIB sliced samples determines that the most brittle phase in the coating is the C-enriched columnar boundary, and identifies the location of failure within the interlayer. As a consequence of the different nanostructure, the coatings exhibit different elastic recovery properties and toughness. 相似文献
957.
958.
D. Galvan V. Ocelík Y. Pei B. J. Kooi Jeff Th. M. De Hosson E. Ramous 《Journal of Materials Engineering and Performance》2004,13(4):406-412
TiB/Ti-6Al-4V metal-matrix composite (MMC) layers were produced on Ti-6Al-4V substrates by laser cladding. A TiB2/Ti powder mixture was used as a precursor to obtain a dispersion of TiB needles in the Ti alloy matrix, with the aid of an
exothermic reaction between TiB2 and Ti. A eutectic microstructure was obtained that consisted of an extremely homogeneous dispersion of TiB eutectic needles
in the Ti alloy matrix, having a volume fraction as high as 0.33. Also, an equilibrium-like microstructure was found, consisting
of a dispersion of both primary and eutectic TiB needles inside the Ti alloy matrix. An analysis of the geometry of the layers
was performed and proved successful in determining the percentage of B. Further, it correctly predicted the variation of atomic
B content as a function of laser power. The relative wear resistance coefficient, defined as the wear coefficient of the uncoated
matrix divided by that of coating, shows an improvement by a factor as high as 1500 for the eutectic microstructure.
This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September
15–17, 2003, in Indianapolis, Indiana, and appeared on pp. 411–18 of the Proceedings. 相似文献
959.
960.
采用SYSWELD有限元模拟软件模拟计算了激光熔凝过程。计算结果表明,激光熔凝是一个快速加热和快速冷却的过程,其温度变化速率可达到104℃/s的数量级;熔凝区的硬度得到了显著的提升,中心部位的硬度小于熔凝区其它区域的硬度;熔凝区的最终残余应力表现为压应力,Mises等效应力在熔凝区与基体的交界处最大,成为形成裂纹的危险区域;碳含量的不均匀变化导致熔凝区的压应力分布不均,中心部位最小。 相似文献