增材制造GH3536合金的高温拉伸及疲劳裂纹扩展性能研究

采用选区激光熔化技术制备GH3536合金试样,经热等静压和固溶处理后对合金试样的显微组织、高温拉伸性能和不同应力比下的裂纹扩展性能进行了分析。结果表明,经热等静压和固溶处理后合金试样内部存在2种不同大小的等轴晶粒,在晶间存在连续片状分布的M₂₃C₆和M₆C碳化物。合金试样的拉伸性能随着温度的升高而不断下降,断裂方式由室温下的韧性断裂转变为900℃下的脆性断裂。在不同应力比下,合金试样的裂纹扩展方式主要为穿晶扩展,裂纹扩展速率随着应力比的不断上升而提高,在高应力比下合金内部的疲劳裂纹更倾向于在取向差较小的晶粒内部扩展。     

Multiplexing optical fiber low coherence and high coherence interferometric system with large range and high resolution for on-line measurement

A novel optical fiber sensing system multiplexing low coherence interferometry and high coherence interferometry that is endowed with large range and high resolution and is stabilized for on-line measurement is presented. An optical fiber Michelson interferometer performing measurement task in the system works in both modes of low coherence interferometry and high coherence interferometry simultaneously by employing a broadband light source and a fiber Bragg grating as an in-fiber reflective mirror. The amplitude of the measurand is determined by the low coherence interferometry while the value of the measurand is measured by the high coherence interferometry. Another optical fiber Michelson interferometer which is incorporated with the one performing measurement task stabilizes the sensing system for on-line measurement by exploiting an electronic feedback loop to reduce the influences that are resulted from environmental disturbances. The measurement range is 6 mm and the measurement uncertainty is less than 2 nm.