M50 steel was irradiated by high current pulsed electron beam(HCPEB)with different pulses.The subsequent tempering was carried out between 500 and 625℃.Microstructure evolution was analyzed by scanning electron microscopy and X-ray diffraction.It is found that the HCPEB treatment could constrain martainsite transformation in the surface layer of the samples.Tempered behavior of HCPEB remelted layer strongly depends on the proportion of retained austenite.Austenite saturated more carbon and metallic elements depict higher tempering stability.During tempered process,carbides precipitates among the grain and phase boundaries.The decreased solution of the elements promotes the retained austenite into martensite.
Tantalum nitride and tantalum carbide films were fabricated using magnetron sputtering of tantalum followed by nitrogen and carbon plasma-based ion implantation （N-PBII and C-PBII）. The phase evolution and morphology of the films were studied using glancing angle X-ray diffraction （GXRD） and transmission electron microscopy （TEM）. It was found that the main phase in the tantalum nitride films was crystalline TaNo.1 whose grain size increases with increasing implantation voltage and phase content increases with increasing implantation dose. In the tantalum carbide film, the main phase was Ta2C. TaC phase also appeared as the implantation dose increased. XRD results from various glancing angles show that the phases with high nitrogen or carbon content, Ta4N5 and TaC, are present in the surface of the films. X-ray photoelectron spectra （XPS） from the tantalum carbide film reveal that the surface carbon content is higher than that of the inner film.
LI ZhongwenGU LeTANG GuangzeMA XinxinSUN MingrenWANG Liqin
