A study of temperature effect on Ta+N ion-implanted hardalloy

Hard alloy were implanted with a dudl-ion of nitrogen and tatalum at temperature of 100℃ and 400℃ at a dose of 8×1017 ions cm-2 .Auger electron spectroscopy (AES) was used to determine the nitrogen and tantalum concentration profiles. Microhardness measurements were performed to evaluate the improvements in surface property. The thickness of implanted layers increased by about an order of magnitude when the temperature was elevated from 100℃ to 400 ℃. A higher surface hardness was also obtained in the higher temperature implantation. Scanning electron microscopy (SEM) image showed distinct microstructural changes, and X-ray diffiaction (XRD) analysis showed the presence of nitrides of tantalum and tungsten on the surface implanted.

Effects of Forest Gaps on Some Microclimate Variables in Castanopsis kawakamii Natural Forest

The objective of this study was to understand the effects of forest gap and variations in different seasons, gap size, locations and diurnal variations on forest microclimate and soil water content. Spatial and temporal distribution features oi air temperature （TA）, soil temperature （Ts）, relative humidity （h） and soil water content （ψ） were measured in Castanopsis kawakamii natural forest gaps created by a severe typhoon or fallen dead trees. The results showed that： （1） the variations of TA, h, and Tsin four seasons were extremely significant. The variations of ψ in four seasons were extremely significant except for those between spring and summer. （a） The diurnal variations of TA and Tswere expressed with a single peak curve. The diurnal variations of h and ψ presented a high-low-high trend （3） The variations of TA, h, and Ts were extremely significant among the large, medium and small gaps in C. kawakamii natural forest. Medium gaps had the highest TA and the lowest h while small gaps were jusl contrary to medium gaps. The variations of T were extremely significant for large, medium and small gaps except those between the medium and large gaps （4） The TA, h, Ts and ψ were decreased from the gap center, canopy gap, expanded gap to understory. These results will help further our understanding of the abiotic and consequent biotic responses to gaps in the mid-subtropical broadleaved forests, which also provide a theoretical basis for the scientific management and population restoration of C. kawakamii natural forest.

Quantitative analysis of microstructure evolution induced by temperature rise during(α＋β) deformation of TA15 titanium alloy

Temperature rise is a significant factor influencing microstructure during（α＋β） deformation of TA15 titanium alloy.An experiment was designed to explore microstructure evolution induced by temperature rise due to deformation heat.The experiment was carried out in（α＋β） phase field at typical temperature rise rates.The microstructures of the alloy under different temperature rise rates were observed by scanning electron microscopy（SEM）.It is found that the dissolution rate of primary equiaxed a phase increases with the increase in both temperature and temperature rise rate.In the same temperature range,the higher the temperature rise rate is,the larger the final content and grain size of primary equiaxed a phase are due to less dissolution time.To quantitatively depict the evolution behavior of primary equiaxed a phase under any temperature rise rates,the dissolution kinetics of primary equiaxed a phase were well described by a diffusion model.The model predictions,including content and grain size of primary equiaxed a phase,are in good agreement with experimental observations.The work provides an important basis for the prediction and control of microstructure during hot working of titanium alloy.