The behaviors of helium clusters and self-interstitial tungsten atoms at different temperatures are investigated with the molecular dynamics method. The self-interstitial tungsten atoms prefer to form crowdions which ...The behaviors of helium clusters and self-interstitial tungsten atoms at different temperatures are investigated with the molecular dynamics method. The self-interstitial tungsten atoms prefer to form crowdions which can tightly bind the helium cluster at low temperature. The crowdion can change its position around the helium cluster by rotating and slipping at medium temperatures, which leads to formation of combined crowdions or dislocation loop locating at one side of a helium cluster. The combined crowdions or dislocation loop even separates from the helium cluster at high temperature. It is found that a big helium cluster is more stable and its interaction with crowdions or dislocation loop is stronger.展开更多
1.Introduction TiAl alloys are lightweight and high-temperature-resistant structural materials having applicability in automotive and aerospace applications owing to their low density and excellent high-temperature pr...1.Introduction TiAl alloys are lightweight and high-temperature-resistant structural materials having applicability in automotive and aerospace applications owing to their low density and excellent high-temperature properties[1-3].High-Nb-containing TiAl(High Nb-TiAl)alloys are considered as a new generation of TiAl alloys for applications at higher service temperatures[4-6].Components of TiAl alloys that have achieved long-term stability in the industry are mainly manufactured by casting,which is the most economical method[7-9].However,the mechanical properties of these com-ponents are limited at room temperature(RT),significantly hinder-ing their broad applications[7,10-12].展开更多
This work mainly deals with the segregating behaviors of Sc and the growth of unique primary Al3Sc in AlSc alloys prepared by molten salt electrolysis. The alloys contain 0.23–1.38 wt%Sc where Sc segregation is obser...This work mainly deals with the segregating behaviors of Sc and the growth of unique primary Al3Sc in AlSc alloys prepared by molten salt electrolysis. The alloys contain 0.23–1.38 wt%Sc where Sc segregation is observed. It is found that a high current density and long electrolysis time are in favor of high Sc content, and so do the high temperature and the addition level of Sc2O3. Sc content at the edge of Al based alloy(average Sc content: 0.75 wt%) can be as high as 1.09 wt%, while it is merely 0.24 wt% at the central area. The cooling rates have a strong impact on the morphology and particle size of primary Al3Sc,but a weak influence on Sc segregation. The cusped cubic and dendritic primary Al3Sc can precipitate in the prepared Al-Sc alloys. In a slightly hypereutectic Al-0.67 wt%Sc alloy, a large and cusped dendrite grows from the edge into the center. The primary and secondary dendritic arms can be as long as 600 and 250 μm, respectively. The Sc segregating behaviors in Al-Sc alloys is due to the mechanism controlled by the limited diffusion rate of Sc in liquid Al. This can involve the establishment of a near spherical discharge interface between liquid Al and the electrolyte. The Sc rich layer near Al-molten salt interface may provide the potential primary nuclei and sufficient Sc atoms for the growth of large dendritic primary Al3Sc.展开更多
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.11705157)the Henan Provincial Key Research Projects,China(Grant No.17A140027)the Ninth Group of Key Disciplines in Henan Province of China(Grant No.2018119).
文摘The behaviors of helium clusters and self-interstitial tungsten atoms at different temperatures are investigated with the molecular dynamics method. The self-interstitial tungsten atoms prefer to form crowdions which can tightly bind the helium cluster at low temperature. The crowdion can change its position around the helium cluster by rotating and slipping at medium temperatures, which leads to formation of combined crowdions or dislocation loop locating at one side of a helium cluster. The combined crowdions or dislocation loop even separates from the helium cluster at high temperature. It is found that a big helium cluster is more stable and its interaction with crowdions or dislocation loop is stronger.
基金National Key R&D Program of China(2021YFB3700501)National Science and Technology Major Project[J2019-VI-0003–0116]+1 种基金National Natural Science Foundation of China(51831001)Funds for Creative Research Groups of China(51921001)。
文摘1.Introduction TiAl alloys are lightweight and high-temperature-resistant structural materials having applicability in automotive and aerospace applications owing to their low density and excellent high-temperature properties[1-3].High-Nb-containing TiAl(High Nb-TiAl)alloys are considered as a new generation of TiAl alloys for applications at higher service temperatures[4-6].Components of TiAl alloys that have achieved long-term stability in the industry are mainly manufactured by casting,which is the most economical method[7-9].However,the mechanical properties of these com-ponents are limited at room temperature(RT),significantly hinder-ing their broad applications[7,10-12].
基金financial support of the project from the Beijing Natural Science Foundation (2184110)the National Natural Science Foundation of China (Nos. 51434005, 51704020 and 51874035)the Fundamental Research Funds for Central Universities of China (No. FRF-TP-17-035A1)
文摘This work mainly deals with the segregating behaviors of Sc and the growth of unique primary Al3Sc in AlSc alloys prepared by molten salt electrolysis. The alloys contain 0.23–1.38 wt%Sc where Sc segregation is observed. It is found that a high current density and long electrolysis time are in favor of high Sc content, and so do the high temperature and the addition level of Sc2O3. Sc content at the edge of Al based alloy(average Sc content: 0.75 wt%) can be as high as 1.09 wt%, while it is merely 0.24 wt% at the central area. The cooling rates have a strong impact on the morphology and particle size of primary Al3Sc,but a weak influence on Sc segregation. The cusped cubic and dendritic primary Al3Sc can precipitate in the prepared Al-Sc alloys. In a slightly hypereutectic Al-0.67 wt%Sc alloy, a large and cusped dendrite grows from the edge into the center. The primary and secondary dendritic arms can be as long as 600 and 250 μm, respectively. The Sc segregating behaviors in Al-Sc alloys is due to the mechanism controlled by the limited diffusion rate of Sc in liquid Al. This can involve the establishment of a near spherical discharge interface between liquid Al and the electrolyte. The Sc rich layer near Al-molten salt interface may provide the potential primary nuclei and sufficient Sc atoms for the growth of large dendritic primary Al3Sc.
