Ti_(2)AlNb-based alloy was joined in a continuous drive friction welding machine under different rotational rates(500,1000 and 1500 r/min).The microstructure and mechanical properties of the joints were investigated.I...Ti_(2)AlNb-based alloy was joined in a continuous drive friction welding machine under different rotational rates(500,1000 and 1500 r/min).The microstructure and mechanical properties of the joints were investigated.It is shown that the weld zone(WZ) is fully composed of recrystallized B2 phase,and the grain size decreases with increasing rotational rate.The thermo-mechanically affected zone(TMAZ) suffers severe deformation during welding,due to which most of original precipitation phase is dissolved and streamlines are present.In the heat affected zone(HAZ),only the fine O phase is dissolved.The as-welded joint produced using 1000 r/min has the best mechanical properties,whose strength and elongation are both close to those of the base metal,while the as-welded joint obtained using 500 r/min exhibits the worst mechanical properties.Post-weld annealing treatment annihilates the deformation microstructure and fine O phase precipitates in the joints,consequently improving the mechanical properties significantly.Decomposed α_(2) phase is a weakness for the mechanical performance of the joint since microcracks are apt to form in it in the tensile test.展开更多
DEAR EDITOR,A new torrent catfish species,Liobagrus chengduensis sp.nov.,is described from the Xihe River,a tributary of the Minjiang River,Qionglai City,Chengdu City,Sichuan Province,China.It can be distinguished fro...DEAR EDITOR,A new torrent catfish species,Liobagrus chengduensis sp.nov.,is described from the Xihe River,a tributary of the Minjiang River,Qionglai City,Chengdu City,Sichuan Province,China.It can be distinguished from all other congeneric species by a unique combination of the following characters:3-4 serrations on posterior edge of pectoral-fin spine;anal fin with 15-16 rays;upper jaw obviously shorter than lower jaw;caudal fin rounded,with 42-44 rays;vertebral column with 36-37 post-Weberian elements;anus close to pelvic-fin insertion;adipose fin posteriorly continuous with caudal fin,with marked incision at confluence;body generally brownish yellow;all fins lacking well-defined light-colored margins,with color fading towards edge.展开更多
基金the financial supports from the Science and Technology Special Project, China (No. K19168)the National Science and Technology Major Project of China (No. 2017-VI-0004-0075)the National Natural Science Foundation of China (No. 52231002)。
文摘Ti_(2)AlNb-based alloy was joined in a continuous drive friction welding machine under different rotational rates(500,1000 and 1500 r/min).The microstructure and mechanical properties of the joints were investigated.It is shown that the weld zone(WZ) is fully composed of recrystallized B2 phase,and the grain size decreases with increasing rotational rate.The thermo-mechanically affected zone(TMAZ) suffers severe deformation during welding,due to which most of original precipitation phase is dissolved and streamlines are present.In the heat affected zone(HAZ),only the fine O phase is dissolved.The as-welded joint produced using 1000 r/min has the best mechanical properties,whose strength and elongation are both close to those of the base metal,while the as-welded joint obtained using 500 r/min exhibits the worst mechanical properties.Post-weld annealing treatment annihilates the deformation microstructure and fine O phase precipitates in the joints,consequently improving the mechanical properties significantly.Decomposed α_(2) phase is a weakness for the mechanical performance of the joint since microcracks are apt to form in it in the tensile test.
文摘DEAR EDITOR,A new torrent catfish species,Liobagrus chengduensis sp.nov.,is described from the Xihe River,a tributary of the Minjiang River,Qionglai City,Chengdu City,Sichuan Province,China.It can be distinguished from all other congeneric species by a unique combination of the following characters:3-4 serrations on posterior edge of pectoral-fin spine;anal fin with 15-16 rays;upper jaw obviously shorter than lower jaw;caudal fin rounded,with 42-44 rays;vertebral column with 36-37 post-Weberian elements;anus close to pelvic-fin insertion;adipose fin posteriorly continuous with caudal fin,with marked incision at confluence;body generally brownish yellow;all fins lacking well-defined light-colored margins,with color fading towards edge.
