The SiC/SiC joints were vacuum brazed at 700℃,740℃,780℃and 800℃for 10 min respectively,using Ag-Cu-In-Ti active filler alloy.The microstructure and joining strength of the joints were characterized by electron pro...The SiC/SiC joints were vacuum brazed at 700℃,740℃,780℃and 800℃for 10 min respectively,using Ag-Cu-In-Ti active filler alloy.The microstructure and joining strength of the joints were characterized by electron probe X-ray microanalyser(EPMA),energy dispersive spectroscopy(EDS),transmission electron microscopy(TEM)and four-point bending strength test.The interface of the joints was composed of three parts:SiC substrate,reaction layer and filler alloy.A representative microstructure of the reaction layer:In-containing layer/TiC layer/Ti5Si3 layer was found from the TEM image.The forming of the In-containing layer could be attributed to the crack or delamination of SiC/TiC interface.The In-containing layer intensified the coefficient of thermal expansion(CTE)mismatch of SiC and the reaction layer,and affected the joining strength.With the increase of the reaction layer’s thickness,the joining strength firstly increased,then declined,and the maximum four-point bending strength reached 234 MPa.展开更多
Considerable progress has been achieved in friction stir welding （FSW） of steels in every aspect of tool fab- rication, microstructure control and properties evaluation in the past two decades. With the development ...Considerable progress has been achieved in friction stir welding （FSW） of steels in every aspect of tool fab- rication, microstructure control and properties evaluation in the past two decades. With the development of reliable welding tools and precise control systems, FSW of steels has reached a new level of technical maturity. High-quality, long welds can be produced in many engineering steels. Compared to traditional fusion welding, FSW exhibits unique advantages producing joints with better properties. As a result of active control of the welding temperature and/or cooling rate, FSW has the capability of fabricating steel joints with excellent toughness and strength. For example, unfavorable phase transformations that usu- ally occur during traditional welding can be avoided and favorable phase fractions in advanced steels can be maintained in the weld zone thus avoiding the typical property degradations associated with fusion welding. If phase transformations do occur during FSW of thick steels, optimization of microstructure and properties can be attained by controlling the heat input and post-weld cooling rate.展开更多
文摘The SiC/SiC joints were vacuum brazed at 700℃,740℃,780℃and 800℃for 10 min respectively,using Ag-Cu-In-Ti active filler alloy.The microstructure and joining strength of the joints were characterized by electron probe X-ray microanalyser(EPMA),energy dispersive spectroscopy(EDS),transmission electron microscopy(TEM)and four-point bending strength test.The interface of the joints was composed of three parts:SiC substrate,reaction layer and filler alloy.A representative microstructure of the reaction layer:In-containing layer/TiC layer/Ti5Si3 layer was found from the TEM image.The forming of the In-containing layer could be attributed to the crack or delamination of SiC/TiC interface.The In-containing layer intensified the coefficient of thermal expansion(CTE)mismatch of SiC and the reaction layer,and affected the joining strength.With the increase of the reaction layer’s thickness,the joining strength firstly increased,then declined,and the maximum four-point bending strength reached 234 MPa.
文摘Considerable progress has been achieved in friction stir welding （FSW） of steels in every aspect of tool fab- rication, microstructure control and properties evaluation in the past two decades. With the development of reliable welding tools and precise control systems, FSW of steels has reached a new level of technical maturity. High-quality, long welds can be produced in many engineering steels. Compared to traditional fusion welding, FSW exhibits unique advantages producing joints with better properties. As a result of active control of the welding temperature and/or cooling rate, FSW has the capability of fabricating steel joints with excellent toughness and strength. For example, unfavorable phase transformations that usu- ally occur during traditional welding can be avoided and favorable phase fractions in advanced steels can be maintained in the weld zone thus avoiding the typical property degradations associated with fusion welding. If phase transformations do occur during FSW of thick steels, optimization of microstructure and properties can be attained by controlling the heat input and post-weld cooling rate.
