The relationship between microstructure and mechanical properties of gas metal arc weld metal with strength over 890 MPa is discussed. The microstructure of the weld metals is characterized with OM, SEM, TEM and EBSD....The relationship between microstructure and mechanical properties of gas metal arc weld metal with strength over 890 MPa is discussed. The microstructure of the weld metals is characterized with OM, SEM, TEM and EBSD. The microstructure of the weld metals is mainly composed of martensite and bainite. Experimental results show that the microstructure with predominant fine lath bainite possesses good toughness of 77 .l, while its yield strength is less than 800 MPa. The microstructure of coarse lath martensite and bainite has the lowest toughness of 43 J and its yield strength is 820 MPa. The mixed microstructure with fine martensite, bainite and retained austenite films bears good combination of toughness and yield strength （62 J and 880 MPa, respectively）. It is concluded that fine effective grain size and ductile phase of austenite films are two main factors to achieve good mechanical properties.展开更多
The influence of aging temperature on phase transformation and mechanical properties of weld metal of maraging steel （grade C300） was studied. Microstructure was analyzed by means of optical microscopy, transmission...The influence of aging temperature on phase transformation and mechanical properties of weld metal of maraging steel （grade C300） was studied. Microstructure was analyzed by means of optical microscopy, transmission e leetron microscopy, scanning electron microscopy and energy dispersive spectrum analysis. Gibbs free energy of Nia Ti and Fez Mo at different temperature was calculated by Thermal-calc software. The microstructure of weld metal in as- welded state is martensite. The yield strength of weld metal after 430 ℃ aging process may increase to 1561 MPa from 890 MPa in as-welded state, which is ascribed to the formation of spinodal constitute and GP zones. After 480 ℃ aging process, there are great deal of NiaTi precipitates in the martensite matrix and 10% reverted austenite phase in the cellular grain boundary, and the yield strength increases to 1 801 MPa. After aging process at 580 ℃ , there are many Fe2 Mo precipitates in the martensite matrix and 30%o reverted austenite phase in the cellular grain boundary, and the yield strength is 1329 MPa, which ls the lowest among the three cases. The phase transformation may also influence the toughness. It is found that precipitates make the toughness decrease and reverted austenite increases it. The mechanism of phase transformation on strength and toughness is discussed.展开更多
基金Item Sponsored by National Basic Research Program of China(2010CB630800)
文摘The relationship between microstructure and mechanical properties of gas metal arc weld metal with strength over 890 MPa is discussed. The microstructure of the weld metals is characterized with OM, SEM, TEM and EBSD. The microstructure of the weld metals is mainly composed of martensite and bainite. Experimental results show that the microstructure with predominant fine lath bainite possesses good toughness of 77 .l, while its yield strength is less than 800 MPa. The microstructure of coarse lath martensite and bainite has the lowest toughness of 43 J and its yield strength is 820 MPa. The mixed microstructure with fine martensite, bainite and retained austenite films bears good combination of toughness and yield strength （62 J and 880 MPa, respectively）. It is concluded that fine effective grain size and ductile phase of austenite films are two main factors to achieve good mechanical properties.
基金Sponsored by National Basic Research Program of China(2010CB630800)
文摘The influence of aging temperature on phase transformation and mechanical properties of weld metal of maraging steel （grade C300） was studied. Microstructure was analyzed by means of optical microscopy, transmission e leetron microscopy, scanning electron microscopy and energy dispersive spectrum analysis. Gibbs free energy of Nia Ti and Fez Mo at different temperature was calculated by Thermal-calc software. The microstructure of weld metal in as- welded state is martensite. The yield strength of weld metal after 430 ℃ aging process may increase to 1561 MPa from 890 MPa in as-welded state, which is ascribed to the formation of spinodal constitute and GP zones. After 480 ℃ aging process, there are great deal of NiaTi precipitates in the martensite matrix and 10% reverted austenite phase in the cellular grain boundary, and the yield strength increases to 1 801 MPa. After aging process at 580 ℃ , there are many Fe2 Mo precipitates in the martensite matrix and 30%o reverted austenite phase in the cellular grain boundary, and the yield strength is 1329 MPa, which ls the lowest among the three cases. The phase transformation may also influence the toughness. It is found that precipitates make the toughness decrease and reverted austenite increases it. The mechanism of phase transformation on strength and toughness is discussed.
