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The relationship between microstructure and mechanical properties of gas metal arc weld metal with strength over890MPa 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 77J,while its yield strength is less than 800MPa.The microstructure of coarse lath martensite and bainite has the lowest toughness of 43Jand its yield strength is 820MPa.The mixed microstructure with fine martensite,bainite and retained austenite films bears good combination of toughness and yield strength(62Jand 880MPa,respectively).It is concluded that fine effective grain size and ductile phase of austenite films are two main factors to achieve good mechanical properties.
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. The experimental results show that the microstructure with predominant fine lath bainite possesses good toughness of 77J, while its yield strength is less than 800MPa. The microstructure of coarse lath martensite and bainite has the lowest toughness of 43J and its yield strength is 820MPa.The mixed microstructure with fine martensite, bainite and retained austenite films bears good combination of toughness and yield strength (62J and 880MPa, respectively) .It is said that fine grain size and ductile phase of austenite films are two main factors to achieve good mechanical properties.