Study on Thermodynamics for Precipitation Behaviors of Solute Elements in Marine Steels Containing Nb Element
The phase transformation behaviors and precipitation behaviors of the second phase particles of ultra-high strength Nb-containing marine steels were calculated by using the ThermoCalc software,and then the calculated results were compared with the experimental results.The calculated results showed that the matrix of this material was the ferrite phase in the balanced state,while the main precipitated phases included Nb(C,N)(FCC-A1#2),Boron nitrides(BN-B4),Mo-enriched(HCP-A3#2),Copper-enriched(FCC-A1#3)and Carbides(M23C6-D84).Among them,the Nb(C,N)phase began to precipitate at 1 171.5℃,whose precipitation amount was 0.056%at 800℃.So if increasing content of both C element and Nb element would significantly promote the precipitation of the Nb(C,N).Secondly,the Mo-enriched phase began to precipitate at 700.4℃,whose precipitation amount was 0.34%at 400℃.Then,the Copper-enriched phase began to precipitate at 675.8℃,whose precipitation amount was 0.88%at 400℃.Lastly,the Carbide phase began to precipitate at 647.7℃,whose precipitation amount was 0.9%at 400℃.Therefore,it could be clear by comparing to the experimental results that the tempered experimental steel was consisted of tempered martensite(BCC phase)at room temperature.Under TEM,only the Nb(C,N)phase was observed,and other phases such as Boron nitride phase,Mo-enriched phase,Copper-enriched phase and Carbide phase were not found.
ultra-high strength marine steelphase transformationprecipitation of second phase particles
万方数据
维普
