Solidification segregation behavior of a Cr-Ni-Mo-Ti-Al high strength stainless steel
The influence of cooling rate on element segregation in a Cr-Ni-Mo-Ti-Al high strength stainless steel was studied using differential scanning calorimetry,in-situ observation under high-temperature confocal laser scanning microscopy and directional solidification experiments.The results show that the solidification sequence of the experimental steel is:L→L+δ→L+δ+γ→L+8+γ+TiN→δ+y+TiN→γ+TiN.As the cooling rate increases,the secondary dendrite spacing of the solidified structure gradually decreases,and the dendrite structure is refined.The functional relationship between the secondary dendrite spacing and the cooling rate is λ2=86.7(GLR)-1/3.In the as-cast microstructure,Mo,Ni,Al and Ti elements belong to positive segregation,while Cr element belongs to negative segregation.Among them,Ni and Ti elements have a greater degree of segregation and are mainly enriched between dendrites.Mo,Cr,and Al elements have a lighter degree of segregation and are evenly distributed in the ingot.The enrichment of Ti element in the residual liquid phase at the end of solidification increases the tendency to form AlN inclusion.As the cooling rate increases,the segregation phenomenon of elements such as Ni and Ti is significantly reduced.
high strength stainless steeldirectional solidificationmicrostructurecompositional segregationinclusion
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