| GH3030 nickel-based superalloy is widely used in aerospace and other fields because of its good performance at high temperature.However,as the application conditions of the alloy become more complex and demanding,it is required to have more superior performance.The static recrystallization(SRX)and grain boundary characteristic distribution(GBCD)of the material have a crucial influence on the properties of the GH3030 alloy.The properties of the material can be effectively improved by adjusting the structure of the alloy.In this paper,the effects of cold-rolled deformation and electropulsing treatment(EPT)on the SRX and GBCD of GH3030 alloy were studied using electron backscatter diffraction(EBSD)detection methods.At the same time,the corresponding conventional heat treatments(CHT)was carried out for comparison.The influence of annealing temperature,time and cold-rolled deformation on the SRX volume fraction,grain size and Σ30(n=1,2,3)grain boundary ratio of GH3030 alloy was observed and analyzed.The corrosion resistance and hardness of GH3030 alloy treated by EPT at different temperature and time was analyzed by electrochemical corrosion experiment and microhardness test.The following research results were obtained.(1)The effect of different heat treatment annealing parameters on the SRX structure of the alloy was analyzed.It was found that EPT can significantly promote the SRX of cold-rolled GH3030 alloy compared with CHT.EPT can quickly increase the SRX volume fraction of the alloy in a shorter time.At the same time,the microstructui’e of the alloy treated by EPT was also more uniform.The recrystallization activation energy of alloy with different heat treatments was calculated by establishing the SRX kinetic equation of the alloy treated by EPT and CHT.As a result,it was found that the recrystallization activation energy of the alloy treated by EPT was lower than that of the alloy treated by CHT.The above showed that EPT can accelerate the SRX behavior of cold-rolled GH3030 alloy.(2)The distribution characteristics of Σ3n(n=1,2,3)grain boundaries with temperature,time and cold-rolled deformation were analyzed with different heat treatment parameters.It was found that the ratio of Σ3 grain boundary increased with increasing temperature,and increased with the extension of annealing time.And compared with the GH3030 alloy treated by CHT,the effect of EPT on the optimization of GBCD was more significant.EPT can increase the alloy’s low ΣCSL grain boundaries ratio in a relatively short time.Σ3n(n=1,2,3)grain boundaries accounted for the vast majority of CSL grain boundaries.Among the Σ3n(n=1,2,3)grain boundaries,the content of Σ3 grain boundary was the highest.Σ3 grain boundary was mainly generated by accidental growth mechanism.And the formation of Σ9 and Σ27 grain boundary was suppressed at higher EPT temperature.(3)Experimental analysis of hardness of cold-rolled GH3030 alloy after EPT and CHT was carried out.It was found that the hardness value of the alloy increased first and then decreased as the temperature of the EPT increased.When the temperature was 750℃,the hardness reached the maximum.On the other hand,the hardness of the alloy decreased with increasing EPT time.In addition,the hardness value of the alloy treated by EPT was significantly lower than that of CHT.The reason was that the electronic wind generated in the EPT processing can open the dislocation entanglement and improve the mobility of the dislocation.Moreover,refinement of grains can increase the hardness of the alloy,and increasing the ratio of Σ30(n=1,2,3)grain boundaries can also increase the hardness of the alloy.(4)Experimental analysis of electrochemical corrosion of cold-rolled GH3030 alloy after EPT was carried out.It was found that the corrosion resistance of the cold-rolled GH3030 alloy after EPT was greatly improved compared with the original alloy.The increase of Σ3n(n=1,2,3)grain boundaries ratio can significantly improve the corrosion resistance of GH3030 alloy. |
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