Optimization Of Grain Boundary Distribution And Corrosion Resistance Of Bronze BFe10-1-1 Alloy

Failure time of copper-nickel BFe10-1-1 alloys,subjected to corrosion during service in seawater environment,is unpredictable and the service life is seriously limited.One of its root causes is that the high-angle random grain boundary network in the alloy is easily eroded in seawater and corrosion occurs along the grain boundary.However,the distribution of low-? CSL grain boundaries in the random grain boundary network is able to break the connectivity of the random grain boundary network and hinder the expansion of corrosion in the random grain boundary network,thereby improving the corrosion resistance of the alloy.In this paper,the grain boundary structure of copper-nickel BFe10-1-1 alloy is optimized through deformation then heat treatment.The grain boundary connectivity of the sample is qualitatively and quantitatively analyzed by electron backscatter ed diffraction combined with grain boundary structure analysis model to predict inter-granular failure resistance of materials.Results are verified by electrochemical and inter-granular corrosion immersion tests,in order to develop the relationship between grain boundary structure and performance and reveal the influencing mechanism of the grain boundary structure on material corrosion resistance.The paper is based on the three originally-creative following contents:(1)The fraction of low-? CSL grain boundaries can be improved and the optimal deformation heat treatment process(9% cold rolling deformation + 800°C/10 min annealing)of GBCD can be optimized by small deformation and high-temperature short-time annealing based on optimization of copper-nickel BFe10-1-1 alloy grain boundary distribution by grain boundary engineering of annealing twins.The special grain boundary ratio after treatment can be as high as 80%,and large-size grain clusters are formed in the alloy.The random grain boundary network is frequently attacked by special grain boundaries.As a result,the connectivity is affected,and optimization of grain boundaries and potential corrosion resistance is improved.Larger or smaller deformation will fail to fully optimize GBCD due to its influence on recrystallization nucleation density and multiple crystal twinning processes.(2)Quantitative analysis is made on the grain boundary structure on a basis of fractal dimension of the maximum random boundary connectivity and grain boundary density by checking the influence of random grain boundary connectivity on inter-granular corrosion resistance of copper-nickel BFe10-1-1 alloys.Different from the traditional grain cluster mode and percolation theory,fractal analysis of maximum random grain boundary connectivity focus on the grain boundary structure influence on inter-granular corrosion rate in the alloy from the view of graph theory.The rules for the selection of the boxes size are considered,and it is believed that the dispersion of the grain size distribution is another performance control factor of copper-nickel BFe10-1-1 alloy except for the specific grain boundary ratio.Grain boundary density of maximum random grain boundary connectivity is studied in terms of samples 'physical properties,and probability of alloy corrosion is evaluated by calculating the grain boundary density of MRBC,which provides a new feasible method for the evaluation and prediction of material properties.(3)Finally,based on the results of electrochemical impedance spectroscopy(EIS)measurements and inter-granular corrosion immersing tests,it is proposed that the better the GBCD optimization effect,the easier the formation of a dense protective corrosion film can be produced,and the inter-granular corrosion will also be arrest by the special grain boundary,improving corrosion resistance of alloys.The theoretical prediction based on the grain boundary structure agrees well with corrosion test results.In particular,the fractal analysis model can accurately predict the corrosion resistance of the alloy based on the quantitative results of the grain boundary structure,enriching the GBE in copper-nickel BFe10-1-1 alloy application.