Research On Thermal Deformation Characteristics And Microstructure Evolution Of Silicon Brass Alloy

Silicon brass alloy are widely used in machinery, automobile and water engineering and other fields with low cost, environmental protection, excellent machinability and unique properties such as wearability, corrosion resistance. However Silicon brass workpieces generally need thermal forming in the practical application because of complicated shape, and with the rapid development of modern science and technology industries, the high temperature property requirement of silicon brass material is higher and higher, so the study of silicon brass thermal deformation characteristics is necessary. Using Gleeble-3500 thermal simulator, metallographic(OM), energy spectrum analysis(EDAX), and hardness testing, and the processing map method based of dynamic material model(DMM) to study the silicon brass thermal deformation characteristic and the microstructure evolution after thermal deformation. The available process temperature,strain rate range and the optimal deformation parameters are made sure during hot plastic deformation,and the hot working process of the alloy is optimized combining the reality plate rolling process. The results showed as follows:(1) Based on the high temperature compression simulation of silicon brass alloy, using Arrhenius hyperbolic sine form which contains the deformation temperature T and deformation activation energy Q to establish the relationships between flow stress and strain rate, deformation temperature, obtained high temperature deformation constitutive equation of silicon brass alloy:In which, the deformation activation energy Q was 190.18 k J·mol-1.(2) Based on the hyperbolic sine form which contains the deformation temperature T and deformation activation energy Q, established the constitutive equation which contains strain of silicon brass alloy:in which (3) Dynamic recrystallization was the main deformation mechanism for silicon brass alloy when high temperature deformation, within a certain range of strain rate, and in the 600~800℃ temperature range, recrystallization occured. In low temperature range, dynamic recrystallization occured only in the grain boundary due to uneven deformation, and it caused recrystallization uneven in the whole deformation matrix; And in the high temperature range, the dynamic recrystallization grain distributed evenly.(4) Combining the dynamic material processing map with microstructure evolution of silicon brass alloy after deformation, the optimal deformation temperature was 650℃~750℃, strain rate was 0.05~10s- 1, and the available process temperature range was 650℃~800℃.(5) Through the analysis of processing map when the strain is respectively 0.1, 0.4, 0.6, learned that with the increase of strain, the instability flow area in processing map trended to high temperature and high strain rate, thus the strain value can not be too high in hot working processes such as rolling.(6) Through hot rolling experiments of the silicon brass alloy plate, in a certain range, with the increase of strain and deformation temperature, dynamic recovery and recrystallization effects were obvious, alpha matrix in the structure changed more and more obviously, and the number of recrystallization were more; In this experimental condition, the recrystallization critical deformation temperature of silicon brass alloy was about 650℃, fully recrystallization deformation temperature was about 750℃,when the deformation temperature was 650℃~800℃.