Multiphase Interaction Mechanism Of QAl9-4 Aluminum Bronze In Hot Deformation

In this study,the dynamic recrystallization ofαphase in the deformation heat treatment of QAl9-4 aluminum bronze was taken as the starting point,the microstructure of two main phases and a variety of second phases co-existed was taken as the research focus,and the interaction mechanism of multiple phases during the thermal deformation of aluminum bronze was thoroughly investigated.The constitutive equation of the QAl9-4 aluminum bronze and the processing map of the QAl9-4 aluminum bronze was obtained by the true stress-true strain curves obtained by the isothermal compression test.Compared with other particle-bearing copper alloys,the increment of thermal activation energy obtained by the constitutive equation is lower.Combined with the smooth region of good power dispersion contour near the eutectoid transformation temperature in the processing map,it is inferred that the alloy will not only be affected by dynamic recovery and dynamic recrystallization but also the phase transformation will directly affect the process.The critical strain model and dynamic recrystallization kinetic model of QAl9-4 aluminum bronze were obtained by constructing the dynamic recrystallization model,and the contribution ofαphase andβphase to the dynamic softening of QAl9-4 aluminum bronze was distinguished by recrystallization net softening.The results show thatαphase dynamic softening contribution is higher,and theαphase dynamic softening contribution increases with the increase of temperature in the set temperature range.The critical strain value of dynamic recrystallization increases gradually with the increase of strain rate and decreases with the increase of temperature.With the increase of temperature,the dynamic recrystallization of the alloy is accompanied by phase transformation.The phase transformation preferentially occurs in theα+γ₂ eutectoid structure,and theα-phase is further consumed with the phase transformation,which leads to the decrease ofαgrain size,and the widmanstatten structure will be produced during the hot deformation quenching process,which will worsen the material properties.In order to eliminate theα+γ₂eutectoid structure which is not conducive to alloy properties during casting and the widmanstatten structure which is deteriorated during quenching after high temperature deformation.Therefore,we take eutectoid transformation as the research direction,hoping to avoid the formation of two phases which have negative effects on alloy by designing temperature deformation test.The isothermal compression of the near eutectoid transformation temperature of QAl9-4 aluminum bronze was carried out,and it was found that there might be dynamic phase transformation characteristics,and the feasibility judgment and comparison of the microstructure content in the samples whether deformed indicated that the material had dynamic phase transformation characteristics.The same method is used to warm roll the near eutectoid transformation temperature,which can effectively control the phase distribution and content.Theαphase grains form heterogeneous structures with different grain sizes,and theαandβphases are distributed in the matrix of the alloy to form heterogeneous structures with different phase compositions,thus forming a"double heterogeneous structure".The warm rolling at the near eutectoid transformation temperature can effectively inhibit the widmanstatten structure during the high-temperature quenching process,which is beneficial to the improvement of the mechanical properties of the alloy.The mechanical properties of the alloy after annealing for four hours after warm rolling quenching are the best,and the product of strength and elongation can reach 25.34 GPa·%,and the wear resistance is excellent.The multi-phase interaction mechanism of aluminum bronze mainly includes:（1）the promotion ofαphase dynamic recrystallization by micron second phase particles in hot deformation through PSN mechanism;（2）Nanometer second phase particles have the effect of dispersion strengthening on the napping effect betweenα-phase recrystallization grain boundary and twin boundary and dislocation;（3）The temperature deformation of near eutectoid transformation temperature effectively promotesα→βphase transformation,which provides a new method for regulating the content and distribution of aluminum bronze phases.