Study On Preparation And Refinement Mechanism Of High-efficiency Grain Refiner Aluminum Titanium Boron

At present,Al-5Ti-1B wire rod is the most commonly used grain refiner for aluminum and aluminum alloy.Due to the restriction of production mode and other factors,the second phase particle size of master alloy is too large and the distribution state is aggregated,which makes it unable to meet the requirements of grain refinement for high-performance aluminum alloy.A large number of Al-5Ti-1B master alloy wires need to be imported from abroad every year.Because of the asymmetric size of Al-5Ti-1B trapezoidal billet,the non-uniform deformation is more serious in the production process,so it is necessary to study it.Both heat treatment and plastic deformation can improve the size,morphology and distribution of the second phase of Al-5Ti-1B,which is beneficial to improve the grain refinement effect.The effects of solution treatment,deformation temperature,deformation degree,deformation rate and deformation direction on Microstructure and morphology,size and distribution of second phase particles of continuous casting Al-5Ti-1B master alloy were studied.The results show that:With the increase of solution temperature（300,400,500,600℃）,the average size of the second phase TiAl₃particles decreases gradually,and the TiB₂distribution tends to disperse,and the volume fraction increases gradually.During the solution treatment of continuous casting Al-5Ti-1B,with the increase of solution temperature（300,400,500,600℃）,the supersaturated ti will precipitate in the form of TiAl₃particles,and the increase and dispersion of the second phase particles will increase the nucleation and particle size,which is conducive to improving the refining effect.With the degree of deformation（ε=0.2,0.4,0.6,0.8）,the average size of the second phase particle TiAl₃shows a trend of"first decrease,then increase",and the second phase particle TiB₂gradually changes from"granular"to"rod"with the increase of deformation degree.The deformation degree is low（ε=0.2,0.4）,the cracks of TiAl₃particles mainly grow to both ends and finally penetrate the whole particle,but the deformation degree is higher（ε=0.6,0.8）,the main crack growth mode of TiAl₃is to grow to one end until spalling from the edge.TiB₂particles are affected by flow stress,dynamic recovery and recrystallization during deformation,which makes TiB₂particle distribution tend to disperse.With the increase of deformation temperature（300,350,400,450,500℃）,the average size of TiAl₃increases first,then decreases,and then increases,and the distribution of TiB₂is more dispersed.During the deformation process,TiAl₃particles produce cracks and crack propagation,which lead to TiAl₃particles refinement.The increase of TiAl₃particles leads to TiB₂distribution thinning.With the increase of deformation rate(.ε=0.01,0.1,1s^-1),the average size of the second phase TiAl₃particles gradually decreases,and the distribution of TiB₂particles tends to disperse.In different directions（transverse and longitudinal）of deformation,TiAl₃particles have good uniformity in transverse compression,TiAl₃particles are smaller in longitudinal compression,while TiB₂particles are basically the same in transverse and longitudinal compression.That is to say,the non-uniform deformation in the deformation process is beneficial to the size and distribution of the second phase particles.