Al5Ti1B Refiner Effect For The Microstructrue And Propertirs Of AL-SI Alloy Piston Of Internal Combustion Engine

Internal combustion engine,as the core power in the field of transportation,plays an important role in modern production and life.As an important core part of the internal combustion engine,the piston’s function is to convert thermal energy into kinetic energy through the explosive combustion of fuel,thus providing power for the locomotive.Its high temperature,high pressure,cyclic alternating load complex work environment and requirement of piston material must have good high temperature strength,dimension stability,excellent comprehensive performance,in order to prevent material performance from failing the requirement of the whole service cycle,and cause the piston wear and crack,causing the other parts inside the engine is damaged,or produce the serious problems such as oil burning,cylinder scuffing,etc.The requirements for piston materials in the changeable and complex working environment include:light weight,good dimensional stability at high temperature,abrasion resistance,excellent strength and hardness.At present,Al-Si casting alloy is the preferred material for piston manufacturing because of its good comprehensive performance.The smaller grain size can improve the strength and elongation of the material.In the process of piston casting,fine grain size can further enhance the mechanical properties of the piston Al-Si alloy and extend the service life of the piston.At present,the most widely used method of grain refinement in the casting process of aluminum piston is to add aluminum titanium boron intermediate alloy into the molten of aluminum piston alloy.In order to improve the refining efficiency,this study studied the effect of refiners on materials with different silicon contents(BH135+alloy containing 12wt.%Si and BH112A alloy containing 9wt.%Si),various phases in the tissues of different parts,as well as the effect on the tensile strength at room temperature and high temperature by adding refiners online.The results show that the addition of A15Ti1B wire has a significant effect on the grain refinement of both alloys.Within the scope of this study,the addition amount of refiner with casting weight ratio of 0.5‰ showed a better refining effect.With the addition of Al5Ti1B wire,the sizes of primary silicon of eutectic BH135+ material,eutectic silicon of sub eutectic BH112A material and intermetallic compounds in the two alloys all decrease to a certain extent.Among them,the reduction of silicon phase and intermetallic compound in the thick area of casting is more obvious than that in the thin area.Moreover,after the addition of refiner,most of the thick area of BH135+ material and the intermetallic compound morphologies changed from long strips to long strips and clumps,which basically accounted for half.In BH112A alloy,the dispersion of eutectic silicon in the matrix is better than that in the absence of refiner,and besides,the size of a-Al decreases obviously after the addition of refiner.To study the effect of A15Ti1B refining agent in the molten Al-Si alloy,thermal analyzer was used in the solidification experiment,the experimental results show that after adding BH135 + alloy melt refining agent,the eutectic temperature of the alloy was improved,the temperature range for the growing up of primary silicon has been minished to a certain extent,which account for the smaller size of primary silicon after the addition of the refiner.After the addition of A15Ti1B refiner,the tensile strength and elongation of BH135+ at room temperature were improved.In BH135 + materials tensile fracture of thin-walled castings,some existence and primary silicon matrix debonding phenomena(normal temperature and high temperature fracture have)has been founded,but in the casting big thick fracture area did not find the case,intermetallic compound and Al Si eutectic appear brittle fracture characteristics,the high temperature strength,elongation and did not have big increase by adding grain recfiner;BH112A materials under high temperature(300 0 C)stretch,α-Al deformation degree than normal temperature,toughening nest significantly,intermetallic compound and Al Si eutectic also presents the characteristics of brittle fracture,tensile strength and elongation are improved.In this study,the online addition of Al5Ti1B wire was used,which was added during the liquid aluminum pouring with an automatic wire feeder.The stirring effect of melt casting was used to make the effective nucleation core in the refiner distributed evenly,and to prevent the refining recession caused by the deposition of fine core particles.