Effect Of Al-Nb-B Refiner On Microstructure And Properties Of Al-Si Piston Alloy

Al-Si alloy is widely used in industry.In industrial production,grain refiners are usually added to refine Al-Si alloy.Al-12Si-4Cu-2Ni-1Mg alloy belongs to Al-Si alloy and is a cast near-eutectic Al-Si piston alloy with high Si content.However,the refining effect of Al-Ti-B/C refiners on this kind of alloy is poor,so it is urgent to develop a new type of A1 based grain refiners to solve the practical problems.In this project,a new Al-Nb-B refiner is prepared,and the refining effect of this refiner on Al-12Si-4Cu-2Ni-1Mg alloy is studied.The research results are as follows:For the application of alloy method,fluoride salt method,two kinds of preparation methods of Al-5Nb-1B refiner have been investigated.The research shows that application Nb powder and KBF4 salt powder fluoride salt law namely,than Al-60Nb and Al-3B block,namely,alloy method,preparation of the Al-5Nb-1B refiner quality is better:the former generated Al3Nb.NbB2 intermetallic compounds,such as quantity and uniform distribution,most of the particle size is less than 5?m.morphology of irregular polyhedron,can combine well with the interface of ?-Al matrix.However,for the latter,the number of nucleation bases such as AlNb is less and the distribution of nucleation bases is uneven.The microstructure and mechanical properties of Al-12Si-4Cu-2Ni-1 Mg alloy with Al-5Nb-1B refiner have been investigated.The research shows that with the increase of Al-5Nb-1B refiner,the secondary dendrite spacing of ?-Al grains decreases,and the mechanical properties of piston alloy gradually improve.The tensile strength and elongation of the piston alloy reached the maximum when the refiner content was 3.0wt.%.The parameters of the piston alloy were 291.5MPa and 1.19%at room temperature,and 85.6MPa and 10.23%at high temperature,respectively.The mixed brittle fracture of cleavage and partial dimples at room temperature,and the ductile fracture of partial dimples at high temperature.The microstructure and mechanical properties of Al-12Si-4Cu-2Ni-1 Mg alloy with Al-5Nb-1B and Al-5Ti-1B refiner have been investigated.As for the refining effect of piston alloy,Al-5Nb-1B refiner is better than Al-5Ti-1B refiner.Al-5Nb-1B refiner reduces the secondary dendrite spacing of ?-Al grains more than that of Al-5Ti-1B refiner.In addition,the former can make the secondary dendrite spacing of ?-Al smaller,the proportion of fine equiaxed crystal is higher,and the distribution is more uniform under the same addition amount of the two.The former makes the tensile strength and elongation of piston alloy better than that of the latter.When the addition of Al-5NB-1B and Al-5Ti-1B refiner is 3.0wt.%,the high temperature tensile strength of the piston alloy with Al-5NB-1B and Al-5Ti-1B refiner is 85.6MPa and 81.2MPa,respectively,and the high temperature elongation is 10.23%and 9.91%,respectively.Compared with Al-5Nb-1B refiner,the addition of Al-5Nb-1B refiner can make the fracture flatness higher,the size of the cleavage platform is smaller,the number of dimples is more,the size is smaller and the distribution is more uniform.At room temperature,the fracture is brittle cleavage,and at high temperature,the ductile fracture is microporous shrinkage.