Numerical Analysis And Experimental Study On Near Net Shape Forming Of SiC_p/Al Composite Section Strip With Simple Shaped Section By Twin-roll Cast

SiC_p/Al composite strip has the advantages of high specific strength,specific modulus,good thermal conductivity,and small thermal expansion coefficient.So it is widely used in aerospace and electronic packaging.Because of the existence of the SiC particles,the composite strip has worse formability,and its parts usually have the characteristic of irregular deformed section.At present,the forming method which has been widely used is preparing the perform body by stirring casting,spray deposition,powder metallurgy,squeeze casting and so on,and then forming the expiring shape by forge or hot rolling,its forming process is complicated,and single cost is higher.In order to shorten the preparation process and solve the problem of secondary forming,6061 aluminum alloy is the research object of this paper,based on the traditional preparation,the preparation of composite slurry by mechanical stirring and the Twin-roll casting process with different groove were studied.The main contents of this paper are as follows:(1)In the preparation of SiC_p/Al composite slurry,the silicon carbide particles were pretreated by high temperature calcination,the particles were added in a small number of times,and time-sharing speed stirring method,the composite casting with different particle diameters was successfully fabricated.Metallographic and preparation technology research shows,the uniformity of SiC_p distribution is proportional to the particle diameter and stirring time,the results show that the larger the diameter of the particles is,the easier the particles are dispersed.The smaller the diameter of the particles is,the easier the agglomeration and the particles into a ring shape distribution,the longer the stirring time is,the better the particle uniformity is.The distribution is optimal when the particle diameter is 80?m.The longer the stirring time is,the better the particle uniformity is.(2)On the basis of the existing cast rolling platform,the mechanical stirring cast rolling experiment platform was set up,and the SiC_p/Al composite strip consisted with different content(4wt%,8wt%,12wt%)and different particle diameter(23?m,80?m)was successfully fabricated.Macro/micro analysis shows,the composite strip with particle diameter of 80?m and the content of 12% has good surface quality,the particle were dispersed uniformly,domindat fracture mechanism of the composites strip is ductile fracture of the matrix,accompanied by the SiC particle fracture,it has good mechanical properties and surface quality to meet the initial design requirements.The heat treatment process shows that the water-cooled and T6 treatment obscures the enhancement effect of the particles,the air-cooling process should be used to analyze the particle enhancement rule.(3)On the basis of the preparation process of SiC_p/Al composite strip,the preparation of SiC_p/Al composite shaped section strip with symmetry and asymmetry was carried out by finite element simulation and experiment.In the aspect of SiC_p/Al composite symmetrical shaped section strip in Twin-roll casting,the effects of casting temperature,solidification process and casting speed on the forming process were analyzed.Analysis results show,when the casting temperature is 953 K and the casting speed is 1.8m/min,the temperature field of the solid/liquid phase is unevenly distributed in the width direction,but there is no temperature singularity in the section width and thickness direction,which has good forming effect.Under the guidance of the above process,the symmetrical deformed section strip of uniform microstructure and morphology was successfully fabricated,the correctness of the finite element results is verified.In the aspect of SiC_p/Al composite asymmetrical shaped section strip in Twin-roll casting,in this paper,the method of numerical simulation,experimental analysis and experimental verification is used.Firstly,the preparation process of symmetric shaped section is applied to the SiC_p/Al process of the asymmetric shaped section strip,no matter whether there is a particle,the surface of the composite shaped section strip have many cracks and non-solidified microstructure,especially concentrated in the groove roller.Then the finite element analysis of the defect generation mechanism is carried out,the temperature field of the molten pool shows that the temperature field is not uniform in the width direction.There is a singularity in the transition from the groove to the no-groove,the deformation rate of the edge and the center of the groove is different in the width direction,it is more prone to crack.Flow field analysis of molten pool shows,it can be seen that the liquid level fluctuation in the groove zone is more serious than that on the side of the no-groove roll,which increases the possibility of the cracks in the groove.Finally,in order to solve the uneven temperature field in the width and thickness direction,this paper presents a spray technology,by changing the contact heat transfer coefficient to improve the temperature field uneven temperature phenomenonin the width of the motlen pool.The experimental results show,after spraying technology,mainly defects concentrated in the groove roller have been eliminated,surface quality of samples has been very good improvement.