The Influence Of Casting Process Parameters On The Structure And Properties Of 7050 Aluminum Alloy

With the more and more application of 7050 aluminum alloy,the advantages of twin roll casting in industrial production are becoming more and more prominent,so there are more and more scholars begin to put roll casting into the production of 7050 aluminum alloy plate.But for the study of cast rolling sheet of 7050 aluminum is less,and in the casting process is easy to crack,so it is important to how to reduce the cracks of cast rolling process.In addition,in the process of 7050 aluminum alloy casting,the microstructure and properties of 7050 aluminum Alloy plates is easy to affect by the casting process parameters and some external conditions.This paper mainly studies the casting process parameters of the size of the roll gap(casting thickness of cast rolling plate)of 7050 aluminum alloy macro surface,including the emergence and development of crack,and the affect of the microstructure and properties.And the effect of cooling rate,the pass reduction and casting after completion of the test of cast rolling sheet by the heat of the casting and rolling performance of plate rolling on microstructure of 7050 aluminum alloy were studied.The results show that:(1)With the decrease of the thickness of 7050 Aluminum Alloy cast rolling plate,the surface of 7050 aluminium alloy is more smooth and bright.And with the decrease of the thickness of cast rolling plate,the temperature is different from the center and surface decreases,and the solidification rate tends to be consistent,so that the crack of the surface is reduced,the quality of casting and rolling plate is higher.In the process of roll casting,with the decreases of thickness of the cast rolling plate,the surface of the casting and rolling plate and core of heat difference is decreases,the grain size of the side surface of cast rolled plate along the rolling direction and the thickness direction decreases,the shape and size of the plate are uniform,the grain aspect ratio increases,the rheological of the material becomes better.The coarse precipitates decreases at grain boundaries,and the rich Cu phase at grain boundaries and some non-equilibrium eutectic(Al Zn Mg Cu)decreases and segregation decreases.(2)With the decrease of the thickness of 7050 aluminum alloy cast rolling plate,the deformation resistance of the material increases with the decrease of grain size.Because the number of cracks of cast rolled plate is reduced,the increase of mechanical properties of materials,which dhows the characteristics of brittle fracture.The hardness of the thickness of cast rolling sheet of 0.5mm is increased by about 10% rather than the thickness of 2mm,the yield strength is increased by about 121%,the tensile strength is increased by about 86%,and the elongation is increased by about 28%.(3)After the hot rolling of casting,with the increase of pass,the surface of cast rolled sheet is more bright,the microstructure is more compact,the grains at the edge are elongated,the hardness and the strength increases gradually.The tensile fracture is intergranular fracture,and the elongation decreases.Whether the microstructure or mechanical properties is become better,but compared to the traditional secondary rolling elongation variation.When the rolling pass greater than 3,the temperature of the plate is low.The surface of the plate begin to appear a lot of crack and fracture phenomenon if the fourth times rolling carried out.(4)After the hot rolling of casting,with the increase of reduction,the surface of cast rolled sheet is more smooth and bright,the crack is less,the microstructure is more compact,the grain is fine and even,the hardness and strength increase.The tensile fracture is intergranular fracture,but the elongation almost have no change.When the reduction is 50%,the properties are the best.But the forming performance becomes worse and the crack edge is obvious after further increasing the amount of reduction.(5)With the increase of cooling rate,the grain size decreases.The grain size of the casting plate after water cooling is the most fine.The eutectic phase of grain boundary of air-cooled casting plate decreases greatly.(6)With the increase of the cooling rate,the hardness,tensile strength,yield strength of the cast rooling plate increased.After air cooling,the mechanical properties of the cast roolinng plate is best.The hardness is 193 HV,the tensile strength is 309.81 MPa and the yield strength is 225 MPa.The material fracture mode is mixed fracture.The results show that,the surface quality of cast rolled sheet can be improved and its microstructure and properties can be improved by reducing the thickness of cast rolling plate in the range of production conditions permitted.After the completion of the casting plate by the heat,which can save energy,increase the heat to a certain extent,rolling reduction and rolling times can be obtained and better performance.The cooling speed after the completion of the rolling casting has a great effect on the performance of casting and microstructure of the rolling plate.The test results show that the microstructure and properties of the casting plate after air cooling treatment are optimal.