Preparation And MAO Investigation Of Al-Mg-Si-B Aluminum Alloy For Mould Cooling Plate

With the rapid develop of steel industry and the speed–up of continuous casting,mould cooling plate has become an important expenditure in continuous casting cost ofproduction. In order to prolong the service life of the mould cooling plate and reducethe cost, the development of new mould cooling plate material has become a new targetfor designers. In this paper, the new Al-Mg-Si-B alloy prepared by adjusting the alloycomposition, uniform, rolled, solution and aging, and micro-arc oxidation（MAO） on its.Using optical microscopy, scanning electron microscopy, X-ray diffraction and laserpulse thermal conductivity meter and other methods, analyzed the effect ofhomogenization, aging time and the B content on microstructure and performance ofalloys. The morphology of surface and cross-section, phase composition, wear-resistingproperty and bond strength are observed and analyzed. Studied the effect of the ceramiccoating on the hardness of the matrix alloy, thermal conductivity and tensile properties.The results show that: With increasing aging time, the G.P. zones continue to formand eventually turned into a stable second phase Mg2Si with an independent crystalstructure, dispersive distributed inside the grain, and the conductivity of alloy firstreduced quickly, and then increased, eventually reached to65%IACS. With increasingthe content of the element B, the tensile strength increased by4.2%, while the thermalconductivity from210.31W/（mK） increased to238.58W/（mK）, an increase of13.4%.After MAO treatment, the ceramic layer is divided into loose layer, dense layer andbuffer layer from the outer surface to the matrix alloy. The ceramic coating and thematrix alloy is micro-metallurgical bonding, the bond strength is greater than theadhesive strength of13.8MPa. The ceramic coating mainly is constituted by the α-Al₂O₃and γ-Al₂O₃. After MAO treatment, the surface hardness of the matrix alloyincreased from60⁸0HV to1100HV, even to1500HV. The yield strength, tensilestrength and elongation of the alloy were slightly decreased, the yield strength reducedby1.4%, the tensile strength and elongation decreased by3.75%and5%respectively.After two hours of friction and wear test, the wear weightlessness of the matrix alloy is39.6mg, while the wear weightlessness after MAO treatment is only4.9mg, so thewear resistance is greatly improved.