Effect Of Laser Pre-precipitation On Microstructure And Properties Of 7075 Alloy

Al-Zn-Mg-Cu alloy has high specific strength and good mechanical properties,it is used in aerospace field.7075 alloy is the most widely used,because of its poor corrosion resistance,it is especially manifested in intergranular corrosion.The corrosion resistance of the alloy can be improved effectively under the premise of maintaining mechanical properties.Laser heat treatment can effectively realize the high temperature pre-precipitation treatment.The laser high temperature pre-precipitation treatment was proposed to investigate the effect of laser high temperature pre-precipitation treatment on the microstructure and properties of 7075alloy by exfoliation corrosion,intergranular corrosion,electrochemical corrosion,hardness,tensile,friction wear,scanning electron microscope,transmission electron microscope,X ray diffraction.The mechanical properties,corrosion resistance and microstructure were analyzed.The results were shown that the corrosion resistance of the alloy was obviously improved by laser high temperature pre-precipitation,which is superior to that of the traditional heat treatment process.When the laser power was 1000 W,the sensitivity of intergranular corrosion to spalling corrosion is low.In the process of polarization,the self-corrosion potential of the alloy was higher,the current density is lower,and the electrochemical corrosion performance was also improved.The hardness,tensile property and wear resistance were improved significantly,and the fracture surface was dimple fracture.After laser high temperature pre-precipitation treatment,the grain on the alloy surface was refined,and the precipitates of the alloy matrix were mostly fine?'phases,which can play the role of dispersion strengthening.The precipitates at grain boundaries are chain distribution.Corrosion channels can be effectively blocked to delay corrosion.And precipitation free zone between matrix become wider,which delays the potential difference between grain boundary precipitates and matrix to a greater extent,making corrosion more difficult.Above all,laser high temperature pre-precipitation treatment can improve the comprehensive properties of the alloy,when the laser power is 1000 W The intergranular corrosion depth was 17?m,the spalling corrosion grade was EA,the self corrosion potential was-1.31 V,the current density was 0.27?A/cm~2,the hardness was 205 HV,the tensile strength was 480 MPa,the average roughness was 5?m,the weight loss was 3 mg.