Study On Strengthening Of Si Excess Type 6201 Aluminum Alloy

In recent years,with the increase in electricity demand,higher requirements have been put forward for power transmission work.6201 aluminum alloy is an Al-Mg-Si alloy,which is widely used in overhead transmission lines because of its high strength,high conductivity and good arc sag characteristics.In long-distance and large-span transmission lines,higher requirements are put forward for the performance of overhead aluminum alloy conductors.In this paper,the strengthening research of 6201 aluminum alloy is carried out by means of alloy composition design and heat treatment process optimization,aiming to explore the optimal composition ratio and aging heat treatment process.In addition,an experimental alloy precipitation kinetic model is established to calculate the activation energy and alloy performance,which provides a theoretical basis for the subsequent strengthening research of 6201 aluminum alloy.The main findings are as follows:1)With the increase of Cu element content,the strength of aluminum alloy increases,the conductivity gradually decreases,the aging reaches the peak time earlier,and the peak strength increases.The addition of Cu promotes the precipitation of needle-like β phases in the alloy,and the density of the β phase number increases,so the strength of the alloy increases rapidly.At the same time,Cu element dissolves into the matrix,resulting in electron scattering,and the conductivity of the alloy decreases.In this paper,the specimen of 0.4-0.8wt%Cu has good comprehensive properties after 1 h solid solution at 550℃ and 24 h aging treatment at 175℃,with tensile strength of 375-391 MPa,yield strength of 346347MPa,and conductivity of 48.1-48.8%IACS.2)After cold drawing deformation,the alloy reaches peak aging in a short time,and the conductivity increases rapidly.Dislocation strengthening caused by pre-deformation increases the strength of the alloy,while dislocations hinder the movement of electrons,resulting in a decrease in the conductivity of the solid-solvent alloy.In the subsequent aging process,the dislocation network provides a path with less resistance for the diffusion of solid solution atoms,thereby promoting the precipitation of the second phase and improving the strength and conductivity of the alloy.3)The apparent activation energies of resistivity and yield strength in the undefor med sample with 0Cu are 94.189 kJ/mol and 76.713 kJ/mol.The apparent activati on energy of the sample with Cu content of 0.3wt%was 79.031kJ/mol and 56.364kJ/mol,indicating that the addition of Cu promoted the precipitation of the β" p hase,reduced its activation energy.The apparent activation energy of the sample with a deformation of 34%was 72.123 kJ/mol and 61.725kJ/mol,indicating that cold deformation reduced the activation energy of the precipitated phase,and theβ"phaseprecipitation speed accelerated,the number increased,and then the perform ance of the alloy was improved.