Organization And Properties Of Conductive Aluminum Alloys Under Heat Treatment

Al-Mg-Si alloy has the advantages of high specific strength,good electrical conductivity and low price,which is widely used in long-distance overhead transmission conductors.Domestic power resources are mainly distributed in the west,however,the high electricity demand areas are mostly distributed in the east and south.Besides,the rapid development of the domestic economy leads to a surge in the number of domestically installed equipment and electricity consumptions.Therefore,the comprehensive performance of the wire requirements in the long-distance overhead transmission mode is getting higher and higher.Aluminum alloy materials for overhead conductors need to have excellent tensile strength and electrical conductivity.However,combining the tensile strength and electrical conductivity of aluminum and aluminum alloy conductors for conventional production is difficult.The higher tensile strength can improve the safety and reliability of the conductor in service,while high electrical conductivity can effectively reduce the energy loss in transmission lines and improve energy efficiency.Therefore,the development of new aluminum alloy conductor materials and their preparation methods with an improvement in tensile strength while ensuring electrical conductivity is a key scientific problem that needs to be solved,which has important economic and social benefits.In this paper,based on Al-0.52Mg-0.31Si（wt.%）alloy,the effects of Ce and B elements on the microinstruction and properties of the alloy were studied separately,and the optimal additions of Ce and B elements in the alloy were obtained.Furthermore,the effects of Ce and B combination alloying on the microinstruction and mechanical and electrical conductivity properties of Al-0.52Mg-0.31Si（wt.%）alloy were further studied,and heat treatment to improve the properties of the alloy.The main results of the study are as follows:（1）The effects of different Ce additions on the organizational properties of cast Al-0.52Mg-0.31S（wt.%）alloy were studied,and the alloy was heat treated to investigate the modulation of the organization and properties of the alloy by heat treatment and to determine the optimal addition of Ce elements to the alloy.In the range of 0～0.4 wt%,the alloy’s tensile strength and electrical conductivity were increased and then decreased with the increase of Ce addition.Ce element led to a refinement of the grains of as-cast alloy and the formation of Al Ce Si and Ce Si phases.In addition,the transformation of theβ-Al₅Fe Si phase toα-Al₈Fe₂Si phase was promoted by the addition Ce.When the Ce content is 0.2 wt.%,the overall performance of the heat-treated alloy is optimal with the electrical conductivity of54.9%IACS,the tensile strength of 157 MPa.With the addition of Ce,the refinement of grain size results in the enhanced of tensile strength of the alloy.Meanwhile,some of the solid solution Fe and Si elements precipitated to form secondary phases,leading to the increase of the electrical conductivity.（2）The effects of different B additions on the organizational properties of cast Al-0.52Mg-0.31Si（wt.%）alloy were investigated,and the alloy was heat-treated to study the modulation of the alloy organization and properties by heat treatment and to determine the optimal addition of B elements to the alloy.In the range of 0.02～0.08 wt.%,the tensile strength and electrical conductivity of the alloy tended to increase and then decrease with the increase of B.The B element can promote the formation of Al Fe Si phase in the as-cast alloy and improve the morphology of the needle-like Al Fe Si phase into spherical shape,which is beneficial to improve the tensile strength and elongation of the alloy,while the purification effect of the appropriate amount of B element on the alloy can effectively improve the The conductivity of the alloy can be effectively improved.When the B addition in the alloy was0.08 wt.%,granular B-containing phase was detected by EDS,and the electrical conductivity of the alloy decreased.The conductivity of the heat-treated alloy was 56.5%IACS at 0.04wt.%B addition,and the tensile strength was 137 MPa,at which time the alloy showed the best overall performance.（3）The effect of Ce and B composite alloying on the tissue properties of cast Al-0.52Mg-0.31Si（wt.%）alloy was studied,and the alloy was heat treated to investigate the modulation of the tissue and properties of the alloy by heat treatment.The results show that the composite addition of Ce and B significantly refines the grain size of the as-cast alloy,with the minimum average grain size of about 190μm,and the comprehensive properties of the alloy are better after the composite alloying of Ce and B.The composite addition of Ce and B increases the precipitation of Fe and Si containing phases,reduces the role of Fe and Si elements in the alloy in electron scattering,and the grain size of the alloy decreases,which improves the tensile strength of the alloy.The conductivity of the heat-treated Al-0.52Mg-0.31Si（wt.%）alloy was 56.7%IACS and the tensile strength was 147 MPa when the addition of Ce element was 0.2 wt.%and the addition of B element was 0.04 wt.%.