Directional Heat Treatment Of Pure Copper Wires

With the continuous progress of technology,electrical equipment and electronic devices tend to be increasingly miniaturized and sophisticated,which put forward higher requirements for the conductivity and fidelity of pure copper wires.Transverse grain boundaries increase the resistivity and produce the capacitance-inductance effect,which leads to the transmission distortion of high frequency signal in polycrystalline pure copper wires.How to eliminate the lateral grain boundaries in pure copper wires is the research focus to improve the conductivity.In allusion to that problem,the influences of the cold-drawing deformation rate and heat treatment process on the secondary recrystallization structure of small diameter cold-drawing pure copper wires were studied in this dissertation.On that basis,the paper studied the influences of the cold-drawing pure copper wires' structure and properties by directional heat treatment,which eliminated the transverse grain boundaries effectively and increased conductivity.The main conclusions are demonstrated as follows:1.It was found that the cold-drawing deformation dramatically affected the directional migration of grain boundaries of pure copper wires.Larger cold-drawing deformation was easier to trigger directional secondary recrystallization in pure copper wires.When the colddrawing deformation was higher than 89%,columnar crystals with larger length-diameter ratio can be acquired.The orientation of columnar crystals tended to become <112> secondary recrystallization texture.2.The process parameters of directional heat treatment have a significant impact on the grain boundaries' directional migration in pure copper wires.Different hot zone temperatures have according optimal withdrawing rates.Grain boundaries are able to directionally migrate effectively and the length-diameter ratio of columnar crystal reaches the maximal.Under the condition of 750? and 15?m/s,the largest length-diameter ratio of columnar crystal is 7,and the electrical conductivity is increased by 5%.3.There are some ‘island' crystals in the coarse columnar crystals after directional heat treatment.Some small grains with low angle grain boundaries or twin boundaries which are hard to migrate are bypassed by the directional migration interface and turn into isolated islands within the columnar grains.4.After directional heat treatment,most of the grain boundaries between the columnar crystals in pure copper wires are ?3 grain boundaries and ?9 grain boundaries which own low energy.