Electrical Resistivity and Tensile Strength Relationship in Heat-Treated All Aluminum Alloy Wire Conductors

Abstract

Thermal processing of all aluminum alloy conductors (AAAC) is an important step that is performed to enhance the electrical and mechanical properties after the drawing process. In these 6xxx alloys, mechanical strength and electrical conductivity are normally two mutually exclusive properties. With the increased demand for high performance power conductors, it is important to understand and control microstructural evolution processes (e.g., recovery and the formation of nanoscale precipitates) in these alloys for better electrical and mechanical characteristics. In this study, heat treatment was performed on as-drawn 6201 AAAC wire conductors. The variations in tensile strength and electrical resistivity were quantitatively studied as a function of both the treatment temperature and holding time. Two wire diameters commonly used in the manufacturing of medium and high voltage power cables were used: 1.7 mm and 3.5 mm. From the obtained data, significant changes in the electrical resistivity and tensile strength were observed with increasing the treatment time. For both wire diameters, it was observed that the correlation between strength and resistivity can be described by a simple exponential relationship. This link could be useful in predicting mechanical strength by monitoring electrical resistivity variations during industrial heat treatment of AAAC wire conductors.

Characteristics of Wires of the Long-Operated Aluminum-Steel Cable at Different Places on an Overhead Power Line Span

“…As an optimal compromise between a sufficiently high electrical conductivity and a satisfactorily low cost of the metal [2,3], OPLs cables use either high-purity or technical-purity aluminum as the material of the conductive wires, including aluminum alloys with small additions less than ~3 wt.% of other elements (the main ones are Mg and Si [4], Fe and Si [3,[5][6][7], Mg and Fe [7], Mg, Si, and Fe [8,9] Mg, Si, Fe, Cu, and Zn [6], etc.). In a stranded all-aluminum cable, one or more layers (wraps) of aluminum or aluminum-alloy wires are concentrically wound around a central wire of the same metal (for short, if accentuation is not needed, we will use the term "Al wires" in both cases of either pure aluminum or its alloy).…”

“…In the literature, stranded all-aluminum cables are referred to as all-aluminum alloy conductors (AAACs) [4,7,8,[20][21][22][23][24][25][26][27] or, separately, all-aluminum conductors (AACs) if all of the wires in the cable are made of high-purity aluminum or aluminum conductor alloy-reinforced (ACAR) if the wires are made of technical-grade aluminum [28]. Stranded steel-aluminum cables are called aluminum conductors (or cable or clad) steel-reinforced (ACSR) [4][5][6][7]11,12,14,15,26,[29][30][31][32][33][34].…”

“…Earlier, to investigate the processes occurring during the operation of cables, cables were studied not only immediately after operation in OPLs [5,11,12,14,15,[24][25][26]30,34] but also after fatigue tests [6,16,[20][21][22][23][27][28][29][31][32][33]35,36], which simulated "aging" of wires (changes in microstructural, structural, and other properties) under real operating conditions or after heat treatment [8][9][10]. Both AAAC [6,8,16,[20][21][22][23][24][25][26][27][28]36] and ACSR [5,6,11,12,14,15,26,[29][30]…”

The Structure of the Near-Surface Layer of the AAAC Overhead Power Line Wires after Operation and Its Effect on Their Elastic, Microplastic, and Electroresistance Properties

“…During operation in an open-air atmosphere, wires in cables of overhead power lines are subjected to various influences, such as Aeolian vibration, sub-span oscillation, galloping, and swaying due to wind, tension, atmospheric corrosion, icing, moisture, fretting wear between wires, strong electromagnetic field, possible lightning strikes, and so on [8,[14][15][16][17]. As a result of these external influences, changes occur in both the structure and microstructure of not only Al of the outer surface layers, but also the inner material of the wires of the cable cores [18][19][20].…”

Effect of Er, Si, Hf, Nb Additives on the Thermal Stability of Microstructure, Electrical Resistivity and Microhardness of Fine-Grained Aluminum Alloys Al-0.25%Zr

“…Modern automotive and aviation technology imposes more and more high requirements to the fine wires in strength and thermal stability of the microstructure, which cannot be met using commercial aluminum alloys anymore. In this connection, aluminum alloys modifications of Al-Mg-Si system alloys [11,16,[28][29][30][31][32][33][34][35][36] (commercial alloys of 6XXX series [28,32,33,36,[38][39][40], Al-Mg-Si-Zr alloys [30], Al-Mg-Si-(Ni,Fe) + (Sc,Zr) [37], Al-Mg-Si-Cu [41], et al), conductor alloys Al-Fe [8,[42][43][44] and novel aluminum alloys multidoped with various rare earth elements (REEs) and transition metals (TMs) -zirconium, scandium, hafnium, yttrium, etc. are being developed extensively [45][46][47][48][49][50][51][52][53][54][55][56].…”