Strength and Electrical Conductivity Relationships in Al-Mg-Si and Al-Sc Alloys

Abstract

Aluminium alloys play an important role in overhead power transmission applications. All-aluminium alloy conductor cables require increasingly hard-to-achieve combinations of high tensile strength and high electrical conductivity. The problem is that a high strength is normally associated with a reduced electrical conductivity. Both heat-treatable 6xxx series aluminium alloys and work-hardening 1xxx series aluminium alloys are important contenders for these applications. By contrast, the addition of rare earths and/or transition metals to aluminium may provide further opportunities to achieve improved combinations of precipitation hardening, substructural hardening and elevated temperature stability. In this work, strength and electrical conductivity relationships are investigated for a range of 6xxx series aluminium alloys and an Al-Sc alloy. The Al-Sc alloy was produced by means of a direct laser metal deposition process that allowed more Sc to be placed into solid solution than by conventional casting or solution treatment. The paper explores the relative effects of composition, cold working and age hardening on the balance of strength and electrical conductivity, including examples of how improved combinations of both strength and conductivity can be achieved.

Review of the Quench Sensitivity of Aluminium Alloys: Analysis of the Kinetics and Nature of Quench-Induced Precipitation

“…For example, alloying elements in solution reduces the electrical conductivity [89], and precipitates may also have a negative influence on the conductivity [90]. The latter is generally lower compared to elements in solution, although the exact value depends on the size and strain field caused by the precipitates [90,91]. Furthermore, the different alloying elements in solid solution impact the electrical properties by substantially different factors [89].…”

Review on recent progress in Al–Mg–Si 6xxx conductor alloys

“…In addition, it was reported that high levels of Si and Mg could even lead to enhanced strain hardening [ 13 ]. The multiplication of dislocations during drawing only slightly deteriorates EC [ 79 ]. Moreover, the quantitative equation shows that a large number of dislocations have a negligible detrimental impact on EC [ 18,26 ].…”

“…At low aging temperatures, the minimum required EC might not be achieved, which could pertain to the remaining solute atoms in the matrix and the precipitates with a given interprecipitate spacing [ 7 ]. With respect to the deformation degree, it was seen that an increase in the degree of cold wire drawing could enhance strength due to strain hardening [ 79 ]. In addition, it was reported that high levels of Si and Mg could even lead to enhanced strain hardening [ 13 ].…”

“…Therefore, NA must be taken into account in terms of strength and EC. Rometsch et al [ 79 ] investigated the effect of NA at the room temperature on the ultimate tensile strength (UTS) and EC in an Al-0.5 Mg-1.1Si alloy without any drawing processes, as shown in Fig. 7 .…”

Modification of Surface and Subsurface Properties of AA1050 Alloy by Shot Peening

“…The commercially pure Al alloys (i.e., AA1050, 1070, 1100) also have notably higher electrical conductivity compared to other Al alloys (e.g., 60.3% IACS for AA1050 vs. 26.1% IACS for AA5483 Al alloy [77]). The strengthening mechanisms obtained by increasing the number of defects in a pure Al lattice (i.e., precipitates and solute atoms) significantly reduce the electrical conductivity [80]. Therefore, it is crucial to enhance the mechanical properties of 1xxx Al alloys considering the demand for electrically conductive Al alloys with better mechanical properties [78].…”