Aluminum alloy wire, aluminum alloy strand wire, covered electrical wire, and terminal-equipped electrical wire

1. An aluminum alloy wire composed of an aluminum alloy,

the aluminum alloy containing at least 0.03 mass % and at most 1.5 mass % of Mg, at least 0.02 mass % and at most 2.0 mass % of Si, and a remainder composed of Al and an inevitable impurity, a mass ratio Mg/Si being not lower than 0.5 and not higher than 3.5,

in a transverse section of the aluminum alloy wire, a rectangular surface-layer void measurement region having a short side of 30 μm long and a long side of 50 μm long being taken from a surface-layer region extending by up to 30 μm in a direction of depth from a surface of the aluminum alloy wire, a total cross-sectional area of voids present in the surface-layer void measurement region being not greater than 2 μm 2 ,

the aluminum alloy wire having

a diameter not smaller than 0.1 mm and not greater than 3.6 mm,

tensile strength not lower than 150 MPa,

0.2% proof stress not lower than 90 MPa,

breaking elongation not lower than 5%, and

electrical conductivity not lower than 40% IACS.

2. The aluminum alloy wire according to claim 1 , wherein

in the transverse section of the aluminum alloy wire, a rectangular inside void measurement region having a short side of 30 μm long and a long side of 50 μm long is taken such that a center of this rectangle is superimposed on a center of the aluminum alloy wire, and a ratio of a total cross-sectional area of voids present in the inside void measurement region to the total cross-sectional area of the voids present in the surface-layer void measurement region is not lower than 1.1 and not higher than 44.

3. The aluminum alloy wire according to claim 1 , wherein

the aluminum alloy further contains at most 1.0 mass % in total of at least one element selected from among Fe, Cu, Mn, Ni, Zr, Cr, Zn, and Ga,

Fe is contained within a range not lower than 0.01 mass % and not higher than 0.25 mass %,

each of Cu, Mn, Ni, Zr, Cr, and Zn is contained within a range not lower than 0.01 mass % and not higher than 0.5 mass %, and

Ga is contained within a range not lower than 0.005 mass % and not higher than 0.1 mass %.

4. The aluminum alloy wire according to claim 1 , wherein

the aluminum alloy further contains at least one of at least 0 mass % and at most 0.05 mass % of Ti and at least 0 mass % and at most 0.005 mass % of B.

5. The aluminum alloy wire according to claim 1 , wherein

the aluminum alloy has an average crystal grain size not greater than 50 μm.

6. The aluminum alloy wire according to claim 1 , the aluminum alloy wire having a work hardening exponent not smaller than 0.05.

7. The aluminum alloy wire according to claim 1 , the aluminum alloy wire comprising a surface oxide film having a thickness not smaller than 1 nm and not greater than 120 nm.

8. The aluminum alloy wire according to claim 1 , the aluminum alloy wire containing at most 8.0 ml/100 g of hydrogen.

9. An aluminum alloy strand wire made by stranding together a plurality of the aluminum alloy wires according to claim 1 .

10. The aluminum alloy strand wire according to claim 9 , wherein

a strand pitch is at least 10 times and at most 40 times as large as a pitch diameter of the aluminum alloy strand wire.

11. A covered electrical wire comprising:

a conductor; and

an insulation cover which covers an outer circumference of the conductor,

the conductor including the aluminum alloy strand wire according to claim 9 .

12. A terminal-equipped electrical wire comprising:

the covered electrical wire according to claim 11 ; and

a terminal portion attached to an end portion of the covered electrical wire.