Steel sheet

1. A steel sheet comprising, as a chemical composition, by mass %:

C: 0.150% or more and 0.300% or less;

Si: 0.30% or more and 2.50% or less;

Mn: 1.50% or more and 4.00% or less;

Al: 0.30% or more and 2.00% or less;

P: 0% or more and 0.0400% or less;

S: 0% or more and 0.0100% or less;

N: 0.0025% or more and 0.0100% or less;

O: 0% or more and 0.0060% or less;

Cr: 0% or more and 0.500% or less;

Ni: 0% or more and 1.000% or less;

Cu: 0% or more and 1.000% or less;

Mo: 0% or more and 0.500% or less;

Ti: 0% or more and 0.200% or less;

Nb: 0% or more and 0.200% or less;

V: 0% or more and 0.500% or less;

B: 0% or more and 0.0100% or less;

W: 0% or more and 0.100% or less;

Ta: 0% or more and 0.100% or less;

Sn: 0% or more and 0.050% or less;

Co: 0% or more and 0.500% or less;

Sb: 0% or more and 0.050% or less;

As: 0% or more and 0.050% or less;

Mg: 0% or more and 0.050% or less;

Ca: 0% or more and 0.040% or less;

Y: 0% or more and 0.050% or less;

La: 0% or more and 0.050% or less;

Ce: 0% or more and 0.050% or less;

Zr: 0% or more and 0.050% or less; and

a remainder comprising Fe and impurities,

wherein a metallographic structure at a ¼ thickness portion includes, by a volume percentage, a total of 50% or more of one or both of martensite and bainite and 8% or more of residual austenite, and a remainder being one or both of ferrite and pearlite,

an average value of aspect ratios of prior austenite grains is 5.0 or more at the ¼ thickness portion,

a number density of AlN is 3000 pieces/mm 2 or more and less than 6000 pieces/mm 2 at a depth position of 30 μm from a sheet surface,

an internal oxidation layer in which at least a part of a crystal grain boundary is coated with an oxide is provided from the sheet surface to a depth of 5.0 μm or more,

a grain boundary coverage of the oxide is 60% or more in a region from the sheet surface to a depth of 5.0 μm, the grain boundary coverage being a ratio of the length of the crystal grain boundary coated with the oxide to the total length if the crystal grain boundary in the region from the sheet surface to a depth of 5.0 μm, and

a tensile strength is 980 MPa or more.

2. The steel sheet according to claim 1 , wherein the steel sheet has a hot-dip galvanizing plating or a hot-dip galvannealing plating.

3. The steel sheet according to claim 1 , wherein a part or all of the martensite at the ¼ thickness portion is tempered martensite, and

a volume percentage of the tempered martensite at the ¼ thickness portion is 5% or more.

4. The steel sheet according to claim 2 , wherein a part or all of the martensite at the ¼ thickness portion is tempered martensite, and

a volume percentage of the tempered martensite at the ¼ thickness portion is 5% or more.