Spiral spring for a horological movement

A spiral spring configured to equip a balance of a horological movement, wherein the spiral spring is made of an alloy consisting of:

• Nb;
• Ti;
• and
• V and/or Ta;
• optionally, Zr;
• optionally, Hf;
• optionally, W;
• optionally, Mo;
• and
• optionally O, H, C, Fe, N, Ni, Si, Cu, and/or Al,
• wherein a Ti content is at least 15 wt. %,
• wherein a total content of the Nb, V, and Ta is in a range of from 40 to 85 wt. %,
• wherein a total content of the Ti, Zr, and Hf is in a range of from 15 to 55 wt. %,
• wherein a W content is in a range of from 0 to 2.5 wt. %,
• wherein a Mo content is in a range of from 0 to 2.5 wt. %,
• wherein a content for each of O, H, C, Fe, N, Ni, Si, Cu, and Al in a range of from 0 to 1600 ppm,
• wherein a sum of the O, H, C, Fe, N, Ni, Si, Cu, and Al, is less than or equal to 0.3 wt. %, and
• wherein the spiral spring has a modulus of elasticity of at least 110 GPa.