If you are replacing the stock bars as part of a lift...yeah, you need an alignment because the front is higher anyway...

If you are JUST replacing the stock with a stronger bar, but keeping the height the same...you DON't need an alignment, as you are not changing the angles, just the spring.

If you measure the wheel arches at all four corners before you change the bars, and after the install, adjust the ride height to the same points....your alignment will be unchanged.