6061-T6 Alterative Material

One possibility would be thixomolded magnesium alloy. It can be molded to net shape with radii on the edges and with much lower porosity than cast aluminum. I don't know how the strength compares exactly, but if some re-design is allowed, it may function as well or better than the aluminum plate. You will need high enough annual volume to warrant the expense of the tooling.

Sorry I put the wrong material it is 7075-T6 not 6061-T6

You say the part is stamped. From the dimensions you gave it was hard to determine the shape. Is this part stamped and formed with flanges, curved sections, or even tubular, or is it simply "blanked" from flat plate?

If it is primarily a blanked part, you might consider alloy steel forging with weight saving features, or redesigning the part to be stamped and formed from thinner (therefore lighter) alloy steel, with its ultimate strength obtained by the new shape, not just the material.

With newer die-cutting and stamping technologies, many steel parts, once redesigned for aluminum to save weight, can now be redesigned in steel with strength gained through geometry.

Think of the strength to weight ratio of a box beam or I-beam versus a solid beam and you will understand what I am talking about. Alloy steels like 4130 may be comparable in strength to 7076-T6, but weigh almost 3 times as much. If the base material is 1/3 the thickness of a blanked aluminum part, then the weight is also 1/3, but so is the strength. Add a few flanges, ribs, channels, dimples, etc. and you dramatically increase the strength without much increase in weight. You may also find that the stamped and formed design includes ample radii on most external features.