The are powdered metal. Metal powder is molded, under heat and pressure, to fuse together to make the blank that is then machined. It is a cheap process, inferior to proper forgings, but it’s cheap.
I seriously doubt that Pratt is only using powdered metal on these engines. They are probably using it in every newer generation engine, because it’s cheap. These engines just happen to be the first to fail, like the Hyundai Theta II engines failed before the Nu series engines failed.
The vendor of the powder is an RTX division, so they can’t even try to pin the blame on a vendor, like Hyundai has, repeatedly, as each new lot of engines fails.
https://www.prattwhitney.com/en/services/other-services/hmi-metal-powders