Some, maybe most, of those longitudinal marks/striations look to me to be tooling marks. The deep ones are probably from a collet chuck used to hold the part while making the threads.

In my experience, large grained, columnar structures are almost always bad news.


P.S. - I forgot to say this earlier - many thanks to MikeX. That was a great post. I'm not disagreeing at all, I'm just trying to discuss this further and learn more about it. Thanks, MikeX.