I showed him similar looking lines on Zildjian cymbals and he`s pretty sure that`s not done by the hammering. The hammer moves the metal but he thinks maybe they make scratch marks in the mold and after hammering you still see those marks when the metal is smoothened. Hammering give more surface area in the same space as one that was not hammered and makes thin and thick spots too. He just wasn`t sure how they do it. He did point out that the one I showed him was hammered so much that the grains go everywhere throughout the cymbal and the metal is stronger and will bend as opposed to a cast not hammered out will snap.
Perhaps you should show him this picture of what a cast ingot looks like using the Zildjian process (top of middle column). An inch thick and a few inches in diameter (think hockey puck):
[img]http://black.net.nz/cym2014/zildjian-process.jpg[/img]
Then ask him again if he really thinks that "scratch marks" in the mold will be there to be seen after the ingot gets reheated and put through a mill up to 7 times* in different directions? You can show him the flattened "pizza dough" blanks coming out in the next photo down. It will be stretched and flattened until it gets big enough to make a much larger diameter cymbal. This process is completely different from the Italian one of casting in the shape of a cymbal.
This is the first time I've heard anybody claim that it is the hammering which creates the interlocking grains in a Zildjian cymbal. All other references refer to that coming from the multi way rolling. Hammering might add a little work hardening to the surface, but that's different. And the flexibility comes from the annealing process, according to all published sources. Is your friend familiar with the unusual tri-phase properties of B20 bronze? That is, CuSn20 or 80% Copper 20% Tin. It has quite different properties from most other bronzes, let alone other materials. Particularly car parts.
I'm not feeling the science here.
* other descriptions say more than 7, but the same principle applies. Interlocking grains created by repeated hot rolling under great pressure and with the blank in different directions.