Abstract: Provided herein are various enhancements for additive manufacturing using titanium and titanium alloy materials. In one example, a method includes inoculating a titanium material with ceramic particles that produce nucleation sites within the titanium material during successive melt and solidification steps of an additive manufacturing process. The nucleation sites promote grain nucleation during solidification of molten titanium material into solid titanium material during the additive manufacturing process.

Abstract: A stir-friction hot-working or welding arrangement uses a pin tool having a ligament 22 and a shoulder 224. The force required for incremental penetration increases markedly when the shoulder is reached. A control system for maintaining a set penetration depth includes a load cell for measuring force or pressure applied to the pin tool. The control system compares a reference signal representing the desired force with the actual force from the load cell, to produce an error signal which controls the penetration force, thereby tending to maintain a desired penetration depth. In a particular embodiment, the reference signal ramps up from a low or zero value at turn-on, to reduce forces applied upon initial penetration. In another embodiment, position signals are used to control a modulator or multiplier, which changes the error signal applied at certain positions of penetration, or at certain velocities of penetration.