Generally, the materials used to make resonators are acoustic material. These materials have typically good fatigue strength and relatively high Q.
Primary acoustic material includes titanium alloys, aluminium alloys, steel, money, and piezoelectric ceramics. Secondary materials include brass and magnesium. Unique materials used for electrodes include brass, copper, beryllium copper, and nickel.
Common acoustic material is as follows
Al–2024: An aluminium alloy is often used for ultrasonic resonators or components that experience relatively low ultrasonic stress.
Al–7075: An aluminium alloy is often used for ultrasonic resonators or components that experience relatively low ultrasonic stress. Al–7075 has a higher yield strength than Al–2024, so it is better suited for threaded components (e.g. Making Ultrasonic transducer front driver).
Ti–6Al–4V: A titanium alloy containing 6% aluminium and 4% vanadium. This is the most widely used titanium alloy. Also called 6–4 titanium or titanium 6–4.
Ti–7Al–4Mo: A titanium alloy containing 7% aluminium and 4% molybdenum. Used by some manufacturers of ultrasonic resonators. Also called 7–4 titanium or titanium 7–4.