TC4 titanium alloy probes are preferred for low-temperature wind tunnels (-100°C) due to their strength retention, but ensuring low-temperature toughness—resistance to brittle fracture—is essential for reliable operation.5-Hole Pitotwelcome to click on the website to learn more!
TC4’s toughness at -100°C stems from its hexagonal close-packed (HCP) structure, which resists the brittle transition that plagues many steels. Its impact toughness (Charpy V-notch) remains above 30 J at -100°C, compared to 10 J for 304 stainless steel at the same temperature. In a cryogenic wind tunnel test, a TC4 probe withstood 500 thermal cycles (from 20°C to -100°C) without cracking, while a stainless steel probe fractured after 150 cycles.
Heat treatment further enhances toughness. A β-annealing process (800°C for 1 hour, air-cooled) refines grain structure, increasing fracture toughness by 15% compared to as-cast TC4. A tensile test at -100°C showed annealed TC4 had 20% higher elongation before fracture than untreated material.
Design considerations include avoiding sharp corners (radius ≥ 0.5mm) to prevent stress concentration, which can initiate cracks in cold environments. A TC4 probe with a sharp-edged head failed in a -100°C test, while a rounded-head model (radius 1mm) performed flawlessly.
For extreme low-temperature tests (-150°C), TC4 can be alloyed with 2% vanadium, improving toughness by 10% and maintaining ductility. This modified TC4 is ideal for aerospace cryogenic simulations, where probe reliability is critical to data integrity.