Cryogenic Temperature‐Dependent Machining Forces and Surface Integrity of Ti–6Al–4V Titanium Alloy

Ti–6Al–4V is a typical difficult‐to‐machine material, and cryogenic environments experimentally enhance its machinability. However, due to inadequate cooling temperature control, its mechanical responses and surface properties during cryogenic machining remain inadequately characterized, leaving critical temperature thresholds for improved machinability unascertained. This study investigates machining‐induced forces and surface integrity of Ti–6Al–4V under a precisely controlled cryogenic environment (20 to −196 °C) using a custom variable‐temperature cryogenic jet system. Influence of cryogenic temperature on cutting forces, surface roughness ( R a ), residual stress, and microstructure is examined at cutting speeds V c (40–80 m min −1 ). Results indicate axial force reverses from tensile to compressive at −60 °C, with a second reversal to tensile below this temperature. R a reaches minima at −100 °C ( V c = 60/80 m min −1 ) and −140 °C ( V c = 40 m min −1 ), with reductions up to 19.2%. Compressive residual stress magnitude increases monotonically with decreasing temperature. Microstructure evolves from acicular α‐phase (conventional cooling) to lamellar colonies at moderate cryogenic temperatures (−50 to −100 °C), and finally to chaotic basketweave structures under ultracryogenic conditions (−150 to −196 °C). This work reveals cryogenic mechanisms governing Ti–6Al–4V machining behavior, identifies critical temperature thresholds, and demonstrates significant potential of the developed variable‐temperature system in advancing cryogenic machining research.