Metallurgical failure analysis of non-separation of isolation pyro valve used in space applications

•During testing at 20 K, membrane separation was not observed in a pyro valve.•Metallurgical analysis was conducted to address the non-separation.•Plastic deformation was observed at the notch location due to strain hardening.•Higher root radius at notch led to metal forming rather than severance.•Importance of maintaining tolerances in critical applications is highlighted.