Correlation of the fracture toughness of titanium with modified instrumented charpy impact test results

Abstract

Twenty samples of Titanium 6A1-4V alloy of three different heats were tested with the purpose of finding a correlation between fracture toughness and the results of instrumented Charpy impact tests with some modifications. Using methods of absorbing vibrations of the specimens during impact had no definite effect of the final results but did improve the smoothness of the Load versus Time curves. Some correlation was found between specimens with similar microstructure and heat treatments but excessive scatter was found when a correlation was attempted with all of the heats. From SEM examination, no difference could be seen in the fracture surfaces of the two similar heats even though they had different fracture toughness values. The third heat, however, showed a great difference. It was concluded that Charpy test results of specimens of different microstructures may be difficult to correlate with fracture toughness but it is possible that the amount to plane strain fracture can be used to find a correction for an accurate correlation.