Thirty-six elements have been alloyed singly with cartridge brass. Ammonia and mercury stress-cracking tests have been conducted on the as-rolled and recrystallized strip. Ultra high purity cartridge brass has also been tested. Silicon improves stress-cracking behavior. High silicon (1 per cent) cartridge brass quenched from high temperature (for example, 800 C.) annealing is exceptionally resistant to ammonia stress cracking. This improvement is not lost by subsequent cold working, but is greatly reduced by subsequent low temperature annealing. Phosphorus, arsenic, barium, cerium, magnesium, tellurium, tin, beryllium, and manganese benefit stress-corrosion resistance under some circumstances, but not others. The other alloying additions tried had no large effect on stress-cracking resistance. None of the elements added accelerated stress cracking. The impurities in commercial brass are not responsible for season cracking.

The study focusses on investigating the heat treatment of β21S titanium alloy in aerospace applications. The aircraft engine components made of this alloy are failing during service; believed to be associated with a lack of ductility due to the hardening of the alloy during use. To accurately analyse the alloy, the manufacturer recommendations on the aging process was to be utilised, where a range was given in the material properties sheet (Appendix A). Four conditions were treated in this range to find the most effective heat treatment; 566°C for 8 hours, 566°C for 16 hours, 679°C for 8 hours, and 679°C for 16 hours. After the heat treatments were applied, and appropriate preparation was completed, hardness tests on each set of heat treatments were completed. The heat treatment with the lowest hardness, and therefore the best ductility, was the condition of 679°C for 8 hours. To further investigate the heat treatments, the peak hardness condition for the material was used to represent the industry condition that was being simulated in the testing process. Previous work has found that the alloy is at its peak hardness at 400°C

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