A series of tests was performed including tensile testing in air under ambient and elevated temperature (630°C), fatigue testing in air under ambient conditions and creep rupture testing at 630°C.
Tensile testing found that the LEI samples gave the highest proof strength under both ambient (~1040MPa) and elevated temperature (~827MPa) conditions.
Compared to wrought at ambient temperature (~1221MPa), a reduction in proof stress by a factor of 1.17 for LEI and 1.21 for HEI was observed.
Fatigue endurance data, plotted in the form of an S-N diagram, showed that LEI samples gave a better fatigue performance than HEI with average lives 2x105 to 4.5x105 cycles greater for a given stress range.
A mean line through each test series was compared at 106 cycles. Wrought material gave the highest fatigue strength at 720MPa followed by LEI (525MPa) and HEI (435MPa) (Fig. 2).