Abstract
The effects of pre-strain on the tensile, creep, and low-cycle fatigue properties of type 304 stainless steel at elevated temperatures have been investigated to evaluate the fabrication-induced cold work effect on the properties of structural materials. The tensile pre-strain was introduced in the test specimens at room temperature at plastic strain levels as high as 15% for tensile tests, 10% for creep tests, and 5% for fatigue tests.
The results obtained are as follows;
(1) The 0.2% offset yield strength, ultimate tensile strength, and creep rupture strength increased with increasing pre-strain. This creep strength improvement is caused by the decrease of steady-state creep rate.
(2) Little difference in the low-cycle fatigue life was observed between the base metal and the pre-strained specimens. This is due to the disappearance of the pre-strain effect by cyclic hardening under fatigue conditions.
(3) Tensile and creep rupture ductilities decreased with increasing pre-strain. However, the reduction in fracture elongation due to pre-strain appears to be almost equivalent to the amount of pre-strain. Therefore, pre-straining causes no additional decrease in creep ductility in long term tests.
