*3.2. The Mechanical Properties of CR Samples*

The engineering stress-engineering strain (σE-εE) curves of 10%, 30%, 50%, 70%, and 90% CR samples are shown together with those of the original sample in Figure 6a. The mechanical properties that changed due to the cold rolling reduction are listed in Table 3. It was found that the original sample exhibited a low average yield strength of 281 MPa and high average elongation of 52%. After 30% cold rolling, its average yield strength increased to 968 MPa with an average elongation of 27.4%. When the cold reduction increased to 90%, the yield strength rose to 1870 MPa, nearly seven times that of the original sample, but the elongation decreased to 1.3%. Figure 6b shows that the average tensile/yield strength increased, but the average elongation decreased, when the cold rolling reduction increased. The average Vickers hardness increased as the cold rolling reduction increased. When the cold reduction increased to 90%, the hardness value increased to 549.4, which is about three times that of the original sample.

**Figure 6.** (**a**) Engineering stress-engineering strain behavior for original, 10%, 30%, 50%, 70%, and 90% CR samples; (**b**) variation average yield/tensile strengths and elongations; and (**c**) Vickers hardness as a function of cold rolling reduction.

**Table 3.** Variation of martensite volume fractions, Vickers harnesses, mean tensile and yield strengths, and mean elongations with % cold rolling reduction for 316LN ASS.

