Pure uranium is a moderately ductile material. However, the mechanical properties depend on crystallographic texture (i. e., preferred orientation of grains) and, thus are in alpha-uranium. The texture is affected by the fabrication history and heat treatment. Grain size and shape are also important parameters affecting the mechanical properties. The tensile properties are sensitive to impurities like carbon or fission products or alloying elements. A typical stress-strain curve of uranium is shown in Figure 7.3. The strength decreases precipitously with increasing tempera­ture, as shown in Table 7.2.

The plastic deformation of uranium generally involves the following mecha­nisms: (i) slip in the {010}(100) system, (ii) {130} twinning, (iii) {172} twinning, and (iv) kinking, cross-slip, {176} twinning, and {011} slip under special condi­tions. Overall, twinning appears to be the major deformation mode at room tem­perature. However, the contribution of slip to plastic deformation increases as the temperature is increased, and above ~450 °C, slip becomes the predominant plas­tic deformation mechanism.