## 3 Results and Discussion
### Flow Properties at Different Strain Rates and Temperatures  
Figure 5 shows the flow stress properties of the different microstructures of LPBF Ti6 Al4V(ELI) produced here, exposed to different strain rates and temperatures. The curves of flow stress for samples C, D, and E are presented in Figure 5a, 5b, and 5c, respectively. The effects of external state variables are clearly seen in these curves, where, generally, the flow stress increases with increasing strain rate and decreases with increasing test temperature for the three different microstructures of LPBF Ti6 Al4V(ELI). The effect of temperature on the flow stress of the alloy is seen in Figure 5a-c to be more significant  
Figure 4: The XRD peaks profiles of (**a**) samples C, (**b**) samples D, and (**c**) samples E.  
compared to that of the strain rate. It is also important to note that the compression samples were not loaded to failure in this study to prevent damaging the loading cells, even though the samples were still loaded to allow sufficient plastic deformation. Thus, the ductility of the samples under the compression test carried out in this study at various levels of strain rate and temperature could not be conclusively discussed. A comparison of the flow stress properties of the three different forms of the alloy produced here is presented in Figure 5d-f at the strain rates of 0.1 s\({}^{-1}\), 0.005 s\({}^{-1}\), and 0.001 s\({}^{-1}\), respectively, and temperatures of 25 \({}^{\circ}\)C, 20 \({}^{\circ}\)C, and 500 \({}^{\circ}\)C, in each case. Generally, samples C recorded the highest values of flow stress at all test strain rates, followed by samples D, while samples E recorded the lowest values. The sharp decline in stress at a strain of approximately 0.1 for some tests conducted at test temperatures of 200 \({}^{\circ}\)C and 500 \({}^{\circ}\)C was related to Gleeble machine errors and not material properties. The values of yield (\(\sigma_{y}\)) and ultimate compressive (\(\sigma_{\text{ucs}}\)) stresses for these samples at various levels of the two external state variables of strain rate and temperature are presented in Table 3 and their trends are shown in Figure 6. The pronounced effect of temperature on the yield and ultimate compressive stresses is clearly shown in Table 3 and Figure 6, where the increase in temperature leads to a decrease in these two material properties for the three forms of the LPBF Ti6 Al4V(ELI) alloy produced here. In contrast, the effect of strain rate on the yield and ultimate compressive stresses of these three forms of the LPBF Ti6 Al4V(ELI) alloy produced here is shown in Figure 6. The increase in temperature leads to a decrease in the stress at the strain rates of 0.1 s\({}^{-1}\), 0.005 s\({}^{-1}\) and 0.001 s\({}^{-1}\), respectively. Figure 5: Effects of strain rate and temperature on samples (a) C, (b) D, and (c) E and a comparison of the curves of flow stress for these samples at strain rates of (d) 0.1 s\({}^{-1}\), (e) 0.005 s\({}^{-1}\) and (f) 0.001 s\({}^{-1}\) and at different test temperatures. alloy is significantly lower. In some cases, especially as the test temperature increases, there is an evident increase in yield and compressive stresses as the strain rate increases (Figure 6). This can be attributed to thermal softening overcoming instantaneous strain hardening and flow stress hardening, as high test temperatures encourage the climbing as well as gliding of dislocations, so that recovery due to the rearrangement of dislocations and the annihilation of dislocation pairs proceeds quickly [35].