## 3 Results and Discussions  
### Fatigue Cycles and Performance  
The high cycle fatigue bending test and the low cycle fatigue compression-traction test were applied in this study on the standard bending fatigue samples and the automotive suspension control components of aluminum semi solid materials, respectively. Table 1 shows the low cyclic fatigue results of the control arm part heat treated using standard T6 and multiple thermal aging heat treatment cycles. Regarding the low cycle fatigue test, one applicable part was tested for each thermal aging condition. There was a slight increase in fatigue life for the thermal aging cycle of WA0 (40,000 cycles) compared to standard T6 (36,000 cycles); while significant enhancement for the thermal aging cycle of WC3 resulted in superior values (72,000 cycles). The other aging cycles did not show a notable enhancement of fatigue life over the standard T6. It is well known that the fatigue performance is highly affected by the strength and ductility properties of the aluminum matrix. A good combination of excellent strength and high ductility can postpone the fatigue cracking failure and increase the fatigue life-number of cycles [14; 15; 16; 17]. For these reasons, the accelerating multiple thermal aging cycles of WC3 were applied to enhance the fatigue mechanical properties, by having compromised values of optimum strength and acceptable ductility compared to those obtained by standard thermal treatments.  
Figure 4: (**a**) Forces acting on vehicle tires due to engine torque, (**b**) simulated vehicle maneuver for 5s [18].  
Regarding the bending fatigue test, the results of the experiment are plotted in the chart shown in Figure 5 and a moving average spine was fitted between the original test values. The results revealed a remarkable increase in the fatigue life of the WC3 thermal aging cycle compared to the standard T6 aging. The results went well, with both results of the applicable part fatigue testing, as well as the results of the tensile testing and quality index indicated in previous works [14; 15]. The multiple thermal aging treatments of WA0 and WC1 show nearly similar average fatigue values of 54,667 and 53,000 cycles, respectively, compared to the standard T6 with 53,000 fatigue cycles. On the other hand, the thermal aging treatment WA1 (59,250 fatigue cycles) showed an enhancement of fatigue life compared to T6. The multiple thermal aging of WB0 showed lower fatigue cycles than T6 with only 25,000 cycles, indicating undesirable mechanical properties for all multiple thermal aging treatments of B cycles. A remarkable 155% enhancement of fatigue life for the interrupted thermal aging treatment of WC3, with an average of 82,000 cycles, which proves its significant impact for obtaining such superior fatigue cycles compared to standard thermal aging T6. This significant enhancement can be related to its high quality index values of excellent strength and high ductility. The WC3 interrupted thermal aging cycles, contributed in formation of well distributed and high density Mg\({}_{2}\)Si precipitates of various sizes, as explained in previous studies [14; 15].  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Thermal Aging treatment** & **Fatigue Cycles** \\ \hline WA0 (T6/T7) Multiple thermal aging cycles & 40,000 cycles \\ \hline WA8 (T6/T7) Multiple thermal aging cycles & 24,000 cycles \\ \hline WB0 (T7/T6) Multiple thermal aging cycles & 30,000 cycles \\ \hline WC1 (T4/T6/T7) Multiple thermal aging cycles & 33,000 cycles \\ \hline WC3 (T4/T6/T7) Multiple thermal aging cycles & 72,000 cycles \\ \hline T6 Standard thermal aging & 36,000 cycles \\ \hline \hline \end{tabular}
\end{table}
Table 1: Fatigue cycles of the A357 aluminum semi-solid applicable parts.  
Figure 5: Results of cantilever bending fatigue test for standard samples.