**3. Cast-Forging**

## **3.1 Model process of cast-forging**

In cast-forging, a preform is cast near the net shape, which is suitable for forging. Processing and energy can be saved by cast-forging. The hot forging of a gravity-cast ingot was conducted as a model of cast-forging [8–10]. The process of gravity casting and hot forging is shown in **Figure 7**. This process is similar to cast-forging.

The cooling rate of the gravity-cast Al-4.5%Mg ingot was 30.6°C/s. A specimen was made for the tensile test and tested to investigate the mechanical properties of the ingot. A square bar was cut out from the as-cast ingot and heated at 500°C for 1 h. The forging was conducted at 50% reduction. The mechanical properties of the

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#### **Figure 7.** *Schematic of process from gravity casting to hot forging.*

**Figure 8.** *Tensile test results for gravity-cast Al-Mg alloys.*

hot-forged rectangular bar were investigated by tensile testing. The dimensions of the test piece are shown in **Figure 1a**.
