| Title |
A study on the microstructural characterstics in the semi-solid state of Al-20Si-5Fe-2Ni at high-frequency induction heating |
| Authors |
이상용(Sang Yong Lee) ; 노진호(Jin Ho Rho) ; 신평우(Pyung Woo Shin) |
| Abstract |
Powder processed(P/M) and spray formed(S/F) Al-20Si-5Fe-2Ni billet were reheated into mushy zone by high frequency induction heating. Evolution of microstructures in the semi-solid stste was investigated according to various heating, cooling and post heat treatment conditions. The results showed the feasibility of net-shape manufacturing of Al-high Si part by thixoforging of spray formed billet. Application of P/M Al-20Si-5Fe-2Ni for thixoforming revealed to be problematic because of the formation of pores in the semi-solid state. It was possible to control the average size of Si intermetallic phases within 10㎛ after thixoforging of S/F Al-20Si-5Fe-2Ni. Cooling rates depending on die temperatures strongly affected the homogenity of microsructures and hardness distribution of the thixoforged part. Microstructural study implied that optimal die temperatures for thixoforging of S/F Al-high Si billet should be in the range of 200-350℃. Inhomogenious macro-& microstructure of thixoforged part could be homogenized by post heat treatment. |