SCREW FORMING IN SEMI-SOLID FORGING OF ALUMINUM ALLOY A7075

This paper reports the screw forming of aluminum alloy A7075 by semi-solid forging. The experimental devices are a servo press machine and a die cushion. The program motion was used for forging. The nominal diameter of screw is M10. The molten aluminum alloy A7075 was stirred and then semi-solid forged into a female screw under 40 tons with 10 seconds holding during forging. The solid phase rate was 0.3. The microstructure of the specimen that is isometric crystal had sphericalization, and refinement. In the results of compression test at room temperature, the maximum compression rate was 29.4 % and the maximum nominal stress was 540 MPa. The screw tightening torque was estimated over 57.55 N center dot m by torque test. This value indicates for produced M10 screw that the strength is over strength category 8.8 of JIS. These results are indicated that the produced screw is suitable for general applications. In the results of optical observation, the male screw of die transferred to the aluminum forgings. And the surface of screw portion had crack free surface. In summary, screw forming by semi-solid forging of aluminum alloy A7075 was possible.