EFFECT OF GATE SHAPE AND FORGING TEMPERATURE ON THE MECHANICAL-PROPERTIES IN THE INJECTION FORGING PROCESS OF SEMISOLID ALUMINUM MATERIAL

Semi-solid materials (SSM) were fabricated under two fabrication condi tions by mechanical stirring. Re-heating conditions of SSM with the tw o fabrication methods (mechanical and electro-magnetic stirring) were studied with two holding times and three re-heating temperatures. SSM forging was conducted with three different die temperatures (T-die = 2 50, 300 and 350 degrees C) and two gate types (straight gate and orifi ce gate). The mechanical properties of semi-solid forging components c an be predicted indirectly, from the microstructure of SSM fabricated at a cooling rate of 0.0094 degrees C s(-1) and a stirring speed of 10 00 rpm. The initial microstructure of the SSM affects the microstructu re of the SSM in the process of re-heating, a smaller initial microstr ucture providing a more globular microstructure after re-heating. The microstructure of SSM held for 15 min is superior to that of SSM held for 20 min in terms of globulization and size. The effect of die tempe rature is not serious to fill a die cavity in straight gate die. The m echanical properties of forging components fabricated at the orifice g ate die are superior to those of components fabricated at the straight gate, e.g. an ultimate strength of U = 320 MPa for the orifice gate c ompared to an ultimate strength of U = 250 MPa for the straight gate. (C) 1998 Elsevier Science S.A.