Method and apparatus for the injection molding of metal alloys

A method of injection molding a metallic material having dendritic properties comprising:

• (a) feeding said material into a screw extruder barrel having a discharge nozzle at one end;
• (b) advancing said material through said barrel in a direction toward said nozzle;
• (c) heating said material as it advances through said barrel to establish a temperature profile which maintains the material in a semi-solid state above its solidus temperature and below its liquidus temperature;
• (d) subjecting the material to shearing as said material advances through the barrel;
• (e) accumulating a quantity of material in an accumulation zone at the said one end of said barrel;
• (f) discontinuing the shearing of said material as said quantity thereof enters said zone;
• (g) raising the temperature of said quantity of material in said zone to a level to inhibit dendritic growth while maintaining said material in its semi-solid state;
• (h) applying force to the material in said zone to inject such material into a mold;
• and
• (i) terminating the application of said force when a predetermined quantity of such material has been injected into said mold.

Apparatus for injection molding a metallic material having dendritic properties, said apparatus comprising:

• (a) an extruder barrel having a discharge nozzle at one end, a material accumulation zone adjacent said nozzle, and an inlet remote from said nozzle;
• (b) feeding means for introducing said material into said barrel via said inlet;
• (c) means for heating material in said barrel to a temperature which is sufficiently high to inhibit dendritic growth;
• (d) means for moving material through said barrel from said inlet into said accumulation zone;
• (e) means for expanding said accumulation zone independently of the movement of material into said accumulation zone and at a rate at least as great as that at which said material is moved into said accumulation zone, thereby avoiding the imposition of appreciable force on material in said accumulation zone;
• (f) means for shearing said material as it moves through said barrel between said inlet and said accumulation zone;
• and
• (g) means for discharging material from said accumulation zone through said nozzle into a mold.

Apparatus for injection molding a metallic material comprising:

• (a) an extruder barrel having a discharge nozzle at one end, a material accumulation zone adjacent said nozzle, an inlet remote from said nozzle, and a shearing zone between said accumulation zone and said inlet;
• (b) means for moving said material through said barrel from said inlet into said accumulation zone;
• (c) means for heating material in said barrel to a temperature between its solidus and liquidus temperatures and which is sufficiently high to maintain said material in a semi-solid thixotropic state;
• (d) means for shearing material as its moves through said shearing zone;
• (e) means for discharging material from said accumulation zone through said nozzle into a mold,
• (f) said heating means including means for concentrating heat at said accumulation zone so as to maintain the temperature of said semi-solid material in said accumulation zone at a level higher than elsewhere in said barrel.

A method of molding an object from a solid substance having dendritic properties, said method comprising heating said substance to a temperature at which said substance comprises a mixture of liquid and solid components;

• shearing said mixture to inhibit dendritic growth;
• delivering said mixture to an accumulation zone;
• discontinuing the shearing of said mixture in said accumulation zone and increasing the temperature of such mixture in said accumulation zone to a level at which said mixture remains semi-solid and dendritic growth is inhibited in the absence of shearing;
• and discharging said mixture from said accumulation zone into a mold.

Apparatus for molding an object from a solid metallic substance having dendritic properties, said apparatus comprising means for heating said substance to a temperature at which said substance is semi-solid and at which dendrictic growth is inhibited;

• means for shearing said semi-solid substance;
• means for moving said semi-solid substance to a zone in which no shearing occurs;
• means for raising and maintaining the temperature of the substance in said zone to a level at which said substance remains semi-solid but dendritic growth is inhibited;
• nozzle means in communication with said zone;
• and means for discharging from said zone through said nozzle means a quantity of said semi-solid substance sufficient to fill a mold, a residue of said semi-solid substance remaining in said nozzle.

A method of injection molding an initially solid metallic material comprising:

• (a) introducing solid particles of said material via an inlet into an extruder barrel terminating at one end in a discharge nozzle;
• (b) advancing said material along said barrel downstream from said inlet toward said nozzle, said barrel having a material accumulation zone upstream of said nozzle into which said semi-solid material is delivered and accumulated between successive discharges thereof through said nozzle;
• (c) heating the material in said barrel to a temperature between its solidus and liquidus temperatures to convert said material to a semi-solid state;
• (d) periodically discharging a quantity of said semi-solid material from said barrel through said nozzle into a mold;
• (e) terminating each discharge of said semi-solid material from said barrel in time to enable a residue of said semi-solid material to remain in said nozzle;
• (f) solidifying said residue to form a solid plug in said nozzle which seals said nozzle;
• and
• (g) expanding said accumulation zone independently of the delivery of said material thereto and at such rate relative to that at which said material is delivered to said accumulation zone as to avoid imposing on material in said accumulation zone between successive discharges a force sufficient to dislodge said solid plug.

Apparatus for injection molding an initially solid, metallic material comprising:

• (a) extruder means having an inlet and a discharge nozzle spaced downstream from said inlet;
• (b) means for introducing solid particles of said material to said extruder means via said inlet;
• (c) means for advancing said material downstream of said extruder means toward said nozzle into an accumulation zone in said extruder means upstream from said nozzle;
• (d) means for heating the material in said extruder means to a temperature between its solidus and liquidus temperatures to convert said material to a semi-solid state;
• (e) means for periodically discharging semi-solid material from said extruder means through said nozzle in such quantity as to cause a residue of said semi-solid material to remain in said nozzle between successive discharges;
• (f) means for solidifying said residue of said material in said nozzle between each successive discharge to form a solid plug;
• and
• (g) means for expanding said accumulation zone between successive discharges at such rate relative to the rate of introduction of material to said accumulation zone as to avoid imposing appreciable force on material in said accumulation zone, thereby avoiding dislodging of said solid plug between successive discharges.