F

Forged Weight = 340 lb Machined Weight = 22 lb

Fig. 4.12. Comparison of Conventional and Isothermal Forging

Forged Weight = 340 lb Machined Weight = 22 lb

1700°F

JLnJ

Forged Weight = 60 lb Machined Weight = 22 lb

Forged Weight = 60 lb Machined Weight = 22 lb

Fig. 4.12. Comparison of Conventional and Isothermal Forging

Forging through the beta transus results in continuous recrystallization of the beta phase with little or no grain boundary alpha formation.

Hot die and isothermal forging are near net shape processes in which the dies are maintained at significantly higher temperatures than in conventional forging. This reduces die chill and increases metal flow. Isothermal forging, as shown in Fig. 4.12, is done at a constant temperature where the flow stress is constant resulting in more uniform microstructures and less property variation. Isothermal forging requires less die pressure and helps insure that the dies are filled during forging. However, expensive high temperature die materials, such as molybdenum alloys, and vacuum or inert atmospheres are required to prevent excessive die oxidation. While conventional die forging can require two or three separate operations, isothermal forging can often be accomplished in a single operation. Like so many other advanced manufacturing processes, forging has greatly benefited from automated process control and computer modeling.15

4.5 Directed Metal Deposition16

Directed metal deposition, also known as laser powder deposition, laser direct manufacturing, and electron beam free form fabrication, is a rather recent development that can help to reduce the cost of titanium parts. A focused laser beam, shown in Fig. 4.13, is used to melt titanium powder and deposit the melt in a predetermined path on a titanium substrate plate. The metal deposited preform is then machined to the final part shape. This near net process leads to

Process Coordinate System

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