United States of America As Represented by the Secretary of the Air Force

Venkat K Seetharaman

Sheldon L Semiatin

Raghavan Srinivasan

James C Malas

Vinod K Jain

Anil Chaudhary

Steven C Medeiros

R Dennis Irwin

Enrique A Medina

Robert L Goetz

W Garth Frazier

Carl A Lombard

S Venugopal

William M Mullins

A method for predicting process parameters for optimization and control of microstructure in metal and alloy products of hot working fabrication processes is described. The method uses state-space material behavior models and hot deformation process models for calculating optimal strain, strain rate and temperature trajectories for processing the material. Using the optimal trajectories and appropriate optimality criteria, suitable process parameters such as ram velocity and die profile for processing the material are determined to achieve prescribed strain, strain rate and temperature trajectories.

Optimization and control of microstructure development during hot metal working

A heat treatment and hot working method for producing a thin sheet of nickel base superalloy single crystals is described, wherein a single crystal preform of an alloy is first heat treated in vacuum at temperatures below the .gamma.' solvus temperature of the alloy in order to obtain an overaged .gamma.' microstructure in the preform, sized and surface ground in order to remove surface defects, and then preferably surrounded by plates and interlayers of refractory metal or alloy and parting agent coatings; the plates are then welded to form an enclosure and evacuated, preheated and soaked at 1093.degree. to 1150.degree. C. and rolled at roll speeds of about 0.12 to 0.25 rods in successive passes, at about 5 to 15% reduction per pass with reheating at the soaking temperature between successive passes, to a reduction in thickness of 50 to 75%; the plates are then removed and the preform is conditioned, repacked and successively rolled to preselected thickness.

Method for hot rolling single crystal nickel base superalloys

A method for extruding metals and alloys, particularly difficult-to-work high temperature alloys, is described which comprises inserting a billet of the metal or alloy into an extrusion can, heating the canned billet to a temperature in a temperature range in which the ductility of the billet material is substantially maximum, cooling the canned billet sufficiently to establish a preselected temperature difference between the billet and can at which the difference between the flow stress of the billet material and the flow stress of the can material is substantially minimum, and extruding the canned billet to preselected shape.

Controlled dwell extrusion of difficult-to-work alloys

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Beavercreek, OH, United States of America

Venkat K Seetharaman