The isothermal forging process has been developed to produce turbine blades made of near fi Ti-alloy Ti-1 OV-2Fe-3Al. It is important to set the preform at the optimumposition of the die in order to get a high precision product. The deformation analysis by using FEM is effective to determine the optimum position.And also it is necessary to avoid buckling induced by the restriction of axial elongation of the material.As a result. Ti-10V-2Fe-3Al blades could be formed precisely by using only one stage of forging, and machining was needed only at the root. The thickness of the oxide layer induced on the surface of the forged blade was only 70,~m. The mechanical properties of Ti-10V-2Fe-3Al blades after forging and annealing were superior to those of Ti-6Al-4V blades and were nearly uniform across the length of the blades.

The effects of cold deformation on the morphology of c( precipitates were examined fo~three f3 titanium ailoys which were each mainly deformed by slip On the other hand, there wasno significant difference reflected by the initial deformation modes in the oc morphology after heavy deformation (60"/• rolling) among the three alloys, and the microstructures were considered to be of a microdupiex structure,

Mechanism of ƒ¿'•¨ƒÁ reverse transformation has been examined by means of dilatometric measurements, X-ray analysis and structural observations in an 18% Ni maraging steel.

Fundam~ental study of the high temperature deformation of titanium aluminide. TiAl, has been conducted in order to develop the manufacturing process using isothermal forging. Theflow stress was exactly expressed using Zenner-Hollomon parameter as well as common metals. The recrystallization occurred during high temperature deformation, and structure was transformed from the lamellar structure to the fine recrystallized grain structure. And there were some deformation conditions where TiAl could be deformed without any defects up to 800/0 degree of reduction from as cast state.On the basis of above information. manufacturing of pancakes was carried out by isothermal forging. It was confirmed that it was possible to work plastically even from cast ingots samples and that mechanical properties could be improved by isothermal forging.These results suggest that the isothermal forging is a extremely effective process for manufacturing processes of TiAi.

No abstract