Cost - Effective TiAl based Materials

Because of their inherent low ductility, TiAl-based materials are difficult to fabricate, especially thin gage titanium gamma aluminide (TiAl) sheet and foil. In this paper, an innovative powder metallurgy approach for producing cost-effective thin gage TiAl sheets (with 356 mm long and 235 mm wide, and a thickness of 0.74, 1.09, 1.55, and 2.34 mm, respectively) is presented. The microstructures and tensile properties at room and elevated temperatures of the thin gage TiAl are studied. Results show that these TiAl sheets have a relatively homogenous chemistry, uniform microstructure, and acceptable mechanical properties. This work demonstrates a cost-effective method for producing both flat products (sheet/foil) and complex “chunky” parts of TiAl for various advanced applications including aerospace and automotive industries. INTRODUCTION Gamma titanium aluminides (TiA1) alloys have received much attention from both the aerospace and automotive industries due to their high specific strength and stiffness and their oxidation resistance [ 1-51. The typical TiAl production method was based on ingot metallurgy (LM) and consists of VAR (Vacuum Arc Remelt) ingot production, its hot isostatic forging, cut and machine the forgings into a rectangle bar, which was encapsulated, hot rolled down to the desired thickness, and, then, de-canning and finished ground to final thickness. The cost of the sheet was too high (in the range of $lO,OOO/lb) because of the high forging rejection rate and manufacturing cost. Research activities have been focused to improve the manufacturing steps and improve a consistency of properties between sheets. Powder metallurgy (PM) approach has been investigated as a lower cost method of producing complex, near net shape components [6, 71. This development focused attention on developing an innovative PM method, but commercially viable conversion practice for cost effective gamma-titanium aluminide materials to produce controlled, uniformly refined sheet structures with optimum mechanical properties in final PM products. TiAl sheet material named Gamma-met This is a preprint or reprint of a paper intended for presentation at a conference. Because changes may be made before formal 1 publication, this is made available with the understanding that H will not be cited or reproduced without the permission of the author. https://ntrs.nasa.gov/search.jsp?R=20030112241 2017-12-05T01:32:22+00:00Z