An investigation of a new near-beta forging process for titanium alloys and its application in aviation components

In this paper, the authors present a new near-beta forging process, in which materials are heated at about 15 degreesC below the beta transus, to improve the combined properties of titanium alloys. Materials processed by the near-beta forging process, followed by rapid water-cooling, then high temperature toughening and low temperature strengthening heat treatments, produce a new kind of microstructure for titanium alloys. This new tri-modal microstructure consists of about 15% equiaxed alpha, 50-60% lamellar alpha and transformed beta matrix. Materials with tri-modal microstructure show a high low cycle fatigue property, high creep-fatigue interaction life, high fracture toughness and a high service temperature without decreasing ductility and thermal stability. The experimental fundamentals of the new process and the strengthening and toughening mechanism have been discussed. A critical issue in the practical application of the near-beta forging process is the control of temperature. A new metallographic inspection method was proposed to solve this problem. This new near-beta forging process has been reliably applied to produce several aeroengine compressor disks, rotators, and other airplane components. (C) 2004 Elsevier B.V. All rights reserved.