Development of a heat treatment strategy for the γ-TiAl based alloy TNM-B1 to increase the hot workability

Abstract

Currently, TiAl turbine blades produced by isothermal forging are commercially used in aircraft jet engines. The limited workability of the HIPed microstructure causes long processing times because of low ram speeds and excessive wear on the costly molybdenum tools due to high forging stresses and temperatures. By introducing a multi-step heat treatment into the industrial forging chain, the formability of the material can be improved, leading to lowered production costs. In this work, the parameters of interest for improved formability are increased β/β 0 phase fractions, increased cellular phase fractions and reduced proportions of lamellar colonies. Several two-step heat treatments were investigated. The parameters of interest were then measured and compared. Subsequently, compression tests were carried out for the most promising heat treatments. It could be shown that a flow stress reduction of around 10% can be achieved by one of these heat treatments (1300 °C/1 h/AC + 1100 °C/5 h/AC). For this heat treatment, reproducibility was also checked using differential scanning calorimetry.

Gefügeeinstellung mittels Schmieden im Mehrfachhub/Microstructure adjustment by forging in multiple strokes - Increasing the degree of freedom during hot forming enables individual component properties

“…In [7] erfolgt eine Darstellung des Phasendiagramms. Eine Studie zur Wärmebehandlung ist in [8] aufgezeigt. Die Dichte des Werkstoffes des angefertigten Abgusses liegt bei 4,16 g/cm³.…”