Effects of Hot Isostatic Pressing and Heat Treatment on the Microstructure and Mechanical Properties of Cast TiAl Alloy

Abstract

Hot isostatic pressing (HIP) and subsequent heat-treatments (HT) are necessary for titanium aluminide (TiAl) casting components. But there are few studies carefully comparing the microstructure changes from the initial as-cast condition to the final heat-treated condition. In this study, the microstructures of Ti-47Al-2Cr-2Nb (at%) alloy in the as-cast, as-HIPed and as-heat-treated conditions were characterized by optical microscopy and scanning electron microscopy. The mechanical properties after HTs were determined by the tensile tests at 700 °C. The results show that after HIP and HTs, all the microstructures exhibit a nearly lamellar (NL) structure and can be divided into an edge region and a central area. The microstructure after HIP in the edge region is normal, while distorted lamellae and many fine recrystallized grains exist in the central area. The yield strengths after three HTs are nearly the same, but the elongation after the HT at 1310 °C is much more than that after HTs at 1185 °C and 1280 °C. A refinement of colony size induced by distorted lamellae in as-HIPed condition is considered responsible for the great improvement in elongation.

Effect of Minimum Quantity of Lubricant on Carbide Tools and Surface Integrity in the Machining of Titanium Aluminides

“…Nevertheless, because of the absence of processing methods suitable for materials with limited ductility, the applicability of TiAl alloys is restricted [8]. Manufacturing processes such as casting [9], powder metallurgy, ingot metallurgy, vacuum arc remelting (VAR), and, thanks to the recent advance of additive manufacturing [10,11], electron beam melting (EBM) [12], are applicable. The major disadvantage of these manufacturing procedures is that the part surface quality and the geometrical precision achieved do not fulfill the challenging specifications of the aeronautical sector [13].…”

A New Method for Preparing Titanium Aluminium Alloy Powder

“…Nowadays, the TiAl-based alloy is still recognized as a high-end material in the world [3,4]. Due to its high specific strength, high temperature resistance [5,6], corrosion resistance, oxidation resistance [7,8], and excellent biocompatibility, the TiAl-based alloy is widely used in the field of high-end materials in modern life [9,10]. For example, large aeroplanes, submarines, aerospace technology, and artificial bones [11][12][13].…”