www.iaset.us editor@iaset.us MICROSTRUCTURE AND MECHANICAL CHARACTERISTICS OF TITANIUM ALLOY TC21 AFTER HEAT TREATMENT M. Abdelhameed 1 , Ramadan N. Elshaer 2 , Khaled M. Ibrahim 3 , A. Sobh 4 & M. El-Shennawy 5 1 Research Scholar, Petrojet Co., Cairo, Egypt 2 Research Scholar, Tabbin Institute for Metallurgical Studies, Cairo, Egypt 3 Research Scholar, Central Metallurgical R&D Institute, Cairo, Egypt 4 Research Scholar, Faculty of Engineering, Helwan University, Cairo, Egypt ABSTRACT Effect of heat treatment on microstructure and mechanical properties of TC21 titanium alloy was investigated. TC21 in annealed condition with an equiaxed α+β structure was solution treated at temperature below β-transus (920⁰C, 15 min) and temperature above β-transus (1020⁰C, 15min, WQ). Aging was applied for both groups of samples (600⁰C, 4h, AC).Treated samples below β-transus showed an equiaxed α+β structure. Samples treated above β-transus have been changed to a solely β-phase with little amount of secondary α-phase precipitated in the formed β-phase due to high cooling rate and aging process. Maximum hardness of 492HV 30 was reported for samples treated at 1020⁰C due to precipitation of secondary lamellar alpha phase and small lathes of martensitic phase (α\\) in β-matrix. Maximum tensile strength of 1447MPa and ductility of 8% were reported for the samples treated at920⁰C due to its structure that contained α, β and α s . Hence, treated samples at 920⁰C showed the best mechanical properties and the most reliable and repeatable characteristics. KEYWORDS: TC21 Titanium Alloy; Heat Treatment; Microstructure; Mechanical Properties Article History Received: 21 Apr 2021 | Revised: 27 Apr 2021 | Accepted: 11 May 2021 INTRODUCTION Titanium and its alloys are commonly used in manufacturing some parts of structure components and engine rotors for the aerospace industry and petroleum sector due to their high strength, low density, high corrosion resistance and low crack propagation [1]. The excellent balance of plasticity and fracture toughness with strength, attention has been paid to this titanium alloy; TC21 in the last decade [2-4]. Titanium alloy scan be classified into three main categories according to microstructure; α, α+β and β alloys. α+β titanium alloys have the best properties compared to other categories. Nowadays, α+β titanium alloys are widely used in aerospace applications, aero-engines, petroleum sector and chemical industries [1-2, 5-6].More than 50% of the used titanium alloys in different applications among α+β titanium category is Ti-6Al-4V alloy. International Journal of Mechanical Engineering (IJME) ISSN (P): 2319-2240; ISSN (E): 2319-2259 Vol. 10, Issue 1, Jan–Jun 2021; 49–56 © IASET