Titanium Research Paper

Titanium was first recognized in 1791 in the iron sand (FeO.TiO2) by William Gregor, an English clergyman, and an amateur mineralogist. After that similar observation was made in 1795 by a German chemist, Martin Klaproth who analyzed a mineral rutile (TiO2) and he named the element titanium after the Titans, the powerful sons of the earth in Greek mythological [Polmer (2006)]. Titanium is the fourth gorgeous metal after aluminum, iron, and magnesium. Extraction of titanium from its ores was not developed on a commercial scale until the Kroll’s process was developed in 1950. Today, a large number of titanium and titanium alloys are used in various applications like chemical and petrochemical industries as well as other consumer goods such as

However, among titanium and its alloy series, commercially pure titanium (cp-Ti) is the second most used for application in the aerospace, chemical industries, and medical devices. Titanium alloys have higher specific strength at elevated temperature than that of aluminum and steel alloys (Fig. 1.2). However, titanium is 40% lighter than steel and 60% heavier in comparison of aluminum.

Titanium undergoes an allotropic transformation from the low temperature α (HCP) phase to the high temperature β (BCC) phase at 882±2 °C. Figure 1.3 shows α to β phase transformation. The temperature at which β to α transformation occurs is called the β-transus and depends on the amount and type of alloying elements added. The alloying elements that are dissolved in titanium may stabilize α or β phase. Titanium and its alloys react with interstitial elements such as oxygen, nitrogen, and hydrogen, below their respective melting points. In its reactions with other elements, titanium may form solid solutions and compounds with metallic, covalent or ionic bonding. Major alloying elements, added to improve mechanical properties and corrosion resistance, are classified as α-stabilizer, or β-stabilizers.The alloying elements are generally classified into three categories as α-stabilizer, β-stabilizer and neutral. The α-stabilizing elements extend the α phase field to higher temperatures, while β-stabilizing elements shift the β phase field to lower temperatures.

Zr and Hf both exhibit the same β to α allotropic phase transformation and are isomorphous with both the phases of titanium. Sn has little influence on the α/β phase boundary.

1.3 CLASSIFICATION OF TITANIUM ALLOYS

Based on the phases present at room temperature, titanium alloys are classified into four different groups of α alloys (commercially pure titanium), near α alloys, β alloys, and α+ β alloys. Figure 1.4 shows the schematically three-dimensional phase diagram, which is composed of two phase diagrams with α and β stabilizing elements respectively. According to this diagram, α alloys comprise of α phase and are exclusively alloyed with α stabilizing elements. If little quantity of β stabilizing elements is added, they are referred to as near α