Commercially Pure (CP) Titanium and Alpha Alloys

Abstract

This chapter describes the processing, microstructure, and properties of α titanium alloys, with emphasis on the various grades of commercially pure (CP) titanium (often referred to as CP-Ti). A definition of α titanium alloys was included in Chap. 2, but it may be useful to include a more detailed one here. All α titanium alloys are based on the low temperature, hexagonal allotropic form of titanium. These alloys can contain substitutional alloying elements (Al or Sn) or interstitial elements (oxygen, carbon, or nitrogen) that are soluble in the hexagonal α phase. These alloys also contain limited quantities of elements that have limited solubility such as Fe, V, and Mo. Table 2.6 lists a representative group of α titanium alloys and grades of CP titanium, along with representative selections of alloys belonging to the α+β and β classes. The grade designations are taken from the American Society for Testing and Materials (ASTM). As the beneficial application of this class of titanium alloys has been recognized, the use has increased. Further, specific alloys have been formulated to improve to environmental resistance of CP titanium and α titanium alloys or to provide comparable performance at reduced cost where expensive additions such as palladium are involved. Consequently, there has been a proliferation of alloy grades. There are now at least 16 identifiable alloys or grades.