Titanium (Ti)
- Practical Electron Microscopy and Database -
- An Online Book -

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At room temperature and ambient pressure, Ti (titanium) has a hexagonal close-packed structure (called α-phase) with the lattice constants listed in Table 1721a. Its unit cell has two atoms at (1/3, 2/3, 1/4) and (2/3, 1/3, 3/4) and the space group number is 194 (P63/mmc). At room temperature and high pressure, it changes to the ω-phase [1,2] with the lattice constants listed in Table 1721b. Its unit cell has three atoms at (0, 0, 0), (1/3, 2/3, 1/2), (2/3, 1/3, 1/2) and the space group is P6/mmm. The α → ω transition in Titanium is a typical example of martensitic transformation.

Table 1721a. Lattice constants of α-titanium at 25 °C.

a (Å)
b (Å)
c/a
2.951 4.684 1.5873*
* Smaller than the ideal ratio of 1.633 for HCP

Table 1721b. Lattice constants of ω-titanium at 25 °C.

a (Å) b (Å) c/a
4.598
2.822
~ 0.61

Table 1721c. Lattice constants of β-titanium.

a (Å) b (Å) c (Å)
3.32
3.32
3.32

Table 1721d. Properties of Ti metal.

Density (g-cm-3)
4.51
Valence states
3s, 3p, 3d, 4s
Reference configuration
3s23p63d24s0
Core radii for angular waves (a.u.)
rs=1.25, rp=1.25, rd=1.65

Specific heat (cp, Jkg-1K-1)

520

Heat conductivity (kh,Wcm-1K-1)

0.17

Melting temperature (Tm, °C)

1668

Vaporization temperature (Tv, °C)

3280

Melt heat (Qm, J-g-1)

403

Vaporization heat (Qv, J-g-1)

8790
Absorption (1-R)
0.40 for 1 µm light
Phase transformation 
at ~882 °C, from bcc (β-phase) at higher temperatures to hcp (α-phase) at lower temperatures

Figure 1721a shows the solid solubility of some impurities (including Ti) in silicon.

Solid solubility of impurities in silicon

Figure 1721a. Solid solubility of impurities in silicon.

Figure 1721b shows the solubility for impurities (including Ti) in SiC.

Solubility for impurities in SiC

Figure 1721b. Solubility for impurities in SiC.

Table 1721e. Most closed packed d-spacing and planes in Ti and Ti-based crystals.

Space group
Structure
Plane
d-spacing (Å)
Ti
P63/mmc (194) hcp (1 0 0) 2.557
I41/amd (141) tetragonal (1 0 1) 0.3509
I41/amd (141) tetragonal (1 0 1) 0.3746

 

[1] Jamieson J.C., Science, 1963, 140, 72; doi:10.1126/science.140.3562.72.
[2] Sikka S.K., Vohra Y.K., Chidaraman R., Prog. Mater. Sci., 1982, 27, 245.

 

 

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