Martensitic Twinning in Alpha + Beta Ti-3.5Al-4.5Mo Titanium Alloy

Abstract

The twinning structure of the orthorhombic α martensite phase in alpha + beta Ti-3.5Al-4.5Mo (wt%) titanium alloy was studied using X-ray diffraction and transmission electron microscopy by water quenching from below transus temperatures. While water quenching from 910 • C induced the formation of {110} • twins, quenching from 840 • C formed the α martensite with {111} • type I twins. The effect of the principle strains on the twinning structure was discussed. As compared to the previous studies, the principle strains play an important role in the formation of the twinning type.

High temperature oxidation resistance and microstructure of laser-shock peened Ti-Beta-21S

“…[16] for the α-Ti phase formed in Ti-Beta-21S by oxidation at 650°C during 50 h. However, the heating induced by the LSP treatment is too low to induce the β → α phase transition. These small peaks at 35.1 and 40.1°could correspond to the martensitic α″-Ti phase which in general can be formed by deformation of β-Ti at room temperature [17][18][19][20]. Here, the formation of α″-Ti would be induced by the recoiled pressure of the laser-shock wave.…”

Surface Modification of the EBM Ti-6Al-4V Alloy by Pulsed Ion Beam

“…It was found that twins were the main substructural elements of martensite plates in layer 1 (Figure 4). The presence of twins appears to be the result of the relaxation of internal stresses [41], arising during high-speed quenching from the β-region. The detection of twins in the samples after PIB modification does not contradict the previously obtained data on twinning in hcp alloys [42], since, in these alloys, the tendency for deformation by twinning is determined by the small value of the ratio of the lattice parameters c/a in comparison with bcc and fcc alloys.…”

Twinning behavior of orthorhombic-α” martensite in a Ti-7.5Mo alloy

“…From crystallographic standpoint, transformation twin structure occurs as a result of a lattice invariant shear (LIS) to accommodate the martensitic transformation strain [41,42]. Several transformation twinning modes have been reported in orthorhombic-αʺ martensite structure, namely, {111} αʺ -type I [19,[22][23][24], <211> αʺ -type II [19,25], and {011} αʺ -compound twinning [19,26,27]. In particular, Inamura et al [19] have proposed an approach to predict the transformation twinning system for LIS by the infinitesimal deformation theory [43].…”

“…Extensive studies have been conducted on the crystal structure of αʺ martensite in β-Ti alloys [17][18][19][20]. These studies reveal that αʺ martensite contains internal twin structure, namely, transformation twin structure, which is associated with transformation strain accommodation from β to αʺ martensite [19,[21][22][23][24]. Different transformation twinning modes have been reported such as {111} αʺ -type I [19,[22][23][24], <211> αʺ -type II [19,25], and {011} α" -compound twinning modes [19,26,27].…”