The effect of microstructure and deformation behavior on the hot ductility of Ti-6Al-2Nb-1Ta-0.8Mo

Bowden, D. M.; Starke, E.A.

doi:10.1007/bf02666352

Cited by 27 publications

(1 citation statement)

References 10 publications

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“…Several researchers have proposed models for the ductility loss. One model, proposed by Starke et al(28), is that at 800°C, the (x allotriomorph is significantly weaker than the adjacent l_ or transformed l_.Slip concentrates in the grain boundary (x and is blocked at a non-Burgers related (x/l_ interface, causing stress concentration and microvoid nucleation. This mechanism is similar to that shown by Greenfield and Margolin (32) to occur at room temperature, but conflicts with the generally reported strengths of the (x and 13phases.…”

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High temperature ductility loss in titanium alloys -- A review

Rath¹,

Imam

Damkroger

et al. 1994

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It is well known that two phase titanium alloy systems suffer from an abrupt drop in ductility at elevated temperatures in the range of 1000 to 1150°K. This loss of ductility is manifested by easy decohesion of polycrystalline aggregates along the grain boundaries of the high temperature be__aphase. If the alloy is in a state of tensile stress at the aforementioned temperatures, :racks ini_,_ate at the grain boundaries and propagate readily through the alloy, leading to premature failure. This phenomenon is a cause of major concern in titanium alloy fabrication and welding. Several mechanisms have been proposed to explain high temperature crack nucleation and growth along the boundaries. A critical review of the phenomenon and possible mechanisms responsible for the observed behavior will be discussed. INTRODUCrlON Several near c_ and (x-l] titanium alloys have been found to have poor hot workability under certain processing conditions. This poor workability, and subsolidus weld cracking, result from a ductility loss in the temperature range of the to 0_transformation. This phenomenon has been studied and found to vary with alloy content, specimen thermal history, and a number of microstructural characteristics. This paper will review and summarize the results of several investigations of this high temperature ductility drop. !_i_ !:__:II:_E R I. Background The high temperature ductility loss observed in 0_-_ titanium alloys is illustrated in Figure 1. This data, from Lewis and Caplan (1), plots %RA for tensile tests performed both on heating and on cooling during a simulated GTA weld thermal cycle. The key features of the thermal cycle were a peak temperature above

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