Titanium alloys strain effects

The a — 0 transformation has a large hysteresis in hydrogenated titanium alloys, and different thermal treatments change their phase content. Various degrees of metastability due to hysteresis are implicit for the alloys after different thermal treatments. Metastable phases undergo transformation to a more equilibrium state during deformation, which can effect the flow of the alloy. Below we consider the effect of the thermal pre-strain treatment on ductility on the strength of the Ti-6A1-2Zr-1.5V-lMo-rH alloys. ... 

I.O. Bashkin, E.G. Ponyatovsky, O.N. Senkov, and V.Yu. Malyshev, The strain-rate effect on the hydrogen-induced workability improvement of titanium alloy VT20 at temperatures 500-800°C, Phys. Met. Metall., 69 167 (1990). 

A study was made of the effect of electrochemical potentials on the durability of double shear type samples consisting of 2 black filled NR and 3 metal discs alternately bonded together. Metals employed were carbon steel. Inconel, stainless steel, titanium and titanium alloy. The influence of dissimilar metals in contact, high cathodic potentials and elastomer strain was evaluated and the results discussed in terms of failure penetration depth. (Tenth Annual Meeting of the Adhesion Society Inc., Williamsburg, Virginia, USA, 22-27 Feb. 1987). 4 refs. 

Hydrogen effect on the mechanical properties discussed below was studied on several a and a+fi alloys with the following nominal composition of metallic components (Russian trade marks given in parentheses) commercial titanium of nominal purity 99.3% (VTl-0), Ti-6Al-2Zr-1.5V-lMo (VT20), Ti-6A1-4.5V (VT6), Ti-6Al-2.5Mo-2Cr (VT3-1), Ti-4Al-1.5Mn (OT4), Ti-6.5Al-4Mo-2Sn-0.6W-0.2Si (VT25u) and others. The main features of their stress-strain behavior due to hydrogenation were much similar, but some individuality was characteristic of each alloy. 

Fig. 10 shows that the flow stress of the hydrogen-alloyed compacts is essentially less than that of the outgassed ones at all test temperatuics. The flow stress relation between the hydrogen-alloyed and outgassed compacts depended on the strain. At equal strains at test temperatures, this ratio could achieve 2 or more. Thus, the effect of hydrogen on the properties of compacted powders is much similar to that observed on bulk titanium. 

In the sensitized mode, smooth stress-strain cun/es are shown above 750 °C (1380 °F), and work hardening occurs below 665 C (1220 °F). At 850 °C (1560 °F), for exampie, the stress level of the reheated material is almost twice that of the sensitized material at low strain. The sensitized mode involved quenching from 1200 °C (2190 °F=) to the test temperature. The reheated mode involved heating to the test temperature in 60 s. Source H.G. Suzuki et al., Effect of Phase Transformation on the Hot Workability of Ti-6AI-6V-2Sn, Ti-5AI-25Sn and Other Alloys, Sixth World Conterence on Titanium, P. Lacombe, R. Tricot, and G. Beranger, Ed., Les Editions de Physique, Psiris, 1988, p 1427-1432... 

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