Structural dispersion of powder titanium in the optimal conditions of dynamic hot pressing

In [1], we studied contact formation in powder titanium during dynamic hot pressing (DHP) and demonstrated that it is possible in principle to produce qualitative products from titanium in a very short time (a few milliseconds). It was shown that during DHP, physical contact of high quality is formed in the temperature range 800–950°C. Such thermomechanical treatment promotes the recrystallization of the material near interparticle boundaries and, thereby, prevents interparticle fracture. Samples made in such conditions undergo dimple intragranular fracture and their mechanical properties are as good as those of conventionally produced titanium. Further improvement of this technology involves the optimization of the hot pressing conditions that would allow structural dispersion and production of titanium materials with better mechanical properties. The precondition for such an improvement follows from the theory of hot-pressing of compact materials stating that high strain rate is one of the factors promoting dynamic recrystallization. For structural dispersion through dynamic recrystallization, it is necessary to provide not only high strain rate, but also appropriate temperature and degree of deformation. Examples of solving such problems for compact iron-based materials can be found in the monograph [2] where dynamic recrystallization conditions are given for various grades of steel. This ideology was followed in [3, 4] to produce high-strength high-speed steels from powder materials. It was shown that dynamic recrystallization occurred at a temperature somewhat above the phasetransition temperature and degree of deformation e = 0.3–0.5. In [3, 4], however, a dense powder compact was subjected to hot pressing and its degree of deformation was determined from the change of its shape. In contrast, we use a porous compact. Its degree of deformation can be found from the change in its density, which, in turn, can be calculated using the plasticity equations for a porous