Hydride Approach in Blended Elemental Powder Metallurgy of Beta Titanium Alloys

The physical bases of hydrogenated titanium powders application in blended elemental powder metallurgy (BEPM) of titanium alloys were earlier developed. Hydrogen as temporary alloying addition for titanium strongly affects diffusion processes upon transformation of powder blends into alloys ensuring production of α+β and metastable β titanium alloys which mechanical properties meet standard requirements. At the same time, synthesis of metastable β alloys is complicated by a big amount of alloying elements which diffusion redistribution upon sintering has a strong impact on microstructure evolution. In present study BEPM hydride approach was expanded for production of biocompatible low modulus Ti-Zr-Nb and Ti-Zr-Nb-Ta alloys having BCC structure which are attractive materials for medical application. The alloys of prescribed compositions were produced using various starting powders, including TiH2, ZrH2, hydrogenated niobium, tantalum and Ti-Nb master alloys. Peculiarities of volume changes of multicomponent powder blends on dehydrogenation were investigated. The specific volume changes of powder components during dehydrogenation affect densification kinetic of powder blends and microstructure of as-sintered alloys.

Thermo-Mechanical Treatment of Titanium Based Layered Structures Fabricated by Blended Elemental Powder Metallurgy

High specific strength of Ti-based alloys and composites makes them highly requested materials in various structural applications, especially when lightweight is desired in high-strength constructions. When these alloys are used in layered structures, far advanced set of characteristics that combine different mechanical properties often non-compatible in a single layer uniform structure can be attained; for instance, high hardness or moduli systems are usually lacking of sufficient toughness. Mechanical properties of individual layer in multilayered materials can be controlled by changing chemical composition and microstructure within each layer specifically. In present study layered materials were formed by combination of the layer of Ti-6Al-4V alloy and metal matrix composites on its base reinforced with fine TiB and TiC particles. Structures were fabricated using blended elemental powder metallurgy (BEPM). The effect of different post-sintering thermo-mechanical treatments on structure of layered BEPM materials was studied. Processing parameters were assessed in terms of their influence on materials’ porosity, grain size and structure, distribution of reinforcement particles and layers integration. The effect of above mentioned structural characteristics on hardness of layered materials was evaluated.