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Structure and properties of nano-crystalline Ti-base alloys obtained by vacuum hot pressing

Dutkiewicz J., Maziarz W.

Advances in Materials Science

2008

Vol. 8, nr 1(15)

27-32

The cp-Ti and Ti-base alloys with additions of Ta and Nb were ball milled and consolidated using vacuum hot pressing. This novel technique allowed to obtain a high level of densification of milled powders up to about 98% and the nanometric grain size level. In the samples of vacuum hot compacted cp- Ti grain size of a single a phase was estimated at 140 nm. With the increase of content the p-stabilizing elements in alloys such as Ta and Nb, structure and a grain size has been changed. In the case of Ti-5Ta-5Nb alloy, also single a phase was observed but with grains size was much smaller, close to 85 nm. The further increasing of the content of Ta and Nb caused further refinement of grain size down to 60 nm and change of structure into two phase [alfa+Beta] and [Beta] in case of Ti-10Ta-10Nb and Ti-15Ta-15Nb alloys respectively. The hardness and Young Modulus were measured using the dynamic hardness tester and calculations of hardness and elastic modulus values were based on Oliver and Pharr model.

Properties of a Nb-V-Ti microalloyed steel influenced by cold rolling and annealing

Janosec M., Schindler I., Palat J., Cizek L., Vodarek V., Mistecky E., Ruzicka M., Dobrzański L. A., Rusz S., Suchanek P.

Journal of Achievements in Materials and Manufacturing Engineering

2007

Vol. 20, nr 1-2

251-254

Purpose: was to investigate impact of cold forming and annealing on microstructural and mechanical properties of HSLA steel. Design/methodology/approach: Testing of Nb-V-Ti microalloyed strip steel was based on a combination of cold rolling, recrystallization annealing, mechanical testing, metallography and TEM. Findings: It was confirmed that by a suitable combination of size of previous cold reduction size and parameters of the following annealing it is possible to influence considerably a complex of mechanical properties of particular strips. Strength as well as plastic properties depended on the course of recrystallization and precipitates' coarsening during annealing. Research limitations/implications: The experiment should be supplemented by the more detailed analyses of microstructure. Practical implications: The results may be utilized for optimization of terms of heat treatment in a cold rolling mill, especially in accordance with specific requirements for a relation between plastic and strength properties of the investigated steel. Originality/value: Research possibilities of VSB-TUO in the sphere of cold rolling of Nb-V-Ti HSLA steel were introduced in combination with the complex approach to processing of the obtained results.

Microstructure of the diffusion layer obtained in Ti6Al2Cr2Mo alloy during glow discharge nitriding

Jeleńkowski J., Major B., Gołębiewski M., Wierzchoń T.

Advances in Materials Science

2003

Vol. 3, nr 2(4)

28--34

This paper presents the results of metallographic, X-ray, and TEM examinations of the microstructure and the sub-structure of the diffusion layer that underlies the TiN + Ti2N layer produced by glow discharge nitriding of the Ti6Al2Cr2Mo alloy. The metallographic examinations show that a two-phase zone α + β - its thick-ness increasing with the increasing process temperature - can be observed underneath the nitride layer after half an hour of nitriding at 940ºC, when the core of the sample has an α - phase structure. The presence of the glow discharge assisting the nitrid-ing process accelerated the thickening of both the nitride zone and the diffusion layer. Morphology of α - phase grains changed as well. The grain lengh-to-thickness ratio decreased. X-ray examinations revealed the presence in the substrate structure of two kinds of solid solution with the α titanium matrix. TEM analysis showed a state of certain ordering of the crystalline lattice and, locally, a tweed-type structure of the β phase.