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Microstructure evolution of pure titanium during hydrostatic extrusion

Wojtas Daniel, Maj Łukasz, Wierzbanowski Krzysztof, Jarzębska Anna, Chulist Robert, Kawałko Jakub, Trembecka-Wójciga Klaudia, Bieda-Niemiec Magdalena, Sztwiertnia Krzysztof

Archives of Civil and Mechanical Engineering

2023

Vol. 23, no. 1

art. no. e9, 2023

Regarding severely deformed materials of potentially high applicability in various industry branches, their microstructure evolution during processing is of vast significance as it enables to control or adjust the most essential properties, including mechanical strength or corrosion resistance. Within the present study, the microstructure development of commercially pure titanium (grade 2) in the multi-stage process of hydrostatic extrusion has been studied with the use of the well-established techniques, involving electron backscatter diffraction as well as transmission electron microscopy. Microstructural deformation-induced defects, including grain boundaries, dislocations, and twins, have been meticulously analyzed. In addition, a special emphasis has been placed on grain size, grain boundary character as well as misorientation gradients inside deformed grains. The main aim was to highlight the microstructural alterations triggered by hydroextrusion and single out their possible sources. The crystallographic texture was also studied. It has been concluded that hydrostatically extruded titanium is an exceptionally inhomogeneous material in terms of its microstructure as evidenced by discrepancies in grain size and shape, a great deal of dislocation-type features observed at every single stage of processing and the magnitude of deformation energy stored. Twinning, accompanied by grain subdivision phenomenon, was governing the microstructural development at low strains; whereas, the process of continuous dynamic recrystallization came to the fore at higher strains. Selected mechanical properties resulting from the studied material microstructure are also presented and discussed.

Wpływ obróbki termoplastycznej tytanu Grade 2 na właściwości nanoindentacyjne

Bańczerowski Jakub

Inżynieria Powierzchni

2021

nr 2

17--21

Czysty tytan jest materiałem pożądanym w biotechnologii ze względu na doskonalą biozgodność oraz brak toksycznych pierwiastków, takich jak wanad czy aluminium. Niestety w stosunku do powszechnie używanego stopu na protezy Ti6Al4V jest on materiałem o niskich właściwościach mechanicznych. Obróbka termoplastyczna tytanu miała na celu poprawę jego właściwości mechanicznych poprzez zredukowanie wielkości ziarna. Wykonano eksperyment polegający na ściskaniu próbek tytanu w podwyższonej temperaturze i przy różnych prędkościach odkształceń. Uzyskano krzywą naprężenie-odkształcenie oraz obrazy mikrostruktury tytanu, które wskazywały na redukcję ziarna. Następnie wykonano pomiary nanoindentacyjne twardości oraz modułu Younga. Wyniki wskazują na nieznaczny wzrost twardości i sztywności w większości przypadków. Dla wysokich prędkości odkształcenia zaobserwowano spadek tych wartości.

Pure titanium is a desired material in biotechnology due to its excellent biocompatibility and the absence of toxic elements like vandium or aluminium. Unfortunately, in comparison to widely used Ti6Al4V alloy it has low strenght properties. Therefore, thermoplastic processing was used as means to improve its mechanical properties by the grain size reduction. An experiment of samples compression in raised temperature and various strain rates was conducted. The stress-strain curves and microstructure observations were made. Both indicated grain reduction. In the next step nanoindentation hardness and Young modulus measurements were made. The results indicate slight increase in hardness and stiffness in most cases. For the high strain rates a decrease in those values was observed.

Prediction of Shrinkage Porosity in Femoral Stem of Titanium Investment Casting

Sutiyoko, Suyitno, Mahardika M., Syamsudin A.

Archives of Foundry Engineering

2016

Vol. 16, iss. 4

157--162

Design of gating system is an important factor in obtaining defect-free casting. One of the casting defects is a porosity caused by internal shrinkage in solidification process. Prediction of the internal shrinkage porosity in the femoral stem of commercially pure titanium (CP-Ti) is investigated based on the gating system design. The objective of this research is to get the best gating system between three gating system designs. Three gating system designs of the femoral stem were simulated in an investment casting method. The internal shrinkage porosity occurs on the largest part and near the ingate of the femoral stem. The gating system design that has ingates cross section area: 78.5; 157; and 128.5 mm2 has the least of the internal shrinkage porosity. This design has the most uniform solidification in the entire of the femoral stem. An experiment is conducted to validate the simulation data. The results of internal shrinkage porosity in the three gating system designs in the simulation were compared with the experiment. Based on the comparison, the trend of internal shrinkage porosity at the three gating system designs in the simulation agrees with the experiment. The results of this study will aid in the elimination of casting defect.