Effect of electropulsing on anisotropy behaviour of cold-rolled commercially pure titanium sheet

The specimens cut from the cold-rolled pure titanium sheet at 0°,45°and 90°to the rolling direction were treated by high density electropulsing(maximum current density J=(7.22-7.96)×10^(3)A/mm^(2),pulse period t_(p)=110μs).The mechanical properties and microstructures of the cold-rolled,electropulsed and conventional annealed commercially pure titanium sheet were examined by using uniaxial tension test machine and optical microscope(OM),respectively.The results show that the deformation behavior of the electropulsed pure titanium sheet is significantly different from that of conventional annealed pure titanium sheet.The difference of the mechanical properties between the 0°,45°and 90°direction specimens is almost diminished.It is mainly due to the increase in dislocation mobility and formation of lamellar microstructure after the electropulsing.

Planar anisotropy of commercially pure titanium sheets

Commercially pure titanium （CP Ti） sheets show typical planar anisotropy due to the inherently crys- tallographic texture and manufacturing process. To char- acterize the planar anisotropic behaviors of CP Ti sheets in the forming process, uniaxial tensile tests of TA0 sheets were performed along rolling, transverse, and diagonal directions at room temperature; corresponding stress-strain curves and Lankford coefficients were obtained. Based on Hi11＇48 and Barlat＇89 yield functions, the planar anisotropy of TA0 sheets was investigated. In order to verify the accuracy of two models, we compared the experimental and predicted values of yield stress and Lankford coeffi- cients. It reveals that Barlat＇89 criterion with M = 10 is good agreement with experimental data, and the obtained function can be used in simulation of forming process.

Mechanical Property Prediction of Commercially Pure Titanium Welds with Artificial Neural Network

Factors that affect weld mechanical properties of commercially pure titanium have been investigated using artificial neural networks. Input data were obtained from mechanical testing of single-pass, autogenous welds, and neural network models were used to predict the ultimate tensile strength, yield strength, elongation, reduction of area, Vickers hardness and Rockwell B hardness. The results show that both oxygen and nitrogen have the most significant effects on the strength while hydrogen has the least effect over the range investigated. Predictions of the mechanical properties are shown and agree well with those obtained using the 'oxygen equivalent' (OE) equations.

Cell Attachment of Periodontal Ligament Cells on Commercially Pure Titanium at the Early Stage

Summary: In order to study the character of periodontal ligament cells (PDLCs) attaching on commercially pure titanium (cpTi) by morphology and metrology on the early stage (24 h), 1×105/ml PDLCs in 2 ml culture medium were seeded on cpTi discs fixed in 24-well culture plates. Morphology of cell attachment was observed by contrast phase microscope, scanning electron microscope (SEM) and fluroscence microscopy. Cell adhesion was analyzed by MTT at 0.5, 1, 2, 4 h respectively. PDLCs could attach and spread on cpTi discs. SEM showed that PDLCs had pseudopod-like protuberance. PDLCs showed different attaching phases and reached saturation in cell number at 2 h. It was concluded that PDLCs had good biocompatibility with cpTi, and showed a regular and dynamic pattern in the process of attaching to cpTi.

Probing into the Yield Plateau Phenomenon in Commercially Pure Titanium During Tensile Tests

To explain the intrinsic mechanism of the yield plateau phenomenon in commercially pure titanium,the tensile behaviors of commercially pure titanium specimens after 91.6%cryorolling and subsequent annealing at 280℃,335℃,450℃and 600℃have been studied.The results show that the yield plateau phenomenon is a result of dislocation behaviors controlled by grain size and thus only exists within a given range of mean grain size.αgrain boundaries are the main dislocation multiplication sources of commercially pure titanium.Fine-grained microstructure could offer numerous dislocation multiplication locations during deformation.Once the applied stress is above the yielding strength,dislocations multiply rapidly and the mobile dislocation density is high.To retrieve the imposed strain rate,the mean dislocation velocity is bound to be low.Therefore,it takes time for them to interact with each other.As a result,the movement of dislocations is hardly blocked and the deformation could continue at a nearly constant applied stress.Consequently,the so-called yield plateau behavior presents in the tensile curves.The disappearance of yield plateau phenomenon in coarse-grained and ultrafi ne-grained microstructures is attributed to the quick realization of the mutual interactions among dislocations at the initial stage of tensile test.

Surface modifications of biometallic commercially pure Ti and Ti–13Nb–13Zr alloy by picosecond Nd:YAG laser

The effects of picosecond Nd:YAG laser irradiation on chemical and morphological surface characteristics of the commercially pure titanium and Ti–13Nb–13Zr alloy in air and argon atmospheres were studied under different laser output energy values.During the interaction of laser irradiation with the investigated materials,a part of the energy was absorbed on the target surface,influencing surface modifications.Laser beam interaction with the target surface resulted in various morphological alterations,resulting in crater formation and the presence of microcracks and hydrodynamic structures.Moreover,different chemical changes were induced on the target materials’surfaces,resulting in the titanium oxide formation in the irradiation-affected area and consequently increasing the irradiation energy absorption.Given the high energy absorption at the site of interaction,the dimensions of the surface damaged area increased.Consequently,surface roughness increased.The appearance of surface oxides also led to the increased material hardness in the surface-modified area.Observed chemical and morphological changes were pronounced after laser irradiation of the Ti–13Nb–13Zr alloy surface.

The Evolution of Hardness Homogeneity in Commercially Pure Ti Processed by ECAP

The evolution of hardness homogeneity in commercially pure titanium processed by equal channel angular pressing （ECAP） for up to 4 passes following route C at room temperature using a die of 90° was investigated by recording the microhardness on the cross-sectional and longitudinal planes of each billet. The results show that the hardness increases significantly after the first pass although there is a region of lower hardness on the cross-section running in a band near the bottom surface of the billet, and then increases by very small amounts in subsequent passes. With increasing numbers of passes, the lower hardness region near the bottom surface disappears and the microhardness values are distributed homogeneously throughout the cross- sectional and longitudinal planes after 4 passes of ECAP. The microhardness values in the central regions of the billet are slightly lower than those of the top and bottom surfaces. The results show that good homogeneity may be achieved throughout the billets after 4 passes of ECAP following route C.

Enhanced Surface Mechanical Properties and Microstructure Evolution of Commercial Pure Titanium Under Electropulsing-Assisted Ultrasonic Surface Rolling Process

The effects of electropulsing-assisted ultrasonic surface rolling process on surface mechanical properties andmicrostructure evolution of commercial pure titanium were investigated. It was found that the surface mechanical prop-erties were significantly enhanced compared to traditional ultrasonic surface rolling process （USRP）, leading to smallersurface roughness and smoother morphology with fewer cracks and defects. Moreover, surface strengthened layer wasremarkably enhanced with deeper severe plastic deformation layer and higher surface hardness. Remarkable enhancementsof surface mechanical properties may be related to the gradient refined microstructure, the enhanced severe plasticdeformation layer and the accelerated formation of sub-boundaries and twins induced by coupling effects of USRP andelectropulsing. The primary intrinsic reasons for these improvements may be attributed to the thermal and athermal effectscaused by electropulsing treatment, which would accelerate dislocation mobility and atom diffusion.