Zihao Ding

Zihao Ding

Ph.D. Candidate at CMU

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Posts

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Blog Post number 1

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projects

publications

Effects of Friction Stir Processing on the Phase Transformation and Microstructure of TiO2-Compounded Ti-6Al-4V Alloy

Published in Metallurgical and Materials Transactions A, 2016

With the aim to improve the surface wear resistance properties of Ti-6Al-4V alloy as well as its biocompatibility as implants in human bodies, TiO2 particles are introduced to strengthen the properties of Ti-6Al-4V through the effect of friction stir processing. The effects of friction stir processing on the phase transformation and microstructure of TiO2-compounded Ti-6Al-4V are investigated systematically. Grain refinement in the stirring zone and phase transformation in the matrix material are observed and discussed in detail. The study provides a new insight on the desired properties of Ti-6Al-4V for biomedical applications using friction stir processing.

Recommended citation: Ding, Z., Zhang, C., Xie, L. et al. Metall and Mat Trans A 47, 5675–5679 (2016). https://doi.org/10.1007/s11661-016-3809-8

Electrochemical and in vitro behavior of the nanosized composites of Ti-6Al-4V and TiO2 fabricated by friction stir process

Published in Applied Surface Science, 2017

Although Ti-6Al-4V has been widely used in biomaterial field. Compared with other classes of materials, it still encounters some problems such as low surface hardness and relative low biocompatibility. To solve these problems friction stir processing (FSP) was applied to fabricate a nanosized composite layer of TiO2 and Ti-6Al-4V. Uniform distribution of TiO2 particles with some clusters on the surface of alloy can be observed. Due to severe plastic deformation and stirring heat, nanocrystallines and amorphous TiO2 can be observed in stir zone. FSPed samples show significant improvement in surface microhardness and biocompatibility due to its modified structure compared with original sample. In addition, through corrosion behaviors of the samples in simulated body fluid, it is found that FSP can enhance whilst TiO2 reduces the possibility and corrosion rate of material in environment of human body.

Recommended citation: Zhang, C., Ding, Z., Xie, L. et al. Applied Surface Science 423, 331-339 (2017). https://doi.org/10.1016/j.apsusc.2017.06.141

Microstructures, mechanical, and biological properties of a novel Ti-6V-4V/zinc surface nanocomposite prepared by friction stir processing

Published in International Journal of Nanomedicine, 2018

This study aims to strengthen the surface mechanical properties and promote the osteogenic capacity of the biomaterial by constructing a Ti-6Al-4V (TC4)/zinc (Zn) surface nanocomposites through FSP.

Recommended citation: Zhu C, Lv Y, Qian C, Ding Z, Jiao T, Gu X, Lu E, Wang L, Zhang F. Int J Nanomedicine. 2018;13:1881-1898 https://doi.org/10.2147/IJN.S154260

Microstructure evolution and superelasticity of layer-like NiTiNb porous metal prepared by eutectic reaction

Published in Acta Materialia, 2018

This work combines several techniques into a novel method to manufacture NiTiNb layer-like porous structures with 3D interconnected channels, which are of vital importance in the biomedical field. NiTi wires and Nb foils are used herein to prepare NiTiNb layer-like porous materials via in situ eutectic reaction. Microstructure, phase transformation and superelasticity of the resultant NiTiNb layer-like porous material are analyzed and discussed, and the interface between NiTi wires and the solidified NiTiNb eutectic region are also studied. Dislocations and stacking faults occurring at interfaces accelerate the eutectic phase transformation. Meanwhile, rod-like eutectic phase pins the motion of screw dislocations, which is beneficial for stress-induced R martensite nucleation. It is believed that much more superelastic recovery and elastic recovery for such a layer-like porous structure are attributed to formation of more martensites during deformation. Furthermore, both reorientation and subsequent de-twinning of <011> type II twins result in the observed stress-plateau, thereby promoting the superelastic recovery.

Recommended citation: Liqiang Wang, Lechun Xie, Lai-Chang Zhang, Liangyu Chen, Zihao Ding, Yuting Lv, Wei Zhang, Weijie Lu, Di Zhang. Acta Materialia 143, 214-226 (2018). https://doi.org/10.1016/j.actamat.2017.10.021

Polydopamine nanomembranes as adhesion layers for improved corrosion resistance in low carbon steel

Published in Advanced Engineering Materials, 2018

Low‐carbon steel is an important commodity material, but poor corrosion resistance has a strong impact on its service life, which leads to great loss in economic development. Polymer coatings serve as barrier layers that confer corrosion resistance. However, robust adhesion between steels and polymer films operating in complex fluids is challenging. This study evaluates the utility of adhesion layers composed of polydopamine, an organic film formed through simultaneous deposition, and polymerization in aqueous phases. Here, polydopamine serves as an intermediary adhesion layer between metallic substrates and polymer coatings. The composition, microstructure, and electrochemical properties of polydopamine nanomembranes are characterized. The impact of polydopamine nanomembranes on adhesion and supplementary corrosion resistance of polymer‐based barrier layers is assessed using a functional assay. These results suggest that polydopamine‐based nanomembranes can serve as effective adhesion‐promoting intermediary layers that retard corrosion and prolong the service life of low‐carbon steels in certain applications.

Recommended citation: Ding, Z., Fatollahi‐Fard, F., Kwon, I.S., Pistorius, P.C. and Bettinger, C.J. (2018). Adv. Eng. Mater., 20: 1800621. https://doi.org/10.1002/adem.201800621

Deformation mechanisms in surface nano-crystallization of low elastic modulus Ti6Al4V/Zn composite during severe plastic deformation

Published in Scripta Materialia, 2018

Decreasing elastic modulus and simultaneously improving biological compatibility has been a major challenge in developing biomedical alloy. In this study, Ti6Al4V/Zn composite with surface nano crystallization is successfully fabricated by friction stir processing (FSP) with simultaneous addition of beneficial Zn element. Nanoscale microstructures in surface region include nanoscaled Zn rich particles (including TiZn2), α nanograins, nanotwins and nano α + β lamellae. Dislocations slip and grain boundary sliding contribute much to the transformation of α-Ti nanograin, while dynamic overlapping of two partial dislocations is the main deformation mechanism for nanotwins. Interestingly, these nanoscale microstructures reduce the elastic modulus of this region.

Recommended citation: Yuting Lv, Zihao Ding, Jing Xue, Gang Sha, Eryi Lu, Liqiang Wang, Weijie Lu, Chunjian Su, Lai-Chang Zhang. Scripta Materialia 157, 142-147 (2018). https://doi.org/10.1016/j.scriptamat.2018.08.007

Gradient Microstructures and Mechanical Properties of Ti-6Al-4V/Zn Composite Prepared by Friction Stir Processing

Published in Materials, 2019

In this work, a biomedical Ti-6Al-4V (TC4)/Zn composite with gradient microstructures was successfully prepared by friction stir processing (FSP). The microstructures and mechanical properties of the composite were systematically studied using scanning electron microscope (SEM), X-ray diffractometer (XRD), transmission electron microscope (TEM), atom probe tomography (APT), and microhardness test. The results show that TC4/Zn composite can be successfully prepared, and gradient microstructures varying from coarse grain to nanocrystalline is formed from the bottom to the upper surface. During FSP, adding Zn can accelerate the growth of β phase region, and the grain size significantly increases with the increasing rotation rate. The grain combination is the main mechanism for grain growth of β phase region. The deformation mechanisms gradually change from dislocation accumulations and rearrangement to dynamic recrystallization from the bottom to the upper surface (1.5 mm–150 μm from the upper surface). The composite exhibits slightly higher microhardness compared with the matrix. This paper provides a new method to obtain a TC4/Zn composite with gradient surface microstructures for potential applications in the biomedical field.

Recommended citation: Lv, Y.; Ding, Z.; Sun, X.; Li, L.; Sha, G.; Liu, R.; Wang, L. Materials 2019, 12, 2795. https://doi.org/10.3390/ma12172795

Microstructure evolution and electrochemical properties of TiO2/Ti-35Nb-2Ta-3Zr micro/nano-composites fabricated by friction stir processing

Published in Materials & Design, 2019

Forming stable anti-corrosion surface layer and homogenized microstructure on the surface of material has become a major challenge in developing biomedical β titanium alloy. In the study, TiO2/Ti-35Nb-2Ta-3Zr anti-corrosion micro/nano-composites with different amount of TiO2 particles were successfully fabricated by one-pass friction stir processing (FSP). The composition, microstructure and electrochemical properties of the material are characterized systematically. In particular, compact passive oxide films formed on surface of the material after electrochemical corrosion are elaborated from constituent, thickness and structural characteristics. Furthermore, the relationship between various FSP parameters, microstructure presented and corresponding corrosion resistance has been discussed in detail. The results show that TiO2/Ti-35Nb-2Ta-3Zr micro/nano-composite layers possess massive uniform β grains with homogeneous dispersive oxygen on the surface. Nanocrystallines surrounded by amorphous phases and α″ martensite accompanied with dislocations are discovered. TiO2/Ti-35Nb-2Ta-3Zr micro/nano-composite layers present outstanding corrosion resistance. More TiO2 added and higher rotation speed promotes the optimization in corrosion resistance forming more compact passive films. The study displays the potential of a new micro/nano-composite with outstanding surface microstructure and corrosion resistance that serves better as a biomedical implant.

Recommended citation: Hao Gu, Zihao Ding, Zhi Yang, Weiqiang Yu, Wenjie Zhang, Weijie Lu, Lai-Chang Zhang, Kuaishe Wang, Liqiang Wang, Yuan-fei Fu. Materials & Design 2019, 169, 107680. https://doi.org/10.1016/j.matdes.2019.107680

A Review on Friction Stir Processing of Titanium Alloy: Characterization, Method, Microstructure, Properties

Published in Metallurgical and Materials Transactions B, 2019

In the past two decades, friction stir processing (FSP) technology has received considerable attention. FSP can be used to adjust and control the microstructure of materials, including eliminating defects, destroying dendrites and controlling fractions in the second stage, and is therefore widely used in titanium and its alloys for biomedical, aerospace and automotive applications. This article comprehensively reviews the methods of studying FSP, the microstructure evolution of materials and the summary of material properties. It begins with the introduction of the FSW system, characterization, structure and elemental analysis, and simulation and performance testing methods, and then introduces the microstructure evolution mechanism of various titanium materials and discusses in detail the material properties of titanium alloy, namely hardness and wear resistance, elasticity and plasticity, corrosion resistance and biocompatibility. Finally, this review presents unresolved issues and outstanding challenges in FSP technology and reveals the direction of this emerging field of research.

Recommended citation: Ding, Z., Fan, Q. & Wang, L. Metall and Materi Trans B 50, 2134–2162 (2019). https://doi.org/10.1007/s11663-019-01634-9

talks

Indexing of EBSD Patterns Using a Convolutional Neural Network

Published:

We propose a new convolution neural network (EBSD-CNN) with residual block and separable convolution to realize high accuracy and near real-time indexing of EBSD patterns. The integrated output of unit quaternions and a disorientation loss function are implemented to adapt the neural net for crystallographic orientation indexing. In addition to validating on simulated EBSD patterns, data from a series of experiments on Nickel with various exposure time have also been tested to study the network’s robustness against pattern noise. The results suggest that a CNN can provide an alternative indexing method to the commercial Hough-transform-based indexing with comparable accuracy and indexing rate. To gain insight into the model, we provide for a visualization of the filters as well as intermediate output in the network. As more features are extracted during the process, the approach also shows potential to measure other material properties that are encoded inside the EBSD patterns.

teaching

Teaching assistant

27-100, Engineering the Materials of the Future, Carnegie Mellon University, Department of Materials Science and Engineering, 2020

This course provides an introduction to how science and engineering can be exploited to design materials for many applications.

work