ICMCTF2013 Session E2-2: Mechanical Properties and Adhesion

Tuesday, April 30, 2013 8:00 AM in Room Golden West

Tuesday Morning

Time Period TuM Sessions | Abstract Timeline | Topic E Sessions | Time Periods | Topics | ICMCTF2013 Schedule

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8:00 AM E2-2-1 Effects of Copper on the Microstructural and Functional Properties of Sputter-Deposited Ni-Ti Thin Films
Mauro Callisti, BrianG. Mellor, Tomas Polcar (University of Southampton, UK)

Sputter-deposited NiTi thin films are known to exhibit unusual properties such as shape memory effect and superelasticity making them attractive materials for MEMS and biomedical applications. Furthermore, their thermoelastic martensitic transformation is accompanied by reversible changes in surface roughness, which is an important factor in tribology. Thus, it might be possible with these films to control surface roughness and/or surface features during the sliding process through external heating with consequent reduction of friction and wear. The application of these films as smart surfaces for tribology requires detailed understanding of microstructural phenomena involved during the martensitic transformation; moreover, low hardness and wear resistance limit the use of these films.

In this study, Ni-Ti-(Cu) coatings deposited by plasma-assisted magnetron sputtering have been investigated. To obtain transformation temperatures higher than room temperature and improved mechanical properties, Ti-rich NiTi films were deposited and co-sputtered with copper, respectively. The coatings with a thickness of 1.5 µm were isothermally annealed at 500°C for 1 h in an argon atmosphere, with the aim to produce coherent precipitates (GP-zones) in the matrix. A scanning electron microscope (SEM) equipped with Energy-dispersive X-ray spectroscopy (EDS) was used to observe cross-section of the coatings and their chemical composition, respectively. Their structure was evaluated by X-ray diffraction (XRD) and the mechanical properties were measured by a depth sensing nanoindenation.

The Ti/Ni ratio in the deposited films was kept constant when a series of five Ni-Ti-Cu coatings was prepared with copper content increasing up to 15 at.%. After annealing of the as-deposited amorphous coatings, XRD analyses showed a dominant martensitic structure at room temperature for all investigated compositions and thus indicating prevalent shape memory behaviour. Doping with copper affected the microstructure, since different kinds and densities of precipitates (i.e. coherent plates and spherical semi-coherent precipitates with the matrix) were identified. Application of the Scherrer equation to the strong martensitic peaks suggested a decreasing crystalline size with increasing Cu content. Nanoindentation revealed the effect of Cu content on mechanical (hardness and Young’s modulus) and functional properties, as well as their variation with change in transformation path, and thus in the native phase from B19’ to B19, for Cu contents lower and higher than 10 at.%, respectively.

8:20 AM E2-2-2 Mechanical Response of Nanotwinned Metallic Coatings
Xinghang Zhang, Daniel Bufford, Yue Liu, Haiyan Wang (Texas A&M University, US)

Nanotwinned metals have received increasing attention recently as high density nanotwins can lead to unique electric, thermal and mechanical behavior, which are largely different from nanocrystalline metals with high angle grain boundaries. Twin boundaries serve as barriers to the transmission of dislocations, and are effective sources and sinks for dislocations during plastic deformation. We will review recent studies on a variety of sputtered nanotwinned fcc coatings, including 330 stainless steel, Cu and Ag. Both coherent {111} and incoherent {112} twin boundaries are observed, and the average twin spacing, on the order of ~ 10 nm, can be achieved by varying deposition conditions. In situ nanoindentation studies reveal that twin boundaries are mobile during deformation. Numerous dislocation-twin boundary interaction mechanisms are discussed.

9:00 AM E2-2-4 Structural and Mechanical Properties of Al-Cu-Fe Quasicrystalline Thin Films
Simon Olsson, Fredrik Eriksson, Esteban Broitman, MagnusGarbrecht Garbrecht, Jens Birch (Thin Film Physics Division, IFM, Linköping University, Sweden); Lars Hultman (Thin Film Physics Division, IFM, Linköping University, Sweden)

Multilayered Al-Cu-Fe thin films have been deposited by triple-target unbalanced high vacuum magnetron sputtering onto Si and Al2O3 substrates. Isothermal annealing was performed using both an in situ XRD furnace, where the phase evolution was monitored, and in a tube furnace at temperatures up to 700 °C and annealing times up to 100 h.

It was found that when using Al2O3 substrates the icosahedral quasicrystalline phase Al62Cu25.5Fe12.5 was formed at about 500 °C which was improving in structural quality and orientation with increasing temperature, but with the addition of a secondary β-phase, Al50(CuFe)50. For a Si substrate, Si starts to diffuse into the thin film at temperatures above 300 °C, preventing the quasicrystalline phase from forming. Instead, the cubic Al62.5-xSixCu25Fe12.5 approximant phase forms at 430 °C. With increasing annealing time at 600 °C the Si content increases from x=8.3 at.% after 4 h to x=12 at.% after 64 h.

To evaluate the mechanical properties of the thin films, the nanohardness, elasticity, friction, wear resistance, and toughness factor have been investigated using a Triboindenter TI-950 from Hysitron. For the quasicrystalline thin films the hardness increases from 10 GPa to 14 GPa with increasing crystal perfection. The hardness of the β-phase was 10 GPa. For the approximant thin films a hardness of 16 GPa was found, which was decreasing to about 10 GPa with increasing Si content. At the same time the mean reduced elastic modulus is decreasing from 220 GPa to 160 GPa. For all films, irrespective of the phase content and annealing procedure, a low friction coefficient against the diamond tip of 0.12±0.03 was measured. The mechanical properties are related to the film microstructure analyzed by X-ray diffraction and high resolution transmission electron microscopy.
9:20 AM E2-2-5 The Microstructure and Mechanical Properties of Nitrogen and Boron Contained ZrCuAlNi Thin Film Metallic Glasses
Tzu-Pin Hsiao (National Taipei University of Technology, Taiwan, Republic of China); Jyh-Wei Lee (Ming Chi University of Technology, Taiwan, Republic of China); Yung-Chin Yang (National Taipei University of Technology, Taiwan, Republic of China); Chia-Lin Li, Jinn.P Chu (National Taiwan University of Science and Technology (NTUST), Taiwan, Republic of China)

In this work, ZrCuAlNi thin film metallic glasses (TFMGs) were grown on Si wafer and AISI420 steels by magnetron sputtering system. Different amount of nitrogen flow rates were controlled by plasma emission monitoring (PEM) during sputtering. And boron element was doped to evaluate the influences on the mechanical properties and microstructure of TFMGs. The supercooled liquid region of TFMG was determined by the differential scanning calorimetry (DSC) analysis. The microstructure was analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The phase structure was confirmed by using x-ray diffraction (XRD). The mechanical properties were measured by nanoindentation. The scratch tester and ball-on-disk wear tests were employed to evaluate the adhesion and tribological properties. The surface roughness was determined by atomic force microscopy (AFM). It was concluded that the glass-forming ability and hardness of TFMGs were strongly influenced by the nitrogen and boron contents. The proper nitrogen and boron concentrations for ZrCuAlNi TFMG were proposed in this work.

9:40 AM E2-2-6 Comparison of Nanoindentation and Micro-tensile Measurements on the Strain-hardening Ability of Nano-scale Metallic Multilayers
Rachel Schoeppner (Washington State University, US); David Bahr (Purdue University, US); Hussein Zbib (Washington State University, US)
Nano-scale metallic multilayers (NMM) exhibit superior mechanical properties and a resistance to harsh environments due to the nature of their interfaces. Incoherent interfaces are generally stronger, acting as barriers to slip transmission, and are also dislocation and radiation-induced defect sinks. Coherent interfaces show more ductility and increased strength due to their ability to act as dislocation barriers between layers. Trimetallic systems, having a combination of coherent and incoherent interfaces, have been shown through both experimental and molecular-dynamic (MD) simulations, to possess superior properties of both types of interfaces; high strength and ductility, as well as a significant strain-hardening ability. Examination of pile-up after indentation can hint at a material’s strain-hardening ability. Sharper tips create higher effective strains when compared to using a blunt Berkovich tip. At these high strains, a material with low strain-hardening ability will have large pile-up zones around the indent; whereas a material with high strain-hardening ability will have smaller pile-up at similar contact areas. Initial indentation experiments revealed a smaller amount of pile-up at similar contact areas in trilayers when compared to bilayer systems, suggesting these trilayer systems have a higher strain-hardening coefficient. Mechanical properties of trilayer mixed interface systems from micro-tensile experiments are compared to those obtained from different tip geometries used in nanoindentation to verify the observed strain-hardening relationship. By specifying the layer thickness and material selection of the multilayer films, both modulus and hardness can be tailored, making them useful as wear resistant coatings. However, with repetitive impact loading, the increased hardness and decreased ductility of the films due to the strain hardening should be considered. This work was supported by a grant to WSU from the U.S. Department of Energy, Office of Basic Energy Science, under Grant No. DE-FG02-07ER46435. This work is also partially supported by Sandia National Laboratories, a Lockheed Martin Company for the United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04 94AL85000.
10:00 AM E2-2-7 High Temperature Instrumented Indentation System: Characterization and Optimization
Michel Fajfrowski, Vincent Jardret (Michalex, France)
High temperature instrumented indentation tests results are presented on a silicate glass, alumina and Tungsten samples at various temperatures between Room Temperature and 1000oC using the HTIIS 1000. This data is used to analyzed the thermal stability of the instrument, characterize key parameters such as load frame stiffness and indenter geometry, and finally determine the elastic and plastic properties of the samples at each temperature. The thermal management concept used in the instrument is described in details. The results show that the thermal management of the instrument provides very good stability during the tests. Tests performed at different maximum loads enable a complete characterization of the instrument and the sample at high temperatures. This work illustrates peculiar behavior of silicate glass compared to other materials, confirming previously published data.
10:20 AM E2-2-8 High-temperature Mechanical Behaviour of TiAlN Coatings
Constantin Ciurea, Vineet Bhakhri (Imperial College London - South Kensington Campus, UK); Paul Mayrhofer (Vienna University of Technology, Austria); Finn Giuliani (Imperial College London - South Kensington Campus, UK)
In this investigation, high-temperature nanoindentation testing was employed to investigate the difference between the deformation behaviour of standard bulk (001)TiN single crystal (SC-TiN) and Ti1-xAlxN coatings system at 295K to 623K. TiAlN system comprised of two sets of coatings 1) Magnetron-sputtered (MS) Ti1-xAlxN (x=0, 0.34, 0.52, 0.62at%) coatings on (001) MgO substrate s and 2) Cathodic Arc-evaporated (CA) Ti1-xAlxN (x=0.44, 0.6, 0.7at%) coatings deposited on WC-6%Co substrate s . High temperature nanoindentation experiments were carried out at three different loading rates of 0.5, 1 and 10 mN/s. This enabled us to capture the indentation hardness data at three different strain-rates at the end of loading sections of these tests. Hardness values for SC-TiN dropped significantly from 21.4±0.4GPa at room-temperature to 13.7±0.5GPa at 623K. The addition of Aluminium (Al) in TiN increased the room temperature hardness for both MS and CA coatings. The temperature dependence of hardness of MS (x=0 and x=0.34at%) and all CA (x=0.44, 0.6, 0.7at%) coatings followed the similar decreasing trend as depicted by SC-TiN. On the other hand, hardness of MS-Ti0.44Al0.56N coating was quite stable in the measured temperature range, with 29.2±1.3 GPa at 295K and decreased slightly to 26.4±1.2 GPa at 573K. A similar stable hardness over temperature range trend was exhibited by MS (x=0.62%) coating, suggesting that increase in Al addition improved not only the hardness but also lead to stable hardness with increasing temperature. Deformation kinetics analyses, carried out on temperature and strain-rate dependence of hardness data, showed that Al addition increased the activation energy for slip from 0.77 eV for SC-TiN to 1.37 eV for MS (x=0.52at%) coating. This indicated that the resistance to plastic flow is higher for MS-Ti0.48Al0.52 N coating compared to bulk SC-TiN and deformation took place by lattice resistance controlled dislocation glide mechanism. These findings were attributed to the presence of cubic-AlN phase in TiAlN matrix, revealed by X-ray diffraction and TEM analyses, which results in a coherently strained lattice rendering mechanical stability to x=0.52 and 0.62at% coatings at elevated temperatures. The cubic-AlN phase was found to be stabilised during deposition process in MS (x=0.52 and x=0.62 at%) coatings, however was absent in remaining MS (x=0 and 34 at%) and all CA (x=0.44, 0.6, 0.7at%) coatings.
10:40 AM E2-2-9 Magnetron Sputtered W-V-N Superhard Nanocomposite Coatings
Harish Sharma, Davinder Kaur (Indian Institute of Technology Roorkee, India)

In this report, we studied the effect of vanadium concentration on W-V-N superhard thin films deposited on Si(100) substrates at 700°C using reactive magnetron sputtering. The concentration of vanadium was varied in the range 0-21 at%. The resulting films microstructure, surface morphology, hardness, young modulus, fracture toughness and adhesion strength were studied by X-ray diffraction, atomic force microscopy, and nanoindentation, respectively. The Results showed that the W-V-N solid solution formed with preferred orientations (111) and (200) for all the W-V-N films. Nanoindentation hardness and young modulus of W-V-N films initially increased and then decrease with increasing vanadium content. The maximum values of hardness (~ 44 GPa) and young modulus (~ 420 GPa) were found for V content in the range of 8- 15 at %. The fracture toughness of ~ 5.22 MPa m1/2 and adhesion strength of ~ 30-45 N was found in W-V-N with silicon substrate. A significant improvement in structural and mechanical properties of W-V-N superhard thin films would make them very useful protective coatings for machining tools.

11:00 AM E2-2-10 Microstructure and Mechanical Properties of Copper-tin Shape Memory Alloy Deposited from an Ionic Liquid Electrolyte
Noushin Moharrami, Swatilekha Ghosh, Sudipta Roy, Steve Bull (Newcastle University, UK)
Shape memory alloys (SMA) are finding an increasing range of industrial applications owing to the fact that a change in shape produced by plastic deformation can be recovered by heating and the materials may show a superelastic effect (i.e. plastic deformation is recovered at even at very large strains). Such materials show great potential as actuators and there has been considerable interest in developing SMA coatings and assessing them using nanoindentation tests. Although most work has been done on NiTi and CuAlZn there remains an interest in developing cheaper, simpler to process materials for mass market applications. Copper-15%Sn shows the shape memory effect and may be deposited by electrodeposition on a range of substrates. Whereas it is difficult to get the correct chemical and phase composition by plating from aqueous electrolytes good results are obtained when plating from an ionic liquid. In this study the nanoindentation response of copper-tin (Cu-Sn) coatings deposited from a Room Temperature Ionic Liquid (RTIL) has been measured and compared to that of coatings deposited from an aqueous electrolyte.
Time Period TuM Sessions | Abstract Timeline | Topic E Sessions | Time Periods | Topics | ICMCTF2013 Schedule