This thesis deals with optimization of production of "Hold-down hinge hook" component, developed from difficult-to-cut titanium alloy Ti-6Al-4V. This work is focused on the material properties of the component, current research and optimization in titanium machinability sphere. Further it contains a part dedicated to the latest trends in development of cutting tools for machining of titanium alloys. This knowledge is furthermore used for the component production optimization in Frencken Brno s.r.o. company. This project continues with analysis of the component‘s current production technology and designs the way of elimination of production bottleneck. This change is presented by component‘s clamp jig, which decreases higher percentage of scrap due to the geometric complexity. This thesis further contains drawing and technological documentation needed for implementation of the improvement suggestions into the production. There was designed a new NC program. This project is accomplished with technical-economical evaluation.

Diploma thesis is specialized to solving of problems machining of diffi-cult machinable materials. There is carried out the analysis of difficult machinable materials in term of chemical composition, physical and mechanical properties. In the following it deals with analysis of machining, specification of geometry, material of cutting tools and cutting conditions.

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Actuator applications of shape memory alloys have typically been limited by their phase transformation temperatures to around 100 degrees C. However, recently with a focus on aerospace and turbomachinery applications there have been successful efforts to increase the phase transformation temperatures. Several of these alloy development efforts have involved ternary and quaternary elemental additions (e.g., Pt, Pd, etc.) to binary NiTi alloys. Experimentally assessing the effects of varying composition and thermo-mechanical processing parameters can be cost intensive, especially when expensive, high-purity elemental additions are involved. Thus, in order to save on development costs there is value in establishing a methodology that facilitates the fabrication, processing and testing of smaller specimens, rather than larger specimens from commercial billets. With the objective of establishing such a methodology, this work compares thermo-mechanical test results from bulk dog-bone tensile Ni29.5Ti50.5Pd20 samples (7.62 mm diameter) with that of thin wires (100 μm-150 µm diameter) extracted from comparable, untested bulk samples by wire electrical-discharge machining (EDM). The wires were subsequently electropolished to different cross-sections, characterized with Scanning Electron Microscopy, Transmission Electron Microscopy and Energy Dispersive X-Ray Spectroscopy to verify the removal of the heat affected zone following EDM and subjected to Laser Scanning Confocal Microscopy to accurately determine their cross-sections before thermo-mechanical testing. Stress-strain and load-bias experiments were then performed on these wires using a dynamic mechanical analyzer and compared with results established in iv previous studies for comparable bulk tensile specimens. On comparing the results from a bulk tensile sample with that of the micron-scale wires, the overall thermomechanical trends were accurately captured by the micron-scale wires for both the constrained recovery and monotonic tensile tests. Specifically, there was good agreement between the stress-strain response in both the martensitic and austenitic phases, the transformation strains at lower stresses in constrained recovery, and the transformation temperatures at higher stresses in constrained recovery. This work thus validated that carefully prepared micron-diameter samples can be used to obtain representative bulk thermo-mechanical properties, and is useful for fabricating and optimizing composition and thermomechanical processing parameters in prototype button melts prior to commercial production. This work additionally assesses potential applications of high temperature shape memory alloy actuator seals in turbomachinery. A concept for a shape memory alloy turbine labyrinth seal is also presented. Funding support from NASA’s Fundamental Aeronautics Program, Supersonics Project (NNX08AB51A) and Siemens Energy is acknowledged.

Shape memory and superelastic applications of NiTi based alloys have typically been limited to near room temperature or to bulk length scales. The objective of this work is two-fold: first, to investigate shape memory behavior at low temperatures in the context of the R-phase transformation in NiTiFe alloys by recourse to arc-melting, differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and mechanical testing at low temperatures; and second, to investigate superelasticity and two-way shape memory behavior at reduced length scales in the context of NiTi by recourse to micro-compression, micro-indentation and TEM studies. Selected compositions of ternary NiTiFe shape memory alloys were arc-melted and thermomechanically processed to investigate the influence of composition and processing parameters on the formation of the R-phase. The methodology used for the processing and characterization of the alloys was established and included microprobe analysis, DSC, TEM and mechanical testing. No phase transformation was observed in alloys with Fe content in excess of 4 at.%. Thermomechanical treatments facilitated the formation of the R-phase in Ni-rich alloys. The range of the transformation between the R-phase and austenite, and the hysteresis associated with it were influenced by the distribution and size of metastable Ni4Ti3 precipitates. The investigation of the microstructural, thermal and mechanical properties of the R-phase transformation in NiTiFe alloys revealed a complex dependence of these properties on processing parameters. The present work also highlighted the hitherto unexplored competition between the two inelastic deformation modes operating in the R-phase (detwinning and stress-induced transformation) and established the preference of one mode over the other in stress-temperature space. iv The complete micromechanical response of superelastic NiTi was examined by performing careful micro-compression experiments on single crystal pillars of known orientations using a nanoindenter tip. Specifically, the orientation dependence of the elastic deformation of austenite, the onset of its transformation to martensite, the gradient and the hysteresis in the stress-strain response during transformation, the elastic modulus of the stress-induced martensite and the onset of plasticity of the stress-induced martensite were analyzed in separate experiments. A majority of the results were explained by recourse to a quantitative determination of strains associated with austenite grains transforming to martensite variants or twinning in martensite. Microstructural studies were also performed on a micro-indentation trained NiTi shape memory alloy specimen to understand the mechanisms governing the two-way shape memory effect. In situ TEM studies at temperature on specimens obtained at different depths below the indent showed the presence of retained martensite along with the R-phase. Previously, while such twoway shape memory behavior has typically been associated with large dislocation densities, this work provides evidence of the role of retained martensite and the R-phase in cases with reduced dislocation densities. Funding support for this work from NSF (CAREER DMR-0239512), NASA (NAG3-2751) and SRI is acknowledged.

Yes / Titanium alloys are known for their excellent corrosion resistance; however, low surface hardness results in poor wear resistance, which limits its potential application. This study employs a novel two-step process to embed a hard Ni coating containing a mixture of nanosized particles (Al2O3 and TiO2) into the surface of the Ti-6Al-4V alloy using an electric arc produced during the inert tungsten gas welding process. The surface of the sample was evaluated using Vickers Microhardness, Scanning electron microscopy, Energy dispersive spectroscopy and pin-on-plate wear testing. Microstructural analysis showed that impregnating the titanium surface with Ni/(Al2O3 and TiO2) nanomaterials resulted in the formation of a hard martensitic structure to a depth of approximately 2 mm below the surface. The changes observed are driven by modification of the surface chemistry and the presence of nickel, causing grain size reduction, solid solution strengthening and dispersion strengthening of the treated layer by the nanoparticles. The hardness of the treated layer increased by more than 180% when 40 nm Al2O3 and 30 nm TiO2 particles were embedded into the surface. Similarly, the wear resistance of the treated surface improved by 100%.

M. Tech. (Department of Metallurgical Engineering, Faculty of Engineering Technology), Vaal University of Technology. / Solid titanium (Ti), Ti-6Al-4V (wt.%), and Ti-24Nb-4Zr-8Sn (wt.%) materials were fabricated from powders using spark plasma sintering (SPS). The starting materials comprised of elemental powders of ASTM Grade 4 titanium (Ti), aluminium (Al), vanadium (V), niobium (Nb), zirconium (Zr), and tin (Sn). The powders were initially characterised and milled prior to sintering. The micronpowders were milled in an attempt to produce materials with nanostructured grains and as a result improved hardness and wear resistance. The produced solid Ti-24Nb-4Zr-8Sn alloy was compared to solid titanium (Ti) and Ti-6Al-4V (Ti64) on the basis of density, microstructure, hardness, corrosion, and biocompatibility. Relative densities above 99.0% were achieved for all three systems. CP-Ti and Ti64 had both 100% relative density, and Ti2448 showed a slightly lower density of 99.8%. Corrosion results showed that all three materials exhibited good corrosion resistance due to the formation of a protective passive film. In 0.9% NaCl Ti2448 had the highest current density (9.05 nA/cm2), implying that its corrosion resistance is relatively poor in comparison to Ti (6.41 nA/cm2) and Ti64 (5.43 nA/cm2), respectively. The same behavior was observed in Hank's solution. In cell culture medium, Ti2448 showed better corrosion resistance with the lowest current density of 2.96 nA/cm2 compared to 4.86 nA/cm2 and 5.62 nA/cm2 of Ti and Ti64 respectively. However, the current densities observed are quite low and insignificant that they lie within acceptable ranges for Ti2448 to be qualified as a biomaterial. Cell proliferation test was performed using murine osteoblastic cells, MC3T3-E1 at two cell densities; 400 and 4000 cells/mL for 7 days incubation. Pure titanium showed better cell attachment and proliferation under both conditions suggesting that the presence of other oxide layers influence cell proliferation. No significant difference in cell proliferation was observed between Ti64 and Ti2448.

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