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Comparative Rheology Measurements and Assessment of MIM Titanium Metal Powder Feedstocks

This paper presents the results of a study on the flow behavior of MIM titanium feedstocks using various measurement techniques, including work done, mechanical energy transfer, and viscosity. The results are compared to data obtained from a capillary rheometer, showing that these processing techniques can provide valid feedstock assessment during manufacturing.

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Comparative Rheology Measurements and Assessment of MIM Titanium Metal Powder Feedstocks

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  1. Distance (10500km) Hamilton, NZ (180k) Xi’an (9000k) Manufacturing, software, high tech. Agriculture, Manufacturing, education. 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  2. Comparative Rheology Measurements and Assessment of MIM Titanium Metal Powder Feedstocks. Paul D. Ewart Centre for Engineering and Industrial Design Waikato Institute of Technology, Hamilton, New Zealand paul.ewart@wintec.ac.nz 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  3. Introduction Background Methodology Results Discussion Conclusion 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  4. Introduction Can standard processing equipment provide flow data of use during processing of titanium MIM feedstocks. Is it a valid assumption that flow behaviour measurement is better represented by a number of processes. Mixing torque, screw work, specific mechanical energy and viscosity during extrusion. Compared with data from capillary rheometer with/without account for end effects and slip. 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  5. Background Complexities of MIM Fine titanium powders and processing Formulation and moulding of feedstock Critical solid loading and viscosity (slip, segregation) Batch to batch variations Economic requirements Limitations of the capillary rheometer Measurement representative of moulding process 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  6. Materials and equipment Feedstock components; LLDPE, PP, PEG8, PEG20, CW, BW and HDH powder Ti64. Processing; Batch mixer with counter rotating roller rotors (prop). Thermal Analysis; Thermal analysis via DTA and TGA (SDT2960). Flow analysis; Co-rotating twin screw extruder (TSE16). Extrusion capillary set. Capillary rheometer (CFT-500D). 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  7. Method Processing Six feedstock formulations. Compounded in batch mixer. Analysis Extrusion capillary trials. Work done on the screw (WD) Mechanical energy transfer (SME) Apparent viscosity (ηa) 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  8. Results Work done on the screw (WD) WD = work done (J/s), N = screw speed (r/s), T = screw torque (N·m) 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  9. Results Mechanical energy transfer (SME) Pmotor = 1250 W, Tmax = 24 Nm, Nmax = 1.67 r/s 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  10. Results Apparent viscosity (ηa) with ηa = apparent viscosity (Pa.s), τa = apparent shear stress (Pa) and γa = apparent shear rate (s-1) see above. 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  11. Results Apparent shear rate Q = volumetric flow (mm3/s), D = diameter of capillary (mm). 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  12. Results Capillary rheometer without/with account for end effects or slip 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  13. Discussion Torsional work done by the screw in relation to the L/D ratio was mostly linear with changing component ratios seen to affected slope of the line. Mechanical energy transfer based on maximum output energy of the extruder and energy input ratio required to extrude. Apparent shear rate used in place of L/D ratio gave no account of end effects, slip or temperature dependence. 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  14. Discussion To account for the range of shear rate and shear stress during moulding, the capillary rheometer is used. Data from the constant temperature testing gave the apparent viscosity and shear rate plots for all feedstocks All showed shear-thinning behaviour over the range of testing. 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  15. Conclusion Feedstock melt flow was tested by simple work, energy, and viscosity measurement techniques and compared to results from capillary rheometer. Agreement of results clearly show that processing data can provide valid feedstock assessment during manufacture. While not providing definitive results they provide good comparative measure where upper and lower bounds have been pre-determined. 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

  16. Questions? … References: See paper for full reference list. Acknowledgements: Johan Verbeek, SeokyoungAhn, WaiCAM and AME Powder Technology Limited. 4th International Conference on Titanium Powder Metallurgy & Additive Manufacturing

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