Reporter ： Ming-Yeh Chuang Teacher ： Chen, Cheng-Ho Date ： 06/11/2015

2 Metal injection Moulding (MIM) Low cost production High material utilization Mouldability The viscous flow of feedstock into the die cavity. Certain rheological Ideal formulationThe formulation of surfactant system. Ti-MIM systemThe same binder composition Powder A Powder D Powder C Powder B

3 Common MIM binder system Plasticizer (waxes) Polymer Surfactant Metal powdersBinder Interaction Ex : Surface wetting, spreading, adsorption, binder strengthening Powder injection moulding (PIM) Stearic Acid First choice in Ti-MIM Suitable surfactant Excellent properties (also used for other PIM)

Argon gas atomized (GA) spherical CP-Ti powder (particle size < 45 μm) Polyethylene glycol (PEG) Polymethyl methacrylate (PMMA) Stearic acid Peanut oil Castor oil 4 Fig. 1. SEM micrograph of GA cp-Ti powder. PEG

5 30 ml Acetone Feedstock 83% PEG 15% PMMA 2% Surfactant 45 °C Stirring Stirring 220 rpm Vacuum 45°C 5 g Ti powder Acetone SA = Feedstock A Peanut oil = Feedstock B Castor oil = Feedstock C

6 Fig. 2. Shear stress versus shear rate graphs for feedstocks at 100 °C. Yield stress ↓ Plastic viscosity ↓ Lower pressure for moulding

7 Fig. 3. Yield stress dependence on temperature for different feedstocks. The decrease in yield stress with temperature is more prominent for feedstock containing SA (feedstock A). PMMA soften Flowability The best moulding temp = 105 and 130°C

8 Fig. 4. Double logarithm of viscosity vs. shear rate plot for different feedstocks in the temperature range of 80– 140 °C. It must be noted that due to extremely low viscosities of feedstock B and C, calculations at 140°C were not possible. Pseudoplastic Higher shear sensitivity Than B and C.

9 Fig. 5. Double logarithm of viscosity vs. shear rate plot of different feedstocks at 120°C.

10 Fig. 6. Temperature dependence of viscosity for feedstocks in the temperature range of 80–130 °C at a shear rate of 1500 s -1.

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12 Fig. 7. Fracture surface morphologies of Feedstock A (left) and Feedstock C (right).

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14 Fig. 8. Comparison of chemical fromula of stearic acid (left) and castor oil (right). It should be kept in mind that castor oil is a combination of different fatty acids. However, ricinoleic, oleic and linoleic acids are the three main ingredients.

15 Fig. 9. Green strength comparison of two feedstocks.

16 Viscosity of feedstock is decreased using oil as surfactant, thereby a higher solid loading can be achieved. It is determined that feedstock containing castor oil as surfactant possessed a higher flexural strength and higher mouldability index value than feedstock containing stearic acid as surfactant. The improved properties are attributed to the more interaction between binder and titanium powder and better dispersion of the powder due to the presence of extra polar groups in castor oil molecule.