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Powder injection molding of Ti–6Al–4V alloy
Journal of Materials Processing Technology 173 (2006) 310–314
Powder injection molding of Ti–6Al–4V alloy Guo Shibo a,b,∗ , Qu Xuanhui b , He Xinbo b , Zhou Ting b , Duan Bohua b a
Jiangxi Key Laboratory of Surface Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013, China b School of Materials Science and Engineering, University of Science and Technology of Beijing, Beijing 100083, China Received 26 October 2004; received in revised form 27 October 2005; accepted 23 December 2005
Abstract An improved wax-based binder was developed for the powder injection molding of Ti–6Al–4V. A critical powder loading of 72 vol% and a pseudo-plastic flow behavior were obtained by the feedstock based on the binder. The injection molding, debinding and sintering processes were studied. An ideal control of carbon and oxygen contents was achieved by thermal debinding in vacuum atmosphere (10−3 Pa). The mechanical properties of as-sintered specimens were almost equivalent to those of the same alloy made by conventional press–sintering process. Good shape retention and ±0.02 mm dimension deviation were achieved. © 2006 Elsevier B.V. All rights reserved. Keywords: PIM; Ti–6Al–4V; Carbon and oxygen control; Mechanical properties
1. Introduction Titanium and titanium alloys have a low density, relatively high strength, excellent corrosion resistance in many media and is known to be biocompatible. This combination of properties makes titanium and its alloys an excellent choice for applications such as watch parts, medical devices, dental parts and sports goods. However, they can only be made with powder metallurgy process. Because of the nature of traditional process, components can only be formed and therefore designed with two dimension of flexibility, the third dimension being reserved for pressing operation. Powder injection molding (PIM), which is derived from plastic injection molding, is a kind of net-shape powder metallurgy forming process [1–4]. PIM has great technique and cost advantages for the production of Titanium alloy components with complex shapes [5,6]. Firstly, the products fabricated by PIM are expected to have more homogeneous microstructure. Since an almost hydraulic pressure is applied during injection molding, the mold is filled up uniformly, which avoids the density gradient in conventional press/sintering process. Secondly, fabrication cost could be eliminated significantly by reducing machining and recycling using of feedstock [7–10].
∗
Corresponding author. Tel.: +86 791 305 2068; fax: +86 791 380 1423. E-mail address: [email protected] (G. Shibo).
0924-0136/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2005.12.001
In this study, an improved wax-based binder was developed for powder injection molding of Ti–6Al–4V. The rheological properties of the feedstock and injection molding process were investigated. This article summarized some of the experimental results. 2. Experiment 2.1. Materials The mixed prealloy powder, which contained 90% gas-atomized prealloy powder (GA Ti–6Al–4V) (Shanxi Bangzhen Co. Ltd.) and 10% hydride–dehydride prealloy powder (HDH Ti–6Al–4V) (Hebei Wuyi Co. Ltd.), was used in this study. The characteristics of the powder were listed in Table 1. The morphology of the powder mixture was shown in Fig. 1. The binder used in this study was consisted of 63% paraffin wax, 12% polyethylene glycol20,000s, 14% low-density polyethylene, 10% polypropylene and 1% stearic acid. Polypropylene partially replacing low-density polyethylene helped to lessening the ash content in the as-debound parts, which would benefit carbon control during debinding and sintering. In addition, polyethylene glycol-20,000s also improved interaction between binder compositions and increased the ratio of solvent debinding.
2.2. Experimental procedure The binder components were pre-mixed together at 155 ◦ C for 2 h in a LH60 Roller mixer. Then, the Ti–6Al–4V powder mixture was mixed with the binder in a designed powder loading. The mixing temperature was 150 ◦ C. Specimens were fabricated in a CJ-ZZ injection molding machine at 165 ◦ C. The injection pressure was 80 MPa and the mold temperature was 30 ◦ C. The solvent debinding was performed for 6 h in a bath
G. Shibo et al. / Journal of Materials Processing Technology 173 (2006) 310–314
311
Table 1 Characteristics of titanium alloy powders Powder type
Mean size (m)
Oxygen content (wt%)
Carbon content (wt%)
Nitrogen content (wt%)
Theoretical density (g cm−3 )
Powder morphology
GA Ti–6Al–4V HDH Ti–6Al–4V
45 25–45
0.18 0.30
0.057 0.049
0.02 0.02
4.43 4.43
Irregular Spheric
Fig. 2. Loading curve of Ti–6Al–4V powder in the improved wax-based binder. Fig. 1. Morphology of the as-received Ti–6Al–4V prealloy powder.
nomenon in injection molding, and powder with good spherical shape. of mixed solvents including heptane + ethanol (8:2). Specimens were taken out and dried for 1 h after bathing. Then, thermal debinding was per150 min
formed in vacuum atmosphere (10−3 Pa) according to schedule 1: 20 ◦ C −→ 60 min 30 min 60 min 90 min 60 min 350 ◦ C −→ 350 ◦ C −→ 420 ◦ C −→ 420 ◦ C −→ 600 ◦ C −→ 600 ◦ C.
The asdebound specimens were sintered in vacuum atmosphere (10−3 Pa) at 1230 ◦ C for 3 h.
2.3. Property measurement An Instron 3211 capillary rheometer was used to measure the viscosities of feedstock. The mechanical properties of the specimens were determined on an Instron material tester. The carbon and oxygen residual were determined, respectively, by CS-8800 and TC-136 analyzer. The microstructure of the green and debound compacts, as well as the sintered alloy, was observed by LEO-1450 scanning electronic microscope.
3.2. Properties of feedstock The SEM morphology of as-molded specimens was shown in Fig. 3. Binder and powder were of good compatibility and mixture was homogeneous. Rheology of the feedstock indicated the relationship between the viscosity of the feedstock and shear rate, temperature. For a pseudo-plastic fluid, there is τ = kγ n , η = τ/γ, where τ is the shear stress, γ the shear rate, k the constant, n the flow behavior exponent and η is viscosity of the feedstock. The value of n indicates the degree of shear sensitivity, which is very important in producing complex and delicate
3. Results and discussion 3.1. Determination of powder loading PIM feedstock represented a balanced mixture of powder and binder. Powder loading largely determined the success or failure of subsequent processes. The density versus composition experiments were carried out to determine the critical powder loading of the feedstock. Fig. 2 showed the relationship between powder loading and density. The experimental density departed from the theoretical density at about 72% because the absence of binder led to the existence of porosity defect. Considering adjustable range of die size, a powder loading of 70% was selected in the subsequent experiments. A very high powder loading was obtained because of good binder improving the rheology of the feedstock and overcoming the phase separation phe-
Fig. 3. SEM morphology of fracture surface of as-molded compacts.
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Fig. 4. Relationship between viscosity η (Pa s) and shear rate γ (s−1 ).
Fig. 6. Correlation between debinding atmosphere and carbon or oxygen content of the specimens.
parts. By plotting the logarithm of shear stress against the logarithm of shear rate for the temperature of 150, 160 and 170 ◦ C as shown in Fig. 4, values of n were calculated as 0.522, 0.528 and 0.529, respectively. By plotting the natural logarithm of viscosity against the reciprocal of temperature as shown in Fig. 5, the flow activation energy E was 27.15 kJ mol−1 . 3.3. Carbon and oxygen control Control of carbon and oxygen content was the most important issue in manufacturing titanium alloy by PIM [11,12]. It determined not only the mechanical properties but also the dimensional stability. Fig. 6 showed the effect of thermal debinding atmosphere on carbon and oxygen content of the specimens. It was found that the residual carbon content in Ar atmosphere was a little less than that in vacuum atmosphere, but the residual oxygen content in Ar atmosphere was higher than that in vacuum atmosphere. Figs. 7 and 8 indicated the influence of debinding temperature and 600 ◦ C holding time in vacuum atmosphere on carbon and oxygen content of the as-debound specimens. It was found that binder was almost removed completely after thermal debinding when specimens were hold at 600 ◦ C for 1 h accord-
Fig. 5. Correlation between viscosity η (Pa s) and reciprocal of temperature.
Fig. 7. Correlation of high debinding temperature and carbon and oxygen content of the specimens.
ing to schedule 1. The contents of carbon and oxygen were 0.095 and 0.26%, respectively. Fig. 9 showed the fracture surface of the compact which had been debound in vacuum atmosphere at 600 ◦ C for 1 h. A lot of interconnected pores occurred and binder around the powder was removed completely.
Fig. 8. Correlation of high temperature holding time and carbon and oxygen content of the specimens.
G. Shibo et al. / Journal of Materials Processing Technology 173 (2006) 310–314
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Table 2 Comparisons of Ti–6Al–4V alloy made by PIM and pressing/sintering process Process
Density (g cm−3 )
Tensile strength (MPa)
Yield stress (MPa)
Elongation (%)
Reduction in area (%)
PIM (traditional binder) PIM (improved binder) PIM (improved binder) + HIP Press/sinter
4.20 4.32 4.42 4.21
720 835 1030 896
645 748 910 827
4.5 9.2 12 12
6 15 21 20
Fig. 9. SEM of fracture surface of the compacts after thermal debinding. Fig. 11. SEM of the as-sintered Ti–6Al–4V compacts made by traditional binder.
3.4. Mechanical properties and microstructure Mechanical properties of Ti–6Al–4V alloy made by PIM were listed in Table 2. Figs. 10 and 11 showed the SEM micrograph. The compacts made by the improved binder have homogenous microstructure and a void ratio of 3.5%, but those made by traditional binder have less homogenous microstructure and a void ratio of 5.0%. The compacts after hot-isostatic pressing (HIP) at 920 ◦ C for 3 h had less than 0.02% void ratio and better mechanical properties, which were similar to those specimens
made by conventional press–sintering process. For the rectangular specimens (6.38 mm × 6.38 mm × 48 mm), the dimension deviation in length was within the range of ±0.02 mm, but that of specimens made with traditional binder was ± 0.06 mm. 4. Conclusions An improved wax-based multi-component binder was developed for PIM of Ti–6Al–4V alloy. The binder and powder were of good compatibility. The viscosity of feedstock accorded with the pseudo-plastic behavior. The flow behavior exponent n, flow activation energy E with a powder loading of 70 vol% were 0.528 and 27.15 kJ mol−1 , respectively. Carbon and oxygen of the as-debound compacts could be controlled more easily in vacuum atmosphere. The binder could be removed completely at 600 ◦ C for 1 h. Carbon and oxygen contents were less than 0.1 and 0.26%, respectively. Ti–6Al–4V alloy components were made by PIM. The tensile strength, yield stress, elongation and reduction in area were 1030 MPa, 12 and 21%, respectively. Good shape retention and ±0.02 mm dimension deviation were achieved. Acknowledgements
Fig. 10. SEM of the as-sintered Ti–6Al–4V compacts made by the improved binder.
This work was financially supported by National 973 Program (TG2000067203) and National 863 Program (2001AA 337050).
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G. Shibo et al. / Journal of Materials Processing Technology 173 (2006) 310–314
References [1] R.M. German, P. Booker, Powder injection molding, Appl. Mech. Rev. 44 (8) (1991) 134–168. [2] A. Kei, K. Yasunari, I. Hiromichi, T. Masaharu, Injection molding of titanium powders, Adv. Powder Metall. 3 (1989) 121–126. [3] K. Tomio, H. Akira, K. Tetsuya, Development of titanium and titanium alloy by metal injection molding process, J. Jpn. Soc. Powder Powder Met. 44 (11) (1997) 985–992 (in Japanese). [4] F.H. Froes, Powder injection molding (PIM) of titanium alloys—ripe for expansion, Mater. Technol. 15 (4) (2000) 295–299. [5] X. Qu, Y. Li, B. Huang, Injection molding process of W–Ni–Fe heavy alloy, Zhongguo Youse Jinshu Xuebao 8 (3) (1998) 436–440 (in Chinese). [6] P.D. Lane, P.J. James, PIM may offer cheaper cutting tools, MPR 49 (7) (1994) 22–27.
[7] R.M. German, Wear application offer future growth for PIM, MPR 54 (6) (1999) 24. [8] K. Kato, Effect of sintering temperature on density and tensile properties of titanium compacts by metal injection molding, J. Jpn. Soc. Powder Powder Met. 46 (8) (1999) 865–869. [9] F.H. Froes, Titanium P/M—an overview, Adv. Powder Metall. Part Mater. (2001) 1298–1318. [10] E.S. Thian, N.H. Loh, K.A. Khor, S.B. Tor, Ti–6A1–4V/HA composite feedstock for injection molding, Mater. Lett. 56 (4) (2002) 522– 532. [11] Y.G. Li, P.A. Blenkinsop, M.H. Loretto, D. Rugg, Effect of carbon and oxygen on microstructure and mechanical properties of Ti–25V–15Cr–2Al (wt%) alloys, Acta Mater. 47 (10) (1999) 2889–2905. [12] K. Yasunari, A. Kei, S. Shiqeya, Application of injection molding to Ti–5 wt% Co and Ti–6 wt% Al–4 wt% V mixed powders, J. Jpn. Soc. Powder Powder Met. 37 (5) (1990) 591–598.
Powder injection molding of Ti–6Al–4V alloy Guo Shibo a,b,∗ , Qu Xuanhui b , He Xinbo b , Zhou Ting b , Duan Bohua b a
Jiangxi Key Laboratory of Surface Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013, China b School of Materials Science and Engineering, University of Science and Technology of Beijing, Beijing 100083, China Received 26 October 2004; received in revised form 27 October 2005; accepted 23 December 2005
Abstract An improved wax-based binder was developed for the powder injection molding of Ti–6Al–4V. A critical powder loading of 72 vol% and a pseudo-plastic flow behavior were obtained by the feedstock based on the binder. The injection molding, debinding and sintering processes were studied. An ideal control of carbon and oxygen contents was achieved by thermal debinding in vacuum atmosphere (10−3 Pa). The mechanical properties of as-sintered specimens were almost equivalent to those of the same alloy made by conventional press–sintering process. Good shape retention and ±0.02 mm dimension deviation were achieved. © 2006 Elsevier B.V. All rights reserved. Keywords: PIM; Ti–6Al–4V; Carbon and oxygen control; Mechanical properties
1. Introduction Titanium and titanium alloys have a low density, relatively high strength, excellent corrosion resistance in many media and is known to be biocompatible. This combination of properties makes titanium and its alloys an excellent choice for applications such as watch parts, medical devices, dental parts and sports goods. However, they can only be made with powder metallurgy process. Because of the nature of traditional process, components can only be formed and therefore designed with two dimension of flexibility, the third dimension being reserved for pressing operation. Powder injection molding (PIM), which is derived from plastic injection molding, is a kind of net-shape powder metallurgy forming process [1–4]. PIM has great technique and cost advantages for the production of Titanium alloy components with complex shapes [5,6]. Firstly, the products fabricated by PIM are expected to have more homogeneous microstructure. Since an almost hydraulic pressure is applied during injection molding, the mold is filled up uniformly, which avoids the density gradient in conventional press/sintering process. Secondly, fabrication cost could be eliminated significantly by reducing machining and recycling using of feedstock [7–10].
∗
Corresponding author. Tel.: +86 791 305 2068; fax: +86 791 380 1423. E-mail address: [email protected] (G. Shibo).
0924-0136/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2005.12.001
In this study, an improved wax-based binder was developed for powder injection molding of Ti–6Al–4V. The rheological properties of the feedstock and injection molding process were investigated. This article summarized some of the experimental results. 2. Experiment 2.1. Materials The mixed prealloy powder, which contained 90% gas-atomized prealloy powder (GA Ti–6Al–4V) (Shanxi Bangzhen Co. Ltd.) and 10% hydride–dehydride prealloy powder (HDH Ti–6Al–4V) (Hebei Wuyi Co. Ltd.), was used in this study. The characteristics of the powder were listed in Table 1. The morphology of the powder mixture was shown in Fig. 1. The binder used in this study was consisted of 63% paraffin wax, 12% polyethylene glycol20,000s, 14% low-density polyethylene, 10% polypropylene and 1% stearic acid. Polypropylene partially replacing low-density polyethylene helped to lessening the ash content in the as-debound parts, which would benefit carbon control during debinding and sintering. In addition, polyethylene glycol-20,000s also improved interaction between binder compositions and increased the ratio of solvent debinding.
2.2. Experimental procedure The binder components were pre-mixed together at 155 ◦ C for 2 h in a LH60 Roller mixer. Then, the Ti–6Al–4V powder mixture was mixed with the binder in a designed powder loading. The mixing temperature was 150 ◦ C. Specimens were fabricated in a CJ-ZZ injection molding machine at 165 ◦ C. The injection pressure was 80 MPa and the mold temperature was 30 ◦ C. The solvent debinding was performed for 6 h in a bath
G. Shibo et al. / Journal of Materials Processing Technology 173 (2006) 310–314
311
Table 1 Characteristics of titanium alloy powders Powder type
Mean size (m)
Oxygen content (wt%)
Carbon content (wt%)
Nitrogen content (wt%)
Theoretical density (g cm−3 )
Powder morphology
GA Ti–6Al–4V HDH Ti–6Al–4V
45 25–45
0.18 0.30
0.057 0.049
0.02 0.02
4.43 4.43
Irregular Spheric
Fig. 2. Loading curve of Ti–6Al–4V powder in the improved wax-based binder. Fig. 1. Morphology of the as-received Ti–6Al–4V prealloy powder.
nomenon in injection molding, and powder with good spherical shape. of mixed solvents including heptane + ethanol (8:2). Specimens were taken out and dried for 1 h after bathing. Then, thermal debinding was per150 min
formed in vacuum atmosphere (10−3 Pa) according to schedule 1: 20 ◦ C −→ 60 min 30 min 60 min 90 min 60 min 350 ◦ C −→ 350 ◦ C −→ 420 ◦ C −→ 420 ◦ C −→ 600 ◦ C −→ 600 ◦ C.
The asdebound specimens were sintered in vacuum atmosphere (10−3 Pa) at 1230 ◦ C for 3 h.
2.3. Property measurement An Instron 3211 capillary rheometer was used to measure the viscosities of feedstock. The mechanical properties of the specimens were determined on an Instron material tester. The carbon and oxygen residual were determined, respectively, by CS-8800 and TC-136 analyzer. The microstructure of the green and debound compacts, as well as the sintered alloy, was observed by LEO-1450 scanning electronic microscope.
3.2. Properties of feedstock The SEM morphology of as-molded specimens was shown in Fig. 3. Binder and powder were of good compatibility and mixture was homogeneous. Rheology of the feedstock indicated the relationship between the viscosity of the feedstock and shear rate, temperature. For a pseudo-plastic fluid, there is τ = kγ n , η = τ/γ, where τ is the shear stress, γ the shear rate, k the constant, n the flow behavior exponent and η is viscosity of the feedstock. The value of n indicates the degree of shear sensitivity, which is very important in producing complex and delicate
3. Results and discussion 3.1. Determination of powder loading PIM feedstock represented a balanced mixture of powder and binder. Powder loading largely determined the success or failure of subsequent processes. The density versus composition experiments were carried out to determine the critical powder loading of the feedstock. Fig. 2 showed the relationship between powder loading and density. The experimental density departed from the theoretical density at about 72% because the absence of binder led to the existence of porosity defect. Considering adjustable range of die size, a powder loading of 70% was selected in the subsequent experiments. A very high powder loading was obtained because of good binder improving the rheology of the feedstock and overcoming the phase separation phe-
Fig. 3. SEM morphology of fracture surface of as-molded compacts.
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G. Shibo et al. / Journal of Materials Processing Technology 173 (2006) 310–314
Fig. 4. Relationship between viscosity η (Pa s) and shear rate γ (s−1 ).
Fig. 6. Correlation between debinding atmosphere and carbon or oxygen content of the specimens.
parts. By plotting the logarithm of shear stress against the logarithm of shear rate for the temperature of 150, 160 and 170 ◦ C as shown in Fig. 4, values of n were calculated as 0.522, 0.528 and 0.529, respectively. By plotting the natural logarithm of viscosity against the reciprocal of temperature as shown in Fig. 5, the flow activation energy E was 27.15 kJ mol−1 . 3.3. Carbon and oxygen control Control of carbon and oxygen content was the most important issue in manufacturing titanium alloy by PIM [11,12]. It determined not only the mechanical properties but also the dimensional stability. Fig. 6 showed the effect of thermal debinding atmosphere on carbon and oxygen content of the specimens. It was found that the residual carbon content in Ar atmosphere was a little less than that in vacuum atmosphere, but the residual oxygen content in Ar atmosphere was higher than that in vacuum atmosphere. Figs. 7 and 8 indicated the influence of debinding temperature and 600 ◦ C holding time in vacuum atmosphere on carbon and oxygen content of the as-debound specimens. It was found that binder was almost removed completely after thermal debinding when specimens were hold at 600 ◦ C for 1 h accord-
Fig. 5. Correlation between viscosity η (Pa s) and reciprocal of temperature.
Fig. 7. Correlation of high debinding temperature and carbon and oxygen content of the specimens.
ing to schedule 1. The contents of carbon and oxygen were 0.095 and 0.26%, respectively. Fig. 9 showed the fracture surface of the compact which had been debound in vacuum atmosphere at 600 ◦ C for 1 h. A lot of interconnected pores occurred and binder around the powder was removed completely.
Fig. 8. Correlation of high temperature holding time and carbon and oxygen content of the specimens.
G. Shibo et al. / Journal of Materials Processing Technology 173 (2006) 310–314
313
Table 2 Comparisons of Ti–6Al–4V alloy made by PIM and pressing/sintering process Process
Density (g cm−3 )
Tensile strength (MPa)
Yield stress (MPa)
Elongation (%)
Reduction in area (%)
PIM (traditional binder) PIM (improved binder) PIM (improved binder) + HIP Press/sinter
4.20 4.32 4.42 4.21
720 835 1030 896
645 748 910 827
4.5 9.2 12 12
6 15 21 20
Fig. 9. SEM of fracture surface of the compacts after thermal debinding. Fig. 11. SEM of the as-sintered Ti–6Al–4V compacts made by traditional binder.
3.4. Mechanical properties and microstructure Mechanical properties of Ti–6Al–4V alloy made by PIM were listed in Table 2. Figs. 10 and 11 showed the SEM micrograph. The compacts made by the improved binder have homogenous microstructure and a void ratio of 3.5%, but those made by traditional binder have less homogenous microstructure and a void ratio of 5.0%. The compacts after hot-isostatic pressing (HIP) at 920 ◦ C for 3 h had less than 0.02% void ratio and better mechanical properties, which were similar to those specimens
made by conventional press–sintering process. For the rectangular specimens (6.38 mm × 6.38 mm × 48 mm), the dimension deviation in length was within the range of ±0.02 mm, but that of specimens made with traditional binder was ± 0.06 mm. 4. Conclusions An improved wax-based multi-component binder was developed for PIM of Ti–6Al–4V alloy. The binder and powder were of good compatibility. The viscosity of feedstock accorded with the pseudo-plastic behavior. The flow behavior exponent n, flow activation energy E with a powder loading of 70 vol% were 0.528 and 27.15 kJ mol−1 , respectively. Carbon and oxygen of the as-debound compacts could be controlled more easily in vacuum atmosphere. The binder could be removed completely at 600 ◦ C for 1 h. Carbon and oxygen contents were less than 0.1 and 0.26%, respectively. Ti–6Al–4V alloy components were made by PIM. The tensile strength, yield stress, elongation and reduction in area were 1030 MPa, 12 and 21%, respectively. Good shape retention and ±0.02 mm dimension deviation were achieved. Acknowledgements
Fig. 10. SEM of the as-sintered Ti–6Al–4V compacts made by the improved binder.
This work was financially supported by National 973 Program (TG2000067203) and National 863 Program (2001AA 337050).
314
G. Shibo et al. / Journal of Materials Processing Technology 173 (2006) 310–314
References [1] R.M. German, P. Booker, Powder injection molding, Appl. Mech. Rev. 44 (8) (1991) 134–168. [2] A. Kei, K. Yasunari, I. Hiromichi, T. Masaharu, Injection molding of titanium powders, Adv. Powder Metall. 3 (1989) 121–126. [3] K. Tomio, H. Akira, K. Tetsuya, Development of titanium and titanium alloy by metal injection molding process, J. Jpn. Soc. Powder Powder Met. 44 (11) (1997) 985–992 (in Japanese). [4] F.H. Froes, Powder injection molding (PIM) of titanium alloys—ripe for expansion, Mater. Technol. 15 (4) (2000) 295–299. [5] X. Qu, Y. Li, B. Huang, Injection molding process of W–Ni–Fe heavy alloy, Zhongguo Youse Jinshu Xuebao 8 (3) (1998) 436–440 (in Chinese). [6] P.D. Lane, P.J. James, PIM may offer cheaper cutting tools, MPR 49 (7) (1994) 22–27.
[7] R.M. German, Wear application offer future growth for PIM, MPR 54 (6) (1999) 24. [8] K. Kato, Effect of sintering temperature on density and tensile properties of titanium compacts by metal injection molding, J. Jpn. Soc. Powder Powder Met. 46 (8) (1999) 865–869. [9] F.H. Froes, Titanium P/M—an overview, Adv. Powder Metall. Part Mater. (2001) 1298–1318. [10] E.S. Thian, N.H. Loh, K.A. Khor, S.B. Tor, Ti–6A1–4V/HA composite feedstock for injection molding, Mater. Lett. 56 (4) (2002) 522– 532. [11] Y.G. Li, P.A. Blenkinsop, M.H. Loretto, D. Rugg, Effect of carbon and oxygen on microstructure and mechanical properties of Ti–25V–15Cr–2Al (wt%) alloys, Acta Mater. 47 (10) (1999) 2889–2905. [12] K. Yasunari, A. Kei, S. Shiqeya, Application of injection molding to Ti–5 wt% Co and Ti–6 wt% Al–4 wt% V mixed powders, J. Jpn. Soc. Powder Powder Met. 37 (5) (1990) 591–598.