- Email: [email protected]
Selective laser melting additive manufacturing of advanced nuclear materials V-6Cr-6Ti
Accepted Manuscript Selective Laser Melting Additive Manufacturing of Advanced Nuclear Materials V-6Cr-6Ti Yang Jialin PII: DOI: Reference:
S0167-577X(17)31193-X http://dx.doi.org/10.1016/j.matlet.2017.08.014 MLBLUE 22991
To appear in:
Materials Letters
Received Date: Accepted Date:
21 July 2017 3 August 2017
Please cite this article as: Y. Jialin, Selective Laser Melting Additive Manufacturing of Advanced Nuclear Materials V-6Cr-6Ti, Materials Letters (2017), doi: http://dx.doi.org/10.1016/j.matlet.2017.08.014
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Selective Laser Melting Additive Manufacturing of Advanced Nuclear Materials V-6Cr-6Ti
Yang Jialin1, 2* 1
State Key Laboratory for Powder Metallurgy, Central South University
2
Institute of Machinery Manufacturing Technology, China Academy of Engineering Physics
* Corresponding author. E-mail: [email protected]
Abstract Selective laser melting (SLM) additive manufacturing technology has been a prevailing method to fabricate components with complex physical geometry or novel structural design. However, original nuclear powder material such as vanadium-based alloy appropriate for SLM processing has yet not been obtained commercially, which significantly restricts the development of nuclear component manufacturing. In this study, near-sphere, uniform and fine V-6Cr-6Ti pre-alloy powder which met the performance demands for SLM processing was successfully obtained by high-energy ball milling. Subsequently, the V-6Cr-6Ti part was fabricated by SLM consolidation of as-prepared pre-alloy powder with double-region orthometric scanning strategy, forming strong texture feature within molten pool. The compression test was performed, showing that the maximum compression stress reached 1078 MPa and the accumulated strain was about 0.32. Keywords: laser processing, nuclear material, deformation and fracture
4
1. Introduction Vanadium alloys are identified as an attractive nuclear material for self-cooled liquid Li blanket in advanced fusion reactors, due to its excellent high-temperature performance, irradiation resistance and satisfying compatibility with liquid metal [1]. Besides, Vanadium alloys have been a promising material for specific structural application, e.g. accelerating or rotating structural components, as it provides the lowest density of the various high melting point metals [2]. Conventional vanadium-based alloy parts are mainly fabricated by casting and forging, which always suffer from a long process flow, high cost and low utilization ratio of raw materials. In addition, properties of vanadium alloys are sensitive to the existence of impurity such as oxygen element which should be controlled strictly during the manufacturing processing. Selective laser melting (SLM) has attracted much attention as the most prevailing part of additive manufacturing technologies, which can efficiently overcome the above challenges and meanwhile obtain novel tailored microstructure and resultant excellent mechanical or physical properties [3, 4]. Nevertheless, few investigations on SLM-fabricated vanadium-based alloys have been reported, which can be attributed to lack of specialized commercial vanadium-based alloys powder developed for SLM technology. In this study, a system work including powder preparation, powder consolidation and property characterization has been carried out to provide an effective method for SLM of vanadium-based alloy components. 2. Experimental The 99.9% purity irregular vanadium, titanium and chromium powders with a mean particle size of 35 µm were used as the raw materials in this study. Then the multi-powders consisting of 88% V, 6% Cr and 6% Ti were homogenously milled by the high-energy Pulverisette 6 planetary mono-mill (Fritsch GmbH, 5
Germany) to obtain pre-alloy powder particles. The ball to powder weight ratio was 10:1. Then different milling times 5, 10, 15, 20, and 25 h were set, while the rotation speed of the supporting disc was fixed at 350 r/min. Subsequently, the SLM processing was performed by the EOSINT M 280 equipment developed by EOS GmbH Electro Optical Systems. By the parameter optimization, the following suitable processing parameters were chosen: the laser powder of 195 W, the scan speed of 700 mm/s, and the powder layer thickness of 40 µm were settled. A simple linear raster scan pattern was used, with a scan vector length of 10 mm and a hatch spacing of 100 µm. A Zeiss Sigma 04–95 field emission scanning electron microscope (FESEM) (Carl Zeiss AG, Germany) equipped with a Bruker XFlash 6160 energy dispersive X-ray spectroscope (EDS) (Bruker Daltonics Inc., USA) was applied to perform high-resolution study of powder particle morphology and microstructural features of SLM-processed specimens as well as the corresponding chemical compositions. Compression tests were carried out at room temperature using a CMT5205 testing machine (MTS Industrial Systems, China) with a cross head velocity fixed at 1 mm/min. 3. Results and discussion Fig. 1 shows particle morphology and composition distribution of the 25 h-milled powder as well as the XRD pattern of powder particle with different milling time. After 25 h ball milling, powder particle displayed near-sphere morphology with an average size of 20 µm. The corresponding EDS mapping demonstrated that the element distribution of powder particle was relative uniform and the Ti element occurred to be slightly segregated (Fig. 1b-d). Based on the XRD pattern, the diffraction peak of the main phase α-V became apparently broadened with ball milling time increasing, indicating that the matrix phase got remarkable refinement. As the ball milling time was increased to 25 h, only a few α-Ti and α-Cr 6
peaks could be found due to solid solution effect induced by cold-welding, therefore giving rise to the formation of α’-V (Ti, Cr).
Figure 1 (a) Powder particle morphology after 25-h ball milling; (b)-(d) the corresponding element distribution; (e) the XRD pattern of powder at various ball milling times. Fig. 2 depicts the typical phase and microstructure features of SLM-fabricated vanadium alloy at the tailored laser processing parameter. By process optimization, the SLM-fabricated part had a smooth surface and high densification degree of nearly 98.7% (Fig. 2a). Besides, phase identification of SLM-fabricated part implied that alloying reaction among V, Cr and Ti was performed sufficiently and ’
original residual α-Ti and α-Cr phase were completely transferred to α -V (Ti, Cr). Note that, double-region orthometric scanning strategy was applied in this study (Fig. 2b). For SLM scanning strategy of single layer, odd tracks were fabricated firstly and then even tracks were consolidated; along the building direction, the scanning direction was perpendicular to each other between adjacent layers. Consequently, two typical microstructures, namely columnar dendrites and cellular grains, could be observed clearly (Fig. 2c). High-magnificent SEM micrograph showed the average size of cellular grain and the spacing of adjacent columnar dendrites were similar, below 1 μm (Fig. 2d). Generally, due to the larger heat diffusion rate in the regions contacting the solidified parts within molten pool, the melt in these regions was inclined to solidify preferentially along the normal direction of 7
edge of molten pool and nucleate and grow with typical columnar dendrites, which had been found in SLM of nickel-based alloy and stainless steel [5, 6]. Note that, some cellular grains could be found at the right upper corner of molten pool when the even track was fabricated, as shown in region A of Fig. 2c. Re-melting occurred in region A due to double-region scanning strategy, giving rise to formation of multi-interfaces including melt-to-air, melt-to-solidified layer and melt-to-solidified track. Complex heat transfer behavior resulted in the nearly isotropous distribution of temperature gradient, thus facilitating the formation of cellular grains. Specially, a mass of cellular grains were observed when the scanning direction of the track was parallel to the current cross-section. Based on the formation mechanism of columnar dendrites, it was reasonable to confirm that the observed cellular grains were the cross-sectional morphology features of columnar dendrites. Furthermore, the microstructure of electron beam welding processed vanadium alloy was also displayed in Fig. 2e and 2f, showing the remarkably coarsening dendritical morphology with dendrite trunk spacing of more than 5 μm.
Figure 2 (a) XRD patterns of SLM-processed part and 25-h milling powder; (b) the applied scanning strategy; (c) and (d) the microstructural features of SLM-processed part; (e) and (f) the microstructural features of electron beam welding processed part.
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Furthermore, to better understand the mechanical behavior of SLM-fabricated vanadium alloy with unique fine microstructure, compression test was performed in this study. During the compression, displacement value of 0.5 mm was set as a signal of test ending for each test and 17 tests were carried out before the sample occurred to break. A little elastic recovery of 0.1~0.2 mm existed after each test and the elastic recovery decreased with test times increasing. The corresponding stress-strain curve was made, as shown in Fig. 3a. For first nine tests, the measured maximum compression stress increased continuously and reached 1078 MPa during the ninth test, while the maximum stress decreased consecutively for the next eight tests. The accumulated strain was about 0.32. Specially, the maximum compression stress for forging processed vanadium alloy was also given, lower than that of SLM-processed part with similar maximum compression strain [7]. The mechanical behavior of vanadium alloy is mainly controlled by dislocation density evolution during static compression at room temperature. Based on the Voyiadjis GZ’s work [8], flow stress σ can be decomposed into equivalent thermal stress σth and equivalent athermal stress σa . Note that, the σ* is mainly influenced by short-distance Peierls stress for bcc-structural vanadium alloy [7], which has nothing to do with strain. The σa depends on long-distance stress field induced by dislocations [9], which can be estimated by the following equation:
σ a = αMµb ρ
(1)
with α, a constant; M, the average Taylor factor; μ, the shear modulus; b, the Burgers vector; and ρ, the dislocation density. In the initial stage, a large number of dislocations are initiated with compression force increasing. To release the dislocations, molten pool boundary sliding occurs preferentially due to lower sliding resistance than grain boundary sliding (Fig. 3b), upon the decomposed compression stress τ reaching the threshold. Subsequently, high-density dislocations aggregate around the bottom of molten 9
pool, thus leading to the occurrence of strain-hardening phenomenon and a resultant increase of equivalent athermal stress according to the Eq. (1). During the ninth test, as the applied compression force further increases, grain boundary sliding starts to occur, this implies that the maximum sliding resistance has been overcome. Then dislocations slid quickly again along the molten pool boundary, finally giving rise to shear fracture of specimen. Figs. 3c give the surface morphology of shear fracture, showing the elongated grains and the sliding direction. The elongated columnar dendrites indicate that existence of molten pool boundary sliding.
Figure 3 (a) The stress-strain curve during compression test; (b) the schematic diagram of grain boundary sliding and molten pool boundary sliding during compression processing; (c) the surface morphology of shear fracture. 4. Conclusion In this study, fine V-6Cr-6Ti pre-alloy powder with near-sphere morphology was successfully obtained by high-energy ball milling. Subsequently, the V-6Cr-6Ti part was fabricated by SLM, forming strong texture feature with ultrafine grain size within various molten pools which significantly influenced the corresponding mechanical property. The measured compression strength was higher than that of conventional technology processed vanadium-based alloy. 10
References [1] J. Zhang, J. Xia, M. Zhang, Y. Qiao, L. Liu, P. Zhai, Tensile fracture mechanism and constitutive models of V-5Cr-5Ti alloy under different strain rate deformation at room temperature, Mater. Lett. 183 (2016) 40-43. [2] Manja Krüger, High temperature compression strength and oxidation of a V-9Si-13B alloy, Scr. Mater. 121 (2016) 75-78. [3] D. D. Gu, Y. F. Shen, G. B. Meng, Growth morphologies and mechanisms of TiC grains during Selective Laser Melting of Ti-Al-C composite powder, Mater. Lett. 63 (2009) 2536-2538. [4] D. D. Gu, Y. F. Shen, Z. J. Lu, Preparation of TiN-Ti5Si3 in-situ composites by Selective Laser Melting, Mater. Lett. 63 (2009) 1577-1579. [5] D. Wang, C. Song, Y. Yang, Y. Bai, Investigation of crystal growthmechanism during selective laser melting and mechanical property characterization of 316L stainless steel parts, Mater. Des. 100 (2016) 291-299 [6] K.N. Amato, S.M. Gaytan, L.E. Murr, E. Martinez, P.W. Shindo, J. Hernandez, S. Collins, F. Medina, Microstructures and mechanical behavior of Inconel 718 fabricated by selective laser melting, Acta Mater. 60 (2012) 2229-2239. [7] Y. Yu, X. Pan, R. Xie, F. Zhang, W. Hu, Study of TWIP effect on strain hardening behavior in V-5Cr-5Ti alloy, Chin. J. Theor. Appl. Mech., 44(2) (2012) 334-341. [8] G. Z. Voyiadjis, F. H. Abed, Microstructural based models for bcc and fcc metals with temperature and strain rate dependency, Mech. Mater. 37 (2005) 355-378. [9] O. Bouaziz, N. Guelton, Modelling of TWIP effect on work-hardening, Mater. Sci. Eng., A 319–321 (2001) 246–249. 11
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(1) Near-sphere, uniform and fine V-6Cr-6Ti pre-alloy powder which met the performance demands for SLM processing was successfully obtained by high-energy ball milling; (2) Strong texture feature within molten pool formed by applying double-region orthometric scanning strategy; (3) The compression test was performed and the compression strength was higher than that of conventional technology processed vanadium-based alloy; (4) Molten pool boundary sliding played an important role in shear deformation during compression processing.
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S0167-577X(17)31193-X http://dx.doi.org/10.1016/j.matlet.2017.08.014 MLBLUE 22991
To appear in:
Materials Letters
Received Date: Accepted Date:
21 July 2017 3 August 2017
Please cite this article as: Y. Jialin, Selective Laser Melting Additive Manufacturing of Advanced Nuclear Materials V-6Cr-6Ti, Materials Letters (2017), doi: http://dx.doi.org/10.1016/j.matlet.2017.08.014
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Selective Laser Melting Additive Manufacturing of Advanced Nuclear Materials V-6Cr-6Ti
Yang Jialin1, 2* 1
State Key Laboratory for Powder Metallurgy, Central South University
2
Institute of Machinery Manufacturing Technology, China Academy of Engineering Physics
* Corresponding author. E-mail: [email protected]
Abstract Selective laser melting (SLM) additive manufacturing technology has been a prevailing method to fabricate components with complex physical geometry or novel structural design. However, original nuclear powder material such as vanadium-based alloy appropriate for SLM processing has yet not been obtained commercially, which significantly restricts the development of nuclear component manufacturing. In this study, near-sphere, uniform and fine V-6Cr-6Ti pre-alloy powder which met the performance demands for SLM processing was successfully obtained by high-energy ball milling. Subsequently, the V-6Cr-6Ti part was fabricated by SLM consolidation of as-prepared pre-alloy powder with double-region orthometric scanning strategy, forming strong texture feature within molten pool. The compression test was performed, showing that the maximum compression stress reached 1078 MPa and the accumulated strain was about 0.32. Keywords: laser processing, nuclear material, deformation and fracture
4
1. Introduction Vanadium alloys are identified as an attractive nuclear material for self-cooled liquid Li blanket in advanced fusion reactors, due to its excellent high-temperature performance, irradiation resistance and satisfying compatibility with liquid metal [1]. Besides, Vanadium alloys have been a promising material for specific structural application, e.g. accelerating or rotating structural components, as it provides the lowest density of the various high melting point metals [2]. Conventional vanadium-based alloy parts are mainly fabricated by casting and forging, which always suffer from a long process flow, high cost and low utilization ratio of raw materials. In addition, properties of vanadium alloys are sensitive to the existence of impurity such as oxygen element which should be controlled strictly during the manufacturing processing. Selective laser melting (SLM) has attracted much attention as the most prevailing part of additive manufacturing technologies, which can efficiently overcome the above challenges and meanwhile obtain novel tailored microstructure and resultant excellent mechanical or physical properties [3, 4]. Nevertheless, few investigations on SLM-fabricated vanadium-based alloys have been reported, which can be attributed to lack of specialized commercial vanadium-based alloys powder developed for SLM technology. In this study, a system work including powder preparation, powder consolidation and property characterization has been carried out to provide an effective method for SLM of vanadium-based alloy components. 2. Experimental The 99.9% purity irregular vanadium, titanium and chromium powders with a mean particle size of 35 µm were used as the raw materials in this study. Then the multi-powders consisting of 88% V, 6% Cr and 6% Ti were homogenously milled by the high-energy Pulverisette 6 planetary mono-mill (Fritsch GmbH, 5
Germany) to obtain pre-alloy powder particles. The ball to powder weight ratio was 10:1. Then different milling times 5, 10, 15, 20, and 25 h were set, while the rotation speed of the supporting disc was fixed at 350 r/min. Subsequently, the SLM processing was performed by the EOSINT M 280 equipment developed by EOS GmbH Electro Optical Systems. By the parameter optimization, the following suitable processing parameters were chosen: the laser powder of 195 W, the scan speed of 700 mm/s, and the powder layer thickness of 40 µm were settled. A simple linear raster scan pattern was used, with a scan vector length of 10 mm and a hatch spacing of 100 µm. A Zeiss Sigma 04–95 field emission scanning electron microscope (FESEM) (Carl Zeiss AG, Germany) equipped with a Bruker XFlash 6160 energy dispersive X-ray spectroscope (EDS) (Bruker Daltonics Inc., USA) was applied to perform high-resolution study of powder particle morphology and microstructural features of SLM-processed specimens as well as the corresponding chemical compositions. Compression tests were carried out at room temperature using a CMT5205 testing machine (MTS Industrial Systems, China) with a cross head velocity fixed at 1 mm/min. 3. Results and discussion Fig. 1 shows particle morphology and composition distribution of the 25 h-milled powder as well as the XRD pattern of powder particle with different milling time. After 25 h ball milling, powder particle displayed near-sphere morphology with an average size of 20 µm. The corresponding EDS mapping demonstrated that the element distribution of powder particle was relative uniform and the Ti element occurred to be slightly segregated (Fig. 1b-d). Based on the XRD pattern, the diffraction peak of the main phase α-V became apparently broadened with ball milling time increasing, indicating that the matrix phase got remarkable refinement. As the ball milling time was increased to 25 h, only a few α-Ti and α-Cr 6
peaks could be found due to solid solution effect induced by cold-welding, therefore giving rise to the formation of α’-V (Ti, Cr).
Figure 1 (a) Powder particle morphology after 25-h ball milling; (b)-(d) the corresponding element distribution; (e) the XRD pattern of powder at various ball milling times. Fig. 2 depicts the typical phase and microstructure features of SLM-fabricated vanadium alloy at the tailored laser processing parameter. By process optimization, the SLM-fabricated part had a smooth surface and high densification degree of nearly 98.7% (Fig. 2a). Besides, phase identification of SLM-fabricated part implied that alloying reaction among V, Cr and Ti was performed sufficiently and ’
original residual α-Ti and α-Cr phase were completely transferred to α -V (Ti, Cr). Note that, double-region orthometric scanning strategy was applied in this study (Fig. 2b). For SLM scanning strategy of single layer, odd tracks were fabricated firstly and then even tracks were consolidated; along the building direction, the scanning direction was perpendicular to each other between adjacent layers. Consequently, two typical microstructures, namely columnar dendrites and cellular grains, could be observed clearly (Fig. 2c). High-magnificent SEM micrograph showed the average size of cellular grain and the spacing of adjacent columnar dendrites were similar, below 1 μm (Fig. 2d). Generally, due to the larger heat diffusion rate in the regions contacting the solidified parts within molten pool, the melt in these regions was inclined to solidify preferentially along the normal direction of 7
edge of molten pool and nucleate and grow with typical columnar dendrites, which had been found in SLM of nickel-based alloy and stainless steel [5, 6]. Note that, some cellular grains could be found at the right upper corner of molten pool when the even track was fabricated, as shown in region A of Fig. 2c. Re-melting occurred in region A due to double-region scanning strategy, giving rise to formation of multi-interfaces including melt-to-air, melt-to-solidified layer and melt-to-solidified track. Complex heat transfer behavior resulted in the nearly isotropous distribution of temperature gradient, thus facilitating the formation of cellular grains. Specially, a mass of cellular grains were observed when the scanning direction of the track was parallel to the current cross-section. Based on the formation mechanism of columnar dendrites, it was reasonable to confirm that the observed cellular grains were the cross-sectional morphology features of columnar dendrites. Furthermore, the microstructure of electron beam welding processed vanadium alloy was also displayed in Fig. 2e and 2f, showing the remarkably coarsening dendritical morphology with dendrite trunk spacing of more than 5 μm.
Figure 2 (a) XRD patterns of SLM-processed part and 25-h milling powder; (b) the applied scanning strategy; (c) and (d) the microstructural features of SLM-processed part; (e) and (f) the microstructural features of electron beam welding processed part.
8
Furthermore, to better understand the mechanical behavior of SLM-fabricated vanadium alloy with unique fine microstructure, compression test was performed in this study. During the compression, displacement value of 0.5 mm was set as a signal of test ending for each test and 17 tests were carried out before the sample occurred to break. A little elastic recovery of 0.1~0.2 mm existed after each test and the elastic recovery decreased with test times increasing. The corresponding stress-strain curve was made, as shown in Fig. 3a. For first nine tests, the measured maximum compression stress increased continuously and reached 1078 MPa during the ninth test, while the maximum stress decreased consecutively for the next eight tests. The accumulated strain was about 0.32. Specially, the maximum compression stress for forging processed vanadium alloy was also given, lower than that of SLM-processed part with similar maximum compression strain [7]. The mechanical behavior of vanadium alloy is mainly controlled by dislocation density evolution during static compression at room temperature. Based on the Voyiadjis GZ’s work [8], flow stress σ can be decomposed into equivalent thermal stress σth and equivalent athermal stress σa . Note that, the σ* is mainly influenced by short-distance Peierls stress for bcc-structural vanadium alloy [7], which has nothing to do with strain. The σa depends on long-distance stress field induced by dislocations [9], which can be estimated by the following equation:
σ a = αMµb ρ
(1)
with α, a constant; M, the average Taylor factor; μ, the shear modulus; b, the Burgers vector; and ρ, the dislocation density. In the initial stage, a large number of dislocations are initiated with compression force increasing. To release the dislocations, molten pool boundary sliding occurs preferentially due to lower sliding resistance than grain boundary sliding (Fig. 3b), upon the decomposed compression stress τ reaching the threshold. Subsequently, high-density dislocations aggregate around the bottom of molten 9
pool, thus leading to the occurrence of strain-hardening phenomenon and a resultant increase of equivalent athermal stress according to the Eq. (1). During the ninth test, as the applied compression force further increases, grain boundary sliding starts to occur, this implies that the maximum sliding resistance has been overcome. Then dislocations slid quickly again along the molten pool boundary, finally giving rise to shear fracture of specimen. Figs. 3c give the surface morphology of shear fracture, showing the elongated grains and the sliding direction. The elongated columnar dendrites indicate that existence of molten pool boundary sliding.
Figure 3 (a) The stress-strain curve during compression test; (b) the schematic diagram of grain boundary sliding and molten pool boundary sliding during compression processing; (c) the surface morphology of shear fracture. 4. Conclusion In this study, fine V-6Cr-6Ti pre-alloy powder with near-sphere morphology was successfully obtained by high-energy ball milling. Subsequently, the V-6Cr-6Ti part was fabricated by SLM, forming strong texture feature with ultrafine grain size within various molten pools which significantly influenced the corresponding mechanical property. The measured compression strength was higher than that of conventional technology processed vanadium-based alloy. 10
References [1] J. Zhang, J. Xia, M. Zhang, Y. Qiao, L. Liu, P. Zhai, Tensile fracture mechanism and constitutive models of V-5Cr-5Ti alloy under different strain rate deformation at room temperature, Mater. Lett. 183 (2016) 40-43. [2] Manja Krüger, High temperature compression strength and oxidation of a V-9Si-13B alloy, Scr. Mater. 121 (2016) 75-78. [3] D. D. Gu, Y. F. Shen, G. B. Meng, Growth morphologies and mechanisms of TiC grains during Selective Laser Melting of Ti-Al-C composite powder, Mater. Lett. 63 (2009) 2536-2538. [4] D. D. Gu, Y. F. Shen, Z. J. Lu, Preparation of TiN-Ti5Si3 in-situ composites by Selective Laser Melting, Mater. Lett. 63 (2009) 1577-1579. [5] D. Wang, C. Song, Y. Yang, Y. Bai, Investigation of crystal growthmechanism during selective laser melting and mechanical property characterization of 316L stainless steel parts, Mater. Des. 100 (2016) 291-299 [6] K.N. Amato, S.M. Gaytan, L.E. Murr, E. Martinez, P.W. Shindo, J. Hernandez, S. Collins, F. Medina, Microstructures and mechanical behavior of Inconel 718 fabricated by selective laser melting, Acta Mater. 60 (2012) 2229-2239. [7] Y. Yu, X. Pan, R. Xie, F. Zhang, W. Hu, Study of TWIP effect on strain hardening behavior in V-5Cr-5Ti alloy, Chin. J. Theor. Appl. Mech., 44(2) (2012) 334-341. [8] G. Z. Voyiadjis, F. H. Abed, Microstructural based models for bcc and fcc metals with temperature and strain rate dependency, Mech. Mater. 37 (2005) 355-378. [9] O. Bouaziz, N. Guelton, Modelling of TWIP effect on work-hardening, Mater. Sci. Eng., A 319–321 (2001) 246–249. 11
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(1) Near-sphere, uniform and fine V-6Cr-6Ti pre-alloy powder which met the performance demands for SLM processing was successfully obtained by high-energy ball milling; (2) Strong texture feature within molten pool formed by applying double-region orthometric scanning strategy; (3) The compression test was performed and the compression strength was higher than that of conventional technology processed vanadium-based alloy; (4) Molten pool boundary sliding played an important role in shear deformation during compression processing.
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