Rare earth heat conduction magnesium alloy and preparation method thereof

Abstract

The invention provides a rare earth heat-conducting magnesium alloy and a preparation method thereof, and relates to the technical field of heat-conducting magnesium alloys. The rare earth heat conduction magnesium alloy provided by the invention comprises 0.1-1% by mass of Sb, the magnesium alloy contains alpha-Mg, Al-RE and RE-Sb phases, and RE comprises at least one of La and Ce; and the magnesium alloy is an Mg-RE-Al-Mn-Sb magnesium alloy. By adding 0.1-1wt% of Sb, an RE-Sb dispersed phase can be separated out in the alloy, alpha-Mg can be refined, meanwhile, a coarse Al-RE phase can be split and refined, the heat-conducting property and the mechanical property of the magnesium alloy are comprehensively improved, meanwhile, the alloy melt flowability is improved, and the casting quality is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of thermally conductive magnesium alloys, and in particular to a rare earth thermally conductive magnesium alloy and a preparation method thereof. Background Art

[0002] With the development of aerospace, new generation weapons and equipment, high-speed trains and new energy vehicles, the number and density of high-power devices will continue to increase, and heat dissipation components will become an important guarantee for the stability of equipment operation. The density of magnesium is 1.74g / cm 3 , which is only 2 / 3 of aluminum and 1 / 5 of copper, making it the lightest metal structural material. At the same time, the thermal conductivity of magnesium is 156W / (m·K), making it a new generation of lightweight thermal conductive materials. However, it is difficult to synergistically improve the thermal conductivity and mechanical properties of magnesium and its alloys. Conventional alloying methods will increase the mechanical strength of magnesium alloys and cause their thermal conductivity to decrease rapidly. For example, the commercial magnesium alloy AZ91D, with the addition of Al and Zn elements to Mg, its room temperature tensile strength increases to 220MPa, but its thermal conductivity rapidly decays to 60W / (m·K) [Research Progress on Thermal Conductivity of Magnesium and Its Alloys. Acta Metallurgica Sinica, 2022, 58(04): 400-411].

[0003] Cast thermally conductive magnesium alloys often achieve synergistic improvements in thermal conductivity and mechanical properties of magnesium alloys through complex microalloying methods and multi-stage heat treatment. For example, Mg-3Al-3Ce-0.25Mn-1.55La-0.6Zn-0.15Ca has a thermal conductivity of up to 110W / (m·K) and a tensile strength of about 220MPa [a high thermal conductivity die-cast magnesium alloy for automotive inverter housing, CN109136699B]. Another example is Mg-3Sm-0.2Zn-0.5Mn, which has a thermal conductivity of up to 100W / (m·K) and a tensile strength of about 140Mpa after multi-stage aging [a new high thermal conductivity die-cast rare earth magnesium alloy and its preparation method, CN104846246A]. Compared with other cast thermal conductive magnesium alloys Mg-Al-X series, Mg-Ca-X series, Mg-Sn-X series [Microstructure evolutionand improvement of thermal conductivity in Mg–2Sn alloy induced by Laaddition.Journal of Materials Research and Technology,2022,17:1380-1389, Microstructure and properties of cast Mg-xSn-2La alloy [J]. Special Casting and Nonferrous Alloys,2009,29(03):266-269+194-195], the tensile strength of Mg-RE-Al-Mn series thermal conductive magnesium alloys reaches 200-250MPa and the thermal conductivity reaches 90-110W / (m·K), which belongs to high-strength and high thermal conductivity cast magnesium alloys [Microstructure and Thermal Conductivity of As-Castand As-Solutionized Mg–Rare Earth Binary Alloys.Journal of Materials Science&Technology, 2017, 33: 1240–1248; Su Chuangye, Research on thermal conductivity mechanism of magnesium alloy based on solid solution atoms and second phase. Shanghai Jiaotong University, 2019 Ying Tao. Research on thermal conductivity behavior of pure magnesium and binary magnesium alloys. Harbin Institute of Technology, 2015; A high-strength and high-thermal conductivity die-casting mixed rare earth magnesium alloy and its preparation method CN 116607055A].

[0004] However, the Mg-RE-Al-Mn series of thermally conductive magnesium alloys have a narrow solidification range and a high liquidus temperature. The gate is prone to solidification in advance during casting, resulting in uneven distribution of defects such as holes. In addition, the porosity near the gate and the core of the casting is relatively high, which greatly affects the thermal conductivity and mechanical properties of the magnesium alloy [Characterization on the formation of porosity and tensile properties prediction in die casting Mg alloys. Journal of Magnesium and Alloys, 2022, 10(7): 1857-1867.]. Even if the casting conditions are optimized and the die casting temperature is increased to 700°C, the improvement in its performance is not obvious.

[0005] The trace addition (on the order of 0.1 wt%) of alkaline earth metals (such as Ca, Sr, Ba) and elements of the fifth and fourth groups (such as Sb, Sn, Pb, Bi) can refine the grains of magnesium alloys and improve their performance, especially increase the fluidity of magnesium alloys and improve casting quality [Magnesium alloying, some potentials for alloy development, Light Metals, 1992, 42, 679-686]. For example, adding 0.1wt% Bi and 0.7wt% Sb to AZ91 magnesium alloy can refine its microstructure and improve its mechanical properties [Yuan Guangyin, Effect of Bismuth and Antimony on Microstructure and Mechanical Properties of Magnesium-Aluminum Alloys, Southeast University 1999]; adding 0.11-013wt% Ca to AS41 magnesium alloy can refine the brittle Mg2Si phase during sand casting, and its as-cast tensile strength reaches the level of AZ91 [Modification of Mg2Si morphology in squeeze cast Mg-A l Zn-Si alloys by Caor P addition.Scripta Materialia, 1999, 41, 333334]; adding 0.2wt% Ca to Mg-Al-Zn can improve the quality of sand casting magnesium alloy, and improve the tensile strength and creep properties of the alloy; adding 0.1wt% Sb to Mg-4Al-1.5RE-0.2Mn, its Sm-Sb, Y-Sb and other rare earth antimony phases refine α-Mg and split the coarse β-Mg 17 Al 12Its tensile strength is increased from 197MPa to 236MPa, and its heat resistance, thermal conductivity and casting fluidity are also slightly improved [Effect of Sb alloying on heat resistance of AE41 magnesium alloy, Journal of Materials Research, 2006, (2): 186-190; A creep-resistant die-cast rare earth magnesium alloy with high strength and high fluidity and its preparation method and application, CN117867349A; A high-strength and ultra-high thermal conductivity die-cast rare earth magnesium alloy and its preparation method CN116254446A].

[0006] The present invention proposes a method for improving the casting quality and performance of rare earth thermal conductive magnesium alloy Mg-RE-Al-Mn (RE = La, Ce, La / Ce) by adding Sb (<1wt%). By adding Sb (<1wt%), RE-Sb dispersed phase is precipitated in the alloy to refine the structure (promote α-Mg nucleation and refine magnesium grains, and split and refine coarse Al 11 RE3) Improve the thermal conductivity and mechanical properties of the alloy, increase the fluidity of the alloy and improve the casting quality. Summary of the invention

[0007] The purpose of the present invention is to provide a rare earth thermal conductive magnesium alloy and a preparation method thereof. By adding 0.1-1wt% Sb, RE-Sb dispersed phase can be precipitated in the alloy to refine α-Mg, and at the same time, coarse Al-RE phase can be split and refined, thereby comprehensively improving the thermal conductivity and mechanical properties of the magnesium alloy, and increasing the fluidity of the alloy melt to improve the casting quality.

[0008] In a first aspect, the present invention provides a rare earth thermal conductive magnesium alloy, which includes 0.1 to 1% Sb by mass, and the magnesium alloy has α-Mg, Al-RE, and RE-Sb phases, and the RE includes at least one of La and Ce; the magnesium alloy is Mg-RE-Al-Mn-Sb magnesium alloy.

[0009] The rare earth thermal conductive magnesium alloy provided by the present invention can improve the thermal conductivity by 3-10 W / (m·K) and the tensile strength by 5-10 MPa by adding Sb element to form RE-Sb dispersed phase in the magnesium alloy, and at the same time improve the elongation of the magnesium alloy, reduce the porosity of the casting after casting, and improve the quality of the casting.

[0010] Optionally, the alloy further comprises, by mass fraction: 3.85-5.15% RE, 1.96-3.05% Al, 0.45-0.55% Mn and the balance Mg.

[0011] Optionally, the magnesium alloy is one of Mg-4RE-3Al-0.5Mn-xSb magnesium alloy, Mg-4La-3Al-0.5Mn-xSb magnesium alloy, Mg-4La / Ce-3Al-0.5Mn-xSb magnesium alloy, Mg-4La / Ce-2Al-0.5Mn-xSb magnesium alloy, and Mg-5La / Ce-3Al-0.5Mn-xSb magnesium alloy, and x is any positive value between 0.1 and 1.

[0012] Optionally, the mass fraction of Sb in the magnesium alloy is 0.1-0.8%, preferably 0.5%.

[0013] In a second aspect, the present invention also provides a method for preparing a rare earth thermal conductive magnesium alloy, comprising weighing pure Mg, pure Al, Mg-Mn master alloy, Mg-RE master alloy and pure Sb in mass percentage for blending; heating and melting pure Mg under a protective atmosphere, sequentially adding pure Al, Mg-Mn master alloy and Mg-RE master alloy and heating and stirring to melt, and then adding pure Sb to melt to obtain an alloy melt; and using a die casting machine to perform injection molding on the alloy melt to obtain a rare earth thermal conductive magnesium alloy casting.

[0014] Optionally, pure Mg is heated to 700-740° C. in a protective atmosphere for melting, wherein the protective atmosphere is a mixture of 1 vol. % SF6 and the balance CO2.

[0015] Optionally, pure Al, Mg-Mn master alloy, and Mg-RE master alloy are added in sequence and heated to 740-780° C. and stirred to melt, and when the melt temperature reaches 750° C., pure Sb is added until it is completely melted.

[0016] Optionally, after the alloy melt is kept at 720°C for 30 minutes, the mold is preheated at 200°C, and the alloy melt is cast by a die-casting machine at a casting temperature of 700°C at a casting pressure of 40MPa and an injection speed of 0.25-5m / s. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Phase analysis diagrams of magnesium alloys in Examples 7 to 8 and Comparative Examples 1 to 5 of the present invention;

[0018] Figure 2 The scanning electron microscope images of the microstructures of the magnesium alloys obtained in Example 8 of the present invention and Comparative Example 3;

[0019] Figure 3 X-ray flaw detector images of magnesium alloy die-casting sheets near the gate in Examples 7 to 9 of the present invention and Comparative Example 3;

[0020] Figure 41 and 2, respectively. The tensile curves of the magnesium alloys in Example 2 and Comparative Example 1, Example 5 and Comparative Example 2, Example 8 and Comparative Example 3, Example 11 and Comparative Example 4, and Example 14 and Comparative Example 5 of the present invention are shown. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with general skills in the field to which the present invention belongs.

[0022] Note: For example, the alloy composition Mg-xRE-yAl-zMn means that RE accounts for x% of the total mass of the alloy, Al accounts for y% of the total mass of the alloy, Mn accounts for z% of the total mass of the alloy, and the remainder is Mg.

[0023] The present invention provides a rare earth thermal conductive magnesium alloy, which includes 0.1-1% Sb by mass fraction, and has α-Mg, Al-RE, and RE-Sb phases in the magnesium alloy, wherein RE includes at least one of La and Ce. In the magnesium alloy, Sb can form a RE-Sb dispersed phase with the RE element, thereby promoting the nucleation and refinement of α-Mg in the magnesium alloy, and at the same time splitting and refining the coarse Al-RE phase, thereby achieving the purpose of improving the thermal conductivity and mechanical properties of the alloy, and can also effectively improve the fluidity of the alloy melt and thus improve the casting quality.

[0024] In some embodiments, the rare earth thermal conductive magnesium alloy provided by the present invention further comprises 3.85-5.15% RE, 1.96-3.05% Al, 0.45-0.55% Mn and the balance Mg by mass fraction. Specifically, the magnesium alloy can be one of Mg-4RE-3Al-0.5Mn-xSb magnesium alloy, Mg-4La-3Al-0.5Mn-xSb magnesium alloy, Mg-4La / Ce-3Al-0.5Mn-xSb magnesium alloy, Mg-4La / Ce-2Al-0.5Mn-xSb magnesium alloy, and Mg-5La / Ce-3Al-0.5Mn-xSb magnesium alloy, and x is any positive value between 0.1 and 1.

[0025] In some embodiments, the mass fraction of Sb in the magnesium alloy is 0.1-0.8%, preferably 0.5%.

[0026] The present invention also provides a method for preparing a heat-conducting magnesium alloy, comprising: weighing pure Mg, pure Al, Mg-Mn master alloy, Mg-RE master alloy and pure Sb in mass percentage for mixing; heating and melting pure Mg under a protective atmosphere, sequentially adding pure Al, Mg-Mn master alloy and Mg-RE master alloy, heating and stirring to melt, and then adding pure Sb to melt to obtain an alloy melt; after calibrating the composition with an electric spark direct reading spectrometer, using a die casting machine to perform die-casting on the alloy melt to obtain a rare earth heat-conducting magnesium alloy casting.

[0027] In fact, the Mg-Mn master alloy used in batching can be a Mg-10Mn master alloy, and the Mg-RE master alloy used can be a Mg-30RE master alloy. Specifically, batching can be performed based on a preset magnesium alloy composition ratio. In fact, the preset magnesium alloy composition can be any Mg-RE-Al-Mn series thermal conductive magnesium alloy in the prior art.

[0028] In some embodiments, pure Mg is heated to 700-740° C. in a protective atmosphere for melting. In fact, pure Mg can be placed in a crucible for heating and melting, and the crucible can be preheated to 200-300° C. in advance. Specifically, the protective atmosphere used is a mixture of SF6 and CO2, wherein the volume fraction of SF6 is 1%.

[0029] In some embodiments, pure Al, Mg-Mn master alloy, and Mg-RE master alloy are sequentially added to a molten Mg melt, stirred and melted, and gradually heated to 740-780°C. When the melt temperature rises to 750°C, pure Sb is added until it is completely melted. This is conducive to uniform dispersion of the elements in the alloy melt. Specifically, after the alloy melt is obtained, a direct reading spectrometer can be used to calibrate and adjust the content of each element in the alloy melt.

[0030] In some embodiments, after the alloy melt is kept at 720°C for 30 minutes, the mold is preheated at 200°C, and the alloy melt is cast by a die-casting machine at a casting temperature of 700°C at a casting pressure of 40MPa and an injection speed of 0.25-5m / s.

[0031] Example 1

[0032] This embodiment 1 provides a method for preparing a rare earth thermal conductive magnesium alloy, comprising the following steps:

[0033] S1. According to the alloy composition Mg-4Ce-3Al-0.5Mn-0.1Sb, pure Mg, pure Al, Mg-10Mn master alloy, Mg-30Ce master alloy and pure Sb are weighed and preheated in an environment of 150°C;

[0034] S2. In a protective atmosphere of 1 vol.% SF6 and 99 vol.% CO2, pure Mg is heated to 720°C in a crucible until it is completely melted, pure Al, Mg-10Mn master alloy, and Mg-30Ce master alloy are added in sequence, and the temperature is raised to 760°C to completely melt under mechanical stirring, and pure Sb is added when the melt temperature reaches 750°C until it is completely melted to obtain an alloy melt;

[0035] S3. The alloy melt is kept at 720° C. for 30 minutes, and the mold is preheated at 200° C., and then the alloy melt is die-casted by a die-casting machine at an injection speed of 3 m / s, a casting pressure of 40 MPa, and a pouring temperature of 700° C. to obtain a magnesium alloy casting.

[0036] Example 2 to Example 15

[0037] Embodiments 2 to 15 provide a method for preparing a rare earth thermal conductive magnesium alloy, which is different from Embodiment 1 in that the alloy composition in the raw material preparation in step S1 is different, as shown in Table 1. In Embodiments 7 to 15, the mixing ratio of La to Ce is 1:1.

[0038] Comparative Examples 1 to 5

[0039] Comparative Examples 1 to 5 provide a method for preparing a rare earth thermal conductive magnesium alloy, which is different from Example 1 in that the alloy composition in the raw material preparation in step S1 is different, as shown in Table 1. In Comparative Examples 3 to 5, the mixing ratio of La to Ce is 1:1.

[0040] Table 1 Alloy composition

[0041]

[0042]

[0043] Performance Testing

[0044] Based on the method described in GB6397-86 "Metal Tensile Test Specimens", the magnesium alloy castings obtained in Examples 1 to 15 and Comparative Examples 1 to 5 were processed respectively, and the tensile strength and elongation of the magnesium alloys were tested using a universal tensile machine of model Labsans 30KN. The test results are shown in Table 2 below.

[0045] Based on GB / T 13748-2005 “Chemical Analysis Methods for Magnesium and Magnesium Alloys”, the magnesium alloys in Examples 7 to 9 and Comparative Example 3 were sampled, and the components were tested using ICP (Inductive Coupled Plasma Emission Spectrometer). The results are shown in Table 3.

[0046] Based on the thermal conductivity determination method described in GB / T 22588-2008 “Flash Method for Measurement of Thermal Diffusivity or Thermal Conductivity”, a laser thermal conductivity meter of model LFA457 was used to measure the room temperature thermal conductivity of the magnesium alloy castings prepared in Examples 1 to 15 and Comparative Examples 1 to 5, respectively. The results are shown in Table 4 below.

[0047] Phase analysis of the magnesium alloys in Examples 7 to 8 and Comparative Examples 1 to 5 of the present invention is performed as follows: Figure 1 As shown, the microstructures of the magnesium alloys obtained in Example 8 and Comparative Example 3 were observed using a scanning electron microscope. Figure 2 As shown, the magnesium alloy castings prepared in Examples 7 to 9 and Comparative Example 3 were tested near the gate using an industrial CT tester XG-1604T / C. Figure 3 As shown, Example 2 and Comparative Example 1, Example 5 and Comparative Example 2, Example 8 and Comparative Example 3, Example 11 and Comparative Example 4, and Example 14 and Comparative Example 5 were subjected to tensile tests, and the tensile curves thereof are shown in FIG. Figure 4 shown.

[0048] Table 2 Tensile strength and elongation test results

[0049]

[0050] Table 3 Measured composition of magnesium alloy

[0051]

[0052]

[0053] Table 4 Room temperature thermal conductivity of magnesium alloys

[0054]

[0055] In combination with Examples 1 to 3 and Comparative Example 1, and from Tables 2 and 4, it can be seen that the addition of Sb element to the Mg-4Ce-3Al-0.5Mn magnesium alloy can synergistically improve the mechanical properties and thermal conductivity. In particular, compared with Comparative Example 1, the addition of 0.5wt.% Sb in Example 2 increases the tensile strength from 217.59MPa to 228.45MPa, the elongation from 9.8% to 10.01%, and the room temperature thermal conductivity from 103.56W / (m·K) to 105.21W / (m·K).

[0056] In combination with Examples 4 to 6 and Comparative Example 2, and from Tables 2 and 4, it can be seen that the addition of Sb element to the Mg-4La-3Al-0.5Mn magnesium alloy can also synergistically improve the mechanical properties and thermal conductivity. Compared with Comparative Example 2, the tensile strength of Example 5 is increased from 238.37 MPa to 251.28 MPa, the elongation is increased from 10.34% to 11.59%, and the room temperature thermal conductivity is increased from 98.27 W / (m·K) to 101.29 W / (m·K).

[0057] Combining Examples 7 to 9, Comparative Example 3, and Tables 2 and 4, it can be seen that adding Sb elements to the Mg-4La / Ce-3Al-0.5Mn magnesium alloy can synergistically improve the mechanical properties and thermal conductivity. Compared with Comparative Example 3, the tensile strength of Example 8 is increased from 249.04MPa to 259.49MPa, the elongation is increased from 12.66% to 13.64%, and the room temperature thermal conductivity is increased from 105.68W / (m·K) to 120.05W / (m·K). At the same time, Figure 1 It can be seen from the above that the magnesium alloys in Examples 7 and 8 have increased La / Ce-Sb phases, and Figure 2 and Figure 3 It can be seen that the addition of 0.5wt.% Sb can 11 RE3 is significantly refined, while Figure 4 It can be seen that the porosity can be reduced after adding Sb.

[0058] In combination with Examples 10 to 12 and Comparative Example 4, and from Tables 2 and 4, it can be seen that the addition of Sb element to the Mg-4La / Ce-2Al-0.5Mn magnesium alloy can synergistically improve the mechanical properties and thermal conductivity. Compared with Comparative Example 4, the tensile strength of Example 11 is increased from 247.69 MPa to 257.64 MPa, the elongation is increased from 11.59% to 12.95%, and the room temperature thermal conductivity is increased from 107.93 W / (m·K) to 122.04 W / (m·K).

[0059] In combination with Examples 13 to 15 and Comparative Example 5, and from Tables 2 and 4, it can be seen that the addition of Sb element to the Mg-5La / Ce-3Al-0.5Mn magnesium alloy can synergistically improve the mechanical properties and thermal conductivity. Compared with Comparative Example 5, the tensile strength of Example 14 is increased from 268.52 MPa to 277.82 MPa, the elongation is increased from 12.70% to 13.00%, and the room temperature thermal conductivity is increased from 92.36 W / (m·K) to 95.31 W / (m·K).

[0060] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A rare earth thermally conductive magnesium alloy, characterized in that: The magnesium alloy comprises 0.1-1% Sb by mass, and has α-Mg, Al-RE, and RE-Sb phases, wherein the RE comprises at least one of La and Ce; the magnesium alloy is a Mg-RE-Al-Mn-Sb magnesium alloy.

2. The rare earth thermally conductive magnesium alloy according to claim 1, characterized in that: In terms of mass fraction, it also includes: 3.85-5.15% RE, 1.96-3.05% Al, 0.45-0.55% Mn and the balance Mg.

3. The rare earth thermally conductive magnesium alloy according to claim 1, characterized in that: The magnesium alloy is one of Mg-4RE-3Al-0.5Mn-xSb magnesium alloy, Mg-4La-3Al-0.5Mn-xSb magnesium alloy, Mg-4La / Ce-3Al-0.5Mn-xSb magnesium alloy, Mg-4La / Ce-2Al-0.5Mn-xSb magnesium alloy, and Mg-5La / Ce-3Al-0.5Mn-xSb magnesium alloy, and x is any positive value between 0.1 and 1.

4. The rare earth thermally conductive magnesium alloy according to any one of claims 1 to 3, characterized in that: The mass fraction of Sb in the magnesium alloy is 0.1-0.8%, preferably 0.5%.

5. A method for preparing the rare earth thermally conductive magnesium alloy according to any one of claims 1 to 4, characterized in that: include: Pure Mg, pure Al, Mg-Mn master alloy, Mg-RE master alloy and pure Sb are weighed and mixed according to mass percentage; pure Mg is heated and melted under a protective atmosphere, pure Al, Mg-Mn master alloy and Mg-RE master alloy are added in sequence, heated and stirred to melt, and pure Sb is added to melt to obtain an alloy melt; the alloy melt is die-casted by a die-casting machine to obtain a rare earth thermal conductive magnesium alloy casting.

6. The preparation method according to claim 5, characterized in that: Pure Mg is heated to 700-740° C. in a protective atmosphere for melting, wherein the protective atmosphere is a mixture of 1 vol.% SF6 and the balance CO2.

7. The preparation method according to claim 5, characterized in that: Pure Al, Mg-Mn master alloy and Mg-RE master alloy are added in sequence and heated to 740-780° C. and stirred to melt. When the melt temperature reaches 750° C., pure Sb is added until it is completely melted.

8. The preparation method according to claim 5, characterized in that: After the alloy melt is kept at 720°C for 30 minutes, the mold is preheated at 200°C, and the alloy melt is cast by a die-casting machine at a casting temperature of 700°C at a casting pressure of 40MPa and an injection speed of 0.25-5m / s.

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