ANTI-FATIGUE IN-SITU ALUMINUM-BASED COMPOSITE MATERIAL FOR HEAVY-LOAD HUBS AND PREPARATION METHOD THEREFOR

Abstract

Provided are an anti-fatigue in-situ aluminium-based nanocomposite material for heavy-load automobile hubs and a preparation method therefor. By means of the fine adjustment of components and a forming process, in situ nano-compositing, micro-alloying and rapid compression moulding techniques are combined. That is, after the addition of elements Zr and B, an in-situ reaction occurs to form a nano ZrB2 ceramic reinforcement which is distributed in aluminium crystals and crystal boundaries and bonded to a metallurgical interface kept firm with the matrix. Moreover, with rare earth elements Er and Y and element Zr as addition ingredients and after the increase in the contents of Cr and Mn, a structure having fine aluminium crystal grains with a large number of micro-alloyed nano precipitated particles contained in the grains, fine and round eutectic silicon grains and a fine Mg2Si phase mainly dispersed inside the grains is obtained in the process of the rapid compression moulding and thermal treatment of the hubs; and thus, the tensile strength, the yield strength and the fatigue strength of an alloy are effectively improved.

Claims

1. An anti-fatigue in-situ aluminum based composite material for heavy-load hubs, comprising, by mass percent, the following chemical components: 6.8-7.5 of Si, 3.0-5.0 of Zr, 0.5-1.0 of B, 0.3-0.45 of Mg, 0.18-0.25 of Er, 0.18-0.25 of Y, 0.15-0.22 of Cr, 0.1-0.12 of Mn, 0.1-0.15 of Ti, 0.08-0.12 of Fe, 0.05-0.1 of Cu, and the balance of Al, characterized in that: said composite material is prepared according to the following steps: microalloying A356.2 aluminum alloy melt, carrying out in-situ nano compounding for the microalloyed A356.2 aluminum alloy melt, carrying out pressurized gravity casting rapid sequential solidification molding for the A356.2 aluminum alloy melt that has been subjected to in-situ nano compounding, and finally, carrying out thermal treatment for the hub formed with casting, combining microalloying, in-situ nano compounding and pressurized gravity casting rapid sequential solidification molding to improve the strength and toughness and anti-fatigue performance of the aluminum based composite material hubs. synergetically.

2. The anti-fatigue in-situ aluminum based composite material for heavy-load hubs according to claim 1, characterized in that microalloying the A356.2 aluminum alloy melt comprises the following steps: refining the-molten and heat-preserved A356.2 alloy melt for degassing, uniformly scattering a layer of covering agent on the surface of the melt, pressing intermediate alloy of microalloying elements into the refined and degassed A356.2 aluminum alloy melt via immersion bell, and stirring uniformly with a graphite rotor and standing for later use.

3. The anti-fatigue in-situ aluminum based composite material for heavy-load hubs according to the claim 2, characterized in that the melting and heat-preservation temperature is 750-760 C., and the intermediate alloy of the microalloying element is AlZr, AlEr, AlY, AlCr and AlMn.

4. The anti-fatigue in-situ aluminum based composite material for heavy-load hubs according to the claim 2, characterized in that the intermediate alloy of the microalloying element is Al-15Zr, Al-20Er, Al-20Y, Al-20Cr and Al-10Mn.

5. The anti-fatigue in-situ aluminum based composite material for heavy-load hubs according to the claim 1, characterized in that carrying out in-situ nano compounding for the microalloyed A356.2 aluminum alloy melt comprises the following steps: pressing B containing alloy or boron salt via the graphite immersion bell into the microalloyed A356.2 aluminum alloy melt, starting the graphite stirring rotor to promote the melting of B containing alloy or promote boron salt to fully contact with the A356.2 aluminum alloy melt and effectively absorb B element, making the introduced B element in-situ react with Zr element introduced during melt microalloying to synthesize the ZrB.sub.2 nano-ceramic reinforcement, and acquiring the composite melt and standing for later use.

6. The anti-fatigue in-situ aluminum based composite material for heavy-load hubs according to the claim 2, characterized in that the microalloying is to adjust the ingredients of A356.2 alloy, i.e., taking rare earth elements Er, Y and Zr as additive ingredients, and improving the content of Cr and Mn, after which the mass percent of elements in A356.2 alloy is as follows: Zr3.0-5.0, Er 0.18-0.25, Y 0.18-0.25, Cr 0.15-0.22 and Mn 0.1-0.12.

7. The anti-fatigue in-situ aluminum based composite material for heavy-load hubs according to the claim 5, characterized in that the in-situ nano compounding is to introduce B element into the microalloyed melt, making it in situ react with Zr introduced into alloy to produce scattered nano-ZrB.sub.2 ceramic reinforcement, wherein the size of ZrB.sub.2 is 15-75 nm, and the content is 2.57-5.14 wt. %.

Description

DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 is the XRD analysis map of the hub made of in-situ nano-particle reinforced A356.2-X based composite material for light-weight high-strength anti-fatigue heavy-load hubs. The diffraction peaks of ZrB.sub.2 and Si can be seen in the map in addition to the diffraction peak of Al.

[0022] FIG. 2 is the tissue graph of the hub made of in-situ nano-particle reinforced A356.2-X based composite material for light-weight high-strength anti-fatigue heavy-load hubs: (a) the OM photo of the morphology distribution of silicon particles in the matrix; and (b) the TEM photo of the nano-ZrB2 reinforcement synthesized in-situ in the crystalline grains. It can be seen from the metallographic structure photo of the composite material in FIG. 2a that the Si phase in the composite material prepared in the present application is in fine spherical shape; and it can be seen from the transmission electron microscope photo of the composite material in FIG. 2b that dispersed nano-ZrB.sub.2 in-situ nano-ceramic reinforcement phases are dispersed inside the prepared composite crystalline grains.

[0023] FIG. 3 is the tissue graph of the A356.2 composite material hub, which is prepared in conjunction with nano compounding and fast pressurized forming technology. It can be seen that compared with the hub made of composite materials (FIG. 2a) which is prepared in conjunction with microalloying, in-situ nano compounding and fast pressurized forming in the example 2, the hub made of A356.2 composite materials which is prepared in conjunction with nano compounding and fast pressurized forming technology has coarser crystalline grains, and the Si phase is relatively coarse and has poor uniformity.

[0024] FIG. 4 is the real product picture of the hub made of in-situ nano-particle reinforced A356.2-X based composite materials for light-weight high-strength anti-fatigue heavy-load hubs.

EMBODIMENTS

[0025] The implementation scheme of the present invention is described further in conjunction with the accompanying drawings: the following examples give the detailed enforcement mode and the specific operation process on the premise of the technical solution of the invention, but the scope of protection of the invention is not limited to the examples below.

EXAMPLE 1

[0026] Taking Al-15Zr, Al-20Er, Al-20Y, Al-20Cr, Al-10Mn and Al-10B intermediate alloy and A356.2 alloy as raw materials, the A356.2-X composite material hub is prepared via pressurized gravity casting rapid sequential solidification molding technology.

[0027] Transferring the molten 500 Kg commercial A356.2 alloy (750-760 C.) is transferred into insulated degassing tundish, and putting the graphite rotor in reversing rotation, into which argon can be introduced, into the tundish for refining and degassing for 5min; scattering a layer of covering agent uniformly on the surface of the alloy melt of the tundish, after the covering agent is scattered uniformly on the surface layer of alloy and forms a protective film, pressing the weighed Al-15Zr, Al-20Er, Al-20Y, Al-20Cr and Al-10Mn intermediate alloy into the alloy melt by the graphite immersion bell through the covering agent, making the graphite rotor rotate reversely for 15 min to promote the fast melting and uniform scattering of the intermediate alloy, standing for 5-10 min for later use, adjusting to make the mass percent of elements in alloy as follows: Zr 3.5, Er 0.2, Y 0.2, Cr 0.18, Mn 0.11; pressing the weighed Al-10B intermediate alloy into the melt using immersion bell with stirring by the graphite rotor for 10 min, making B element (the content is 0.65 wt. % of A356.2-X composite material hub) in-situ react with the Zr element uniformly dispersed in the melt to synthesize the uniformly dispersed nano-ZrB.sub.2 ceramic reinforcement; removing the graphite stirring rotor, stopping heat preservation and heating, cooling the composite melt to 720-730 C., removing the surface covering agent to acquire the composite melt, and standing for 5-10 min for later use; and transferring the composite melt into the heat-preserving furnace of pressurized gravity casting rapid sequential solidification molding device for casting forming of the hub (pressurized solidification pressure is 150 MPa), and finally, carrying out thermal treatment for the casting blank of the hub to acquire the machined hub blank.

[0028] Sampling analysis indicates that after T6 (545 C.3.5 h+135 C.3 h) treatment, the elasticity modulus of the spoke is 77 GPa, strength is up to 325 MPa, the percentage elongation is 13.6%, cracks are avoided under 1.210.sup.5 flexural fatigue tests and 1.310.sup.6 radial fatigue tests, which exceeds U.S. SAE J1204 Standard Requirements for Motor Home Hubs (tensile strength 300 MPa, percentage elongation 10%, 510.sup.4 flexural fatigue tests, and 610.sup.5 radial fatigue tests).

EXAMPLE 2

[0029] Taking Al-15Zr, Al-20Er, Al-20Y, Al-20Cr and Al-10Mn intermediate alloy, KBF.sub.4 and A356.2 alloy as raw materials, the A356.2-X composite material hub is prepared via the pressurized gravity casting rapid sequential solidification molding technology.

[0030] Using Al-15Zr, Al-20Er, Al-20Y, Al-20Cr and Al-10Mn intermediate alloy for introduction of microalloying element, firstly, adjusting the mass percent of the elements in alloy as follows: Zr 4.5, Er 0.25, Y 0.18, Cr 0.22, Mn 0.12 (the specific steps are the same as those of the example 1); pressing the weighed KBF.sub.4 into the melt using immersion bell and stirring by the graphite rotor for 10 min, making B element (the content is 0.89 wt. % of A356.2-X composite material hub) in-situ react with the Zr element uniformly dispersed in the melt to synthesize the uniformly dispersed nano-ZrB.sub.2 ceramic reinforcement; removing the graphite stirring rotor, stopping heat preservation and heating, cooling the composite melt to 720-730 C., removing the surface covering agent to acquire the composite melt, and standing for 5-10 min for later use; and transferring the composite melt into the heat-preserving furnace of the pressurized gravity casting rapid sequential solidification molding device for the casting forming of the hub (pressurized solidification pressure is 250 MPa), and finally, carrying out thermal treatment for the casting blank of the hub to acquire the machined hub blank. FIGS. 1 and 2 are respectively the XRD map and tissue graph of the hub made of A356.2-X based composite material, and FIG. 4 is the real product picture of the hub made of in-situ nano-particle reinforced A356.2-X based composite material for light-weight high-strength anti-fatigue heavy-load hubs prepared according to the present invention.

[0031] Sampling analysis indicates that after T6 (545 C.3.5 h+135 C.3 h) treatment, the elasticity modulus of the spoke is 80 GPa, strength is up to 345 MPa, the percentage elongation is 13%, cracks are avoided under 1.510.sup.5 flexural fatigue tests and 1.510.sup.6radial fatigue tests, which exceeds U.S. SAE J1204 Standard Requirements for Motor Home Hubs (tensile strength 300 MPa, percentage elongation 10%, 510.sup.4 flexural fatigue tests, and 610.sup.5radial fatigue tests).

EXAMPLE 3

[0032] Taking Al-15Zr, Al-15Er, Al-10Y, Al-5Cr and Al-10Mn intermediate alloy, KBF.sub.4, and A356.2 alloy as raw materials, the A356.2-X composite material hub is prepared via the pressurized gravity casting rapid sequential solidification molding technology.

[0033] Using Al-15Zr, Al-15Er, Al-10Y, Al-5Cr and Al-10Mn intermediate alloy for introduction of microalloying element, firstly, adjusting the mass percent of the elements in alloy as follows: Zr 4.0, Er 0.2, Y 0.25, Cr 0.18, Mn 0.1 (the specific steps are the same as those of the example 1); pressing the weighed KBF.sub.4 into the melt using immersion bell and stirring by the graphite rotor for 10 min, making B element (the content is 0.77 wt. % of A356.2-X composite material hub) in-situ react with the Zr element uniformly dispersed in the melt to synthesize the uniformly dispersed nano-ZrB.sub.2 ceramic reinforcement; removing the graphite stirring rotor, stopping heat preservation and heating, cooling the composite melt to 720-730 C., removing the surface covering agent to acquire the composite melt, and standing for 5-10 min for later use; and transferring the composite melt into the heat-preserving furnace of the pressurized gravity casting rapid sequential solidification molding device for the casting forming of the hub (pressurized solidification pressure is 50 MPa), and finally, carrying out thermal treatment for the casting blank of the hub to acquire the machined hub blank.

[0034] Sampling analysis indicates that after T6 (545 C.3.5 h+135 C.3 h) treatment, the elasticity modulus of the spoke is 79 GPa, strength is up to 315 MPa, the percentage elongation is 14.7%, cracks are avoided under 110.sup.5 flexural fatigue tests and 1.210.sup.6 radial fatigue tests, which exceeds U.S. SAE J1204 Standard Requirements for Motor Home Hubs (tensile strength 300 MPa, percentage elongation 10%, 510.sup.4 flexural fatigue tests, and 610.sup.5 radial fatigue tests).

Comparison Embodiment

COMPARISON EXAMPLE 1

[0035] Taking Al-15Zr intermediate alloy, KBF.sub.4, and A356.2 alloy as raw materials, the A356.2 composite material hub is prepared via the pressurized gravity casting rapid sequential solidification molding technology (microalloying is not used).

[0036] Using Al-15Zr intermediate alloy for introduction of Zr element, and adjusting the mass percent of Zr element in alloy to 4 wt. % (the specific steps are the same as those of the example 1); pressing the weighed KBF.sub.4 into the melt using immersion bell and stirring by the graphite rotor for 10 min, making B element (the content is 1.09 wt. % of alloy, so the molar ratio of Zr to B in alloy is 1:2) in-situ react with the Zr element uniformly dispersed in the melt to synthesize the uniformly dispersed nano-ZrB.sub.2 ceramic reinforcement; removing the graphite stirring rotor, stopping heat preservation and heating, cooling the composite melt to 720-730 C., removing the surface covering agent to acquire the composite melt, and standing for 5-10 min for later use; and transferring the composite melt into the heat-preserving furnace of pressurized gravity casting rapid sequential solidification molding device for the casting forming of the hub (pressurized solidification pressure is 250 MPa), and finally, carrying out thermal treatment for the casting blank of the hub to acquire the machined hub blank. FIG. 3 is the tissue graph of the A356.2 composite material hub prepared only by combining nano compounding and the fast pressurized forming technology. It can be seen that compared with the composite material hub (FIG. 2a) prepared in conjunction with microalloying, in-situ nano compounding and fast pressurized forming in the example 2, the composite material hub in the comparison example has coarser crystalline grains, and the Si phase thereof is relatively large and has poor uniformity.

[0037] Sampling analysis indicates that after T6 (545 C.3.5 h+135 C.3 h) treatment, the elasticity modulus of the spoke is 80.3 GPa, strength is up to 305 MPa, the percentage elongation is 10.7%, cracks are avoided under 1.010.sup.5 flexural fatigue tests and 7.810.sup.5 radial fatigue tests. Although it exceeds U.S. SAE J1204 Standard Requirements for Motor Home Hubs (tensile strength 300 MPa, percentage elongation 10%, 510.sup.4 flexural fatigue tests, and 610.sup.5radial fatigue tests), compared with the composite material hub prepared in conjunction with microalloying, in-situ nano compounding and fast pressurizing forming in the example 2, its performance is still reduced substantially.

COMPARISON EXAMPLE 2

[0038] Taking Al-15Zr, Al-20Er, Al-10Y, Al-10Cr and Al-10Mn intermediate alloy and A356.2 alloy as raw materials, the A356.2-X alloy hub is prepared via pressurized gravity casting rapid sequential solidification molding technology (nano compounding is not used).

[0039] Using Al-15Zr, Al-20Er, Al-10Y, Al-10Cr and Al-10Mn intermediate alloy for introduction of microalloying element, firstly, adjusting the mass percent of the elements in alloy as follows: Zr 0.5, Er 0.25, Y 0.18, Cr 0.22, Mn 0.12 (the specific steps are the same as those of the example 1); removing the graphite stirring rotor, stopping heat preservation and heating, cooling the alloy melt to 720-730 C., removing the surface covering agent to acquire the composite melt, and standing for 5-10 min for later use; and transferring the composite melt into the heat-preserving furnace of the pressurized gravity casting rapid sequential solidification molding device for the casting forming of the hub (pressurized solidification pressure is 250 MPa), and finally, carrying out thermal treatment for the casting blank of the hub to acquire the machined hub blank.

[0040] Sampling analysis indicates that after T6 (545 C.3.5 h+135 C.3 h) treatment, the elasticity modulus of the spoke is 71 GPa, strength is up to 302 MPa, the percentage elongation is 12.1%, cracks are avoided under 610.sup.4 flexural fatigue tests and 7.410.sup.5 radial fatigue tests, which exceeds U.S. SAE J1204 Standard Requirements for Motor Home Hubs (tensile strength 300 MPa, percentage elongation 10%, 510.sup.4 flexural fatigue tests, and 610.sup.5 radial fatigue tests). Compared with the composite material hub prepared in conjunction with microalloying, in-situ nano compounding and fast pressurized forming in the example 2, its performance is still reduced substantially.

COMPARISON EXAMPLE 3

[0041] Taking Al-15Zr, Al-20Er, Al-10Y, Al-10Cr and Al-10Mn intermediate alloy, KBF.sub.4 and A356.2 alloy as raw materials, the A356.2-X composite material hub is prepared via the ordinary gravity casting forming technology (the fast pressurized forming technology is not used).

[0042] Using Al-15Zr, Al-20Er, Al-10Y, Al-10Cr and Al-10Mn intermediate alloy for introduction of microalloying element, firstly, adjusting the mass percent of the elements in alloy as follows: Zr 4.5, Er 0.25, Y 0.18, Cr 0.22, Mn 0.12 (the specific steps are the same as those of the example 1); pressing the weighed KBF.sub.4 into the melt using immersion bell and stirring by the graphite rotor for 10 min, making B element (the content is 0.89 wt. %) in-situ react with the Zr element uniformly dispersed in the melt to synthesize the uniformly dispersed nano-ZrB.sub.2 ceramic reinforcement; removing the graphite stirring rotor, stopping heat preservation and heating, cooling the composite melt to 720-730 C., removing the surface covering agent to acquire the composite melt, and standing for 5-10 min for later use; and transferring the composite melt into the heat-preserving furnace of the ordinary gravity casting forming equipment for the casting forming of the hub, and finally, carrying out thermal treatment for the casting blank of the hub to acquire the machined hub blank.

[0043] Sampling analysis indicates that after T6 (545 C.3.5 h+135 C.3 h) treatment, the elasticity modulus of the spoke is 78.3 GPa, strength is up to 315 MPa, the percentage elongation is 11.4%, cracks are avoided under 1.110.sup.5 flexural fatigue tests and 9.210.sup.5 radial fatigue tests. Although it exceeds U.S. SAE J1204 Standard Requirements for Motor Home Hubs (tensile strength 300 MPa, percentage elongation 10%, 510.sup.4 flexural fatigue tests, and 610.sup.5 radial fatigue tests), compared with the composite material hub prepared in conjunction with microalloying, in-situ nano compounding and fast pressurizing forming in the example 2, its performance is still reduced.