Bismuth trioxide coated ceramic phase reinforced aluminum-based composite material
The technical field is as follows:
the invention relates to a novel composite material, in particular to a method for coating bismuth oxide (Bi) on the surface of a ceramic phase reinforcement2O3) A reinforced aluminum matrix composite.
Background art:
in recent years, ceramic phase reinforced metals, especially reinforced aluminum matrix composites, are gaining widespread attention. The most attractive properties of this material are its excellent properties of high strength, high modulus and low coefficient of thermal expansion. Great attention has been paid to the potential superiority of ceramic phase reinforced aluminum matrix composites, and some composites have been used in the automotive, aerospace, astronomical and general engineering fields. Although commercial application is emerging, the low plasticity of the composite material is a fatal weakness, which becomes a difficulty that the composite material cannot be used for producing parts at room temperature by using a conventional forming method, and the application prospect of commercializing the composite material is severely limited. Moreover, most aluminum matrix composite parts can only be formed by thermoplastic processing due to the inherent low plasticity limit. The composite material must therefore be subjected to a thermoplastic deformation process at a temperature well above room temperature. The composite material is subjected to plastic deformation at the medium temperature, the matrix is not softened, the rotation of the reinforcement and the plastic deformation of the matrix cannot be coordinated, the reinforcement can be damaged, and the mechanical property of the composite material is seriously reduced; if the plastic deformation of the composite material is carried out at a high temperature close to the liquid-solid phase line of the matrix, the reinforcement is easy to rotate and damage is reduced because the matrix is softened and even liquid phase occurs, but because the deformation temperature is close to the liquid-solid phase line of the matrix, the reinforcement in the matrix is unevenly distributed, an enrichment area and a depletion area are formed, the mechanical property of the material is also reduced, and the secondary processing cost of the composite material is increased because the deformation temperature is too high.
The invention content is as follows:
the invention aims to develop a bismuth trioxide coated ceramic phase reinforced aluminum matrix composite, which not only can reduce the thermoplastic deformation temperature of the composite and reduce the hot processing cost of the composite, but also can reduce the damage of a reinforcement in the plastic deformation process of a matrix, and the composite still has good mechanical properties after thermal deformation. The composite material of the invention is prepared by bismuth trioxide (Bi)2O3) The ceramic phase reinforcement comprises three components, namely a ceramic phase reinforcement and an aluminum matrix, wherein the volume fraction of the ceramic phase reinforcement accounts for 5-50% of the total volume fraction, and the addition amount of the bismuth trioxide accounts for 2-20% of the mass of the ceramic phase reinforcement.
The maximum deformation resistance and resistance difference of the bismuth trioxide-coated reinforced aluminum-based composite material and the aluminum-based composite material without bismuth trioxide coating on the surface of the ceramic phase reinforcement at different temperatures are shown in figure 1. As can be seen from the figure: with the increase of the deformation temperature, the deformation resistance of the two materials is reduced, and the difference value of the deformation resistance isIncreasing and then decreasing with increasing temperature. The difference value of the deformation resistance of the two composite materials has a steep slope after 270 ℃, after the deformation temperature is higher than 270 ℃, the metal bismuth on the interface is completely melted, but the matrix is not softened, and the liquid phase on the interface plays a role in lubrication and coordination in the deformation process, so that the difference value of the deformation resistance of the two composite materials is suddenly increased; after the deformation temperature is higher than 320 ℃, the matrix gradually begins to soften, the binding capacity for the rotation of the ceramic phase reinforcement is weakened, although a trace amount of liquid phase on the interface also plays a certain lubricating role, the softening of the matrix plays a decisive role, the ceramic phase reinforcement is easy to rotate, and therefore the difference of the maximum deformation resistance of the ceramic phase reinforcement and the maximum deformation resistance of the ceramic phase reinforcement is reduced. The scanning photographs of the two composites after deformation at 350 ℃ are shown in FIGS. 2 and 3, respectively, and the scanning photographs of the two composites are compared, and at the same temperature, no Bi is contained2O3The damage condition of the composite material ceramic phase reinforcement is higher than that of the composite material containing Bi2O3The composite material is much more severe, andand the average grain size of the ceramic phase reinforcement is smaller, so that the fact that the metal Bi on the interface of the ceramic phase reinforcement and the matrix reduces the maximum compressive deformation stress, reduces the damage quantity of the ceramic phase reinforcement and improves the plastic forming capability of the material is powerfully proved.
The invention has the following advantages:
(1) coating bismuth trioxide on the surface of the ceramic phase reinforcement can prevent the reinforcement from carrying out interface reaction with elements in the matrix;
(2) the bismuth trioxide and aluminum are subjected to aluminothermic reaction to generate metal bismuth with a low melting point, and the specific aluminothermic reaction equation is as follows:
the metal bismuth with low melting point is distributed on the interface of the reinforcement and the matrix, which is beneficial to the thermoplastic deformation of the ceramic phase reinforced aluminum matrix composite;
(3) the plastic deformation is carried out at the temperature 270 ℃ higher than the melting point of the metal bismuth, the bismuth on the interface is changed into liquid, the lubrication effect is realized on the interface, compared with the aluminum-based composite material of which the surface of the reinforcement is not coated with the bismuth trioxide, the thermoplastic deformation capability of the composite material is improved, the damage of the ceramic phase reinforcement is obviously reduced, and the mechanical property of the aluminum-based composite material after the thermoplastic deformation is not reduced.
Description of the drawings:
FIG. 1 is a graph showing the maximum deformation resistance and resistance difference of the ceramic phase reinforcement surface coated with bismuth trioxide reinforced aluminum matrix composite and the aluminum matrix composite not coated with bismuth trioxide under different temperature compression deformation, wherein the left coordinate is the relationship between the maximum rheological stress of the two composites and the temperature, and the right coordinate is the relationship between the difference between the maximum rheological stress of the two composites and the temperature; FIG. 2 shows the surface of the reinforcement coated with bismuth trioxide (Bi)2O3) Enhancing the surface topography of the aluminum-based composite material after thermal deformation; FIG. 3 shows the non-coated bismuth trioxide (Bi)2O3) Is subjected to thermal deformationAnd (5) surface topography map.
The specific implementation mode is as follows:
the first embodiment is as follows: the composite material of the present embodiment is composed of bismuth (Bi) oxide2O3) The ceramic phase reinforcement comprises three components, namely a ceramic phase reinforcement and an aluminum matrix, wherein the volume fraction of the ceramic phase reinforcement accounts for 5-50% of the total volume fraction, the addition amount of bismuth trioxide accounts for 2-20% of the mass of the ceramic phase reinforcement, and the surface of the ceramic phase reinforcement is coated with the bismuth trioxide firstly; the surface is then coated with a bismuth trioxide ceramic phase and aluminum or an aluminum alloy to prepare a composite. The surface-coated bismuth trioxide ceramic phase reinforced aluminum-based composite material is subjected to thermoplastic deformation at a temperature of 270 ℃ higher than the melting point of metal bismuth, so that the thermal deformation temperature and the processing cost of the composite material can be reduced, the damage of a ceramic phase reinforcement is obviously reduced, and the mechanical property of the aluminum-based composite material subjected to thermoplastic deformation is not reduced. The ceramic phase reinforcement is one or a mixture of a plurality of short fibers, particles and whiskers, wherein the short fibers are Al2O3、SiC、B2O3One or more of TiN and Al as particles2O3、SiC、Al18B4O33、Si3N4、AlN、B4C. One or more of TiC, and crystal whisker of SiC, AlN, 9Al2O3·2B2O3(Al18B4O33)、Si3N4、2MgO·B2O3(Mg2B3O5) One or a mixture of more of the above; the aluminum matrix is pure aluminum or aluminum alloy.
The second embodiment is as follows: the difference between the present embodiment and the first embodiment is that the volume fraction of the ceramic phase reinforcement is 8% of the total volume fraction, and the addition amount of the bismuth trioxide is 5% of the mass of the ceramic phase reinforcement.
The third concrete implementation mode: the difference between the first embodiment andthe second embodiment is that the volume fraction of the ceramic phase reinforcement is 15% of the total volume fraction, and the addition amount of the bismuth trioxide is 10% of the mass of the ceramic phase reinforcement.
The fourth concrete implementation mode: the difference between this embodiment and the first, second and third embodiments is that the volume fraction of the ceramic phase reinforcement is 20% of the total volume fraction, and the addition amount of the bismuth trioxide is 8% of the mass of the ceramic phase reinforcement.
The fifth concrete implementation mode: the difference between this embodiment and the first, second, third and fourth embodiments is that the volume fraction of the ceramic phase reinforcement is 25% of the total volume fraction, and the addition amount of the bismuth trioxide is 14% of the mass of the ceramic phase reinforcement.
The sixth specific implementation mode: the difference between this embodiment and the first, second, third, fourth and fifth embodiments is that the volume fraction of the ceramic phase reinforcement is 40% of the total volume fraction, and the addition amount of the bismuth trioxide is 18% of the mass of the ceramic phase reinforcement.
The seventh embodiment: the difference between this embodiment and the first, second, third, fourth, fifth and sixth embodiments is that the volume fraction of the ceramic phase reinforcement is 32% of the total volume fraction, and the addition amount of bismuth trioxide is 16% of the mass of the ceramic phase reinforcement.
The specific implementation mode is eight: the difference between this embodiment and the first, second, third, fourth, fifth, sixth and seventh embodiments is that the volume fraction of the ceramic phase reinforcement is 12% of the total volume fraction, and the addition amount of the bismuth trioxide is 10% of the massof the ceramic phase reinforcement.