| Ceramic particle reinforced aluminum-based composites have excellent properties such as high specific modulus,high specific strength,and good abrasion resistance,and have been widely used in production and life.Compared with single-phase reinforced aluminum-based composites,dual-phase reinforced aluminum-based composites exhibit superior mechanical properties.Studies have shown that the size of the reinforcing phase and its distribution in the aluminum matrix are the main reasons affecting the performance of ceramic particles reinforced aluminum matrix composites.When the size of the reinforcing phase is microscale,the strength and elastic modulus of the composite will increase,but its shape and toughness will decrease.The nano-level reinforcing phase can significantly increase the strength of the composite material without reducing its plastic toughness,but those nano-level reinforcing phases easily aggregate in the aluminum matrix to reduce the performance of the composite.Micro-nano hybrid dual-phase reinforced aluminum-based composites have been widely concerned in recent years due to their excellent room temperature,high temperature mechanical properties and wear resistance.Among the ceramic particles of many reinforcing phases,the thermal expansion coefficients of TiC,TiB2 and aluminum are relatively low while the lattice matching degree are high,so they are also currently used as the ceramic particles reinforcing phase.Therefore,fabricating the micro-nano dual phase(TiB2-TiC)/Al-Cu-Mg composites by in-situ reaction will be favorable for the manipulation of the reinforcement particles size by the content of ceramic phases,and then the distribution of the particles in the aluminum matrix is affected.In addition,those in-situ as-synthesized composites have excellent room temperature,high temperature mechanical properties and excellent wear resistance,which have practical guiding significance for the application of aluminum-based composite materials in industrial and aerospace fields.In this paper,micro-nano dual phase reinforced aluminum-based composites were prepared for the Al-Ti-B4C system based on the principle of bionics by dense integration of combustion synthesis.The reaction mechanism of the Al-Ti-B4C system was studied,and the effects of different ceramic contents and different TiB2/TiC molar ratios on the microstructure,room temperature and high temperature compression properties and wear properties of the composites were analyzed.The mechanisms of improving the mechanical properties and wear resistance of composites were revealed.This paper has the following three innovations:1)It is revealed that the reaction process of the Al-Ti-B4C system is:Al+Ti+B4C?Al3Ti+Ti+B4C?AlnTi+TiCx+TiB2+TiaAlbCc?Al+TiCx+TiB22)It reveals the influence rules and mechanism of microstructure,ceramic particle size,and room temperature and high temperature compressive properties of micro-nano dual phase(TiB2-TiC)/Al-Cu-Mg composites with different ceramic volume fractions and different TiB2/TiC molar ratios:a)The micro-nano dual phase(TiB2-TiC)/Al-Cu-Mg composite with different ceramic contents prepared by combustion synthesis had a dense structure without obvious pores and defects.With the increase of the ceramic content in the composite,the size of the synthesized ceramic particles increases.When the volume fraction of ceramics is increased from 10 vol.%to 60 vol.%,the ceramic particle size is increased from 160nm to 1.8 ?m.b)At room temperature,with the increase of the volume fraction of ceramic TiB 2 and TiC,the ultimate compressive strength,yield strength and fracture strain of micro-nano dual phase(TiB2-TiC)/Al-Cu-Mg composites increase first and then decrease trend.When the micro-nano dual phase(TiB2-TiC)/Al-Cu-Mg composite ceramic particles have a volume fraction of 40 vol.%,The composite had the best compression performance,the ?UCS,?0.2 and ?f was 1091MPa,776MPa and 13.5%,respectively.The 40 vol.%micro-nano dual phase(TiB2-TiC)/Al-Cu-Mg composite has the best compression performance at temperatures of 473K and 523K.At 473K,the ?UCS,?0.2 and ?f were 805MPa,547MPa and 9.86%,respectively.At 523K,the?UCS,?0.2 and ?f were 471MPa,337MPa and 6.26%,respectively.c)It was revealed that the yield strength and ultimate compressive strength of 40 vol.%micro-nano dual phase(TiB2-TiC)/Al-Cu-Mg composites were reduced as the molar ratio of TiB2/TiC decreased from 3:1 to 1:3 at room temperature gradually decrease,the fracture strain increases first and then decreases.The ultimate compressive strength,yield strength and fracture strain of 40 vol.%micro-nano dual phase(TiB2-TiC)/Al-Cu-Mg composites when TiB2/TiC molar ratio is 3:1 was 938MPa?1301MPa and 3.63%,respectively.At high temperature,the yield strength and ultimate compressive strength of the composites are greatest when the molar ratio of TiB2/TiC is 3:1.At 473K,when the TiB2/TiC molar ratio is 3:1,the ?UTS,?0.2 and ?f were 886MPa,782MPa and 4.12%,respectively.At 523K,the ?UTS,?0.2 and ?f were 556MPa,450MPa and 2.98%,respectively.At 573K,the ?UTS,?0.2 and ?f were 436MPa,352MPa and 2.91%,respectively.d)Reveals the strengthening mechanism of micro-nano TiB2 and TiC ceramic particles reinforced aluminum matrix composites:?The existence of TiB2 and TiC ceramic particles play a role in pinning the grain boundaries and hindering the dislocations and grain boundary movements,so that dislocations are entangled to form dislocation networks.?The good interfacial bonding between the ceramic particles and the aluminum matrix can effectively transfer loads.?The larger the thermal expansion coefficient difference between the ceramic particles and the aluminum matrix,the thermal mismatch strain will occur during the natural aging process to form high density dislocations to strengthen the composite material.3)Reveals abrasive wear behavior of micro-nano dual phase(TiB2-TiC)/Al-Cu-Mgcomposites with different ceramic contents at normal temperature and the influence of dry friction and wear behavior of different TiB2/TiC molar ratio to(TiB2-TiC)/Al-Cu-Mg composites:a)It was revealed that the micro-nano-duplex(TiB2-TiC)/Al-Cu-Mg composites with different ceramic contents have wear rules of 5N,ION,and 15N and abrasive grain sizes of 13 ?m,23 ?m,and 40 ?m,respectively.As the volume fraction of ceramic particles in the composite increases,the wear resistance of the composite gradually increases.The relative abrasion resistance of 60 vol.%micro-nano-duplex(TiB2-TiC)/Al-Cu-Mg composites with a particle size of 40 ?m and an applied load of 10 N is 10 vol.%(TiB2-TiC)/Al-Cu-Mg composites increased by 1.58 times.The mechanism by which ceramic particles enhance the wear resistance of aluminum-based composites is that the presence of ceramic particles increases the hardness of the composite material and enhances the load-bearing capacity of the composite material.In addition,the presence of TiB2 and TiC ceramic particles causes passivation of Al2O3 abrasive particles.Thereby,the abrasion resistance of the composite material is improved.b)It revealed the sliding wear of micro-nano-duplex(TiB2-TiC)/Al-Cu-Mg composites with different ceramic contents and molar ratios of TiB2/TiC at 473K,sliding speeds of 0.32m/s and 0.47m/s,accompanying with applied loads of 30N and 40N.Under the same sliding speed and applied load,the friction coefficient of the composites gradually decreases with the increase of the volume fraction of ceramic particles.When the friction velocity is 0.32m/s and the applied load is 30N,when the volume fraction of ceramic particles of the micro-nano-duplex(TiB2-TiC)/Al-Cu-Mg composites increase from 10 vol.%to 60 vol.%friction coefficient of composites reduced from 0.418 to 0.253.The wear rate per unit volume is reduced from 4.52 X 10-11m3/m to 3.78×10-11m3/m.When the applied load and sliding speed are constant,the molar ratio of TiB2/TiC in the 40 vol.%(TiB2-TiC)/Al-Cu-Mg composite increases from 1:3 to 3:1,and the friction coefficient decreases 0.116,the volume wear rate is reduced by 0.37×10-11m3/m.c)It is revealed that the mechanism of the micro-nano-duplex(TiB2-TiC)/Al-Cu-Mg composites at high temperature sliding wear performance were:?The oxide film formed by the oxidation reaction on the worn surface reduces the contact area between the "soft phase" aluminum matrix and the grinding pair in the composite material,and improves the wear resistance of the composite material.?As the bearing phase,the harder ceramic particles can bear larger applied pressure,effectively transmit the load,and resist the plastic deformation of the composite material.?The good interfacial bonding between TiB2 and TiC ceramic particles and the aluminum matrix makes it difficult for ceramic particles to fall off the worn surface,which improves the strength and hardness of the composite material,and plays an important supporting role in the stability of the composite material.?The mechanical mixing layer formed on the surface of the composite material reduces the effective contact area between the aluminum substrate and the pair of grinding pairs,which have a relatively low surface hardness and melting point,and the supporting effect of the ceramic particles on the mechanical mixing layer,which improves the Abrasion resistance at high temperatures.?The resistance of ceramic particles to dislocations and pinning of grain boundaries improves the strength of composite materials at room temperature and high temperature. |
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