| Ceramic particle regulated Al-Cu alloy has the advantages of low density,high specific strength and good plasticity,while Ti C and Ti B2 ceramic particles have good wettability and lattice matching with?-Al,and no interfacial reaction,and they are ideal particle reinforcements for Al-Cu alloys.At present,most studies on Ti C and Ti B2 ceramic particles regulated Al-Cu alloys are single-phase Ti C or Ti B2 particle reinforcement,and there are few reports on dual-phase Ti C+Ti B2 particles regulated Al-Cu alloys.Therefore,it is of great significance to study the influence of dual-phase Ti C+Ti B2 ceramic particles on the Al-Cu alloy and the performance enhancement mechanism.In addition,in addition to the type of particles,the size of the particles determines the properties of the alloy to a large extent.Compared with micro-particles,nano-particles can simultaneously improve the mechanical properties of Al-Cu alloys at room temperature and high temperature,and have a more excellent strengthening effect.Among the commonly used methods for preparing ceramic particles,the ex-situ method tends to contaminate the surface of the particles and cause agglomeration,while the in-situ method and the master alloy method have poor process stability and high cost and harsh conditions,which limit their application.Therefore,exploring an economical,practical and efficient new type of in-situ nano-ceramic particle regulate Al-Cu alloy preparation process has great significance for further improving the room temperature and high temperature mechanical properties of Al-Cu alloys and making them suitable for industrial production has great practical application value.The main innovations of this article are as follows:(1)Revealing the interfacial combination and formation mechanism of in-situ single-phase Ti C and dual-phase Ti C+Ti B2 in Al-Cu matrix:the(Al-Cu)-Ti-C and(Al-Cu)-Ti-B4C reaction systems were used to prepare high volume fraction Ti C/Al-Cu and Ti C+Ti B2/Al-Cu composites.The study found that the reaction intensity and heat release of the(Al-Cu)-Ti-B4C system are lower,and B4C has higher stability and the diffusion distance(C and B)by diluting each other.Therefore,the 60 vol.%Ti C+Ti B2/Al-Cu composite has excellent interface continuity between the ceramic particles and the aluminum matrix,and the interface bonding strength and interface stability are better than 60 vol.%Ti C/Al-Cu composite.(2)Revealing the mechanical properties,thermophysical properties and strengthening mechanism of high content single-phase Ti C and dual-phase Ti C+Ti B2 strengthened Al-Cu alloys:compared with 60 vol.%Ti C/Al-Cu composite,the compressive yield strength,compressive strength,plastic strain and total strain of 60 vol.%Ti C+Ti B2/Al-Cu composite are increased by 70.5%,60.7%,69.8%and 56.5%respectively,the wear resistance is increased by 1.7 times,and the thermal expansion coefficient at 373 K is reduced by 5.9%.The performance enhancement mechanism is that the solid interface between the ceramic particles and the matrix effectively transfers the load,and the ceramic particles also effectively resist the load and limit the plastic deformation of the material.(3)Revealing the influence mechanism of the reaction system ratio on the formation of dual-phase nano Ti C+Ti B2 in melt:using Al-Ti-B4C,Al-Ti-B4C-B and Al-Ti-B4C-C as the reaction system,the nano Ti C+Ti B2 ceramic particles were successfully prepared in ZL205A alloy melt using a new type of melt generation method.The study found that as the Al content in the Al-Ti-B4C system decreases,the size of the Ti C+Ti B2 increases.As the molar ratio of Ti C/Ti B2 increases,Ti C increases and Ti B2 decreases,and the size of Ti C is smaller than Ti B2,the size of Ti C+Ti B2 decreases.(4)Revealing the influence of the size,content and ratio of the dual-phase nano Ti C+Ti B2 in melt on the microstructure and solidification behavior of Al-Cu alloys and the regulation mechanism:as the size of Ti C+Ti B2 increases,the degree of refinement of the as-cast structure of the alloy decreases.As the content of Ti C+Ti B2 and the molar ratio of Ti C/Ti B2 increase,the degree of refinement of the as-cast structure increases first and then decrease.When the Al-Ti-B4C system with 80 wt.%Al content is added to in-situ generate0.3 wt.%nano Ti C+Ti B2,the as-cast structure of the alloy is refined the most.The regulation mechanism of the as-cast structure refinement is that nano Ti C+Ti B2 increases the initial temperature of?-Al grain and Al2Cu eutectic phase nucleation during solidification,shortens the time required for growth and reduces the degree of nucleation and re-blow supercooling,effectively promote the nucleation of?-Al crystal grains and Al2Cu eutectic phase and hinder growth.(5)Revealing the influence of the size,content and ratio of the dual-phase nano Ti C+Ti B2 in melt on the mechanical properties of Al-Cu alloy and the strengthening mechanism:as the size of Ti C+Ti B2 increases,the degree of refinement of the mechanical properties of the alloy decrease.As the content of Ti C+Ti B2 and the molar ratio of Ti C/Ti B2increase,the mechanical properties of the alloy increase first and then decrease.When the Al-Ti-B4C system with 80 wt.%Al content is added to in-situ generate 0.3 wt.%nano Ti C+Ti B2,the alloy has the most stable and excellent room and high temperature mechanical properties,and the yield strength,tensile strength,total strain and strength-ductility balance at room temperature reached 503.5 MPa,553.3 MPa,9.34%and4.36×103 MPa·%,respectively,which increased by 16%,14.3%,17%and 41.8%compared to the matrix alloy,the yield strength,tensile strength,and total strain at 493 K and 533 K reached 200.2 MPa,268.5 MPa,5.92%and 162.5 MPa,206.7 MPa,4.85%,respectively,and the strength-ductility balance reached 1.08×103 MPa·%and 0.72×103 MPa·%.The strengthening mechanism of mechanical properties is fine-grain strengthening,precipitation strengthening,Orowan strengthening and thermal mismatch strengthening. |
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