Design And Preparation Of In Situ TiC Particle-Reinforced Aluminum Matrix Composites

The traditional strengthening process of aluminum-silicon alloy used in piston material is not easy to meet the requirements of working conditions,and TiC particle-reinforced aluminum matrix composites have the advantages of low density of traditional aluminum alloy,high hardness and high melting point of TiC particles,and TiC can refineα-Al particles,so they have good application prospects.However,the presence of Si element in aluminum-silicon alloy will lead to the decomposition of TiC to produce strip phase,and the agglomeration phenomenon will occur in the aluminum melt due to TiC’s own characteristics,and the long strip phase Al Ti Si phase exists in the organization.poor stability of TiC and strong agglomeration of TiC are the difficulties that limit the application of TiC on the ground.In this paper,the TiC/Al-12Si composite preparation process with better generation effect is obtained by improving TiC stability and weakening TiC agglomeration phenomenon.Based on the first principle theory,this paper firstly investigates the way of Si elements entering the C vacancies in TiC,calculates the stability of the ternary compound formed after the doping of B,N and O elements,explores the bonding interface and bonding sites of Al/TiC interfacial model,and calculates the nature of the Al/TiC interface alloyed with Ce,La,Mg,Mo and Si elements by using VASP software.The alloying elements suitable for stabilizing TiC were selected by the calculation and their stabilization mechanisms were analyzed.Then different kinds of B sources（KBF₄,BN,B₄C）with different rare earth Ce additions（0.2%,0.4%,0.6%）were added to the Al-5Ti-0.22C alloy respectively according to the calculation results to obtain the B sources that can stabilize TiC and the suitable rare earth additions.Finally,the Al-12Si composites with different TiC contents（TiC contents of 3%,5%and 7%）were prepared according to certain compositions and order.The microstructure and mechanical properties of the composites were studied by using metallographic microscope（DM2Z00M/MCIZ0HD）,X-ray diffraction analyzer（XRD-6000）,scanning electron microscope（Quanta 400F）,transmission electron microscope（FEI Talos F200X）,electronic universal tensile tester（CMT5504GL）and other equipment.The main results are as follows The main findings are as follows:（1）When there are a large number of C vacancies in TiC,Si elements have the potential to enter the C vacancy lattice in TiC;the compounds formed by N and O element doping are more stable,while the excess of B sources will lead to the decrease of TiC stability;the entry of B elements into C vacancies in TiC can weaken the catalytic ability of Si atoms located in some sites.（2）The（100）Al/TiC interface at the Top site,the（110）Al/TiC interface at the Bridge site,and the A2-Ti truncated（111）Al/TiC interface are modeled as more stable Al/TiC co-grid interfaces.The alloyed Al/TiC interface found that Ce and Mo elements increased the adhesion of Al/TiC;meanwhile,the calculation of the layer fault energy after Ce doping found that Ce elements reduced the plasticity of Al/TiC interface.（3）The Al-5Ti-0.22C intermediate alloy was used as the substrate to screen the suitable B-source as KBF₄,with the addition of KBF₄ at 0.1%and Ce element at 0.2%.The final preparation process is to first add the pure aluminum matrix with Al,Ti,C mixed powder at 1200°C,then lower the temperature at 800°C to add rare earth Ce and KBF4 together and then add Si.（4）The microstructure of TiC/Al-12Si composites with 3%,5%and 7%addition amounts were analyzed and found that Al3Ti and TiC gradually increased with the increase of TiC addition amount,and the Al3Ti phase was massive phase,and the TiC particles were obviously agglomerated in the specimen with 7%TiC addition amount.The room temperature tensile strength of the composites was found to increase and then decrease with the increase of TiC content,reaching a maximum value of 173.51 MPa at 5%TiC content,while the elongation reached a maximum value of 8.87%at 3%TiC addition.