Microstructure And Properties Of Aluminum Matrix Composites With The Addition Of Barium Plumbate And Their Deformation Behavior At High Temperature

In order to meet the requirements of high specific stiffness, high specific strength, anti-radiation property and high damping capacity in the space area, the BaPbO₃/2024Al (Abbreviated by BPOp/2024Al) and (Al₁₈B₄O₃₃ + BaPbO₃)/Al (Abbreviated by (ABOw+BPOp)/Al) composites were fabricated by powder metallurgy and squeeze casting, respectively. The volume fraction of the BPOp is 5% in both composites, and that of ABOw in (ABOw+BPOp)/Al composite is 20%.The microstructure of both composites were analysed by DSC, XRD and TEM. The tensile mechanical properties at room temperature, radiation protection properties and damping properties were measured. The mechanisms for radiation protections, damping behavior and hot deformation including hot extrusion and hot compression were analysed in detail.According to TEM and DSC results, during the fabrication process, BPOp reacted with 2024Al and Al in both composites to produce nanosized Pb particles and amophous phases, respectively. In BPOp/2024Al composite, reaction products, Pb and amorphous phase were distributed in the matrix of the composite in the form of cluster. And the reaction between BPOp and 2024Al reduced tensile properties of BPOp/2024Al composite. In (ABOw+BPOp)/Al composite, reaction products, Pb and amorphous phase formed a interfacial layer at the interface between Al and ABOw, which weakened the bonding strength between Al and ABOw, as a result, decreasing the mechanical property of the composite at room temperature. The introduction of ABOw plays a significant reinforcing role in (ABOw+BPOp)/Al composite.The crystal structure and lattice parametre of complex intermetallic Al63.5Mn10.5Cu9.5Fe7.6Si8.9 in 2024Al were determined by TEM for the first time. The intermetallic has an ordered body center cubic lattic with a lattice parameter of 1.265nm. The formation mechanism and the effect of the intermetallic on mechanical property of BPOp/2024Al were studied.The radiation protection properties and damping capacities of both composites were improved by the addition of BPOp. The increase of radiation protection property in both composites should be attributed to the heavy elements, Ba and Pb in BPOp. The theoretical results of radiation protection property is in good agreement with experimental results, which shows that the reaction between BPOp and matrix will not influence the radiation protection property of the composites according to the theoretical calculations. The damping capacity of BPOp/2024Al composite is dependent on the intrinsic damping of nanosied Pb. The improved damping capacity of (ABOw+BPOp)/Al composite was explained by the intrinsic damping of Pb and weak interfacial bonding between ABOw and Al due to the existence of interfacial layer.According to hot extrusion and hot compression tests of BPOp/2024Al composte, the hot deformation resistance reduced with increasing deformation temperature, especially, depressed sharply when the deformation temperature is above the melting point of Pb. Firstly, the matrix of BPOp/2024Al composte will recover, recrystallize and even soften as increasing the temperature; secondly, liquid Pb will release deformation stress concentration, therefore, decrease the dislocation density of the matrix; finally, liquid Pb with extremely low mechanical propery will lower significantly the mechanical property of BPOp/2024Al composte, and reduce the deformation resistance.Hot extrusion experiments show that the extrusion resistance of (ABOw+BPOp)/Al composite is lower than that of ABOw/Al composite. It can be explained by two ways: firstly, interfacial layer can release stress concentration and decrease deformation dislocation around whiskers; sencondly, liquid Pb can favor the glide and rotation of whiskers. Hot compression of (ABOw+BPOp)/Al composite exhibits a brittle fracture characteristic, which is caused by weak interfacial bonding under shear stress at high temperature. Therefore, (ABOw+BPOp)/Al should be deformed by hot extrusion with three-dimensional stress state.