【作者】 范国华；

【导师】 耿林；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2009， 博士

【摘要】 针对航天领域对材料高比刚度、高比强度、抗辐射和高阻尼性能的需要,本文采用粉末冶金和挤压铸造方法分别制备了BaPbO₃体积百分数为5%的BaPbO₃/2024Al和(Al₁₈B₄O₃₃ + BaPbO₃)/Al复合材料,分别简写为BPOp/2024Al和（ABOw+BPOp）/Al。采用DSC、XRD和TEM研究了两种复合材料的微观组织,测试了两种复合材料的室温拉伸性能、辐射防护性能、阻尼性能和热挤压热压缩变形性能,阐述了复合材料辐射防护和阻尼机制,探讨了热挤压热压缩变形机理。TEM和DSC分析结果表明,在复合材料制备过程中,BPOp与2024Al及Al基体分别发生化学反应,生成纳米级Pb颗粒和非晶相。在BPOp/2024Al复合材料中,Pb与非晶相以团簇形式分布于2024Al基体中,这一化学反应降低了BPOp/2024Al复合材料的室温拉伸性能;在（ABOw+BPOp）/Al复合材料中,Pb与非晶相以界面层形式分布于ABOw-Al界面处,含Pb界面层降低了界面结合强度,弱化了（ABOw+BPOp）/Al复合材料室温力学性能;ABOw的引入对（ABOw+BPOp）/Al复合材料具有显著补强作用。采用TEM首次确定了2024Al合金中复杂金属间化合物Al63.5Mn10.5Cu9.5Fe7.6Si8.9的点阵结构、测量了点阵常数,这一金属间化合物具有有序的体心立方结构,点阵常数大约为1.265nm。系统研究了复杂金属间化合物的形成机理及对BPOp/2024Al复合材料力学性能的影响。BPOp的引入明显提高了BPOp/2024Al和（ABOw+BPOp）/Al复合材料的辐射防护性能和阻尼性能。BPOp中含有重金属元素Ba、Pb,从而提高了复合材料的辐射防护性能。辐射防护计算结果与试验结果的吻合显示,制备过程中的化学反应不影响复合材料的辐射防护性能。BPOp/2024Al复合材料的阻尼能力明显依赖于Pb相的本征阻尼。（ABOw+BPOp）/Al复合材料阻尼性能明显依赖于Pb相的本征阻尼以及弱的界面结合引起的界面阻尼。BPOp/2024Al复合材料的热挤压和热压缩变形结果显示,随变形温度升高复合材料变形抗力降低,在Pb熔点以上变形时,热变形抗力明显降低。首先,温度升高,BPOp/2024Al复合材料基体发生回复、再结晶,基体软化;其次, Pb液相出现后,有效松弛了变形引起的局部应力集中,降低了BPOp/2024Al复合材料基体位错密度;另外,Pb液相力学性能极低,液相出现明显降低BPOp/2024Al复合材料力学性能,导致复合材料变形抗力降低。（ABOw+BPOp）/Al复合材料热挤压变形结果显示,（ABOw+BPOp）/Al复合材料热挤压变形抗力较ABOw/Al明显降低。一方面,含Pb界面层能有效的松弛变形过程中晶须附近的应力集中,减少晶须附近基体的变形位错;另一方面,液相Pb有利于界面滑动、晶须转动。（ABOw+BPOp）/Al复合材料热压缩变形表现出明显脆性材料压缩变形特征,主要是由于高温变形时,界面层弱化了ABOw-Al间界面结合强度,在剪切应力作用下,晶须大量拔出,导致沿与压缩方向呈45°平面脆性断裂。所以,（ABOw+BPOp）/Al复合材料热变形更适合于存在三向应力状态的热挤压变形。更多还原

【Abstract】 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.更多还原