Development of Aluminum Alloys with High Strength and High elasticity Controlled Structurally by Solidification Processing.

建立了挤压铸造法制备SiC晶须增强Al-Li和Al-Mg合金复合材料的制备工艺，明确了其性能与组织控制的关系，为开发低密度、高强、高弹性的铝合金奠定了基础。结果表明，挤压铸造过程中，铝基熔体中的Li或Mg溶质原子与SiC晶须预制件中的SiO_2发生反应，形成沿基体合金熔体浸润路径形成的Li或Mg低浓度区。采用专门设计的制造方法，将耗尽区穿出复合铸锭外侧，获得了无锂、镁耗尽区的良好复合铸锭。结果表明：SiCw/Al-Li合金复合材料具有明显的时效硬化，而其他可时效硬化的铝合金复合材料没有或只有轻微的时效硬化。固溶处理后，复合材料中的T_1相优先在淬火过程中产生的高密度位错上析出。在SiCw/Al-Li合金复合材料中，弹性模量和屈服强度随SiC晶须体积分数的增加而线性增加。在SiCw/Al合金复合材料中，固溶温度冷却过程中产生的拉伸残余应力降低了材料的抗拉屈服强度，提高了材料的抗压屈服强度。x射线衍射法测得的复合材料中平均残余拉伸应力的大小与复合材料中基体的屈服强度密切相关。由于拉伸残余应力的降低和复合材料基体中平均位错密度的增加，复合材料冷却至液氮温度后恢复到室温的抗拉屈服强度显著提高。在含有大量SiO_2相的Al-Mg合金复合材料中，晶须/基体界面处以MgAl_2O_4为主要反应相形成了良好的连接。通过合理选择SiO_2相量，控制界面反应产物的种类和厚度，从而控制界面连接强度，提高复合材料的屈服强度。少

On the Al-Li and the Al-Mg alloys composites reinforced with SiC whiskers fabricated by the squeeze casting, the preparation technique was established and the relation between the properties and the structure control was clarified for the purpose of the development of aluminum alloys with the low density, high strength and elasticity.It was found that the low concentration region of Li or Mg shaped along the infiltration path of matrix alloy melts in the composites was formed during squeeze casting by the reaction between the Li or Mg solute atom in aluminum matrix melts and the SiO_2 presented in the SiC whisker preform. Sound composite ingots without the Li or Mg depleted region was obtained by using the fabrication method specially designed so as to through out of the depleted region for outside of composite ingots.The remarkable age hardening of the SiCw/Al-Li alloys composites was obtained, despite of no or slight age hardening of the other age hardenable aluminum alloys composite … More s. The prominent age hardening of Al-Li based alloy composites was obtained by the precipitation of metastable delta' and/or T_1 phases. The T_1 phase in the composites was precipitated preferentially on the dislocations of high density generated during quenching after the solution treatment. In the SiCw/Al-Li alloys composites, the elastic modulus and yield strength were increased linearly with increasing the SiC whisker volume fraction.In the SiCw/Al alloy composites, the tensile yield strength was decreased and the compressive yield strength was increased by the tensile residual stress induced during cooling from the solution treatment temperature. The magnitude of the averaged tensile residual stress measured by X-ray diffraction method in the composites was strongly dependent on the yield strength of the matrix in composites. The tensile yield strength of the composite restored to room temperature after cooled into liquid nitrogen temperature was significantly increased by the double effects due to both the decrease of the tensile residual stress and the increase of the average dislocation density in the matrix of the composite.In the Al-Mg alloy composite contained a large amount of the SiO_2 phase, the good connection at the interface caused by the formation of the MgAl_2O_4 as the main reaction phase at the whisker/matrix interface was achieved. The control of the connecting strength at the interface and the improvement of the yield strength for the composite materials are obtained by the control of the kind of the interface reaction products and the thickness due to the proper choice of the amounts of SiO_2 phase. Less