A study on the production of high temperature supercomposites and strengthening by mesoscopic structural controlling

通过改变凝固速度、添加第四元素和热处理等方法对原位复合材料进行了细观组织控制。结果发现，随着凝固速率的增加，增强相的相间距离减小，在试样内部形成的晶胞直径增大，α相的形状由纤维状变为片状。此外，加入Re和Ir作为第4元素后，我们发现两者的加入使相间距离变大，其形貌也变为片层状。高温下研究了复合材料的结构稳定性，纤维与基体之间不存在界面反应相。对复合材料进行最长500小时的热处理，研究了复合材料的硬度变化和形貌变化。结果表明，经过500小时的热处理，未添加添加剂的样品硬度下降了10%左右，添加Re和Ir作为第4元素的样品硬度下降幅度较小，这两种元素提高了复合材料的高温稳定性。对结构可控复合材料进行了高温拉伸试验，并对其高温强度和高温塑性进行了评价。结果表明，该合金在800℃时的极限抗拉强度最高可达1198 MPa，该高温强度与工业镍基高温合金（如ma - m247和CMSX-2）的高温强度相当。高温氧化试验结果表明，复合材料的抗氧化性能优于市售镍基高温合金，并通过添加Re和Ir进一步提高了其抗氧化性能。

Mesoscopic structure controlling for supercomposites (in-situ composites reinforced with refractory metal fibers) was carried out by solidification speed change, the 4th-element addition and heat treatment. Consequently, we found that as the solidification rate increase, the inter-phase distance of reinforcements decreases, the diameter of the cell formed in the inside of a sample increase, and the shape of alpha phase changes from fiber-like shape to lamella-like one. Furthermore, as a result of adding Re and Ir as the 4th element, we found that inter-phase distance became large and its morphology also changed to lamella by addition of both elements. The structural stability of supercomposite sample was investigated at elevated temperature, and there was no interface reaction phase between fiber and matrix. The heat treatment of a maximum of 500 hours was performed and hardness change and morphology change of supercomposite were investigated. It was shown clearly that the hardness of additive-free samples decreased about 10% by heat treatment of 500 hours, the decrease in hardness of the sample, which added Re, and Ir as the 4th element was small and that these two elements raised the high temperature stability of supercomposite. The high temperature tensile test for the structural controlled supercomposite was performed, and high temperature strength and high temperature ductility were evaluated. Consequently, the samples showed the ultimate tensile strength of a maximum of 1198 MPa at 800℃, and this high temperature strength was equivalent to that of commercial nickel-base superalloys, such as Mar-M247 and CMSX-2. As a result of the high temperature oxidization test, supercomposite had the oxidation resistance superior to the commercial nickel-base superalloy, and it was shown that the oxidation resistance was further improved by adding of Re and Ir.