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对高温金属纤维增强自生复合材料的细观结构进行了控制。结果表明，随着凝固速率的增大，增强相的相间距离减小，试样内部形成的胞状结构直径增大，α相的形状由纤维状变为片状。此外，作为添加Re和Ir作为第4元素的结果，我们发现，通过添加这两种元素，相间距离变大，并且其形态也变为薄片。研究了超复合材料试样在高温下的结构稳定性，纤维与基体之间不存在界面反应相。进行了最多500小时的热处理，并研究了超复合材料的硬度变化和形貌变化。结果表明，无添加剂的试样经500 h热处理后硬度下降约10%，添加Re、Ir和第4元素的试样硬度下降幅度较小，这两种元素提高了超复合材料的高温稳定性。对该结构控制超复合材料进行了高温拉伸试验，评价了其高温强度和高温塑性。因此，样品在800℃下显示出最大1198 MPa的极限拉伸强度，该高温强度与商用镍基高温合金如Mar-M247和CMSX-2相当。高温氧化试验结果表明，复合材料的抗氧化性能比普通镍基高温合金有上级的提高，加入Re和Ir后，复合材料的抗氧化性能进一步提高。

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.