Processing for multi-functions・Materials development

在高温结构材料的众多性能中选择了强度、断裂韧性和抗氧化性，并对谐波材料设计进行了研究。通过控制合金行为和微观结构，合成了两相均为热动力平衡的延性颗粒-弥散难熔金属间化合物和陶瓷原位复合材料。采用高频浮区熔炼法制备的定向凝固共晶ZrC/Mo原位复合材料，室温断裂韧性约为20 MPam^<1/2>， 1500℃时强度高达420 MPa。高断裂韧性是由于ZrC和Mo之间的解聚引起的裂纹偏转，而在1500C时的高强度是由于固溶体强化和组织细化。Mo-Si-B合金在不牺牲室温断裂韧性的情况下，显著提高了合金的高温强度。提出了“伪原位复合材料”的新概念，发现伪原位Mo-Si-B-O复合材料在1400C时具有优异的抗氧化性能。在对扩散连接进行基础研究的基础上，成功地对Fe_3Al基合金和CrMo钢进行了复合热轧。复合热轧薄板具有高强度、良好的抗氧化性和高断裂韧性。

Strength, fracture toughness and oxidation resistance were selected among many properties for high temperature structural materials and harmonic material design was studied.In-situ composites consisting of ductile particle-dispersion refractory intermetallics and ceramics in which both the phases are thermodynamically equilibrated were synthesized by controlling alloying behavior and microstructure. Directionally solidified eutectic ZrC/Mo in-situ composite, which is prepared by the high frequency floating zone melting method, shows the room temperature fracture toughness of about 20 MPam^<1/2> and high strength at 1500C of 420 MPa. The high fracture toughness is attributable to crack deflection arising from decohesion between ZrC and Mo and the high strength at 1500C is due to solid solution strengthening and microstructure refinement.High temperature strength of Mo-Si-B alloys is shown to increase significantly by alloying without sacrificing room temperature fracture toughness. The new concept of "pseudo in-situ composite" is presented and pseudo in-situ Mo-Si-B-O composite is found to exhibit excellent oxidation resistance at 1400C.Based on the fundamental research of the diffusion bonding, clad hot rolling is successfully carried out using Fe_3Al base alloys and CrMo steel. The clad hot rolled sheet shows harmonically high strength, good oxidation resistance and high fracture toughness.