以预合金化的粉末尺寸 D50为3．3μm 的 NbSS 固溶体相细粉末，粉末尺寸 D50分别为22．1μm 和23．5μm 的Nb5 Si3和 Cr2 Nb 化合物粉末为原料，采用放电等离子烧结技术制备 NbSS／Nb5 Si3两相合金和 NbSS／Nb5 Si3／Cr2 Nb 三相合金，研究显微组织形貌、室温和高温力学性能及高温氧化性能。结果表明：两相合金的显微组织由 NbSS 基体和呈均匀岛状分布的 Nb5 Si3组成，三相合金中 NbSS 有相互连接成基体的趋势，而 Nb5 Si3和 Cr2 Nb 相也以块状散布在 NbSS 中。NbSS／Nb5 Si3两相合金和 NbSS／Nb5 Si3／Cr2 Nb 三相合金的室温断裂韧性值 KQ 分别达到15．1MPa·m1／2和11．3MPa· m1／2，室温下合金中 NbSS 相以韧窝型断裂为主，对 Nb-Si 基合金的室温断裂韧性有利，而 Nb5 Si3和 Cr2 Nb 相为脆性断裂。1250℃时 NbSS／Nb5 Si3／Cr2 Nb 合金的压缩强度高于 NbSS／Nb5 Si3合金，但当温度上升到1350℃时两者强度出现反转。Cr2 Nb 相对合金高温抗氧化性能有利，1250℃下静态氧化100h 时 NbSS／Nb5 Si3合金的氧化增重为233mg／cm2，大于 NbSS／Nb5 Si3／Cr2 Nb 合金的175mg／cm2。
Pre-alloyed NbSS solid-solution fine powder with a D50 size of 3.3μm,pre-alloyed Nb5 Si3 and Cr2 Nb compound powders with D50 size respectively of 22.1μm and 23.5μm were used as raw materi-als,and two-phase NbSS/Nb5 Si3 alloy and three-phase NbSS/Nb5 Si3/Cr2 Nb alloy were fabricated by Spark Plasma Sintering (SPS).The microstructure,mechanical properties and oxidation behavior at room and/or high temperatures were investigated.The results show that the microstructure of the NbSS/Nb5 Si3 alloy consists of the NbSS matrix and the uniformly distributed Nb5 Si3 islands.As for the NbSS/Nb5 Si3/Cr2 Nb alloy,the NbSS phase tends to connect to be the matrix,while the Nb5 Si3 and Cr2 Nb blocks scatter in the NbSS phase.Fracture toughness K Q at room temperature of the two-phase and three-phase alloys are 15.0MPa·m1/2 and 11.3 MPa·m1/2 ,respectively.The NbSS phase is found to fail in a dimple mode under bending,which is greatly beneficial to K Q of the bulk Nb-Si based alloys;while the Nb5 Si3 and Cr2 Nb phases fracture in a brittle mode.At 1250℃,the compressive strength of the NbSS/Nb5 Si3/Cr2 Nb alloy is higher than that of the NbSS/Nb5 Si3 alloy,whereas it is contrary at 1350℃.The Cr2 Nb phase plays a positive role in oxidation resistance at high temperature. Air exposed at 1250℃ for 100h,the oxidation mass gain of NbSS/Nb5 Si3 alloy is 233mg/cm2 ,greater than 175mg/cm2 of the NbSS/Nb5 Si3/Cr2 Nb alloy.
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