P、B在低膨胀Thermo-Span合金铸态组织中的分布及影响

Distribution and Effect of P and B on As-Cast Microstructure of Low Thermal Expansion Superalloy of Thermo-Span

采用扫描电镜(SEM)、电子探针(EMPA)和热分析测量仪研究了微量元素P和B在Thermo-Span合金铸态组织中的分布及对合金铸态组织熔点温度的影响。结果表明:P和B强烈向铸态组织心部偏聚,并促进Laves相的析出。当P含量增加到0.05%时,合金中析出Ti-P相;而当B含量增加到0.05%时,合金中形成B-Nbphase与基体的共晶Laves相组织;合金铸态组织熔点温度显著降低。P对合金铸态组织熔点温度影响不大。

Using scanning electron microscope equipped with electron probe （EPMA） and thermal analytic measure equipment, the effect of trace element phosphorus and boron on as-cast microstructure of Thermo-Span alloy has been investigated. The results show that P and B trends to segregate at the center in the ingot, which caused the precipitation of Laves phases. When the content of phosphorus is 0.05% and boron 0.05%, phosphorus exists in Laves phase in Ti-P phase modified, and boron in B-Nb phase modified mainly segregates at eutectic Laves phase. By measuring the incipient melting temperature, it is found that there is no difference between adding phosphorus and without phosphorus. However, increasing boron content to 0.05%, the incipient melting temperature decreases significantly.