Determinação Experimental Das Relações De Fases Do Sistema Nb-Ti-Si Na Seção Isotérmica a 1.200°C

Abstract

ResumoForam estudadas experimentalmente as relações de fases do sistema NbTiSi na seção isotérmica a 1200 °C. Ligas fundidas em forno a arco em atmosfera de argônio a partir de Nb, Ti e Si de alta pureza (˃ 99,9 %), foram tratadas termicamente a 1200 °C durante 264 h em forno tubular, em atmosfera de argônio, encapsuladas em tubos de quartzo. As ligas tiveram sua microestrutura caracterizada por difração de raios-X, microscopia eletrônica no modo elétrons retroespalhados e por microsonda. EXPERIMENTAL DETERMINATION OF NBTISI SYSTEM PHASE RELATIONS IN 1,200°C ISOTHERMAL SECTION AbstractWe studied experimentally the phase relationship of the system NbTiSi in the isothermal section at 1200 °C. Alloys cast in arc furnace, under argon atmosphere, from Nb, Ti and Si of high purity (˃ 99.9%), were heat treated at 1200 °C for 264 h in a tubular furnace, under argon atmosphere, encapsulated in quartz pipes. The alloys had their microstructure characterized by X-ray diffractometry, scanning electron microscopy in backscattered electrons mode and electron beam microprobe analysis. Seven ternary regions were determined, Nb 5 Si 3 + (Nb, Ti) 3 Si + (Nb, Ti, Si), Nb 5 Si 3 + (Nb, Ti) 3 Si + Ti 5 Si 3 , Ti 5 Si 3 + (Nb, Ti) 3 Si + (Nb, Ti, Si), Nb 5 Si 3 + Ti 5 Si 4 + Ti 5 Si 3 , Nb 5 Si 3 + Ti 5 Si 4 + NbSi 2 , NbSi 2 + Ti 5 Si 4 + TiSi, NbSi 2 + TiSi 2 + TiSi e NbSi 2 + TiSi 2 + Si SS . There is good agreement of the results with the calculated and experimental proposals in the literature for this isothermal section of NbTiSi system. Small compositional changes are suggested for the location of the observed ternary fields.