compositions among TisAl (aa),TiAl (y),NbTiAla(y1),NbAls()and TiAls (in Nb-Ti-Al ternary system,with Al being from 25at%to 75at%,Nb 0at% to 25at%and Ti (25-75)at%.The actual compositions are shown in Fig.1. The bulk samples for structure study were prepared from 4NAl,2N8Nb and 3NTi by arc melting in a gettered argon atmosphere in a small button of 50g.In excess 5 remelts were performed to ensure mixing of the alloys,The chemical anlysis of the alloy having the NbTiAls composition confirmed the gaseous content was not to be of quantity to significantly influence phase stru- cture(Table 1).The samples for property study were melted by a vacuum induction furnace.The macrosegregation was investigated by a electronprobe at the different location of the ingot,The result showed that the composition from the edge to the centre of the ingot was reasonably homogenous.In orde to eliminate the microsegregation homogenization was performed,The homno- genizing processing flow chat can be seen in Fig.2.Smnall metallographic and Tablel Analysed gaseous content in NbTiAla alloy metho d N,Ppm O,ppm non-comsumablc arc melting <100 65 vacuum induction melting <100 473 mechanical samples were then made by electric spark cutting,Phase identifi- 的 cation was determined by means of microscopy (SEM TEM),microanalysis (EDX),structure analysis (selected area diffraction,microiiffraction,conver- gent beam diffraction and X-ray diffraction).Compessive test was performed on a Gleeble machine at various temperatures up to 1100C.The strain rate was chosen at 10-2/s and 10-5/s (corresponding to the strain rates for hot de- formation and creep respectively).Tensile test was also performed for part of the alloys on a MTS machine.Fracture mode under tcnsile condition was observed by SEM.Static oxidation test and oxidation kinetics measurement were carried out in high temperature furnace in air at from 900 to 1200C 2 Results and Discussion 2,1 Microstructure Studies Limited work has been done on the phase diagram of Nb-Ti-Al ternary system.Relatively little has been concluded on the central area of the phase diagram,especially on the presence of the ternary intermetallic compound NbTiAls.Published reports are subject to controversy1-.Zazharovt2, claimed the existence of NbTiAls having a tetragonal lattice unit of a= 159脚， 。 。 ， 。 。 个 ， 夕 ， 金 。 夕 ， 。 叮 。 叮 一 一 ， ， 一 写 毯 了 ， 。 皿 几 。 。 几 、 。 ， ， 一 了压 从 ， ， 才护 ， ， ， 一 了 一 。 一 盯 ℃ 。 。 一 “ 、 。 ， 。 、、 ‘‘ 认 了 ‘ ℃ 一 一 。 ， 公 让 〔 一 毛 〕 。 〔 泣 二