The Isothermal Section Of The (Ho,Gd,Er)-Ti-Si Ternary System

Phase equilibrium relations of the Ho-Ti-Si ternary system at 973 K,Gd-Ti-Si ternary system at 1073 K and Er-Ti-Si ternary system at 1273 K were experimentally researched by means of X-ray diffraction(XRD),scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS).The binary compounds Ti5Si3,Ti5Si4,TiSi,TiSi2,Ho5Si3,Ho5Si4,HoSi,αHoSi2-b,and βHoSi2-a are proved to exist at 973 K.The isothermal section of the system at 973 K consists of 14 there-phase regions,27 two-phase regions and 14 single-phase regions.Previously reported HoTiSi and Ho2Ti3Si4 ternary compounds were confirmed to exist at this temperature.The maximum solubilities of Ti in HoSi2-b,Ho5Si4 and Ho5Si3 are confirmed to be 8.0 at.%,7.2 at.%,and 6.0 at.%,respectively.The compositional range of the Ti5Si3 system is from Ti61Si39 to Ti63.4Si36.6.There are 9 binary compounds,i.e.Ti5Si3,Ti5Si4,TiSi,TiSi2,GdSi2,Gd3Si5,GdSi,Gd5Si4 and Gd5Si3 in the Gd-Ti-Si ternary system at 1073 K.The existence of two ternary compounds GdTiSi and Gd1.9Ti3Si4 have been confirmed.The results show that this isothermal section consisted of 14 three-phase regions,27 two-phase regions,and 14 single-phase regions.The solubilities of Ti in Gd5Si4 and Gd5Si3 were determined to be up to 3.0 at.%and 2.5 at.%.The strange solid solution region of GdSi2-x and Ti5Si3 were found in this work.The 1273 K isothermal section of this system consisted of 12 three-phase regions,24 two-phase regions,and 13 three-phase regions.There are eight binary compounds in this system.Which are Ti5Si3,Ti5Si4,TiSi,TiSi2,Er3Si5,ErSi,Er5Si4 and Er5Si3.Two ternary compounds ErTiSi and Er1.9Ti3Si4 exist in this system..Ti exists in solid solution in Er5Si4 and Er5Si3,and their maximum solid solubility are 9.8 at.%and 6.8 at.%,respectively.Ti5Si3 and Er3Si5 have larger solid solution range at 1273 K.