PROCESS FOR ROLLING BILLETS OF HYPEREUTECTOID γ+α-ALLOYS AND METHOD FOR MAKING BILLETS FOR SUCH PROCESS Russian patent published in 2001 - IPC

FIELD: plastic working of metals and alloys, particularly, working billets of titanium aluminides such as TiAl (γ+α₂ phase) and Ti₃Al (γ phase) made by casting or powder metallurgy method. SUBSTANCE: method comprises steps of rolling initial billet with preliminarily prepared fine-grain structure to sheet or to foil of predetermined thickness and grain size in range of deformation rate α₂ 1/c and in temperature range (T* +-Te) C, where T* is 400-700 C and Te is temperature of eutectoid conversion, during one or several stages realized as N passes in isothermal or quasi-isothermal conditions; selecting heating temperature of billet for each next stage Ti+1 according to condition Ti+1=Ti, where Ti is temperature of billet heating at previous stage; at first stage setting Ti=To, where To is temperature of deformation at final stage during making billet for rolling or setting Ti+1= Ti+10^-3-10¹Ti+1 or Ti+1= Ti-Δti+1, where ΔTi+1 is selected according to condition of admissible grain growing and Δti+1 - according to condition of deformability or deformability and lowered oxidation capability of alloy. Initial billet for rolling is made by heating and deforming in temperature range (700-Te) C, where Te is temperature of eutectoid conversion, at rate values Δ 1/c during i stages, n transitions at each stage and with total deformation degree 10^-4-10^-1 providing fine grain size due to recrystallization. Temperature Ti and deformation rate Σε for each stage are determined according to results of testing of N samples with size of grain/colony di (di= d bil) by means of single axis compression at isothermal conditions in above mentioned range of temperature and deformation rate while taking into account size of recrystallized grains and specific recrystallized volume. Number of stages is determined according to smooth lowering of grain size in initial billet until necessary value. EFFECT: manufacture of sheet and foil with normalized structure, preparation of fine-grain microstructure in initial billets for rolling. 37 cl, 5 tbl, 8 dwg, 17 ex