Effects Of Ti/Zr Content And Sintering Temperature On Microstructure And Mechanical Properties Of ODS-NiCrAl Alloys

Nickel-based superalloy has excellent high-temperature strength,oxidation resistance,and corrosion resistance,which is widely used in aerospace and nuclear power.Solution strengthening and precipitation strengthening are mainly used to improve the high temperature strength of the superalloy.However,when the service temperature is higher than 1000?,the dissolution of ?' phase may reduce the high temperature strength and limit the use of superalloy.Oxide dispersion strengthened(ODS)technology can improve superalloy high temperature strength.In the paper,mechanical alloying(MA)and hot isostatic pressing(HIP)methods were used for preparing oxide dispersion strengthed.NiCrAl alloys(ODS-NiCrAl),ODS-Ni20Cr4.5AlxTiyZr alloys.The effects of HIP temperature(1100?/1150?),and(Ti=0.5,1.5,2.5 wt%)and(Zr=0,0.6,1.2 wt%)contents on the microstructure and mechanical properties of ODS-NiCrAl alloy were studied systematically.The following conclusions are obtained:(1)ODS-Ni20Cr4.5Al0.5Ti alloy was produced by MA and HIPed at 1100? and 1150?,respectively,Ultrafine and nano grains are formed in this ODS-NiCrAl alloys.The average grain size is 0.49 ?m(1100?)and 0.54 ?m(1150?).In the alloys HIPed at 1100?and 1150?,the large oxides are observed as Al2O3 and Y4Al2O9,and the nanoscale oxide is mainly Y2TiO5.With the increase of the sintering temperature,the size of the oxides increases and the number density decreases;(2)The addition of Ti and Zr can refine the grain size.With the increase of Ti content,the average grain size of the alloys decreases from 0.49 ?m to 0.37 ?m.The proportion of ultrafine grain(100?500 nm)increases,and the proportion of low angle grain boundaries(2?15°)increases from 27.4%to 35.9%.With the increase of Zr element content,the average grain size of the alloys decreases from 0.49 ?m to 0.31 ?m.The proportion of ultrafine grain(100?500 nm)increases,and the proportion of low angle grain boundaries(2?15°)increases from 27.4%to 39.1%;(3)The addition of Ti and Zr can refine the large oxides.With the increase of Ti element content,the average size of large oxides(mainly Al2O3 and Y4Al2O9)decreases from 45.0nm(Ti=0.5%)to 38.6 nm(Ti=2.5%),and the number density increased from 2.8×1020m-3 to 4.2 ×1020 m-3.With the increase of Zr element content,the average size of large oxides decreases from 45.0 nm(Zr=0%)to 30.2 nm(Zr=1.2%),and the number density increases from 2.8×1020 m-3 to 8.6×1020 m-3;(4)The addition of Ti and Zr can refine the nanoscale oxides.In the Ti-containing ODS-NiCrAl alloys,with the increase of Ti element content,the nanoscale oxides is mainly Y2TiO5.The average size of nanoscale oxides decreases from 13.0 nm(Ti=0.5%)to 7.4 nm(Ti=2.5%),and the number density increases from 1.1×1022 m-3 to 7.6×1022 m-3.In the Zr-containing ODS-NiCrAl alloys with 0.5wt%,with the increase of Zr element content,the nanoscale oxides are mainly Y4Zr3O12.The average size of nanocale oxides decreases from 13.0 nm(Zr=0%)to 6.12 nm(Zr=1.2%),and the number density increases from 1.1×1022 m-3 to 9.9×1022 m-3.(5)With the increase of Ti and Zr content,the high temperature tensile strength of ODS-NiCrAl alloy increases.When the content of Ti element is 2.5%,the tensile strength reaches 507 MPa at 600? and 328 MPa at 700?.When the content of Zr element is 1.2%,the tensile strength reaches 609 MPa at 600? and 416 MPa at 700?.