Effect of cooling rate on quenching precipitation behavior of 7050 aluminum alloy
The quenching precipitation behavior of 7050 aluminum alloy was studied by high-throughput experiment based on end-quenching,combined with scanning electron microscopy(SEM),electron backscattering diffraction(EBSD),transmission electron microscopy(TEM),high-resolution transmission electron microscopy(HRTEM)and scanning transmission electron microscopy(STEM).The results show that,with the decrease of cooling rate,the electrical conductivity increases,and the types and nucleation locations of quenching precipitates increase.The position order of favorable nucleation precipitation is high angle grain boundary,low angle grain boundary(subgrain boundary),recrystallization grain(Al3Zr particles),dislocation and subgrain(Al3Zr particles).The precipitation sequence of the quenching precipitated phase is η phase,S phase,T phase and Y phase.With the decrease of cooling rate,η phase precipitates in high angle grain boundaries,low angle grain boundaries,recrystallization(Al3Zr particles)and part of subgrains successively.When the cooling rate rate is lower than 630℃/min,the S phase precipitates in subgrains(boundaries),and the T phase precipitates in recrystallized grains(Al3Zr particles)and subgrains(boundaries)with high dislocation density.When the cooling rate is lower than 164℃/min,Y phase precipitates at the dislocation of subgrains,η phase and T phase also precipitate inside subgrains.
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