Microstructural Evolution and Softening Behavior of Simulated Heat-Affected Zone in 2219 Aluminum Alloy

摘要

The effect of peak temperature(T_p)at 200,300,400,500 and 550°C on the microstructural evolution and softening behavior of the simulated heat-affected zone(HAZ)was studied in the 2219-T87 alloy by electron-backscatter diffraction,transmission electron microscopy,X-ray diffraction,micro-hardness and micro-tensile tests.The results showed that the grain size in the HAZs at 200–500°C was comparable,but the number density of the strengthening precipitates(GP zones/h^0)decreased with increasing T_p.At a T_pof 550°C,the grain size significantly decreased and the distribution of the misorientation angles corresponded to the Mac Kenzie distribution.The GP zones/h^0phase coarsened and translated into h phases at T_pvalues in the range of 200–400°C.Increasing the T_pto 500°C and above,some h^0phases translated into h phases and others dissolved into the a-Al matrix which led to an increase in the solid solution strengthening.The reduction of the number density of the GP zones/h^0was responsible for the softening behavior.