Abstract：Wire arc additive manufacturing (WAAM) is a novel and important method for forming high-performance HSLA steel components. In order to reveal the microstructural evolution behavior of HSLA steel during WAAM,the temperature field,thermal cycle,heat affected zone partition and its microstructure transformation of component during deposition were investigated. The results showed that in WAAM process,the deposited metal of HSLA steel consisted of solidification zone (SZ) and heat affected zone,and the latter could be divided into coarse austenitic-grain zone (CAZ),normalizing zone (NZ) and tempering zone (TZ). Under the action of thermal cycle,SZ successively turned into CAZ,NZ,and finally became TZ. Meanwhile,Residual ferrite nuclei,high-density dislocations near inclusions,ferrite sympathetic nucleation,grain boundaries pinning by second-phase particles,and continuous dynamic recrystallization all facilitated the microstructure refinement,making coarse columnar grains,grain boundary ferrites,ferrite slide plates,a small amount of acicular ferrites and pearlites evolved into fine equiaxed ferrites and pearlites,beneficial for improving strength,toughness and inhibiting mechanical anisotropy. The vertical,horizontal tensile strength of WAAMed component were 519.6,520.8 MPa respectively,and impact energy at -20 ℃ was 124.7,122.1 J respectively.
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2021, Vol. 56 
