摘要
用光镜及透射电镜对 Cr5Mo/ A30 2 接头长时间时效过程中熔合区 σ相析出进行了研究。结果表明 ,σ相首先在焊缝奥氏体晶界形核长大 ,奥氏体内σ相与基体存在( 0 0 1 ) σ∥ ( 1 1 1 ) γ、[1 1 0 ]σ∥ [1 1 2 ]γ 位向关系 ,σ相的形成符合 Johnson- Meh1方程 ;增碳层σ相在长时间时效形成过程中伴随着二次碳化物的溶解 。
The σ -phase precipitation in prolonged aging Cr 5Mo/A 302 welding fusion zoon is studied with the optic microscope and the transmission electron microscopy.The result reveals that σ -phase predominates by forming nucleus and growing along the boundaries;There is an orientation relationship between σ -phase within austenitic grains and the austenitic matrix:(0 0 1) σ//(1 1 1) r [1 1 0] σ//[1 1 2] r;The forming of σ -phase fits the equation of Johnson-Mehl;The forming of σ-phase in prolonged aging joint is accompanied with dissolution of carbide and the carbon diffusion which enhances the formation of σ -phase.
