高温时效对Super304H钢奥氏体点阵常数的影响

Lattice Parameter Evolution of Super304H Steel γ Phase Aged at High Temperature

利用金相显微镜、电子探针、透射电镜和X射线衍射等多种分析手段研究了不同时效温度下新型耐热钢Super304H奥氏体点阵常数的变化规律.结果表明,Super304H钢经700～1350℃一系列温度时效后,其组织均为单一的奥氏体（γ）基体＋析出相,γ基体点阵常数a变化反映了析出相的析出与溶解的变化过程.Super304H钢供货状态下因绝大部分合金元素固溶于基体,γ基体点阵发生较大畸变a值较大,700℃时效后因M23C6和Nb（C,N）析出a值变小,至850℃时a值最小,超过850℃后因M23C6逐步溶解引起晶格膨胀,到1000～1050℃时a值接近供货条件时的a值.1150℃时因Nb（C,N）大量析出a值又变小,继续升温时因Nb（C,N）发生熟化元素重新固溶a值增大.

The effects of aging temperature on lattice parameter of novel stainless steel Super304H γ phase was investigated by the means of optical microscopy, electron probe microanalysis（EPMA）, transmission electron micros- copy（TEM）, and X-ray diffraction（XRD）. Results show that the microstructure of Super304H steel after aging at 700--1350 ℃ consists of austenite matrix and precipitated. The lattice parameter of austenite matrix shows some changing at different aging temperature, and this variation corresponded to the precipitated phases precipitated or re- dissolved. Due to the solid solution effect of alloying elements, lattice stortion of 7-matrix occurs for the as-received Super304H steel, resulting in the relatively high a value. After aging at 700 ℃, a value decreases due to the precipita- tion of M23C6 and Nb（C,N）. After aging at 850 ℃ a value reaches its minimum. Owing to the dissolution of M23C6 in the matrix, a value increases with aging temperature higher than 850 ℃. The a value of samples aged at 1000-- 1050 ℃ is close to that of as-received steel. With aging temperature higher than 1150 ℃, a value decreases due to the precipitation of Nb（C,N）. Further heating results in the increase of a value because of occurrence of ripen and dissolution of Nb（C,N）.