長時時效后Super304H奧氏體熱強鋼中析出相的強化效應Strengthening effect of precipitate phase in Super304H austenitic heat-resistant steel after long-term aging

利用透射電子顯微鏡(TEM)研究Super304H奧氏體熱強鋼在650 ℃下不同時間(10~10000 h)時效過程中3種析出相的析出行為，并對其強化機理進行分析；同時，利用三維原子探針(3DAP)研究Super304H不銹鋼在650 ℃時效1 h后富Cu相的早期析出行為。并詳細分析富Cu相共格應變的強化機制。結果表明：細小彌散的富Cu相均勻且高度穩(wěn)定地分布在奧氏體基體上，當650 ℃時效時間達到10000 h，球形的富Cu相依然保持在納米級別，直徑約為32 nm。在時效過程中，富Cu相與奧氏體基體始終保持完全共格的關系。Super304H不銹鋼顯微硬度的顯著提高是由于細小彌散的富Cu相起到共格應變強化的作用，晶內較大尺寸的MX相也能夠通過釘扎位錯起到一定的強化作用；晶界上呈鏈狀分布的M₂₃C₆相亦具有輔助強化作用。

The precipitation behavior of three precipitate phases in Super304H austenitic heat-resistant steel during long time aging (10-10000 h) at 650 ℃ was investigated by transmission electron microscopy (TEM), and the relevant strengthening mechanism was analyzed. Three dimensional atom probe (3DAP) was used to study the early stage of precipitation behavior of Cu-rich phase of Super304H aged at 650 ℃ for 1 h after solution treatment at high temperature. The coherency strain strengthening mechanism of Cu-rich phase has been investigated in detail. The results show that the dispersed fine Cu-rich precipitates exhibit spherical morphology and keep highly stable in austenite matrix, which have the size of about 32 nm in diameter, even after aging at 650 ℃ for 10000 h. The coherent relationship between Cu-rich phase and matrix is preserved during the whole aging process. Due to the coherency strain strengthening effect of Cu-rich phase, the microhardness of Super304H steel increases significantly; simultaneously, the MX phase can also pin the dislocations to induce the additional strengthening effect. Moreover, the chain-like M₂₃C₆ phase precipitated at grain boundaries can also contribute to the strengthening effect for Super304H steel.

全文下載：http://pan.baidu.com/s/1sjOI9UP