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本文利用透射电子显微镜研究了18Ni(350)马氏体时效钢中的析出相,利用三个低指数晶带的电子衍射一致地鉴别出材料经510℃×3h时效后析出相为Ni_3Mo,Ni_3Ti及弥散的逆转变奥氏体。试样在受1900 MPa应力,室温连续恒载2万小时及120℃连续恒载1万小时后,原有析出相束发生转变,但析出相及逆转变奥氏体数量略有增加,尺寸略微变大,且发现在120℃温度环境下析出相变化速率比室温时变化速率大。从微观组织角度说明了经室温2万小时恒载及120℃恒载1万小时后,材料性能不会发生明显变化。 另外,本文在时效工艺改进方面做了初步研究。发现在现行的510℃×3h时效工艺基础上延长时效时间到8h,此时强度基本不下降,而韧性得到了较大改善。若从提高时效温度方面着手改进时效工艺,那么当温度不超过540℃时效3h,组织结构保证不发生明显变化。
In this paper, the transmission electron microscopy of 18Ni (350) martensitic steel precipitation phase, the use of three low-index crystal band electron diffraction identified the material after 510 ℃ × 3h aging precipitates Ni_3Mo, Ni_3Ti and Dispersion of reverse transformation austenite. After the sample was subjected to 1900 MPa stress, continuous continuous load at room temperature for 20,000 hours and continuous load at 120 ℃ for 10,000 hours, the original precipitated phase beam changed, but the amount of precipitated phase and reversed transformed austenite slightly increased Become larger, and found that the rate of change of the precipitated phase at a temperature of 120 ° C is larger than that at room temperature. From the microscopic point of view shows that after 20,000 hours at room temperature and 120 ℃ constant load 10000 hours, the material properties will not change significantly. In addition, this article made a preliminary study on the aging process improvement. Found in the current 510 ℃ × 3h aging process based on the extension of the aging time to 8h, then the basic strength does not decline, while the toughness has been greatly improved. If we improve the aging process to improve the aging process, then when the temperature does not exceed 540 ℃ aging 3h, organizational structure does not guarantee significant changes.