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Ni-15Cr-6W-3Mo-2Al-2Ti变形高温合金的室温抗张强度、塑性和冲击性能,随着合金中Si含量的变化呈现马鞍型的变化,即在0.4—0.6%Si范围内出现一个低塑性、低拉伸强度和低冲击韧性区。造成这种现象的本质原因是由于Si含量变化改变了晶界碳化物沉淀析出顺序、析出类型、析出量和析出形态。该合金晶界碳化物析出可分为四个阶段:第一阶段,<0.1%Si时,只有单一的M_(23)C_6析出;第二阶段,>0.1%Si以后,除M_(23)C_6外,M_6C开始析出,一直到0.4%Si时增加2缓慢;第三阶段,0.4—0.6%Si时,M_6C大量析出逐渐取代M_(23)C_6;第四阶段,>0.6%Si以后,M_6C量占绝对优势,但增加幅度比第三阶段小得多。从晶界形态来看,第一、二、四阶段皆属不连续的链状形式,只有第三阶段晶界呈现连续膜状。因此,造成性能下降的原因不是因为析出M_6C,而是它的形态,当它以颗粒状分布在晶界上时是一个很好的强化相。第三阶段的不正常析出是性能下降的本质因素。本研究结果打破了只要镍基合金中MO+1/2>W>6%(重量百分比)就形成M_6C的经验判据,“Si”才是该合金碳化物沉淀析出过程的控制因素。本文还对比了冶炼工艺差别对碳化物析出过程的影响。
Room temperature tensile strength, ductility and impact properties of Ni-15Cr-6W-3Mo-2Al-2Ti superalloy changed saddle-like with the change of Si content in the alloy, ie, a range of 0.4-0.6% Si Low plasticity, low tensile strength and low impact toughness zone. The nature of this phenomenon is due to changes in the Si content changes in the grain boundary carbide precipitation precipitation order, type of precipitation, precipitation and precipitation patterns. In the first stage, only a single M_ (23) C_6 precipitates at <0.1% Si, and after the second stage,> 0.1% Si, except M_ (23) C_6 M_6C precipitates gradually and increases slowly until 0.4% Si. In the third stage, when M_6C is 0.4-0.6% Si, a large amount of M_6C precipitates and gradually displaces M_ (23) C_6. In the fourth stage, the amount of M_6C The absolute advantage, but the increase is much smaller than the third stage. From the grain boundary morphology point of view, the first, second and fourth stages are discontinuous chain form, only the third phase grain boundaries showed a continuous film. Therefore, the reason for the decrease in performance is not due to the precipitation of M_6C, but its morphology, which is a good strengthening phase when it is distributed on the grain boundaries in granular form. The third phase of the abnormal precipitation is an essential factor in performance degradation. The results of this study break the empirical criteria that M_6C is formed as long as MO + 1/2> W> 6% (weight percent) in the nickel-base alloy. “Si” is the controlling factor for precipitation of this alloy carbide. The paper also compared the impact of smelting process on carbide precipitation process.