共查询到19条相似文献,搜索用时 234 毫秒
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热轧态中锰TRIP钢首先经650 ℃退火2 h,随后在550 ℃进行等温时效热处理,采用场发射扫描电镜(FE-SEM)研究该钢中P的偏聚和时效析出行为的变化情况。结果表明,中锰TRIP钢中P在晶界的偏聚是一种非平衡偏聚现象,临界时间约为50 h,与理论计算结果48 h较为吻合。在局部偏聚区域内,C与P存在共偏聚的关系,即P偏聚量高的地方,C含量也高。而合金元素Nb具有抑制P偏聚的效果,在20~70 h时效时间内,可以相对降低6.57%~19.5%的最大P偏聚量。根据电子背散射衍射(EBSD)菊池线分析,P偏聚量低于2.28at%时,P为固溶状态,高于2.28at.%时,P为析出状态。 相似文献
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业已证实,淬火硼钢中硼向奥氏体晶界的偏聚,是在冷却过程中发生的一种非平衡的晶界偏聚。本文通过解变温扩散方程,导出了非平衡晶界偏聚的理论公式,建立了晶界贫硼区宽度与淬火加热温度、冷却速度以及非平衡晶界偏聚扩散激活能与扩散常数之间的关系,理论预言与实验结果较好地吻合。 根据实验结果和理论分析,提出这种非平衡晶界偏聚的机制,是在冷却过程中,过饱和空位或双空位带着硼原子向晶界(空位阱)迁移的结果。 基于这种非平衡晶界偏聚的新概念,可以较完满地说明影响硼钢淬透性的众多复杂因素。 相似文献
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硼向奥氏体晶界的非平衡偏聚 总被引:5,自引:0,他引:5
采用高分辨率的径迹显微照相技术,研究了淬火硼钢中硼向奥氏体晶界偏聚的规律,定量地测定出跨过奥氏体晶界的硼的成分剖面图以及非平衡晶界偏聚的特征参量(晶界贫硼区宽度、晶界富集程度和富集带宽度)。试验表明,这种偏聚具有如下特征: 在偏聚晶界的两侧存在有一定宽度的贫硼区,晶界偏聚的硼是在冷却过程中由该区富集而来;这种偏聚对冷却速度很敏感,急速冷却可以抑制这种偏聚。冷却速度降低,晶界偏聚由连续的偏聚带,逐步发展为不连续的聚集直至明显地析出硼相,贫硼区宽度与冷却速度的平方根成反比;它的温度关系与晶界平衡偏聚预言相反,随淬火温度升高,晶界偏聚程度与贫硼区宽度增加。通过试验,论证了淬火钢中硼向奥氏体晶界的偏聚,是在冷却过程中发生的一种非平衡的晶界偏聚现象。 相似文献
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采用高分辨率的径迹显微照相技术,研究了淬火硼钢中硼向奥氏体晶界偏聚的规律,定量地测定出跨过奥氏体晶界的硼的成分剖面图以及非平衡晶界偏聚的特征参量(晶界贫硼区宽度、晶界富集程度和富集带宽度)。试验表明,这种偏聚具有如下特征: 在偏聚晶界的两侧存在有一定宽度的贫硼区,晶界偏聚的硼是在冷却过程中由该区富集而来;这种偏聚对冷却速度很敏感,急速冷却可以抑制这种偏聚。冷却速度降低,晶界偏聚由连续的偏聚带,逐步发展为不连续的聚集直至明显地析出硼相,贫硼区宽度与冷却速度的平方根成反比;它的温度关系与晶界平衡偏聚预言相反,随淬火温度升高,晶界偏聚程度与贫硼区宽度增加。 通过试验,论证了淬火钢中硼向奥氏体晶界的偏聚,是在冷却过程中发生的一种非平衡的晶界偏聚现象。 相似文献
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用PTA法研究了Fe-30%Nj合金中硼在晶界的偏聚行为.实验表明,在550—1200℃保温后,用不同方式冷却的试样中存在有平衡与非平衡两类硼偏聚,其形成机制各不相同,而且试验条件的影响亦不同.保温时形成的平衡偏聚在低温淬火试样中起主要作用.在高温加热后,用通常冷速冷却时,晶界偏聚主要来源于冷却过程中产生的非平衡偏聚.实际试样中观察到的硼偏聚是这两类偏聚的叠加,主要偏聚方式的转折温度区受冷却速度影响,在中等冷速下,这个转折温度在650—750℃之间。 相似文献
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LIQing-fen LILi LIUEr-bao CUIXiu-fang LIUDong CHENHong-bin 《材料热处理学报》2004,25(5):263-266
The non-equilibrium grain-boundary segregation of phosphorus in step cooling process in an industrial steel,12CrlMoV, is studied based on the effective-time-method and compared with that in isothermal holding process. The non-equilibrium grain-boundary segregation concentration of phosphorus was measured with Auger Electron Spectroscopy (AES) and calculated based on the kinetic equations of non-equilibrium grain-boundary segregation. Results show that the calculated result is in good accordance with the experimental observation. 相似文献
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喷射成形1.8C-1.6Al超高碳钢快速凝固组织研究 总被引:2,自引:0,他引:2
铸造1.8C-1.6Al超高碳钢(UHCS)由于冷速较低,晶粒粗大,珠光体片间距也较大,品界形成了粗大的碳化物网络,同时合金元素产生偏析,品内生成了大块的合金渗碳体,使得它在室温下为脆性,机加工性能极差。喷射成形1.8C—1.6Al超高碳钢则利用喷射成形工艺冷却速度大的特点细化了晶粒,减小了珠光体的片间距,提高了硬度与强度,同时降低了元素偏析程度。同时发现:在铸态1.8C-1.6Al超高碳钢中和在喷射成形1.8C-1.6Al超高碳钢中Al在晶内的分布情况正好相反,由反偏析转变为正偏析。 相似文献
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Zijian Yu Xi Xu Baotian Du Kang Shi Ke Liu Shubo Li Xiuzhu Han Tao Xiao Wenbo Du 《金属学报(英文版)》2022,35(4):596
In this study, the Mg-4Y-1Gd-1Nd-xCa-1Zn-0.3Zr (x = 0 and 0.4 wt%) cast alloys with low rare earth concentration were prepared in different routes of heat treatments, and their microstructures and mechanical properties were investigated. The Mg-4Y-1Gd-1Nd-1Zn-0.4Ca-0.3Zr cast alloy with ultimate tensile strength (UTS) of 264 ± 7.8 MPa, tensile yield strength (TYS) of 153 ± 1.2 MPa and elongation to failure (EL) of 17.2 ± 1.2% was successfully developed by appropriate heat treatment. The improved mechanical performance was attributed to the combined strengthening effects of fine grains, Mg24RE5, $\beta ^{\prime}$, $\beta _{1}$, $\gamma ^{\prime}$ and LPSO phases. In the heat treatment process, cooling method of T4 treatment affected the microstructure, which consequently determined the mechanical properties air cooling, rather than water cooling, gave rise to the formation of $\gamma ^{\prime}$ phase in the alloy without Ca addition. However, Ca addition facilitated the formation of $\gamma ^{\prime}$ phase, and the $\gamma ^{\prime}$ phase precipitated in the alloy after T4 treatment either by water cooling or by air cooling, but the air cooling increased the number density of $\gamma ^{\prime}$ phase in comparison to the water cooling. Although the $\gamma ^{\prime}$ phase strengthened the studied alloys, the formation of $\gamma ^{\prime}$ phase inhibited the precipitatition of $\beta ^{\prime}$ and $\beta _{1}$ phases in the following T6 treatment, and consequently reduced the strengthening effect of $\beta ^{\prime}$ and $\beta _{1}$ phases. The results showed that the mechanical performance of the studied alloys was largely determined by the precipitation of $\gamma ^{\prime}$ phase, which was regulated by the Ca addition and the cooling method of T4 treatment. 相似文献
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J.Z.Tan 《金属学报(英文版)》2004,17(2):139-146
Based on the theory of grain boundary segregation,a kinetics model of temper embrittlement caused by long-term service for hot-wall hydrofining reactors was studied.The kinetics model was applied to phosphorus (P) segregation in 2.25Cr-1Mo steel used for a hot-wall hydrofining reactor,and the kinetics of grain boundary segregation of impurity P in the steel exposed to the process environment of the hydrofining reactor was calculated on the basis of the model.The Auger electron spectroscopy test was performed in order to determine the grain boundary concentration of P.The experimental result is agreement with the theoretical calculated data. The results show that the kinetics equation is reasonable for predicting the levels of grain boundary segregation of impurity P in 2.25Cr-1Mo steel used for hot-wall hydrofining reactors. 相似文献
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J.Z. Tan College of Mechanical Power Engineering Nanjing University of Technology Nanjing China 《金属学报(英文版)》2004,17(2)
Based on the theory of grain boundary segregation, a kinetics model of temper em-brittlement caused by long-term service for hot-wall hydrofining reactors was studied.The kinetics model was applied to phosphorus (P) segregation in 2.25Cr-1Mo steelused for a hot-wall hydrofining reactor, and the kinetics of grain boundary segrea-tion of impurity P in the steel exposed to the process environment of the hydrofiningreactor was calculated on the basis of the model. The Auger electron spectroscopytest was performed in order to determine the grain boundary concentration of P. Theexperimental result is agreement with the theoretical calculated data. The results showthat the kinetics equation is reasonable for predicting the levels of grain boundarysegregation of impurity P in 2.25Cr-1Mo steel used for hot-wall hydrofining reactors. 相似文献
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