镍对Fe-Cu-Ni合金中铜析出行为的影响

 利用透射电子显微镜(TEM)对Fe-Cu和Fe-Cu-Ni合金中铜颗粒的析出形貌及成分进行观察。同时根据Cahn-Hilliard非经典形核理论和Modified Langer Schwartz模型对合金中沉淀的析出过程进行模拟计算。扫描透射电镜(STEM)试验结果表明,镍元素在沉淀核心处浓度很低,而在颗粒-基体界面处存在富集现象,添加元素镍可降低沉淀颗粒的形核功,促进沉淀析出和长大粗化。该试验结果与理论模型预测结果一致。     

合金元素对Mg-Gd系合金组织及时效硬化行为的影响

利用扫描背散射电子像(SEM-BSE)和透射电子显微像(TEM)观察,研究了MgGd3,MgGd3Nd0.3和MgGd3Nd0.3Zn0.33种合金的铸态、固溶态显微组织结构,同时利用显微硬度仪研究了3种固溶态合金在200℃下的时效硬化行为。结果表明:3种合金经过520℃固溶处理后,均能使富稀土的初生相有效地固溶,形成可时效强化的过饱和固溶体合金。其200"C时效后峰值硬度的实现都源于基体中微细β’析出相的形成和弥散分布,而随后硬度随时效时间的变化趋势却有所不同。添加稀土元素Nd,有助于加快合金的时效响应。Nd和Gd共存时的析出强化使MgGd3Nd0.3合金在0～120 h时效阶段具有高于其他两种合金的硬度。过渡族元素Zn的添加,虽然使MgGd3Nd0.3Zn0.3的硬度相比MgGd3Nd0.3略低,但能够在长时间时效中保持硬度不明显下降。基于透射电镜观察,着重分析对比了在200"C 85 h时效条件下的3种合金的显微结构特征,讨论了添加Nd和Zn元素对析出相尺寸、形貌和分布特征的影响。     

Cd元素对Al-4Cu合金析出过程的影响

通过显微硬度、拉伸性能测试、透射电镜及高分辨检测等分析手段研究Cd在Al-4.0Cu合金中的微合金化作用。结果表明:100℃时效时,由于Cd元素的空位结合能较高,Cd元素的添加可抑制GP区的形成,减缓时效响应速率,使得含Cd合金的峰值硬度和强度降低;在150℃时效时,含Cd合金中析出的Cd′粒子为θ′相提供了非均匀形核位置,促进了θ′相的大量析出,使合金峰值抗拉强度大幅度提高。Cd′粒子与θ′相和铝基体的位向关系为(110)_(Cd)‖(001)_(Al)‖(001)_θ。     

微量La对于残余元素Cu的析出影响

利用光学显微镜、扫描电镜及能谱观察含铜Q235钢中夹杂物分布及元素析出行为,观察到铜可以在Mn S夹杂物上异质形核,与垂体型Mn S夹杂物相比,铜更易在球形Mn S上析出,其析出相为富铜相而非硫化亚铜或者硫化铜。添加60×10-6La可使Mn S夹杂物弥散分布,且细化夹杂物,减少15μm以上较大尺寸夹杂物,显著增加5μm以下夹杂物。La在本实验钢中优先形成氧化物而非硫化物,SEM观察结果与Factsage软件计算结果吻合。SEM观察发现添加痕量镧可以使含铜析出相的分布更分散,TEM观察发现Cu、La之间存在复合析出相,经热力学计算得出最易出现的析出相为Cu37La3相。     

Mg含量对Al-4.8Cu-xMg-1.0Ag合金组织与力学性能的影响

通过对显微硬度与疲劳裂纹扩展速率的测试以及扫描电镜和透射电镜观察等实验手段,研究Mg含量对Al-Cu-Mg-Ag合金时效析出过程与力学性能的影响.结果表明:随着Mg含量的上升,合金的时效响应速率加快,而硬度则先上升后下降,在Cu/Mg质量比接近6时,合金硬度最高;Mg含量的提高可为主要析出相Ω相提供更多的形核位置,使得...     

铜对19Cr-1.6Mo铁素体不锈钢力学性能和腐蚀行为的影响

 采用力学性能测试、时效处理、电化学测试、显微硬度以及TEM微观分析等分析手段,研究了19Cr-1.6Mo和19Cr-1.6Mo-0.5Cu两种超纯铁素体不锈钢的力学性能和在3.5%NaCl腐蚀介质中的耐腐蚀性能。试验结果表明：合金元素铜的添加,提高了试验用钢的强度,同时降低了Δr值;随着时效时间的增加,铜析出相尺寸在不断的增加且均匀分布,基体的显微硬度由HV148增加到HV162;合金元素铜的添加降低了试验用钢在氯离子溶液下的耐点蚀能力,尤其是随着时效时间的增加,点蚀电位值由390mV降低到290mV,耐点蚀能力呈明显的下降趋势。     

含Li的Al-Zn-Mg-Cu合金时效析出过程

采用小角度X射线散射技术和硬度测试,对含0.65wt.%Li的Al-Zn-Mg-Cu合金定量研究了在120℃单级时效过程中析出相尺寸和体积分数的演变规律,探讨了Li元素在该时效前中期对析出相析出行为的影响,分析了时效过程中显微硬度与析出相之间的关系。结果表明,随着时效时间的延长,析出相半径分成了高速、中速和低速三个增长阶段,而体积分数则分成了快速增加和渐缓增加两个阶段;Li在时效前中期作用显著,不仅促进了合金固溶-淬火后GP(I)区的迅速形成,还缩短了析出相体积分数达到最大值的时间;显微硬度与析出相半径和体积分数在时效前中期均呈现出良好的正相关关系,析出相类型转变过程的缓慢导致合金硬度维持峰值时间较长。     

铝锂合金高强化成分设计

总结了铝锂合金高强化成分设计的发展过程,综合了课题组主合金元素Cu、Li含量,微合金元素Mg、Ag、Zn及稀土(RE)元素等对Al-Cu-Li系铝锂合金力学性能及析出相影响规律的研究结果。铝锂合金中Cu/Li比例较低时有利于时效时δ′相(Al3Li)析出,但不利于强度的提高;而Cu/Li比增加则有利于时效时T1相(Al2CuLi)及θ′相(Al2Cu)析出,从而有效提高铝锂合金的强度。微合金化元素Mg能有效促进T1相形核析出,加速铝锂合金时效响应速度,提高T1相析出密度,进而提高铝锂合金强度;Mg+Ag及Mg+Zn复合添加能进一步促进T1相析出,提高T1相分布密度;Mg+Ag+Zn三元复合微合金化具有最好的促进T1相形核析出及提高铝锂合金强度的效果。在高Cu/Li比铝锂合金中添加微量RE元素将导致时效时含Cu强化相T1相及θ′相减少,降低铝锂合金强度。铝锂合金高强化成分设计的思路应是在Mg、Mg+Ag、Mg+Zn或Mg+Ag+Zn微合金化基础上,提高Cu+Li总量并保持较高Cu/Li比。     

含铜钢的时效硬化

研究了时效温度和保温时间对时效硬化型超低碳含铜钢的显微组织和硬度的影响。对时效处理后的含铜钢进行了显微硬度测试及组织观察,分析了时效工艺与硬度、显微组织及时效析出粒子之间的对应关系。用电子显微镜观察到了峰值时效试样及过时效试样中析出的细小ε-Cu粒子以及时效初期形成的过渡结构,证实了铜在钢中的时效硬化作用。     

Cu、Ni在含铜时效钢表面氧化层中的富集

研究了Cu、Ni在含铜时效钢表面氧化层中的富集规律.研究发现,无Ni含铜钢在1 100～1 200 ℃会形成液态富铜相,并向奥氏体晶界渗透,成为表面裂纹源.而在1 000 ℃和1 300 ℃均不形成液态富铜相.Ni加入到含铜钢中,改变了氧化层中富铜相的结构,促进了Ni-Cu富集相以颗粒状保留在氧化层内,抑制了Cu向基体中的渗透,从而改善了含铜时效钢的热脆性问题.     

Effect of Cu Content on Aging Precipitation Behaviors of Cu-Rich Phase in Fe-Cr-Ni Alloy

The precipitation characteristics and effect on strengthening mechanism of Cu-rich phases during short-time and long-time aging for Super 304H steels with different Cu content were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that the size of Cu-rich phase particles increases, the interspace of Cu-rich phase particles decreases and the density of Cu-rich phases increases with the increase of Cu content during short-time aging (approximately 800 h) at 650 ℃ for Super 304H steels. During long-time aging (more than 2000 h) at 650 ℃, Cu-rich phase precipitates sufficiently and the strengthening effect of Cu-rich phase is preferable in Super 304H steel containing Cu of 4%. The strengthening effect of Cu-rich phase in Super 304H steels containing Cu of 2.2% or 5% is weaker than that with Cu of 4% during long-time aging (more than 2000 h).     

析出相对塑料模具钢LJ338ESR腐蚀性能的影响

利用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、硬度仪、电化学分析仪,研究了塑料模具钢LJ338ESR经不同固溶和时效温度处理后的组织、硬度和腐蚀性能变化。结果表明,固溶温度为1 000～1 090℃时,随固溶温度上升,合金元素及NbC更多地溶入基体中,使得组织的均匀性增加,水冷后马氏体量增加,导致硬度上升,而耐蚀性能增强。时效温度为300～450℃时,随温度上升,细小富Cu相形核并与基体形成共格bcc结构,共格应变能逐渐增大,导致硬度上升,而耐蚀性能减弱;当时效温度为450～600℃时,随温度上升,富Cu相逐渐由共格过渡到非共格态,共格应变能降低,导致硬度下降,而耐蚀性能增强。600℃形成的逆变奥氏体进一步提高了耐蚀性。     

Effect of Cu contents on aging precipitation behaviors of Cu-rich phase in Fe-Cr-Ni alloy

 Abstract: The precipitation characteristics and effect on strengthening mechanism of Cu-rich phases during short-time and long-time aging in the Super 304H steels with different Cu contents were investigated by the use of X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The results show that the size of Cu-rich phase particles increases, the distance of Cu-rich phase particles decreases and the density of Cu-rich phases increases with the increase of Cu content during short-time aging (~ 800 h) at 650℃ in the Super 304H steels. During long-time aging (>2000 h) at 650℃, Cu-rich phases precipitate sufficiently and the strengthening effect of Cu-rich phases is preferable in the Super 304H steel with 4% Cu. The strengthening effect of Cu-rich phases in the Super 304H steels with 2.2 % Cu or 5 % Cu is weaker than that with 4% Cu during long-time aging (>2000 h).     

回火温度对Ti-V-Mo复合微合金钢组织及硬度的影响

摘要：利用OM、SEM、TEM、EBSD和维氏硬度计等手段研究了回火温度对Ti-V-Mo复合微合金钢组织转变及硬度的影响，探讨了 (Ti,V,Mo)C在不同回火温度下的析出规律及其对硬度的作用机制。结果表明，在450～600℃回火时，随着回火温度的升高，硬度呈直线上升趋势，在600℃回火时硬度具有最大值450HV。随着回火温度的升高，试验钢马氏体板条块宽度由7.3μm增大至9.9μm，600℃回火时析出相粒子的平均尺寸为5nm，10nm以下的(Ti,V,Mo)C粒子可高达90%，理论计算沉淀强化增量导致硬度上升90.7HV，远高于基体软化造成的硬度损失，因而析出强化是影响Ti-V-Mo复合微合金钢硬度的主要因素。在600～650℃回火，大小角度晶界分布比例基本相同，马氏体板条块的平均尺寸变化不大，但是析出相的平均尺寸由5nm提高到5.6nm，尺寸小于5nm的(Ti,V,Mo)C粒子所占比例逐渐下降，导致硬度下降。     

Decomposition of Fe-Ni martensite: Implications for the low-temperature (≤500 °C) Fe-Ni phase diagram

The low-temperature (<500 °C) decomposition of Fe-Ni martensite was studied by aging martensitic Fe-Ni alloys at temperatures between 300 °C and 450 °C and by measuring the composition of the matrix and precipitate phases using the analytical electron microscope (AEM). For aging treatments between 300 °C and 450 °C, lath martensite in 15 and 25 wt pct Ni alloys decomposed with γ [face-centered cubic (fcc)] precipitates forming intergranularly, and plate martensite in 30 wt pct Ni alloys decomposed with γ (fcc) precipitates forming intragranularly. The habit plane for the intragranular precipitates is {111}_fcc parallel to one of the {110}_bcc planes in the martensite. The compositions of the γ intergranular and intragranular precipitates lie between 48 and 58 wt pct Ni and generally increase in Ni content with decreasing aging temperature. Diffusion gradients are observed in the matrix α [body-centered cubic (bcc)] with decreasing Ni contents close to the martensite grain boundaries and matrix/precipitate boundaries. The Ni composition of the matrix α phase in decomposed martensite is significantly higher than the equilibrium value of 4 to 5 wt pct Ni, suggesting that precipitate growth in Fe-Ni martensite is partially interface reaction controlled at low temperatures (<500 °C). The results of the experimental studies modify the γ/α + γ phase boundary in the present low-temperature Fe-Ni phase diagram and establish the eutectoid reaction in the temperature range between 400 °C and 450 °C. Formerly Research Assistant, Department of Materials Science and Engineering, Lehigh University     

Plasma Nitriding Behavior of Fe-C-M (M = Al, Cr, Mn, Si) Ternary Martensitic Steels

Change in surface hardness and nitrides precipitated in Fe-0.6C binary and Fe-0.6 mass pct C-1 mass pct M (M = Al, Cr, Mn, Si) ternary martensitic alloys during plasma nitriding were investigated. Surface hardness was hardly increased in the Fe-0.6C binary alloy and slightly increased in Fe-0.6C-1Mn and Fe-0.6C-1Si alloys. On the other hand, it was largely increased in Fe-0.6C-1Al and Fe-0.6C-1Cr alloys. In all the Fe-0.6C-1M alloys except for the Si-added alloy, fine platelet alloy nitrides precipitated inside martensite laths. In the Fe-0.6C-1Si alloy, Si-enriched film was observed mainly at a grain boundary and an interface between cementite and matrix. Crystal structure of nitrides observed in the martensitic alloys was similar to those in Fe-M binary ferritic alloys reported previously. However, there was a difference in hardening behavior between ferrite and martensite due to a high density of dislocations acting as a nucleation site of the nitrides and partitioning of an alloying element between martensite and cementite changing the driving force of precipitation of the nitrides.     

钒钢的技术进展

 介绍了V在钢中的应用及V微合金化技术最新进展。通过含V钢中增N,利用廉价的N元素,优化了V的析出,显著提高沉淀强化效果,达到节约V用量及降低成本的目的。V-N钢中V（C,N）在奥氏体中析出,起到晶内铁素体核心作用,明显细化铁素体晶粒。V在贝氏体中的析出起到明显强化作用,提高了贝氏体的强度。V-N微合金化技术在高强度钢筋、高强度型钢、非调质钢、薄板坯连铸连轧高强度带钢等产品中获得广泛应用。     

中温时效对022Cr21Ni2Mn5N钢析出行为及冲击韧性的影响

采用Thermo-Calc软件对022Cr21Ni2Mn5N双相不锈钢的近平衡态析出相进行了计算分析。采用光学显微镜、透射电镜、物理化学相分析方法对经中温时效处理后试验钢第二相的析出温度、种类、数量和位置进行了观察和研究,并分析了第二相析出行为对钢的冲击韧性的影响机理。结果表明:022Cr21Ni2Mn5N双相不锈钢在600~700℃中温时效时的析出相主要为六方结构的Cr_2N相和面心立方结构的M_(23)C_6相,未见σ相析出。中温时效时,受制于该钢较低的C含量,M_(23)C_6相析出位置仅局限于相界、晶界处。该钢较高的N含量促进钢中Cr_2N相析出,并在相界、晶界和铁素体晶内均有发现。时效初期M_(23)C_6和Cr_2N均具有较高的析出速度,时效时间继续延长析出量增长放缓。时效处理时间和温度直接影响钢的冲击性能:时效初期第二相的快速析出导致钢的冲击功急剧下降;时效足够长时间,第二相析出量达到饱和,钢的冲击功趋于稳定值;并且600℃长时时效时,钢的冲击功值达到最小。     

Possibilities of strengthening of Fe-Cu alloys upon isothermal aging

The kinetic theory of diffusion phase transformations is used to calculate the time it takes for the ɛ phase to form in Fe-Cu alloys at various temperatures. The fine structure and hardness of alloys containing from 0.6 to 5.5 at % Cu and aged in the martensite state are studied. The calculated and experimental data are in good agreement. The cooling rate of copper-bearing alloys that provides the maximum hardness upon the precipitation of ɛ-phase particles of a given size is estimated.