N18锆合金沉淀相分布特征的研究

主要通过定量金相法对7种加工状态的N18锆合金第二相颗粒(SPPs)进行研究,通过统计分析计算得到第二相大小、体积分数、分布规律等结果。7种加工样品分别为:锻造开坯态、热轧态、热轧退火态、冷轧态、冷轧退火态、终轧态、终轧退火态;同时还讨论第二相在加工过程中的长大因素和控制方法以及在随后退火过程中第二相与晶界的相互作用。     

冷轧道次加工率对锆合金板材性能的影响

研究了锆板在相同变形量下冷轧道次加工率对最终成品板材组织、性能及尺寸精度的影响。结果表明:冷轧锆合金板材显微组织为纤维状,随轧制道次加工率的增加,纤维组织越来越细。经过580℃/120 min退火后,锆合金板材纤维组织转化为等轴状晶粒;随冷轧道次加工率的增加,再结晶组织晶粒呈细化趋势,含Nb、Fe和Cr元素的Zr-Fe-Nb第二相粒子越易在晶界析出,有利于板材的力学性能的提升,而不利于耐腐蚀性能的提升。     

冷轧形变量和退火温度对Cu-44%Ni 合金的微观组织及织构演变的影响

研究了冷轧变形量和退火温度对Cu-44%Ni合金中立方织构的形成及微观组织演变的影响。结果表明增大变形量和提高退火温度均有利于立方织构的形成,而且在变形量大于90%和退火温度高于900 ℃的条件下,可以得到非常强的立方织构。另一方面,随着变形量的增加,退火孪晶(Σ3晶界)和大角度晶界降低;但是在等温退火中,随着退火温度的增加,Σ3晶界和大角度晶界先迅速的增加,然后逐渐减少。冷轧变形量99%的Cu-44%Ni 合金在1100 ℃高温退火1h后可以获得了99.8%的立方织构,并且大角度晶界和退火孪晶界分别为2.5%和1.3%。     

冷轧形变量和退火温度对Cu-44%Ni合金的微观组织及织构演变的影响（英文）

研究了冷轧变形量和退火温度对Cu-44%Ni合金中立方织构的形成及微观组织演变的影响。结果表明,增大变形量和提高退火温度均有利于立方织构的形成,而且在变形量大于90%和退火温度高于900℃的条件下,可以得到非常强的立方织构。另一方面,随着变形量的增加,退火孪晶(Σ3晶界)和大角度晶界降低;但在等温退火中,随着退火温度的增加,Σ3晶界和大角度晶界先迅速的增加,然后逐渐减少。冷轧变形量99%的Cu-44%Ni合金在1100℃高温退火1 h后可以获得了99.8%的立方织构,并且大角度晶界和退火孪晶界分别为2.5%和1.3%。     

铁素体区轧制Ti和Ti+Nb超低碳BH钢实验研究

进行了Ti和Ti+Nb超低碳BH钢的铁素体区热轧以及冷轧、退火实验。结果表明,两种超低碳BH钢铁素体区热轧后纵截面晶粒均明显拉长成纤维状,接近冷轧态组织,只有少量等轴晶粒。经后续冷轧和高温盐浴连续退火后均发生了再结晶,形成了等轴铁素体晶粒。两种超低碳BH钢的热轧、冷轧和退火织构均在{111}<121>和{111}<112>处具有峰值,Ti-ULC-BH钢退火板纤维织构组分在{111}<112>处强度最大为16,Ti+Nb-ULC-BH钢退火板纤维织构组分在{111}<121>处强度最大为11,这与反映深冲性能的r值高低相一致。EBSD微观取向分析结果表明,两种超低碳BH钢退火板的铁素体晶粒间微观取向主要是以大角度晶界(>15°)为主,晶界取向差均主要分布在25°～60°;Ti-ULC-BH钢退火板织构中<111>织构占到了75.7%;Ti+Nb-ULC-BH钢退火板织构中<111>织构占60.5%。     

去应力退火对薄壁钛管表面残余应力的影响

在不同退火温度和保温时间下对冷轧TA18薄壁管进行真空去应力退火处理,通过X射线衍射分析了无缝管表面轴向残余应力在退火前后的变化规律。结果表明:冷轧TA18管外表面轴向保留了较大的残余压应力;经真空去应力退火处理后,残余应力有了大幅下降。其应力松弛随退火温度的提高,效果变佳;随保温时间的延长,残余应力先快速下降后趋于稳定。在正交实验范围内,经450℃保温2 h并随炉冷却后,管材外表面轴向上的残余应力已基本消除,且仍为压应力状态。经Zener-Wert-Avrami公式计算后表明,管材退火时的应力松弛受回复过程控制,从金相组织观察中进一步证实了在实验范围内没有出现再结晶。去应力退火阶段,TA18管织构基本不变,仍保留着冷轧时沿TD方向倾斜的双峰基面织构状态,进一步降低了织构对残余应力测定所带来的影响。     

退火对Zr-Sn-Nb-Fe-Si新锆合金薄板带材组织性能的影响

针对锆合金带材冲压成形时易破裂的问题，研究了再结晶退火对Zr-Sn-Nb-Fe-Si新锆合金薄板带材组织性能的影响。结果表明，随着退火温度的升高，新锆合金薄板带材的最大减薄率减小;第二相颗粒弥散分布于新锆合金晶粒内部及晶界，其形貌基本为球状，尺寸较大第二相为Zr(NbFe)₂，较小为β-Nb;新锆合金带材具有■两类织构，其中■取向的晶粒与形变基体的取向差为30°/<0001>。随着再结晶退火温度的升高，第二相颗粒产生的钉扎作用不能阻碍锆合金重合点阵∑13晶界的快速迁移，导致■取向的再结晶晶粒择优长大，吞并形变基体，小角度晶界占比降低，大角度晶界占比升高，造成再结晶织构由■转变为■，改善晶粒变形的均匀性，提高带材冲压时塑性变形的均匀程度，因此再结晶退火有利于改善新锆合金薄板带材的冲压成形性能。     

Zr-Sn-Nb-Fe锆合金板材轧制及热处理过程中的晶粒组织演变

采用光学显微镜(OM)和扫描电镜(SEM)分析研究了Zr-Sn-Nb-Fe锆合金板材在热轧及退火→中间冷轧及退火→成品轧制及退火的全工艺流程中晶粒组织的演变规律。结果表明,热轧后合金组织沿轧制方向呈带状分布,晶粒粗大并破碎变形;中间冷轧和成品轧制后合金为沿轧制方向带状分布的细小形变组织,合金组织明显细化;中间退火和成品退火后合金中晶粒再结晶程度较热轧退火时明显提高,晶粒取向差逐渐向正态分布变化,晶粒组织也逐渐均匀化和细化,最终获得细小、均匀分布的完全再结晶晶粒组织,晶粒度12级。     

CoCrFeMnNi高熵合金冷轧及退火后的晶界特征

采用电子背散射衍射（EBSD）技术研究了冷轧变形（90%）CoCrFeMnNi高熵合金在800 °C退火再结晶过程中的晶界特征分布（GBCD）。结果表明,退火0.08 h后,合金发生初次再结晶,组织中形成高达56.92%的低å重合位置点阵（CSL）晶界,其中å3晶界和å9+å27晶界的比例分别为53.04%和2.12%,且大部分低åCSL晶界处于大角度晶界网络上,打破了大角度晶界网络连通性,其GBCD得到优化。延长退火时间（0.08～10 h）,合金晶粒异常长大至二次再结晶完成,强a-{110}织构所占体积分数从49.53%增大至66.65%;低åCSL晶界的总比例和å3晶界的比例均下降,å9+å27晶界比例先上升后下降,大角度晶界网络连通性逐渐趋于完整。与此同时,该合金的维氏硬度与其再结晶晶粒尺寸满足Hall-Petch关系。     

激光强化法提高锆管轧制用孔型寿命研究进展

激光冲击强化是一种新型金属材料强化技术,能够通过在部件近表面引入残余压应力的方式显著提高金属材料的抗疲劳性能。文章研究了激光强化技术在锆合金冷轧用孔型试块和成品精磨孔型受力区域的应用,并用X射线衍射法测量试块冲击表面层产生的残余压应力大小及深度。结果表明:采用激光强化后的试块残余压应力随着深度的增加而降低,同时还发现在试块约1 mm深度处,其残余压应力数值与淬火后的残余压应力数值基本保持一个水平;采用激光强化后的孔型轧制后的管材尺寸、表面质量、直线度均满足要求、超声和涡流检测结果均合格。退火后管材的室温拉伸、氢化物取向因子以及收缩系数(CSR)检测结果全部满足产品技术条件要求,且与平时生产批次的管材性能基本相当;采用激光强化孔型的方法可有效的提高孔型的使用寿命。     

Microstructure,texture and grain boundaries character distribution evolution of ferritic stainless steel during rolling process

In order to better understand the texture, microstructure and grain boundaries character distribution evolution of ferritic stainless steel, the texture, microstructure and grain boundaries character distribution of ferritic stainless steel (hot rolled sheet, cold rolled sheet and annealing sheet) with 11 wt%Cr content were studied using X-ray diffraction and electron back scattered diffraction technique. The texture of the hot and cold rolled sheets has a through-thickness texture gradient. In the center layer of the hot and cold rolling sheet, α-fiber texture was observed which was attributed to ideal plane strain deformation. Close to the surface a Gross orientation was detected which was attributed to shear deformation. During annealing, the γ-fiber was formed attributed to recrystallization process. The microstructure of the hot and cold rolled sheets was non-homogeneous through the sheet thickness, while, the microstructure of annealing sheets was homogeneous through the sheet thickness. Grain boundaries character distribution results show that there are many low angle grain boundaries in hot and cold rolled sheets and many high angle grain boundaries and coincidence site lattice after annealing. The above results indicated that the changes in texture are closely related to the grain boundaries type.     

Effects of cold working path on strain concentration, grain boundary microstructure and stress corrosion cracking in Alloy 600

Grain boundary microstructure, strain distribution and stress corrosion cracking (SCC) in one dimensional (1D), two dimensional (2D) and three dimensional (3D) cold worked Alloy 600 were investigated. The cold working decreased the annealing twins and increased low angle boundaries. 2D cold working caused lower strain concentration at grain boundaries than 1D and 3D cold working. The intergranular SCC (IGSCC) susceptibility was the highest in 1D cold worked alloy while lowest in 2D cold worked alloy. The IGSCC susceptibility displayed a strong correlation with the grain boundary strain concentration and the grain boundary microstructure.     

Effects of cold working degrees on grain boundary characters and strain concentration at grain boundaries in Alloy 600

Strain concentration at grain boundaries and grain boundary microstructure in cold worked Alloy 600 were characterized. Excluding the annealing twin boundaries, the base and 20% cold worked alloys exhibited higher random grain boundary fractions than the 8% and 40% cold worked alloys. An increased low angle boundaries and decreased annealing twins were observed with deformation. The 20% cold worked alloy displayed a maximum strain concentration at grain boundaries. The stress corrosion cracking growth in cold worked Alloy 600 in high temperature water showed a strong correlation with the strain concentration at grain boundaries.     

CERIUM-INDUCED GRAIN BOUNDARY STRENGTHENING OF Ni_3Al ALLOYS

1.IntroductionSincel979,agreatdealofresearch{1-5]hasbeendirectedtowardshowtoimprovetheductilityofintermetalliccompoundNi3AIbecauseofitsspecialproperties.ThisaluminidewithanL12orderedcrystalstructurebelowtheperitectictemperature(1395"C)[']hasgoodhigh-temperaturepropertiesl2l5]andcorrosion.esista.ce[7].However,themainprob1emfOrNisAlasahigh-temperaturestrllcturalmaterialisitslowductilitvandbrittlenesswhenitisinthepolycrystallinefo.m[8].Thisbrittlenesseffectivelyhindersitsfabricationintousefll…     

Incoloy825合金热变形过程中的本构模型和特殊晶界演变

采用原始JC模型、修正JC模型和应变补偿Arrhenius方程，描述了Incoloy825合金在不同温度（950～1150 °C）和应变速率（1~10 s^-1）下经摩擦和温升修正后的应力-应变曲线。结果表明，修正后曲线具有明显的动态再结晶特征。与原始JC模型和修正的JC模型相比，Arrhenius应变补偿模型更适合于描述Incoloy825合金热变形过程中的应力应变行为。温度和应变速率对特殊晶界的演变有显著影响。特殊晶界长度分数与动态再结晶分数呈正相关。与冷轧后退火处理工艺相比，热变形工艺调控的特殊晶界长度分数较低，热变形工艺不适合用来调整特殊晶界分数，其原因是在热变形过程中动态再结晶的大量形核造成较小的晶粒团簇。     

Zr-Sn-Nb新型锆合金板材加工过程中不均匀组织与织构演变

利用XRD,SEM-ECC,TEM和EBSD技术,研究了Zr-Sn-Nb系新型锆合金板材加工过程的微观组织及织构演变.结果表明,β相淬火得到的随机织构经热轧后形成沿横向倾斜的基面织构,随后的加工过程均保留该织构;热轧及两次冷轧后的基面织构都为〈1010〉方向平行于轧向(〈1010〉//RD),而退火后转变为〈1210〉方向平行于轧向(〈1210〉//RD).淬火形成的网状魏氏组织经热轧转变为不均匀形变组织,两次冷轧使组织的不均匀性更显著,最终退火得到完全再结晶组织;轧制形成的难变形晶粒多为晶粒C轴平行于轧板法向(C//ND)的取向;最终退火板材的大晶粒多为〈1210〉//RD的基面织构,小晶粒则以〈1010〉//RD为主.结合锆合金的变形及再结晶机制对轧制时产生的不均匀组织及再结晶过程的织构转变进行了分析.     

Zr-sn-Nb新型锆合金板材加工过程中不均匀组织与织构演变

利用XRD,SEM-ECC,TEM和EBSD技术,研究了Zr-Sn-Nb系新型锆合金板材加工过程的微观组织及织构演变.结果表明,β相淬火得到的随机织构经热轧后形成沿横向倾斜的基面织构,随后的加工过程均保留该织构;热轧及两次冷轧后的基面织构都为(1010)方向平行于轧向((1010)∥RD),而退火后转变为(1210)方向平行于轧向((1210)∥RD).淬火形成的网状魏氏组织经热轧转变为不均匀形变组织,两次冷轧使组织的不均匀性更显著,最终退火得到完全再结晶组织;轧制形成的难变形晶粒多为晶粒C轴平行于轧板法向(C∥ND)的取向;最终退火板材的大晶粒多为(1210)∥RD的基面织构,小晶粒则以(1010)∥RD为主.结合锆合金的变形及再结晶机制对轧制时产生的不均匀组织及再结晶过程的织构转变进行了分析.     

Application of Grain Boundary Engineering to Improve Intergranular Corrosion Resistance in a Fe–Cr–Mn–Mo–N High-Nitrogen and Nickel-Free Austenitic Stainless Steel

Optimization of grain boundary engineering(GBE) process is explored in a Fe–20Cr–19Mn–2Mo–0.82N high-nitrogen and nickel-free austenitic stainless steel, and its intergranular corrosion(IGC) property after GBE treatment is experimentally evaluated. The proportion of low Σ coincidence site lattice(CSL) boundaries reaches 79.4% in the sample processed with 5% cold rolling and annealing at 1423 K for 72 h; there is an increase of 32.1% compared with the solution-treated sample. After grain boundary character distribution optimization, IGC performance is noticeably improved. Only Σ3 boundaries in the special boundaries are resistant to IGC under the experimental condition. The size of grain cluster enlarges with increasing fraction of low ΣCSL boundaries, and the amount of Σ3 boundaries interrupting the random boundary network increases during growth of the clusters, which is the essential reason for the improvement of IGC resistance.