Residual stress and precipitation of Mg-5Zn-3.5Sn-1Mn-0.5Ca-0.5Cu alloy with different quenching rates

The effect of the quenching rate after solution treatment on the residual stress and precipitation behavior of a high strength Mg-5 Zn-3.5 Sn-1 Mn-0.5 Ca-0.5 Cu plate is studied.The simulation results show decreasing temperature gradient in the plate with decreasing quenching rate,which leads to weakened inhomogeneous plastic deformation and decreased residual stress.No dynamic precipitation on the grain boundary happens after either cold water cooling or air cooling,however,air cooling leads to dynamic precipitation of Mg-Zn phase on Mn particles around which a low-density precipitate zone develops after aging treatment.Moreover,the fine and densely distributed Mg-Zn precipitates observed after aging treatment of the cold water cooled alloy are replaced by coarse precipitates with low density for the air cooled alloy.Both the low-density precipitate zone near Mn particles and the coarsening of precipitates are the source of the decrease in hardness and tensile properties of the air cooled alloy.The residual stress drops faster than the hardness with decreasing quenching rate,which makes it possible to lower the residual stress without sacrificing too much age-hardening ability of the alloy.

Characterization of γ′ precipitates in a nickel base superalloy quenching from aging temperature at different rates

The characteristics of γ′ precipitates in a superalloy quenched from 1050°C at different rates were investigated using field emission scanning electron microscope（FESEM）.When quenched from 1050°C, the size of primary aging γ′ precipitates has a small increase in the specimens that experienced iced-brine-quenching, oil-quenching, and air-cooling-quenching conditions and a drastic increase in the specimen that experienced a furnace-cooling-quenching condition.The cooling γ′ precipitates have unimodal distributions after quenching at the air-cooling rate and bimodal distributions after quenching at the furnace-cooling rate, but there are not these distributions in the specimens that experienced iced-brine-quenching and oil-quenching conditions.When aging at 760°C, the size of primary aging γ′ precipitates appears unaffected in the specimens that experienced iced-brine-quenching, oil-quenching, and air-cooling-quenching conditions.However, it has a drastic increase in the specimen that experienced a furnace-cooling-quenching condition, and it is interesting that the bigger cooling γ′ precipitates have a coalescence and octodendritic shape.The microhardness study indicates that the hardness has no variation in the specimens that experienced iced-brine-quenching, oil-quenching, and air-cooling-quenching conditions and has a drastic decrease in the specimens that experienced a furnace-cooling-quenching condition and obtains the minimum microhardness value 390.8 HV.

Critical cooling rate on carbide precipitation during quenching of austenitic manganese steel

Critical cooling rate to avoid carbide precipitation during quenching of austenitic manganese steel was investigated by means of optical microscopy,image analyzer and numerical analysis.An efficient heat treatment analysis program including temperature-dependent material properties was developed for the prediction of cooling rate and probability of carbide precipitation during quenching by finite difference method.Time-dependent heat transfer coefficient was adopted to achieve more precise results.Area ratio of carbide precipitation was measured by image analyzer to determine the critical point of carbide precipitation.Temperature-dependent critical cooling rate at that point was calculated by the developed numerical program.Finally,the probability of carbide precipitation on the whole area of specimen can be predicted by the proposed numerical program and the numerical result of a specimen was compared with the experimental result.

Quenching Rate for the Porous Medium Equation with a Singular Boundary Condition

We study the porous medium equation ut=(um). 0<x<∞, t>0 with a singular boundary condition (um) (0,t)=u-β(0,t). We prove finite time quenching for the solution at the boundary χ=0. We also establish the quenching rate and asymptotic behavior on the quenching point.

Measurement and Calculation of Quenching Rate Constants for PCl(b)

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CO_(2)浓度及配比对焦炭溶损特性影响

研究块焦、粉焦混合焦炭在CO_(2)气氛下的反应特性可有效提高干熄焦质量、降低溶损率,故采用自制高温焦炭反应测定装置,研究不同粒径配比及不同浓度CO_(2)条件下的碳素溶损反应,结合光学显微镜分析及Coats-Redfern法探讨了混合不同粒径干熄焦的溶损机理。结果表明,不同浓度下粉焦比例增加,粉焦溶损率为混合焦炭溶损率的0.7~0.9倍,较多CO_(2)与粉焦发生碳溶反应,导致块焦-粉焦混合焦炭溶损率随粉焦比例增加而增加。但在不同浓度下块焦和粉焦的各向同性组织含量降低而各向异性组织含量明显增加,其中,粉焦各向异性指数高于块焦,且平均增长4%,其反应活性也高于块焦,反应活化能随CO_(2)浓度、粉焦比例的增加而降低;且同一浓度下,焦炭中粉焦比例越多,碳溶反应越易进行。在低浓度下,粉焦比例对混合焦炭溶损率有显著影响,随粉焦比例增加活化能降幅最大为30%。研究结果可为进一步降低干熄焦溶损率提供理论依据。

淬火速率对不同成分铝合金组织和性能的影响

研究了淬火速率对6060和6061铝合金组织、力学性能、电导率和硬度的影响。6060和6061铝合金的淬火速率分别为393.24、519.06℃/min。试验结果表明,6061铝合金的晶粒尺寸大于6060铝合金,其屈服强度、抗拉强度和维氏硬度均高于6060铝合金,而电导率低于6060铝合金。在T4状态下6061铝合金的延伸率低于6060铝合金,在T6状态下两者的延伸率相同。淬火速率对铝合金组织和性能具有较大影响,6061铝合金的淬火敏感性高于6060铝合金。

一体化严重事故分析程序的验证与分析

针对我国国产反应堆严重事故分析程序的发展需要,西安交通大学开发了一体化严重事故分析程序(modular severe accident analysis program,MOSAP)。为了验证MOSAP程序在再淹没期间相关模型的合理性和准确性,以QUENCH-06实验为例,利用MOSAP程序对实验进行建模,并将MOSAP程序的计算结果与实验结果以及国际通用程序的计算结果进行了对比。结果表明,对于包壳轴向温度、包壳氧化层厚度和氢气产量,MOSAP程序计算结果与实验值和国际通用程序计算结果符合良好。在计算包壳轴向温度和氧化层厚度方面,MOSAP程序计算结果优于国际通用程序计算结果。文中结论对MOSAP程序堆内模块验证和整个模块的验证具有一定的参考意义。

Optimization of Quenching Process for ZTAP/ High Chromium Cast Iron Composites

In order to solve the problem of cracking of ZTAP(Zirconia toughened alumina ceramic particles)reinforced HCCI(high chromium cast iron)matrix composites,the quenching process was optimized.ZTAP reinforced HCCI matrix composites were prepared by infiltration method with gravity sand casting.The thermal expansion curves of HCCI and the composites were measured at different cooling rates by Glebble-3500.The microstructure of the HCCI matrix and the composites were characterized by X-ray diffraction,light microscopy,SEM,ESD,and EPMA.The tested mechanical properties include Rockwell hardness and impact toughness.The deformation differences of HCCI and the composite at different cooling rates were obtained according to the test results of thermal expansion coefficient curve and changes in microstructure and mechanical properties,and air cooling was the most favorable for the composites to have good hardness and not easy to crack.The cooling rate during air cooling is approximately equal to 21℃/s in this work.When the quenching process was air cooling,the impact toughness and hardness of the composites are 3.7 J/cm^(2) and 61.8 HRC,respectively,and the deformation difference between the composites and HCCI was 20μm at 300℃.

无缝钢管的组织变化对其淬透性的影响研究

采用Gleeble 3500热模拟机测定高强韧性钢种HG05调质态无缝钢管的静态CCT曲线,制定钢的临界淬火冷却速度,并取样分析HG05热成形无缝钢管的外中内层均为贝氏体和铁素体组织,铁素体组织变化较大,中间层铁素体尺寸最大,平均约为10μm;内层铁素体体积分数最多,约为12.4%。以调质态钢临界淬火冷却速度对热成形钢管外中内层进行热模拟淬火,得到未完全淬透组织。调质组织均匀,加热奥氏体形核核心少,热模拟加热后奥氏体晶粒大,临界淬火冷却速度为20℃/s,而热成形组织的临界淬火冷却速度要大。

Sensitivity of the Impact Toughness and Microstructure of 15CrNi3MoV Steel Under Different Quenching Rates

The sensitivities of the mechanical properties and microstructure of 15CrNi3MoV alloy steel under different quenching rates were investigated in the present study.After subjection to quenching with four different cooling rates(water cooling,forced air cooling,static air cooling and furnace cooling)followed by tempering,the microstructure was characterized by scanning electron microscopy(SEM),electron back-scattered diffraction(EBSD),and transmission electron microscopy(TEM);and the low-temperature(−20°C)impact toughness was evaluated.The results showed that the tempered microstructure and mechanical properties had high sensitivity to the quenching rate.With a decrease in the quenching rate,the low-temperature impact energy of tempered specimens decreased with increasing fluctuation.Correspondingly,the fracture morphology changed from completely ductile to brittle.In addition,as the quenching cooling rate decreased,the as-quenched matrix changed from a lathy to a polygonal structure with the presence of carbides and martensite-austenite(M-A)constituents,and the effective grain size increased.Tempered martensite with dispersed fine carbides was found in the tempered water cooling specimen,and tempered bainite with a polygonal structure containing large carbides and rare incomplete undecomposed M-A constituents was found in the tempered forced air cooling,static air cooling and furnace cooling specimens.The small effective grain size and fine carbides contributed to the good temperature impact toughness of the tempered water cooling specimens.

丙烯腈装置急冷塔回收率影响因素分析及提升措施

丙烯腈作为纤维、橡胶、树脂等合成中不可或缺的原料,在腈纶纤维、丙烯酰胺、丁腈橡胶、乙二腈、ABS树脂和AS树脂等生产中逐步得到了广泛应用。但是国内丙烯腈装置一般运用丙烯氨氧化法生产技术,这让丙烯腈产品回收率不足90%,而国外丙烯腈回收率普遍在98%左右,技术上的差异对企业经营效益提升与技术发展造成了不利因素。基于此本文将简述丙烯腈装置回收率现状,然后分析了丙烯腈装置回收率影响因素,最后提出了丙烯腈装置回收率提升措施。

随机环境中带迁入分枝过程的淬火收敛速率

在随机环境分枝过程(BPRE)的研究基础上,引入了带迁入分枝模型,探讨了在上临界情形下,(W_(n))在淬火分布P_(ξ)下淬火收敛速率的问题,并给出相应的证明,其中W_(n)=Z_(n)Π_(n),Z_(n)为迁入分枝过程(BPIRE),Π_(n)为规范化序列。

篦冷机系统节能改造实践应用

SFC4×6推动棒式冷却机存在故障率高、极冷效果差、热回收效率低,功耗高等问题,采用天津水泥院第四代步进式带中置辊式破碎机篦式冷却机替代改造。步进式带中置辊式破碎机篦式冷却机采用具有科恩达效应的固定斜坡篦板,水平活动篦床基于步进式原理设计,篦床列间装有气封装置和尘封装置,篦床无漏料;中置辊式破碎机可将红料和大块料破碎粒径至<25mm,二次冷却效果好。改造后,出冷却机熟料温度稳定在100℃以下,冷却机热回收效率由54%提高至78%,二次风温稳定在1150℃~1200℃,发电量提高至29~30kW·h/t,设备运转率提高,达到了预期改造目标。

7055铝合金的TTP曲线及其应用

采用分级淬火的方法测定了7055铝合金的温度-时间-性能（TTP）曲线，并结合合金实际淬火冷却曲线通过淬火因子分析方法预测了合金的硬度。结果表明，合金TTP曲线的“鼻尖”温度大约为355℃，淬火敏感温度区间为210-420℃。淬火因子分析方法预测的合金硬度值和实测值吻合较好，淬火敏感温度区间的冷却速率对合金硬度有决定性影响。根据理论计算认为，要获得最大硬度，淬火敏感温度区间的平均冷却速率需大于500℃／s。

淬火速度对7085铝合金显微组织和应力腐蚀的影响(英文)

采用力学性能测试、慢应变速率拉伸实验,结合扫描电镜和透射电镜及电化学测试等方法,研究淬火速度对7085铝合金组织和应力腐蚀性能的影响。结果表明,随着淬火速度的降低,合金晶界析出相的尺寸和间距增大,晶界析出相的Cu含量降低;合金的抗应力腐蚀性能随着淬火速度的减少先增强后减弱。晶界析出相的尺寸和分布以及Cu含量是影响合金抗应力腐蚀性能的主要因素。

淬火速率和锆含量对7055型铝合金晶间腐蚀的影响

研究淬火速率和锆含量对7055型铝合金晶间腐蚀的影响,并结合金相显微镜和透射电镜对其机理进行分析和讨论。结果表明:淬火速率和锆含量的增加都可提高合金的抗晶间腐蚀能力,当锆含量大于0.1%时,合金晶间腐蚀的淬火敏感性明显减小;微量锆的添加阻碍了再结晶,细化了晶粒;淬火速率的提高减小了晶界无沉淀析出带的宽度,因而提高了合金抗晶间腐蚀能力。

淬火速率对7085铝合金时效行为的影响

通过末端淬火实验、硬度测试、透射电子显微镜和差示扫描量热法,研究淬火速率对7085铝合金时效行为的影响。结果表明:在末端淬火过程中,距离淬火端越近,淬火速率越大,时效后的峰值硬度越高。当时效温度较低时,淬火速率越大,则空位扩散激活能越小,时效处理后的硬度达到峰值的时间越短,硬度值越大;随着时效温度的提高,不同淬火速率样品达到峰值的时间不断接近;当时效温度达到160℃时,不同淬火速率样品达到峰值的时间相同,均为10 h。TEM分析结果表明:随着淬火速率降低,淬火过程中析出的平衡相η数量和尺寸也随之增加,时效后析出的强化相η'数量减少,尺寸增加,弥散程度降低。

淬火速率对7055铝合金组织和力学性能的影响

通过常温力学性能测试和透射电镜(TEM)研究了淬火速率对7055铝合金组织和力学性能的影响.结果表明,一定时效条件下,合金的力学性能随淬火速率降低而下降.组织观察发现,淬火速率小时,合金在冷却过程中于A l3Zr粒子和晶界非均匀形核析出粗大η平衡相,降低固溶体过饱和程度,削弱时效强化效果.时效时这些粗大η平衡相继续长大并在周围形成无沉淀析出带.晶界无沉淀析出带宽度随淬火速率降低而增大.对合金力学性能下降的原因进行了分析和探讨.