共查询到20条相似文献,搜索用时 65 毫秒
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研究了不同的型壳保温温度对一种铸造单晶高温合金DD98铸态组织、热处理组织和持久性能的影响。结果表明,随着上下区型壳保温温度的升高,固液界面前沿的温度梯度增大,而糊状区的宽度减小。铸态下,随着上下区型壳保温温度的升高,其一次和二次枝晶间距均减小,枝晶间和枝晶干上的γ’尺寸差别减小,并且枝晶间的γ’形状也逐渐变得规则,合金的显微偏析程度降低。热处理后,高的型壳保温温度可获得尺寸细小的γ’和较少的残留共晶。合金的持久寿命随着型壳保温温度的升高而增加,但相应的持久延伸率降低。 相似文献
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利用所设计的阶梯试样进行定向凝固试验和模拟,研究定向凝固过程型壳加热温度对单晶高温合金铸件显微组织和“雀斑”形成的影响。分析糊状区的温度场及形貌。结果表明,升高型壳加热温度,一次和二次枝晶间距减小,糊状区液相的渗透率和对流通道的宽度降低,“雀斑”形成倾向性降低,“雀斑”宽度减小,“雀斑”区域枝晶碎片减少。此外,随着型壳加热温度的升高,糊状区液相冷却速率增加,糊状区熔体的冷却时间减少,液体流动对枝晶的破碎程度得到削弱,这进一步降低单晶高温合金铸件“雀斑”形成的倾向性。 相似文献
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乐献刚 《稀有金属材料与工程》2016,45(8):2057-2063
单晶凝固过程中温度场均匀性控制对单晶制备过程特别重要。本文以国内广泛应用的第二代单晶高温合金DD6为研究对象,研究型壳中央散热对其凝固组织与持久性能的影响。结果表明,与合金中柱型壳相比,石墨中柱型壳能有效地改善单晶凝固过程中温度场的均匀性,提高温度梯度,有利于保持单晶凝固过程中热流方向的平直。因此,石墨中柱型壳有利于降低一次枝晶间距,细化γ-γ’共晶相,减少单晶生长方向与[001]方向的角度差,使单晶高温合金获得较高的持久寿命。 相似文献
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采用非自耗电弧熔炼方法经多次重熔制备了Ti45Al-6Nb-xCo合金(x=0, 0.5, 1, 2和4 at.%),研究了不同Co含量合金的组织结构和高温抗氧化性能。结果表明,增加合金中的Co含量能够细化α2+γ片层组织,促进合金中形成γ和B2相,并抑制α2相形成;合金中Co含量超过2 at.%会导致富Co相析出和组织粗化。1000℃空气中的恒温氧化结果表明,适量的Co合金化能够显著改善TiAl-Nb合金的高温抗氧化性能;Ti45Al-6Nb-1Co合金的氧化的抛物线速率常数约为1.36×10-2mg2/cm4h,较Ti45Al-Nb合金低约1个数量级;但Co含量超过2 at.%后,随Co含量增加,合金的氧化速率呈增加趋势。 相似文献
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对比研究了壳型填铁丸和普通湿砂型两种工艺条件下稀土对凸轮轴用CuCrMoNi多元低合金铸铁组织和性能的影响。研究结果表明,适量的稀土与Mn、S元素相互作用形成富含稀土、Mn、S的复合化合物作为石墨核心,有利于铸铁组织和性能的改善,砂型工艺下较佳的稀土加入量为0.02%~0.04%,而壳型填铁丸工艺下稀土的较佳加入量呈下降趋势。当稀土加入量达到并超过0.06%后,铸铁中出现D、E型石墨,并伴有初生铁素体,性能了低,特别是在壳型填铁丸工艺条件下,合金铸铁对稀土的敏感性提高,强度性能的下降幅度比普通湿砂型工艺大。 相似文献
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概括地介绍了高温合金叶片的三氧化二钴表面孕育、硅溶胶-硅酸乙酯复合型壳及真空浇注等精铸工艺,并对结果进行了简单的分析和说明。 相似文献
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采用雾化法制备了Fe_(18)Ni_(23)Co_(25)Cr_(21)Mo_8WNb_3C_2高温合金粉末,并对其物相、显微形貌和热稳定性进行了表征。在此基础上,将雾化粉末进行真空热压烧结和二次烧结,获得了奥氏体为基体、M_6C碳化物作为主要强化相的铁镍钴基高温合金。结果表明,真空热压烧结后,组织分布较均匀,抗拉强度较高,但是延伸率较低。对热压烧结块材进行二次烧结,有利于合金块材的基体和强化相组织分布更加均匀,在抗拉强度略有降低基础上较大幅度提高烧结块材延伸率。 相似文献
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研究了细晶铸造对K418B合金显微组织及力学性能的影响。结果表明,细晶铸造改善了合金中初生MC和γ′相的分布形态,并使它们的平均尺寸减小。细晶铸造K418B合金在650℃的低周疲劳寿命至少是普通铸造的4倍。 相似文献
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利用扫描电子显微镜、光学显微镜、疲劳试验机、拉伸试验机等研究了一种新型镍基粉末高温合金(WZ-A3)不同状态下的显微组织、拉伸性能、低周疲劳性能及其断口形貌。结果表明:1150℃挤压消除了合金热等静压残余的粉末原始颗粒边界(Previous Particle Boundary,PPB)。随着温度提高,热等静压+热处理(WZ-A3-HIP)和热等静压+热挤压+热处理(WZ-A3-HEX)两种状态样品拉伸强度呈现出先下降(室温到400℃)到不变(400~550℃)再下降(550~800℃)的变化规律。观察拉伸断口发现室温PPB降低了WZ-A3-HIP样品延伸率,700℃升高800℃时两种状态样品断口由穿晶-沿晶混合型转变为沿晶断裂模式为主。小应变(0.6%、0.8%)控制疲劳时,WZ-A3-HEX样品疲劳寿命值优于WZ-A3-HIP,后者裂纹源主要由夹杂物引起。大应变(1.0%、1.2%、1.4%)时,两种状态样品寿命值接近。应变1.2%时,疲劳裂纹源均为多源平台型断裂。 相似文献
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安震 《稀有金属材料与工程》2019,48(7):2297-2304
利用电子探针、场发射扫描电镜等先进检测手段分析了粉末冶金FGH96合金在不同固溶热处理条件下的组织演变和力学性能。结果表明:通过电子探针分析粉末冶金FGH96合金涡轮盘边缘部分,发现可观察到亮白色颗粒状的硼化物相,对照元素面扫描图像,可以判定硼化物相主要为富含元素W和Mo;随着固溶温度从1080℃增加至1160℃,抗拉强度和屈服强度都小幅度增加,而随着冷却速率的增加抗拉强度和屈服强度相应增加;通过不同固溶温度处理后FGH96合金的蠕变性能相当,而随着冷却速率的增加,蠕变抗力大大增加。 相似文献
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The microstructural evolution and mechanical properties of a spray-formed superalloy were studied in this paper. Based on a better understanding of the microstructural evolution of the spray-formed superalloy during solution treatment, an optimum solution treatment process was obtained, namely, at 1,140 °C for 6 h, and air cooling(AC). The effects of the ageing treatments on the mechanical properties of the post-solution-treated spray-formed superalloy were evaluated using ageing harden curves and tensile testing. The results indicated that the maximum hardness value was achieved at 850 °C for 8 h, AC. Due to co-precipitation of primary and secondary c0 precipitates during the heat treatment,the spray-formed superalloy obtained an excellent combination of yield strength(YS = 1,110 MPa), ultimate tensile strength(UTS = 1,503 MPa), ductility(elongation, EL = 21%) and excellent stress rupture properties at 650 °C(UTS = 1,209 MPa, EL = 15.8%). The heat treatment also improved the rupture life at 650 °C/950 MPa and 750 °C/539 MPa up to 140 h without rupturing. The tensile-fractured surfaces exhibit ductile transgranular failure feature. The optimum heat treatment process was determined to be 1,140 °C/6 h+850 °C/8 h+AC. 相似文献
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In this work,friction stir processing (FSP) was applied to the high-strength and high-melting-point Ni-Fe-based superal-loy (HT700) for the first time with negligible wear of the stir tool.Different rotation rates were chosen to investigate the effect of heat input on microstructure and tensile properties at different temperatures of friction stir processed Ni-Fe-based superalloy.The results showed that with increasing rotation rate,the percentage of high-angle grain boundaries and twin boundaries gradually decreased whereas the grain size initially increased and then remained almost constant;the difference in tensile properties of FSP samples with rotation rates of 500-700 rpm was small attributing to their similar grain size,but the maximum strength was achieved in the FSP sample with a rotation rate of 400 rpm and traverse speed of 50 mm/min due to its finest grain size.More importantly,we found that the yield strength of all FSP samples tensioned at 700 ℃ was enhanced clearly resulting from the reprecipitation of γ'phase.In addition,the grain refinement mechanism of HT700 alloy during FSP was proved to be continuous dynamic recrystallization and the specific refinement process was given. 相似文献
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IntroductionChromiumfrelowexpansionsuperalloysbasedonthesystemFeNiCoNbTiareatractiveforaerospaceandlandbasedgasturbine... 相似文献
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Zhen Lu Chengcai Zhang Nana Deng Haiping Zhou Ruirui Fang Kuidong Gao Yukuo Su Hongbin Zhang 《金属学报(英文版)》2022,35(10):1673-1687
The influence of selective laser melting(SLM) process parameters on the microstructure and mechanical properties of a typical Ni-based superalloy was researched. The optimum parameters of P = 170 W, V = 0.8 m/s were determined, under which the SLMed samples exhibited both the largest relative density of 99.57% and the best mechanical properties, including the microhardness(329.3 ± 3.8 HV), yield strength(726 ± 8.1 MPa), ultimate tensile strength(900 ± 5.9 MPa) and elongation((31.9 ± 0.24)%). The... 相似文献
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It is well known that solid solution-strengthened alloy 617 and γ' precipitation-strengthened alloy 263 have excellent mechanical properties and corrosion resistance at high temperatures.Hyper-supercritical power plants work at temperatures above 700 ℃,and these superalloys are considered candidate materials for steam turbines components of these power plants.In this study,gas tungsten arc weldability of these superalloys was evaluated,and the effects of postweld heat treatment(PWHT) on the microstructural characteristics and the mechanical properties of their weld metals were investigated.Scanning transmission electron microscopy,energy-dispersive spectroscopy and electron probe microanalysis were utilized for the investigation.The experimental results confirmed that these weld metals had different characteristics in microstructure and mechanical properties.PWHT resulted in the precipitation of intergranular carbides,γ' particles and an increase in tensile strength of these superalloy weld metals.Furthermore,fine γ' particles,which were not detected in the as-welded metal of alloy 263,were precipitated after PWHT and those particles were the reason for the drastic increase in tensile strength. 相似文献
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采用铜模喷铸与等温时效相结合的方法,研究了快冷K424高温合金的非平衡凝固组织及其沉淀相析出行为。结果表明,铜模喷铸合金组织发生了显著细化,二次枝晶间距相比铸态大幅降低,溶质偏析的减弱有利于抑制粗大碳化物及共晶组织形成。随铜模内径下降,枝晶形貌由无方向性等轴晶逐渐转变为择优生长的定向枝晶。经800~1000℃等温时效30min后,快冷合金的过饱和固溶体组织中开始析出γ′相。随时效温度提高,沉淀相尺寸及体积分数同时增加。900℃×30min时效后可获得大量细小均匀的球形γ′相,快冷合金的显微硬度(HV)高达478,相比原始非平衡态合金提高了13%。 相似文献