热处理冷速对FGH97盘件显微组织和蠕变性能的影响

对FGH97粉末高温合金盘件进行热处理,采用光学显微镜、扫描电子显微镜、能谱仪和蠕变试验机研究了不同固溶冷速下合金的显微组织、蠕变性能和蠕变机制。研究表明:随固溶冷速的增加,γ′相尺寸减小,富Ti、Nb、Hf的MC型碳化物由连续析出变为颗粒状弥散析出。在750℃/450 MPa蠕变试验条件下,固溶冷速为94℃/min的样品性能明显优于43℃/min。FGH97粉末高温合金在750℃/450MPa条件下的蠕变机制为位错切割γ′相,在晶界处产生应力集中导致裂纹的萌生,裂纹沿着晶界碳化物扩展,最终导致材料的断裂。弥散颗粒状分布的碳化物能有效抑制微裂纹的贯通。     

Performance investigation of resin bonded ferro-silicon nitride-corundum refractories after creep at 1300 °C

Novel tempered resin bonded ferro-silicon nitride-corundum refractories containing 0 wt%, 15 wt% and 25 wt% ferro-silicon nitride were prepared respectively. Creep tests were performed under a load of 0.2 MPa at a temperature of 1300 °C for 50 h in air. The results showed that creep performance was significantly improved by the addition of ferro-silicon nitride. Ferro-silicon nitride-corundum containing 15 wt% ferro-silicon nitride initially presented a steady-state stage and was able to remain stable from the beginning of the holding time until 50 h of creep testing. All the specimens exhibited cold crushing strength more than 100 MPa both before and after creep testing. Phase composition and microstructure were analyzed following the creep experiments. The results showed that Si₂N₂O and O’-sialon crystals formed in situ during creep testing, in addition to the conversion of α-Si₃N₄ to β-Si₃N₄. Liquid Fe₃Si from the ferro-silicon nitride component accelerated the formation of the O’-sialon and prolonged the growth of β-Si₃N₄, which improved the creep performance significantly. Fe₃Si liquid migrated into the pores, and some Fe₃Si coexisted with residual carbon from the resin, which filled a part of pores and protected the specimens from severe oxidation.     

小冲杆蠕变试验微试样的应变分析

在假设以弹塑性薄膜变形分析所获得的试样中心挠度与非蠕变中心应变之间的关系近似等于蠕变时试样中心挠度与中心蠕变应变之间的关系的基础上 ,使用塑性薄膜伸张变形模型模拟小冲杆试样的蠕变变形过程 ,设计了以小冲杆试验实测中心挠度数据估算试样中心蠕变应变以至材料蠕变性能的方法 ,并具体推导得到了特定小冲杆试验装置和试样尺寸对应的蠕变应变工程估算方程     

转化管蠕变参量的二元回归分析

对于以温度和应力为变量的幂函数型蠕变参量,本文提出了一种二元回归分析方法,计算了ＨＫ４０转化炉管新材料的稳态蠕变速率参量和蠕变损伤速率参量的咽归系数,并搪塞了材料常数对这两个蠕变参量的影响。回归出的蠕变参量解析式与试验数据拟合得颇好。特别对于极少量的试验数据,更能显示本文方法的有效性。     

露天矿顺层蠕动边坡稳定性动态分析探讨

进行了阜新海州露天矿北帮东部一号断层区顺层蠕动边坡变形、失稳机理分析讨论。根据老化理论提出了软弱夹层的一般流变方程τ =Ao( 1 δ·tα) ·γm ( 1 σmH) ,确定由等速蠕变向加速蠕变过渡的临界应变量作为破坏时刻的破坏应变量γs,从而建立长期抗剪强度与应力作用时间变化的关系τ =Ao·γs( 1 δ·tα) Ao·γsH ( 1 δ·tα) ·σm=c σm·tgφ ,对于非稳定蠕动变形 ,等速蠕变阶段的应变速率与剪应力超过长期极限强度的程度有关 ,在此基础上探讨并建立顺层蠕动边坡的流变稳定性分析方法 ,评价蠕动边坡变形、失稳的动态演化     

Fabrication and mechanical performance of Ti2AlN prepared by FAST/SPS

Highly dense bulk Ti₂AlN with high purity was successfully fabricated at 1400 °C by Field Assisted Sintering Technology (FAST/SPS) using Ti, Al, TiN as starting powders. Aluminum content appears to play a determinant role to attain high phase purity, where the optimum content has been achieved for a starting molar composition of 1:1.02:1 for Ti, Al, and TiN, respectively. Elastic modulus and hardness were determined via micro-indentation testing at room temperature. Regarding abrasive behavior, sandblasting tests with compressed air of 2 bar were carried out. In addition, creep tests in air in the temperature range of 900−1200 °C were performed to characterize the steady state deformation behavior under constant applied stresses ranging from 20−100 MPa.     

Tensile creep behavior of SiCf/SiC ceramic matrix minicomposites

Single fiber-tow minicomposites represent the major load-bearing element of woven and laminate ceramic matrix composites (CMCs). To understand the effects of fiber type, fiber content, and matrix cracking on tensile creep in SiC_f/SiC CMCs, single-tow SiC_f/SiC minicomposites with different fiber types and contents were investigated. The minicomposites studied contained either Hi-Nicalon™ or Hi-Nicalon™ Type S SiC fibers with a boron nitride (BN) interphase and a chemical-vapor-infiltrated-silicon-carbide (CVI-SiC) matrix. Tensile creep was performed at 1200 °C in air. A bottom-up creep modeling approach was applied where creep parameters of the fibers and matrix were obtained separately at 1200 °C. Next, a theoretical model based on the rule of mixtures was derived to model the fiber and matrix creep-time-dependent stress redistribution. Fiber and matrix creep parameters, load transfer model results, and numerical modeling were used to construct a creep strain model to predict creep damage evolution of minicomposites with different fiber types and contents.     

超声波衰减系数法评估材料损伤的研究

通过试验研究得出影响超声波衰减的各种因素与衰减系数的定量关系,找出衰减系数在材料损伤过程中的变化规律,并应用于实际材料剩余寿命的评估。     

Creep oxidation behaviour and creep strength prediction for Alloy 617

Creep experimental data was obtained by a series of creep tests with different stress levels at 950 °C for Alloy 617. Oxidation behaviour was investigated by observing the microstructures of fractured specimens after the creep tests. Oxidation thickness was measured quantitatively with the creep rupture times, and the oxidation microstructures were represented by a SEM image. In addition, the long-term creep strength for Alloy 617 was predicted by using a multi-constant method with two C instead of the conventional one with a unique C in the Larson-Miller (LM) parameter. For 10⁵ h at 950 °C, the creep strength for the conventional method was 7.2 MPa, but for the multi-constant method it was reduced to 4.7 MPa. The conventional method did not thoroughly match with the creep rupture data, and revealed an overestimation for the prediction of the long-term creep strength. On the other hand, the multi-constant method revealed a good agreement with the creep rupture data, and its method was thus more accurate than the conventional one. This multi-constant analysis can be used to accurately predict the long-term creep rupture of Alloy 617.     

梨果实蠕变基本流变特性研究

应用TA-XT2i质地分析仪对梨果实进行蠕变测试,结果表明,蠕变试验条件对蠕变变形量的影响是载荷大于蠕变时间,载荷越大,蠕变时间越长,蠕变变形量越大,越容易发生损伤.