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1.
对Nb521铌合金进行了电子束焊工艺试验研究,优化了工艺参数,分析了焊缝表面成形及焊接接头组织、常温和高温力学性能。结果表明:Nb521具有良好的电子束焊接性能,焊缝常温拉伸强度、屈服强度均能达到母材的95%以上,延伸率达到母材的86.7%,在1 600℃以下焊缝性能良好。  相似文献   
2.
Equilibrium swelling and rheological tests were adopted to systematically investigate the effects of softener type and dosage on the crosslink densities. The results turned out that the chemical crosslink density could be distinguished from the physical crosslink density by comparing the results of equilibrium swelling and rheological tests. The liquid butadiene (LB) as a softener leads to the greatest reduction in crosslink density, followed by polyethylene wax (PW) and paraffinic oil (PO). The tensile strength decreases with increasing PO content while shows peak values with increase of LB and PW contents. The dependencies of chemical crosslink density on the aging time under 150°C are quite different for the three softeners, which can be expected from the double crosslinking networks consisting of small softener and large main crosslinking networks. Further investigation has been performed to correlate the tensile strength with chemical crosslink density of ethylene propylene diene monomer elastomer vulcanizates. Three different linear relationships can be obtained for the softeners independent of the aging time. It can now be expected from this study that the role of some new softeners in rubber compounds is not only confined to plasticization but also forms crosslinking networks in the peroxide-cured rubbers.  相似文献   
3.
研究了不同Sn含量流变铸造AZ91合金的组织演化、拉伸行为及磨损性能。结果表明:Sn的合金化改变了Al在镁基体中的固溶度,并且显著细化了微观组织。加入0.8%(质量分数,下同)的Sn后,合金平均晶粒尺寸从105.0 μm降至42.1 μm。高熔点的金属间化合物为析出相提供了异质形核点,这些弥散析出的第二相在流变凝固过程中有效地细化了镁基体。弥散分布的第二相抑制了枝晶组织生长,从而进一步提升了合金的力学性能。随着Sn含量的增加,合金磨损率显著降低,磨粒磨损逐渐消失。3.0%Sn合金化的流变铸造AZ91合金具有最高的抗拉伸强度以及最好的耐磨损性能。  相似文献   
4.
使用Berkovich压头,采用恒载荷法对氧化镓的(100)及(010)晶面进行纳米压痕试验,通过数据拟合获得氧化镓晶体的蠕变应力指数。单晶氧化镓(100)晶面的蠕变应力指数范围在15.5~27.8,(010)晶面的蠕变应力指数范围在46.1~63.4。纳米压痕法能够有效测量氧化镓的蠕变变形量;氧化镓的2个晶面均呈现了初始蠕变和稳态蠕变2个阶段,其中,(100)晶面具有较明显的初始蠕变阶段和稳态蠕变阶段,但是(010)晶面的初始蠕变阶段不明显;保载载荷与氧化镓的蠕变位移、等效压痕应力呈正相关,对蠕变应力指数没有明显影响;氧化镓不同晶面的蠕变应力指数差异很大,(010)晶面较(100)晶面具有更大的蠕变应力指数,具有更强的抗蠕变性能,更适合精密机械加工。  相似文献   
5.
In this study, a kind of Ni-based superalloy specially designed for additive manufacturing (AM) was investigated. Thermo-Calc simulation and differential scanning calorimetry (DSC) analysis were used to determine phases and their transformation temperature. Experimental specimens were prepared by laser metal deposition (LMD) and traditional casting method. Microstructure, phase constitution and mechanical properties of the alloy were characterized by scanning electron microscopy (SEM), transmission scanning electron microscopy (TEM), X-ray diffraction (XRD) and tensile tests. The results show that this alloy contains two basic phases, γ/γ', in addition to these phases, at least two secondary phases may be present, such as MC carbides and Laves phases. Furthermore, the as-deposited alloy has finer dendrite, its mean primary dendrite arm space (PDAS) is about 30-45 μm, and the average size of γ' particles is 100-150 nm. However, the dendrite size of the as-cast alloy is much larger and its PDAS is 300-500 μm with secondary and even third dendrite arms. Correspondingly, the alloy displays different tensile behavior with different processing methods, and the as-deposited specimen shows better ultimate tensile stress (1,085.7±51.7 MPa), yield stress (697±19.5 MPa) and elongation (25.8%±2.2%) than that of the as-cast specimen. The differences in mechanical properties of the alloy are due to the different morphology and size of dendrites, γ', and Laves phase, and the segregation of elements, etc. Such important information would be helpful for alloy application as well as new alloy development.  相似文献   
6.
付中原 《轧钢》2021,38(5):105-108
针对普阳钢铁有限公司生产的6 mm厚钛微合金化S355JR薄规格钢板出现室温冲击不合的问题,对其化学成分、组织性能及生产工艺进行了分析。结果表明,连铸二冷强冷细化了TiN颗粒,使加热时更多的有效Ti溶解并于轧后析出,导致铁素体硬化是钢板常温冲击不合的原因。为此,在不便改变连铸工艺的前提下,调整了S355JR钢的化学成分,严格控制C、Ti含量,并将Mn质量分数由1.2%降至1.0%,有效地改善了6 mm厚S355JR钢板的常温冲击性能,提高了产品合格率。  相似文献   
7.
A new technique for preparing semisolid slurry, namely, distributary-confluence runner (DCR), was combined with die-casting (DC) to conduct rheological die-casting (R-DC) of A356 alloy. The mechanism of DCR for semisolid slurry preparation was determined via numerical simulations and experiments. The microstructure and mechanical properties of A356 alloys prepared via DC and R-DC were studied. High-quality slurry containing numerous primary α-Al (α1-Al) with an average size of 49 μm and a shape factor of 0.81 could be prepared via DCR. Simulation results indicated that the unique flow state and physical field changes during slurry preparation were conducive to accelerating the uniformity of melt temperature and composition fields, nucleation exfoliation, and spherical growth. Compared with the alloy prepared via DC, the tensile strength, yield strength, and elongation of A356 alloy prepared via R-DC increased by 19%, 15%, and 107%, respectively.  相似文献   
8.

The 2024 aluminum alloy was prepared with different ultrasonic processes. Effects of ultrasonic treatment parameters including ultrasonic power, treatment time, treatment temperature, and frequency resonance, as well as C2Cl6 degasser on degassing of the 2024 aluminum alloy were investigated. Results indicate that increasing ultrasonic power at the same ultrasonic treatment time can improve the degassing effect. The optimum degassing efficiency can be obtained under the resonant ultrasound condition. With the combination of 1% C2Cl6 addition and 150 W ultrasonic treatment for 40 s, the hydrogen content of the alloy is decreased by 52.9%. At the same time, the tensile strength and elongation are increased by 28.3% and 92.3%, respectively, and the yield strength is slightly increased by 6.7%. The degassing mechanism is also discussed.

  相似文献   
9.
超高性能混凝土(Ultra-High Performance Concrete, UHPC)抗拉强度对抗扭承载力的贡献不可忽略,其构件抗扭承载力计算公式不同于常规混凝土。为检验该公式的可靠度水平,该文基于试验结果和公开文献中的相关数据,得到了UHPC抗拉强度及抗扭承载力模型不定性统计参数。在综合考虑荷载组合、箍筋配筋率、UHPC抗拉强度和钢筋强度等关键参数的基础上,运用Monte Carlo方法对3240种组合下UHPC梁抗扭承载力状态进行了可靠度分析,考查了各关键参数对可靠指标的影响并进行了敏感性分析。结果表明:按现行UHPC规范计算配筋UHPC梁抗扭承载力,其可靠度水平满足要求且可靠指标远高于目标指标;UHPC抗拉强度等级越高且材料分项系数取值越大,配筋率对可靠指标的影响越显著;其抗拉强度对可靠指标影响较显著,钢筋强度对可靠指标的影响可忽略。为充分利用UHPC抗拉强度,基于敏感性分析结果,结合目标可靠指标,校准了不同等级UHPC抗拉强度材料分项系数(强度等级UT05、UT07和UT10的材料分项系数分别为1.25、1.17和1.11)。最后,给出了不同等级抗拉强度建议设计值,可分别取3.45MPa、5.67MPa和9.01MPa。  相似文献   
10.
To investigate the evaluation method of hydrogen compatibility of A286 superalloy in high pressure hydrogen gas, SSRT tests of hydrogen-charged specimens were conducted at ambient temperature at various strain rates. The relative reduction in area (RRA), one of the ductility parameters, was determined. The hydrogen content in the hydrogen-charged specimen was the same as the equilibrium hydrogen content on the specimen surface at 150 °C in 70 MPa hydrogen gas. The strain rate dependence of RRA was smaller than that of RRA obtained in 70 MPa hydrogen gas at 150 °C. All the hydrogen-charged specimens showed slip-plane fractures in the grains in their cores. However, the specimens in 70 MPa hydrogen gas at 150 °C showed fracture surfaces morphology ranging from dimples to quasi-cleavages and intergranular fractures with decreasing strain rate. These dissimilarities are expected to arise from differences in the hydrogen concentration behaviors of the specimens during the deformation process.  相似文献   
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