氢对Ni3Al合金中微观缺陷的影响

对二元Ｎｉ３Ａｌ和含０．５２ａｔ．％的Ｎｉ３Ａｌ合金样品进行电解充氢，并测量其ｅ＾＋寿命谱。结果可见，ｅ＾＋在合金缺陷中的寿命最初随充氢时间的增加而下降，随后达到一个最小值，接着随充氢时间的增加而增加。含０．５２ａｔ．％Ｂ的Ｎｉ３Ａｌ合金比二元Ｎｉ３Ａｌ合金的氢效应程度小，这说明加入少量的硼可提高Ｎｉ３Ａｌ合金的抗氢能力。     

混合稀土和Ce对Ni_3Al合金氧化行为和力学性能的影响

本文研究了不同含量混合 RE 和 Ce 对 Ni_3Al-B 和 Ni_3Al-B-Cr-Zr 合金在1050℃,0.1MPa 下氧化行为的影响,以及混合 RE 对 Ni_3Al-B-Cr-Zr 合金不同温度下瞬时拉伸性能的影响。结果表明,合金中加入少量的稀土元素,促进 Al_2O_3形核,加速致密氧化膜形成,提高合金的抗氧化性。混合 RE 以固溶方式进入氧化膜,细化 NiO 和 Al_2O_3晶粒,增加塑性,不易剥落。少量 Ce 加入 Ni_3Al-B-Cr-Zr 合金,有利于形成细小密集“树根状”氧化物,使氧化膜紧密粘附在基体金属表面。加入0.1%RE 使Ni_3Al-B-Cr-Zr 合金低温抗张强度升高,对塑性影响不大,但对高温强度和塑性有害。     

Unravelling Light‐Induced Degradation of Layered Perovskite Crystals and Design of Efficient Encapsulation for Improved Photostability

Layered halide perovskites have recently shown extraordinary potential for low‐cost solution‐processable optoelectronic applications because of their superior moisture stability over their 3D counterparts. However, few studies have investigated the effect of light on layered hybrid perovskites. Here, the mechanically exfoliated nanoflakes of the 2D perovskite (PEA)₂PbI₄ (PEA, 2‐phenylethylammonium) are used as a model to investigate their intrinsic photostability. The light‐induced degradation of the flakes is investigated by using in situ techniques including confocal laser scanning microscopy, wide‐field fluorescence microscopy, and atomic force microscopy. Under resonant photoexcitation, (PEA)₂PbI₄ degrades to PbI₂. It is clearly shown that this process is initiated at the crystal edges and from the surface. As a consequence, the photoluminescence of (PEA)₂PbI₄ is progressively quenched by surface traps. Importantly, the light‐induced degradation can be suppressed by encapsulation using hexagonal boron nitride (hBN) flakes and/or polycarbonates. This report sheds light on a specific mechanism of light‐induced degradation in layered perovskites and proposes a new encapsulation method to improve their photostability.     

电磁离心铸造NiAl共晶合金的显微组织和力学性能

利用电磁离心铸造(EMCC)工艺制备NiAl/Cr(Mo)共晶合金,研究了合金的显微组织和压缩性能.结果表明, 合金显微组织细小,由激冷区、共晶区和亚共晶区组成.激冷区以初生β-NiAl相为主,共晶区由β-NiAl和α-Cr(Mo)相构成,亚共晶区由初生β-NiAl和β-NiAl/α-Cr(Mo)共晶组成. EMCC NiAl共晶合金1000℃压缩行为遵从幂指数规律: ε=Aσn.合金的室温断裂方式以基体NiAl的解理断裂和NiAl/Cr(Mo)的相界面剥离为主.     

Ni3Al—Fe基合金组织与力学性能的研究

本文研究了合金化的Ni_3Al-Fe基合金高温变形后的组织及瞬时拉伸性能和700—900℃的蠕变持久性能,结果表明,合金由γ′的β相组成,其晶粒在温度低于1000℃时保持稳定;屈服强度在<600℃时也保持稳定;合金的高温塑性好,蠕变研究表明,该合金在700—900℃蠕变由位错攀移控制,其蠕变激活能为439kJ/mol,应力敏感系数为4.     

EFFECTS OF Cr AND Nb ON MICROSTRUCTURES AND MECHANICAL PROPERTIES OF Fe_3Al ALLOYS

The effects of Cr and Nb on tensile properties at room and elevated temperatures and also onthe microstructure have been investigated.An improvement in ductiliy plasicity and thecleavage strength of Fe_3AI may result from adding Cr;the improvement is more pronouncedat over 400℃.The formation of Fe_2Nb containing A1 precipitates in the Fe_3AI+Nb alloyprovide significant strengthening effect.Additions of Cr and Nb in Fe_3AI can cause a signifi-cant improvement in the yield strength at 550℃.     

NiAl／TiC纳米材料机械合金化合成机理

四种元素粉末的混合物在室温下球磨，当球磨时间达到１０７ｍｉｎ时，原位热分析监测到一个放热化学反应的发生，分析表明大量的ＮｉＡｌ和ＴｉＣ化合物反应生成，其反应合成机理属于燃烧合成反应机制，包含着两个独立的化学反应，即Ｎｉ＋Ａｌ→ＮｉＡｌ，Ｔｉ＋Ｃ→ＴｉＣ燃烧反应后，还存在少量的元素粉末进一步球磨导致ＮｉＡｌ和ＴｉＣ的逐渐生成，终产物中ＴｉＣ的晶粒尺寸约为ＮｉＡｌ晶粒尺寸的２．５倍，与传统观点相反，归     

EFFECT OF PHOSPHORUS ON SOLIDIFICATION,ELEMENT SEGREGATION AND η-PHASE PRECIPITATION IN GH 761 ALLOY

本文用金相、电子探针等方法研究了磷对ＧＨ７６１合金凝固过程、元素偏析及η相析出的影响。结果表明，随合金中磷含量升高，磷大量地偏析于枝晶间，强烈地降低合金的终凝温度，促进Ｔｉ，Ｎｉ等元素的偏析，抑制Ｍｏ，Ｂ，Ｓ，Ｓｉ等元素的偏析，磷显著地促进η相的析出，降低η相析出温度。     

EFFECT OF GRAIN BOUNDARY PRECIPITATES ON IMPACT TOUGHNESS AND NOTCH SENSITIVITY OF Fe-Ni-BASE SUPERALLOY GH135

采用不同温度进行中间热处理,以改变晶界沉淀相的类型、形态和数量。测定了室温和-196℃的冲击韧性。用扫描电镜和电子显微镜观察了冲击断口和断口萃取复型。结果表明,当晶界二次TiC沉淀很少或TiC以薄片状密集分布于晶界时,合金具有缺口敏感性;TiC或Laves相以较大而厚的片状沿晶析出,或以颗粒状分布于晶界时,合金无缺口敏感性. 晶界TiC沉淀很少或呈颗粒状分布时,合金冲击韧性高,呈穿晶韧性断裂;TiC或Laves相呈片状沿晶分布时,冲击值低,冲击试样断口表现为沿晶脆性断裂。     

Ni3Al（Z）合金室温拉伸性能及Zr韧化机制的探讨

热处理温度显著影响Ni3Al(Zr)合金的显微组织和室温力学性能。本实验采用SEM，TEM，AES等手段对轧制处理后的试样进行了研究。随着热处理温度升高，再结晶体积百分数增加，再结晶晶粒尺寸增大，室温拉伸强度降低。但室温拉伸塑性随热处理温度升高而增加，在850℃热处理时达到最大值，然后随热处理温度升高而显著降低。俄歇能谱(AES)研究表明Zr在850℃热处理时的晶界偏聚量明显高于1100℃热处理时的偏聚量，说明Zr在室温的塑化作用与其在晶界的分布有关。