B对无序态和有序态Ni_3Fe合金环境氢脆的影响

为了阐明金属间化合物中H_2所致脆性的机理及B在抑制这类氢脆的作用,研究了B对无序态和有序态Ni_3Fe合金氢脆的影响及其预渗氧后断口沿晶深度的影响.结果表明:B能同时降低H在无序态和有序态Ni_3Fe合金中的表观扩散系数,而且不管是否添加B,H在无序态Ni_3Fe合金中的表观扩散系数始终大于H在有序态Ni_3Fe合金中的表观扩散系数.因此,不能简单地从B影响Ni_3Fe合金中H扩散来解释B能明显抑制有序态Ni_3Fe合金在H_2中的环境氢脆.     

Fe_3Al系合金环境氢脆研究SCIEI

研究了晶粒尺寸、形状、应变速率及预氧化对Ｆｅ_３Ａｌ系合金环境氢脆的影响，结果表明，细化晶粒能显著提高Ｆｅ_３Ａｌ合金在纯氧中的塑性及强度，但不能根本改善其环境氢脆敏感性；随着应变速率的提高，Ｆｅ_３Ａｌ合金在空气中的延伸率增加；Ｆｅ_３Ａｌ在空气及氢气中的脆化程度相似；预氧化能部分消除Ｆｅ_３（Ａｌ，Ｃｒ，Ｂ）合金的环境氢脆。实验结果可用表面化学反应是Ｆｅ_３Ａｌ材料环境致脆的控制步骤这一假设予以解释．     

硼含量对有序态(Fe,Co)3V合金环境氢脆的影响

通过在真空和氢气环境下的拉伸实验,研究了硼含量对有序态(Fe,Co)_3V合金力学性能和环境氢脆的影响。结果表明,当在有序态(Fe,Co)_3V合金中添加0.02%B(质量分数)时,相对于无硼合金,合金的晶粒尺寸减小了27.5%,合金在真空和氢气中的抗拉强度和延伸率均达到最大值;而当硼含量继续增加时,合金的晶粒尺寸、合金在真空和氢气中的力学性能均保持不变。无硼有序态(Fe,Co)_3V合金在氢气中呈现严重的环境氢脆,当在合金中添加0.02%B后,合金氢脆因子降低了34.4%,合金的断口形貌由完全沿晶断口转变为穿晶和沿晶的混合断口;当合金中的硼含量继续增加时,合金的氢脆因子不再降低,恒定在50%左右,即硼原子只能部分抑制有序态(Fe,Co)_3V合金在氢气中的环境氢脆。     

Ni2Cr合金室温环境氢脆的研究

对Ni2Cr合金在不同环境气氛及动态渗氢中的脆化进行了系统研究,并从能量学方面分析了影响合金脆化的因素。结果表明,Ni2Cr合金在室温空气及氢气中不存在明显的环境氢脆,动态渗氢拉伸时Ni2Cr合金存在严重的氢脆敏感性,无序和高度有序合金脆化严重,部分有序合金氢脆敏感性较小。     

Ni-Al-Mn形状记忆合金的有序化、马氏体相变和铁磁性转变

过去对形状记忆合金有序化和铁磁性转变的研究 ,主要集中于Ｆｅ Ｐｔ、Ｆｅ Ｐｄ、Ｆｅ Ｍｎ Ｓｉ和Ｆｅ Ｎｉ基马氏体合金 ,然而对于有色金属系列合金的研究极少。从实用观点和理论相稳定性观点来看 ,在Ｎｉ Ａｌ Ｍｎ合金系中发生的这些转变特性非常重要。日本东北大学的研究者们研究了Ｎｉ Ａｌ Ｍｎ合金的低温时效对其有序—无序转变、马氏体转变和磁转变的影响 ,并且阐明了这一合金系在有序化转变、马氏体相变与磁转变之间的关系。研究用的合金Ｎｉ( 12～ 2 7 5)Ａｌ ( 15～ 38)Ｍｎ(原子百分数 )三元合金 ,是由镍、铝、锰的纯金属原料…     

W, Co, Ni对时效合金强度和韧性的影响

研究了Ｗ,Ｃｏ,Ｎｉ对时效合金强度和韧性的影响。结果表明：高Ｃｏ的ＦｅＷＣｏ合金有强的时效硬化能力,但其韧性较低。以Ｎｉ取代部分Ｃｏ之后,合金的韧性得到大的提高。ＦｅＷＣｏ合金的Ｃｏ量约２３％,Ｗ,Ｍｏ总量超过１８％时,硬度增加甚少,韧性损害较大,而ＦｅＷＣｏＮｉ的Ｃｏ当量达２３％,Ｗ,Ｍｏ总量达２４％时获得最佳的强度和韧性的配合。萃取化合物的Ｘ射线衍射（ＸＲＤ）分析表明,时效合金的主要金属间化合物是Ｆｅ３Ｗ２型,还有Ｆｅ７Ｗ６和Ｆｅ２Ｗ型化合物。淬火态、退火态萃取物的化学分析表明,时效合金中,Ｗ,Ｍｏ主要存在于化合物中,而Ｃｏ,Ｎｉ主要存在于固溶体中。时效硬化主要通过Ｗ,Ｍｏ金属间化合物的析出引起。而Ｃｏ,Ｎｉ主要通过影响析出相的数量、析出物形态及分布状态来影响时效硬化。     

Si在变形Ni—Cu—Fe—Mn—Si合金中的行为

研究了热处理后前后变形Ｎｉ－Ｃｕ－Ｆｅ－Ｍｎ－Ｓｉ合金中的Ｓｉ的存在形式，在晶界及晶内的分布状态和结构，并研究了在热处理状态下，合金性能的变化，ＸＲＤ分析表明：Ｎｉ－Ｃｕ－Ｆｅ－Ｍｎ－Ｓｉ合金基体为面心方立结构，在热加工状态（Ｒ态）下，Ｎｉ－Ｃｕ－Ｆｅ－Ｍｎ－Ｓｉ合金除Ｎｉ３Ｓｉ相外，还出现了Ｎｉ３１Ｓｉ１２相。该相为立方结构。ＴＥＭ分析表明：第二相（Ｎｉ３Ｓｉ）在晶界和晶内弥散分布，少量在晶界聚     

304不锈钢氧离子溅射的同步辐射光电子能谱原位研究：Ⅰ …

利用同步辐射光电子能谱（ＳＲ－ＸＰＳ）原位研究了经３ｋｅＶＯ２＾＋溅射的ＳＵＳ３０４不锈钢中Ｆｅ、Ｎｉ、Ｃｒ合金元素与氧离子的化学反应活性差异及三种金属元素间的相互作用规律,经低能氧离子溅射后,不锈钢表面形成了一薄层氧化物膜,元素Ｃｒ和Ｎ分别以Ｃｒ２Ｏ３和ＮｉＯ形式存在;铁元素的氧化产物随氧离子溅射量的增加分别以ＦｅＯ、ＦｅＯ和Ｆｅ２Ｏ３共存、全部生成Ｆｅ２Ｏ３的形式存在,在ＳＵＳ３０４不锈钢钢中     

304不锈钢氧离子溅射的同步辐射光电子能谱原位研究Ⅰ.钢中金属元素的氧化行为

利用同步辐射光电子能谱（ＳＲ－ＸＰＳ）原位研究了经 ３ ｋｅＶ Ｏ２＋溅射的 ＳＵＳ ３０４不锈钢中 Ｆｅ、Ｎｉ、Ｃｒ合金元素与氧离子的化学反应活性差异及三种金属元素间的相互作用规律．经低能氧离子溅射后,不锈钢表面形成了一薄层氧化物膜,元素Ｃｒ和Ｎｉ分别以Ｃｒ２Ｏ３和ＮｉＯ形式存在;铁元素的氧化产物随氧离子溅射量的增加分别以ＦｅＯ、ＦｅＯ和Ｆｅ２Ｏ３。共存、全部生成Ｆｅ２Ｏ３的形式存在．在ＳＵＳ ３０４不锈钢中,铬元素与氧离子的化合能力最强,铁元素次之,镍元素的化合能力较弱．同纯金属与氧离子的化合行为比较发现：三种金属元素合金化后,铁、铬元素与氧离子的化合能力提高,而镍元素的氧化速度降低．氧化过程中铁元素与银元素间存在相互作用,只有当铁元素与氧离子反应生成Ｆｅ２Ｏ３后,镍元素才开始氧化．     

NaH2PO2与H3PO3对Ni^2＋与Fe^2＋电化学行为的影响

极谱法研究表明：ＮａＨ２ＰＯ２，Ｈ３ＰＯ３的存在能抑制Ｆｅ＾２＋的析出，并导致Ｎｉ－Ｆｅ合金电沉积中的共沉积转为正常共沉积现象。欲提高沉积层中Ｆｅ的含量，需通过提高镀液中Ｆｅ＾２＋浓度或增大Ｎｉ＾２＋的阴极极化来实现。     

The influence of atomic order on H2-induced environmental embrittlement of Ni3Fe intermetallics

The different sensitivity to H₂-induced environmental embrittlement for the ordered and disordered Ni₃Fe alloys has been investigated. The results show no environmental embrittlement in disordered Ni₃Fe in gaseous H₂ when tested at room temperature. However, the H₂-induced environmental embrittlement for the ordered Ni₃Fe becomes severer as the degree of order increases. The results of testing on simultaneous hydrogen charging show that disordered Ni₃Fe embritted as hydrogen atoms are forced into the material, implying that the embrittlement of ordered Ni₃Fe in gaseous H₂ is due to the acceleration of the kinetics of catalytic reaction to produce more atomic hydrogen. Further more, the hydrogen adsorption test of Ni₃Fe powder shows that the amount of chemically adsorbed hydrogen in the ordered state at room temperature is significantly larger than that adsorbed by the disordered materials, indicating that the more sensitive to H₂-induced embrittlement in the ordered Ni₃Fe is essentially due to accelerated catalytic reaction to produce more atomic hydrogen.     

Hydrogen embrittlement of a Ti-strengthened 250 grade maraging steel

Constant extension-rate tensile tests are performed to investigate the effects of strain rate and environmental hydrogen concentration on the tensile properties of various aged T-250 specimens. The 426 °C (800 °F) underaged specimens are very sensitive to strain rate; the 482 °C (900 °F) peak-aged specimens exhibit a reduced ductility under low strain rates; and the 593 °C (1100 °F) overaged specimens are insensitive to strain rate when tested in air. The excellent resistance to embrittlement of the overaged specimens in gaseous hydrogen could be associated with the extensive formation of reverted austenite and the incoherent Ni₃Ti precipitates. The tensile-fractured surfaces of such specimens reveal a ductile dimple fracture. However, the peak-aged specimens are susceptible to gaseous hydrogen embrittlement, and the embrittled region shows a primary fracture mode of quasi-cleavage. The least resistant to hydrogen embrittlement of the underaged specimens is characterized by a more brittle fracture appearance, that is, intergranular fracture, under a low strain rate or in the gaseous hydrogen environment.     

Effect of boron doping on the mechanical properties of ordered Ni–Mo alloys

HASTELLOY B-2 alloy was found to exhibit environmental embrittlement when tested in air and hydrogen at ambient temperature after atomic ordering introduced by a heat treatment at 700 °C for 24 h. Molybdenum in the HASTELLOY B-2 alloy was probably reactive enough to dissociate water vapor in air to generate atomic hydrogen, resulting in hydrogen embrittlement. The percentage of transgranular fracture increased as the test environment changed from hydrogen gas to moist air or water vapor, and vacuum or oxygen. With the addition of 100 wt ppm B, the environmental embrittlement was completely eliminated, with the tensile properties independent of both test environment and strain rate. The fracture mode remained the same, i.e. ductile dimpling, after B-doping when tested in different environments. The immunity of the B-doped B2 alloy to environmental sensitivity remained even after long-term heat treatment. Auger analysis does not detect any boron segregation at the grain boundaries. The mechanism of boron doping in eliminating the environmental embrittlement in the Ni–Mo alloy is apparently different from that in many L1₂-type alloys such as Ni₃Al and Ni₃Si.     

Effect of Strain Rate on Stress Corrosion Cracking of 316L Austenitic Stainless Steel in Boiling MgCl2 Environment

Stress corrosion cracking behaviors of AISI 316L austenitic stainless steel at slow strain rates in two environments of air and MgCl₂ at ambient temperature and 154 °C were investigated. The results revealed that a decrease in strain rate, during testing in boiling MgCl₂ environment, led to a rigorous deterioration of the mechanical properties of the material, causing brittleness of the steel. The results obtained from fractography indicated that the samples tested in air had typical ductile fracture surface appearances, while the fracture surfaces of the samples tested in a corrosive environment showed a combination of intergranular and transgranular fracture modes, having a brittle macroscopic appearance. The transgranular mode became predominant as strain rate decreased. The results suggested that the presence of deformation bands in front of crack tips were responsible for transgranular cracking caused by stress corrosion.     

H2-induced environmental embrittlement in ordered and disordered Ni3Fe: An electronic structure approach

The different behaviors in H₂-induced environmental embrittlement in ordered and disordered Ni₃Fe are associated with differences in their electronic structures. The experimental study on electronic structures of ordered and disordered Ni₃Fe has been carried out by electron energy-loss spectroscopy (EELS). The onset energy of Ni L_2,3 edges from ordered phase is 0.3 eV lower than that from disordered phase, while the 3d occupancy of Ni atoms in ordered phase is 0.07 electrons/atom less than that in disordered phase. Severe H₂-induced environmental embrittlement in ordered phase is attributed to rather negative dissociative adsorption energy of hydrogen at surfaces, which arises from upward shifting of the valence band center of Ni.     

Gaseous hydrogen embrittlement of T-250 laser welds

The tensile properties of laser-welded T-250 maraging steel are measured, with attention paid to the influence of strain rate and gaseous hydrogen on the fracture behavior of welded specimens. Post-weld heat treatments are performed on laser-welded specimens to obtain underaged (WU), peak-aged (WP), and overaged (WO) specimens. Hydrogen embrittlement (HE) affects the tensile fracture behavior of the welded specimens; HE changes not only the fracture mode but also the fracture location. Without the influence of hydrogen, the fracture location is at the softest region, the weld metal (WM), and the fracture appearance reveals a ductile dimple fracture. For welds sensitive to HE, the fracture is initiated at the heat-affected zone (HAZ) with coarse grain size, and the associated fracture surface exhibits intergranular and quasi-cleavage fractures that are brittle in nature. In addition, the HAZ with coarse grain size is more prone to HE, as compared to other regions in the welded specimens. The WU specimens are susceptible to HE in air under a low strain rate, while the WP specimens are only susceptible to gaseous hydrogen embrittlement (GHE). However, the WO specimens are immune to GHE and insensitive to strain rate.     

On the intergranular fracture behavior of high-temperature plastic deformation of 1420 Al-Li alloy

Compared with generic industrial a1uminumalloys, Al-Li a1loys have remarkable advantagesinc1uding low density high specific strength,and rigidity. They are widely used in manyfields, such as aviation, spaceflight, energy en-gineering, weapon industry, etc. TherefOre,every country pays much attention to them.The l420 alloy belongs to Al--Mg--Li-Zr seriesalloys [ l, 2]. lt has excellent corrosion resistanceand good weldability besides the common ad-vantages of generic Al-Li alloys. lt can be…     

Effect of atomic ordering on the hydrogen-induced environmental embrittlement of Ni4Mo intermetallics

Hydrogen induced environmental embrittlement of a Ni₄Mo alloy in different degree of ordered conditions was investigated by tensile tests in various atmosphere. The results show that the disordered Ni₄Mo alloy is not susceptible to embrittlement in hydrogen gas, but very susceptible to embrittlement in hydrogen charging. However, for the ordered Ni₄Mo alloy, there is similar deterioration in ductility when the environment changes from oxygen to hydrogen gas and simultaneous hydrogen charging. It indicates that the atomic ordering does not influence the dynamic hydrogen charging-induced environmental embrittlement, but has a considerable effect on the gaseous hydrogen-induced environmental embrittlement. In addition, hydrogen absorption and desorption of the Ni₄Mo alloy with disordered and ordered structures were also investigated using gas chromatographic analysis. The results show that the atomic ordering can promote gaseous hydrogen absorption at room temperature. This suggests that the atomic ordering accelerates the kinetics of the catalytic reaction for the dissociation of molecular hydrogen into atomic hydrogen due to the change of the outer layer electron structure and therefore exacerbates the hydrogen gas-induced environmental embrittlement.