Study on the inhibition of hydrogen embrittlement of 7050 aluminum alloy in humid air by MAO coating

2020 ◽  
Vol 67 (4) ◽  
pp. 387-394
Author(s):  
S.W. Cai ◽  
Y. Zong ◽  
T.S. Hua ◽  
R.G. Song
Keyword(s):  
Hydrogen Embrittlement ◽  
Compressive Stress ◽  
Hydrogen Permeation ◽  
Fracture Morphology ◽  
Thickness Measurement ◽  
Humid Air ◽  
Content Type ◽  
Induced Stress ◽  
7050 Aluminum Alloy ◽  
Micro Arc Oxidation

Purpose This paper aims to verify the inhibition of the hydrogen permeation effect of the coating and to quantitatively and qualitatively characterize the coating-induced stress. Design/methodology/approach By means of slow strain rate tensile testing (SSRT) in humid air, thickness measurement, fracture morphology, cross-section morphology and surface morphology, hydrogen content measurements, flow stress difference method. Findings The results demonstrate that the mechanism of the inhibition of hydrogen embrittlement by the coating is mainly attributed to the repression of hydrogen permeation and the additional coating-induced compressive stress. Originality/value It is proven that the micro-arc oxidation (MAO) coating does inhibit hydrogen entry into the alloy, and the stress induced by the MAO coating is compressive stress, which can restrain the hydrogen embrittlement of the alloy. Therefore, the mechanism of the inhibition of hydrogen embrittlement is dominated by the mechanisms of both hydrogen permeation inhibition and coating-induced stress.

Surface integrity of quenched steel 1045 machined by CBN grinding wheel and SiC grinding wheel

2017 ◽  
Vol 8 (2) ◽  
pp. 179-187 ◽  
Author(s):  
Kankan Ji ◽  
Xingquan Zhang ◽  
Shubao Yang ◽  
Liping Shi ◽  
Shiyi Wang ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Surface Morphology ◽  
Compressive Stress ◽  
Surface Integrity ◽  
Grinding Wheel ◽  
Micro Hardness ◽  
Content Type ◽  
Quenched Steel ◽  
Cut Depth ◽  
Cbn Grinding Wheel

Purpose The purpose of this paper is to evaluate surface integrity of quenched steel 1045 ground drily by the brazed cubic boron nitride (CBN) grinding wheel and the black SiC wheel, respectively. Surface integrity, including surface roughness, sub-surface hardness, residual stresses and surface morphology, was investigated in detail, and the surface quality of samples ground by two grinding wheels was compared. Design/methodology/approach In the present work, surface integrity of quenched steel 1045 machined by the CBN grinding wheel and the SiC wheel was investigated systematically. All the specimens were machined with a single pass in the down-cutting mode of dry condition. Surface morphology of the ground specimen was observed by using OLYMPUS BX51M optical microscopy. Surface roughness of seven points was measured by using a surface roughness tester at a cut-off length of 1.8 mm and the measurement traces were perpendicular to the grinding direction. Sub-surface micro-hardness was measured by using HVS-1000 digital micro-hardness tester after the cross-section surface was polished. The residual stress was tested by using X-350A X-ray stress analyzer. Findings When the cut depth is increased from 0.01 to 0.07 mm, the steel surface machined by the CBN wheel remains clear grinding mark, lower roughness, higher micro-hardness and higher magnitude of compressive stress and fine microstructure, while the surface machined by the SiC grinding wheel becomes worse with increasing of cut depth. The value of micro-hardness decreases, and the surface roughness increases, and the surface compressive stress turns into tensile stress. Some micro-cracks and voids occur when the sample is processed by the SiC grinding wheel with cut depth 0.07 mm. Originality/value In this paper, the specimens of quenched steel 1045 were machined by the CBN grinding wheel and the SiC wheel with various cutting depths. The processing quality resulted from the CBN grinding wheel is better than that resulted from the SiC grinding wheel.

Dependence of hydrogen embrittlement on annealing time in medium-Mn steels

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Juanping Xu ◽  
Jinxu Li ◽  
Zheng Wang ◽  
Hao Fu ◽  
Ming Wu
Keyword(s):  
Hydrogen Embrittlement ◽  
Annealing Time ◽  
Martensite Transformation ◽  
Design Methodology ◽  
Warm Rolling ◽  
X Ray Diffraction ◽  
Electron Backscattered Diffraction ◽  
Content Type ◽  
X Ray ◽  
Two Samples

Purpose The purpose of this paper is to investigate the effect of the soft annealing time on the microstructure and hydrogen embrittlement (HE) of Fe-0.22C-11.54Mn-2.05Al steels. Design/methodology/approach Steels A and B with different morphologies were prepared by cold rolling after warm rolling, long/short softening annealing and finally annealing at 700 °C for 30 min. Uncharged and charged samples were subjected to tensile, and HE behavior was studied by electron backscattered diffraction, scanning electron microscopy and X-ray diffraction. Findings The two samples exhibited similar tensile strengths. The homogeneous equiaxed microstructure of steel B was found to be more conducive to relieve its HE sensitivity. Steel A exhibited bimodal-grained microstructures – blocky and lath. The formation of crack in the blocky grains of steel A resulted in a significant reduction in its plasticity and tensile strength. Originality/value The high HE susceptibility of steel A is mainly connected with the inhomogeneity of martensite transformation.

Additive manufacturing of elastomeric foam with cell unit design for broadening compressive stress plateau

2018 ◽  
Vol 24 (9) ◽  
pp. 1579-1585 ◽  
Author(s):  
Xiaowei Zhu ◽  
Yanqiu Chen ◽  
Yu Liu ◽  
Yongqiang Deng ◽  
Changyu Tang ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Compressive Stress ◽  
Foam Cell ◽  
Cell Structure ◽  
Performance Testing ◽  
Elastic Buckling ◽  
Stress Plateau ◽  
Content Type ◽  
Direct Ink Writing ◽  
Unit Design

Purpose The purpose of this paper is to provide additive manufacturing-based solutions for preparation of elastomeric foam with broaden compressive stress plateau. Design/methodology/approach Mechanic models are developed for obtaining designs of foam cell units with enhanced elastic buckling. An experimental approach is taken to fabricate the foams based on direct ink writing technique. Experimental and simulation data are collected to assist understanding of our proposals and solutions. Findings A simple tetragonal structured elastomeric foam is proposed and fabricated by direct ink writing, in which its cell unit is theoretically designed by repeating every four filament layers. The foam exhibits a broader stress plateau, because of the pronounced elastic buckling under compressive loading as predicted by the authors’ mechanic modeling. A two-stage stress plateaus as observed in the foam, being attributed to the dual elastic buckling of the cell units along two lateral directions of the XY plane during compression. Research limitations/implications Future work should incorporate more microscopic parameters to tune the elastomeric foam for mechanic performance testing on linear elastic deformation and densification of polymer matrix. Practical implications Additive manufacturing offers an alternative to fabricate elastomeric foam with controlled cell unit design and therefore mechanics. Our results comment on its broad space for development such superior cushioning or damping material in the fields of vibration and energy absorption. Originality/value This work has contributed to new knowledge on preparation of high performance elastomeric foam by providing a better understanding on its cell structure, being printed using direct ink writing machines.

An approach to reduce stress and defects: a hybrid process of laser cladding deposition and shot peening

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiaoyu Zhang ◽  
Dichen Li ◽  
Jiale Geng
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Laser Cladding ◽  
Shot Peening ◽  
Hybrid Process ◽  
Layer By Layer ◽  
Residual Tensile Stress ◽  
Forming Process ◽  
Content Type ◽  
Thermal Forming

Purpose Laser cladding deposition is limited in industrial application by the micro-defects and residual tensile stress for the thermal forming process, leading to lower fatigue strength compared with that of the forging. The purpose of this paper is to develop an approach to reduce stress and defects. Design/methodology/approach A hybrid process of laser cladding deposition and shot peening is presented to transform surface strengthening technology to the overall strengthening technology through layer-by-layer forming and achieve enhancement. Findings The results show that the surface stress of the sample formed by the hybrid process changed from tensile stress to compressive stress, and the surface compressive stress introduced could reach more than four times the surface tensile stress of the laser cladding sample. At the same time, internal micro-defects such as pores were reduced. The porosity of the sample formed by the hybrid process was reduced by 90.12% than that of the laser cladding sample, and the surface roughness was reduced by 43.16%. Originality/value The authors believe that the hybrid process proposed in this paper can significantly expand the potential application of laser cladding deposition by solving its limitations, promoting its efficiency and applicability in practical cases.

Influence of moisture concentration and hydrophobic material on induced stress in FCBGA package under reflow

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Elwin Heng ◽  
Mohd Zulkifly Abdullah
Keyword(s):  
Reflow Process ◽  
Test Vehicle ◽  
Moisture Concentration ◽  
Reflow Soldering ◽  
Content Type ◽  
Soldering Process ◽  
Induced Stress ◽  
Microelectronics Industry ◽  
Hydrophilic Materials ◽  
Hydrophobic Material

Purpose This paper focuses on the fluid-structure interaction (FSI) analysis of moisture induced stress for the flip chip ball grid array (FCBGA) package with hydrophobic and hydrophilic materials during the reflow soldering process. The purpose of this paper is to analyze the influence of moisture concentration and FCBGA with hydrophobic material on induced pressure and stress in the package at varies times. Design/methodology/approach The present study analyzed the warpage deformation during the reflow process via visual inspection machine (complied to Joint Electron Device Engineering Council standard) and FSI simulation by using ANSYS/FLUENT package. The direct concentration approach is used to model moisture diffusion and ANSYS is used to predict the Von-Misses stress. Models of Test Vehicle 1 (similar to Xie et al., 2009b) and Test Vehicle 2 (FCBGA package) with the combination of hydrophobic and hydrophilic materials are performed. The simulation for different moisture concentrations with reflows process time has been conducted. Findings The results from the mechanical reliability study indicate that the FSI analysis is found to be in good agreement with the published study and acceptable agreement with the experimental result. The maximum Von-Misses stress induced by the moisture significantly increased on FCBGA with hydrophobic material compared to FCBGA with a hydrophilic material. The presence of hydrophobic material that hinders the moisture desorption process. The analysis also illustrated the moisture could very possibly reside in electronic packaging and developed beyond saturated vapor into superheated vapor or compressed liquid, which exposed electronic packaging to higher stresses. Practical implications The findings provide valuable guidelines and references to engineers and packaging designers during the reflow soldering process in the microelectronics industry. Originality/value Studies on the influence of moisture concentration and hydrophobic material are still limited and studies on FCBGA package warpage under reflow process involving the effect of hydrophobic and hydrophilic materials are rarely reported. Thus, this study is important to effectively bridge the research gap and yield appropriate guidelines in the microelectronics industry.

Investigation of hydrogen diffusion behavior in 12Cr2Mo1R(H) steel by electrochemical tests and first-principles calculation

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiang Qiu ◽  
Kun Zhang ◽  
Qin Kang ◽  
Yicheng Fan ◽  
Hongyu San ◽  
...  
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Hydrogen Atom ◽  
Hydrogen Embrittlement ◽  
First Principles ◽  
Hydrogen Diffusion ◽  
First Principles Calculations ◽  
Content Type ◽  
Diffusion Behavior ◽  
Hydrogen Diffusion Coefficient

Purpose This paper aims to study the mechanism of hydrogen embrittlement in 12Cr2Mo1R(H) steel, which will help to provide valuable information for the subsequent hydrogen embrittlement research of this kind of steel, so as to optimize the processing technology and take more appropriate measures to prevent hydrogen damage. Design/methodology/approach The hydrogen diffusion coefficient of 12Cr2Mo1R(H) steel was measured by the hydrogen permeation technique of double electrolytic cells. Moreover, the influence of hydrogen traps in the material and experimental temperature on hydrogen diffusion behavior was discussed. The first-principles calculations based on density functional theory were used to study the occupancy of H atoms in the bcc-Fe cell, the diffusion path and the interaction with vacancy defects. Findings The results revealed that the logarithm of the hydrogen diffusion coefficient of the material has a linear relationship with the reciprocal of temperature and the activation energy of hydrogen atom diffusion in 12Cr2Mo1R(H) steel is 23.47 kJ/mol. H atoms stably exist in the nearly octahedral interstices in the crystal cell with vacancies. In addition, the solution of Cr/Mo alloy atom does not change the lowest energy path of H atom, but increases the diffusion activation energy of hydrogen atom, thus hindering the diffusion of hydrogen atom. Cr/Mo and vacancy have a synergistic effect on inhibiting the diffusion of H atoms in α-Fe. Originality/value This article combines experiments with first-principles calculations to explore the diffusion behavior of hydrogen in 12Cr2Mo1R(H) steel from the macroscopic and microscopic perspectives, which will help to establish a calculation model with complex defects in the future.

Effects of Microstructure on the Hydrogen Embrittlement Resistance of Ultra High Strength Martensitic Steel Sheets

2021 ◽  
Vol 1016 ◽  
pp. 1331-1336
Author(s):  
Kosuke Shibata ◽  
Takuya Hiramatsu ◽  
Atsuhiro Shiraki ◽  
Junichiro Kinugasa ◽  
Tatsuya Asai ◽  
...  
Keyword(s):  
Low Temperature ◽  
Hydrogen Embrittlement ◽  
Carbon Content ◽  
Fracture Morphology ◽  
Hydrogen Trapping ◽  
Tempered Martensite ◽  
Interstitial Carbon ◽  
Steel Sheets ◽  
Embrittlement Resistance ◽  
Hydrogen Embrittlement Resistance

In this study, the relationship between hydrogen embrittlement resistance (HER) and the microstructure of low temperature tempered martensite was investigated using steel sheets which were controlled by carbon content and tempering conditions. Focusing on transition carbides and interstitial carbon content which are peculiar microstructures to low temperature tempered martensite, microstructure was evaluated by synchrotron radiation X-ray diffraction (SR-XRD). The HER was evaluated by U-bending and fracture surface was observed after the slow strain rate test (SSRT). As the result, the HER was improved and fracture morphology was changed from intergranular to quasi-cleavage when the high carbon content and high temperature tempering were adopted. In the steels improved the HER, the increase of the volume fraction of transition carbides and the decrease of interstitial carbon content was confirmed. Hydrogen trapping by the transition carbides could explain the change of the HER and fracture morphology. These results suggested that the hydrogen trapping by the transition carbides was effective to improve the HER of the low temperature tempering martensitic steels.

How to exploit ion-induced stress relaxation to grow thick c-BN films

2002 ◽  
Vol 74 (3) ◽  
pp. 489-492 ◽  
Author(s):  
P. Ziemann ◽  
H.-G. Boyen ◽  
N. Deyneka ◽  
P. Widmayer ◽  
F. Banhart
Keyword(s):  
Stress Relaxation ◽  
Compressive Stress ◽  
Ion Irradiation ◽  
Cubic Phase ◽  
Medium Energy ◽  
High Quality ◽  
Induced Stress

A recently developed procedure is reviewed allowing thick (>1 mm), high-quality c-BN films (>80 % c-BN) to be grown. It is based on the observation that compressive stress inevitably present in such films can be released by medium-energy (some hundred keV) ion irradiation without destroying the cubic phase.

Hydrogen Permeation Properties of Nb-Based Two-Phase Compounds

2007 ◽  
Vol 561-565 ◽  
pp. 467-470
Author(s):  
Yuji Yamaguchi ◽  
Kyosuke Kishida ◽  
Katsushi Tanaka ◽  
Haruyuki Inui ◽  
Sho Tokui ◽  
...  
Keyword(s):  
Hydrogen Embrittlement ◽  
Hydrogen Permeation ◽  
Membrane Surface ◽  
Hydrogen Permeability ◽  
Eutectic Structure ◽  
Growth Direction ◽  
Directionally Solidified ◽  
Two Phase ◽  
Cast Sample ◽  
Lamellar Type

Nb-NiTi and Nb-CoTi eutectic alloys were directionally solidified in an optical floating zone furnace. Rod-type eutectic structures with Nb rods aligned parallel to the growth direction are obtained for Nb-41Ni-40Ti grown at relatively slow growth rates below 1.0mm/h, while lamellar-type eutectic structures are obtained for Nb-35Co-34Ti grown at the same condition. The hydrogen permeability for the Nb-41Ni-40Ti DS alloy with Nb rods perpendicular to the membrane surface is 2.60×10-8mol H2 m-1 Pa-1/2 at 673K, which is about 2.5 times higher than that of as-cast sample. No hydrogen embrittlement is observed between 573 and 673K, indicating that the Nb-NiTi rod-type eutectic structure effectively suppresses the hydrogen embrittlement of Nb during hydrogen permeation.

Fracture Failure Analysis of 304 Stainless Steel Elbow

2018 ◽  
Author(s):  
Yian Wang ◽  
Guoshan Xie ◽  
Libin Song ◽  
Meng He ◽  
Fakun Zhuang ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Chemical Composition ◽  
Hydrogen Embrittlement ◽  
Failure Analysis ◽  
Hydrogen Content ◽  
Fracture Morphology ◽  
Optical Microscope ◽  
304 Stainless Steel ◽  
High Hydrogen ◽  
Delayed Cracking

A cracking incident of a 304 stainless steel elbow serving in the synthesis gas purification device occurred during running. In order to get an understanding of the failure mechanism, a failure analysis was performed on the cracked elbow in this paper. The chemical composition, mechanical properties of strength, toughness and hardness, hydrogen content were identified and determined. The metallographical structure was observed and analyzed by optical microscope (OM) and X-Ray Diffraction (XRD), while the fracture morphology was observed by scanning electron microscope (SEM). The results showed that the chemical composition of the cracked elbow meet the requirements for China standard, while comparing with GB/T 14976-2012 standards, the strength and elongation of the leaked elbow are higher and lower respectively, and the hardness of the leaked elbow was higher than quality certificate documents that of HB ⩽ 187. Large quantities of martensite and δ-ferrite were observed in elbow, which indicated that the elbow was not well solid solution heat treated required by specification (1050°C,30min). The fracture morphology presents typical brittle fracture. The hydrogen content of cracked elbow was significant higher than that of other 304 stainless steel elbow serving in the environment without hydrogen. It is acknowledged that martensite showed higher sensitivity of hydrogen embrittlement compared with austenite. Furthermore, the operating temperature of cracked elbow was in the range of high hydrogen embrittlement sensitivity. Depending on the metallographical structure, strength, service environment, hydrogen content and fracture morphology, it can be concluded that hydrogen induced delayed cracking was the dominant mechanism of the failure.

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