Stress Corrosion Performance Research Articles

Comparative study on stress corrosion resistance of 7150/7055/7A56 aluminum alloys

Abstract The effect of the alloying degree of 7xxx aluminum alloys on stress-corrosion resistance and microstructure was explored. The relationship between the microstructure characteristics and stress-corrosion performance of the three 7xxx aluminum alloys was analyzed. The results show that with an increase in alloying degree, the quantity of precipitated phases along grain boundaries notably increases, and the connectivity between precipitated phases is significantly enhanced, leading to an increased tendency for alloy dissolution. Anodic dissolution causes intergranular corrosion, making grain boundaries serve as channels for rapid crack propagation under tensile stress, thereby increasing the alloy’s stress-corrosion susceptibility. The stress-corrosion sensitivities of the three alloys are as follows: 7150 < 7055 < 7A56.

Research on stress corrosion cracking behavior of stainless steel bellows expansion joints used in GIS equipment

This article conducts metallographic structure, martensite content, Vickers hardness, and stress corrosion performance tests on two commonly used stainless steel bellows expansion joints with different materials and geometric parameters in the power grid. The material properties and stress corrosion sensitivity of 304 and 316 stainless steel bellows are compared. The results indicate that the martensite content is highest at the peak position and lowest at the trough position in the bellows. As the curvature radius of the bellows decreases, the martensite content increases at the same position. Under the same conditions, the content of deformed martensite in 304 stainless steel is much higher than that in 316 stainless steel. After soaking in boiling MgCl2 solution for 7 days, the stress corrosion crack length of 304 stainless steel bellows is greater than that of 316 stainless steel. As the curvature radius of the ripple decreases, the crack length of 304 stainless steel bellows increases from 1.38 mm to 11.39 mm, while the crack length of 316 stainless steel bellows only increases from 0.32 mm to 7.32 mm.

Investigating the impact and mechanisms of electromagnetic treatment on stress corrosion performance in 7075 aluminum alloy

Investigating the impact and mechanisms of electromagnetic treatment on stress corrosion performance in 7075 aluminum alloy

Effect of excitation vibration on mechanical property and stress corrosion resistance of cast steel

Cast steel parts can realize rapid prototyping effectively, which is suitable for complex structural design. However, due to the large residual stress, the problem of mechanical property degradation is more obvious. In order to solve this problem, a high temperature excitation vibration treatment scheme is proposed in this paper. By applying different excitation frequencies and impact forces, the effects of mechanical properties and stress corrosion properties are studied and verified. Based on the finite element software ANSYS, the modal shape and resonant frequency of the cast steel parts are obtained, and verified by the sweep frequency module in the excitation vibration system. According to the characteristics of modal shape, five typical detection paths are set, and stress sensors are arranged every 200 mm. In order to obtain the specific effects of excitation frequency and impact force amplitude on mechanical properties, nine parts samples were prepared on the same production line according to the matching requirements of test parameters. In addition, the main external parameters that remain unchanged during vibration excitation are set as initial 750 ℃ and vibration excitation time of 60 s, which can fully affect the effect of austenite transformation. Keeping the synchronization of test parameters in different samples, the distribution rules of residual stress under different excitation frequencies and forces are obtained and analyzed. In the aspect of mechanical properties, the microstructure, hardness, yield strength and tensile strength of the specimens subjected to vibration were compared and analyzed. In the aspect of stress corrosion performance research, stress corrosion cracking test was carried out in weak acid environment to obtain the tensile stress curve and fracture morphology of the specimen. The results show that the excitation vibration at high temperature can effectively eliminate the residual stress of cast steel parts, but the increase of excitation frequency does not correspond to the effect of residual stress elimination. When the exciting force exceeds a certain value, the stress relief effect cannot be further improved. Excitation vibration can reduce the internal hardness of cast steel parts to a certain extent, and improve the yield strength and tensile strength. At the same time, it has a positive role in promoting the improvement of stress corrosion resistance.

Effect of Coating on Stress Corrosion Performance of Bridge Cable Steel Wire

Hot galvanization on steel surfaces can isolate the steel from corrosive environments and alleviate the stress corrosion cracking caused by the anodic dissolution mechanism. However, the cathodic protection potential of the coating is excessively negative, which may aggravate the hydrogen embrittlement problem. The effect of a coating on the stress corrosion performance of bridge cable wire was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), a thermal desorption analysis (TDA), an electrochemical workstation, and an FIP test. The results show that hot-dip ZnAl and ZnAlMg alloy coatings can significantly prolong the stress corrosion fracture time of steel wire substrates. From a macroscopic perspective, the stress corrosion cracking fracture is a brittle fracture caused by hydrogen embrittlement. Moreover, the coating type has little effect on the fracture morphology of bridge cable wire. In NH4SCN solution (50 °C, 20 wt.%), a corrosion product layer composed of ZnS and Al2O3 was formed on the surface of the coated steel wire. The electrochemical analysis showed that the corrosion resistance of the ZnAlMg coating was better than that of the ZnAl coating, which was the main reason for the improvement of the stress corrosion performance.

Laser cavitation processing of mild steel: Surface integrity, microstructure and stress corrosion performance

Laser cavitation peening (LCP) is a new and effective technology for surface modification. The Q235 steel was processed by LCP and aluminum foil was employed as a coverage layer. Moreover, the Q235 steel was also treated by laser cavitation peening without a coverage layer (LCPwc). The surface integrity, microstructure, and stress corrosion behavior of Q235 steel processed by LCP and LCPwc were systemically studied. According to the experimental results, the mechanisms of LCP strengthening and stress corrosion performance of Q235 steel were revealed. The results indicate that LCP and LCPwc result in the surface plastic deformation of Q235 steel. The residual compressive stress is induced and microhardness is enhanced. On the surface layer of Q235 steel, the grains were refined and many dislocation structures produce. The impact of LCPwc and LCP enhances the yield strength and ultimate strength of Q235 steel, while the elongation decreases. The corrosion resistance and mechanical properties of Q235 steel are improved significantly after the processing of LCPwc and LCP. The Q235 after LCP processing has better mechanical properties while the LCPwc treatment makes the material have better anti-corrosion performance.

Stress corrosion inhibition mechanism of hot rolled medium thickness Al–Zn–Mg–Cu plate by cryogenic-aging treatment

In this article, a novel cryogenic-aging treatment was realized by introducing the deep cryogenic treatment (DCT) in liquid nitrogen prior to artificial aging. The stress corrosion performance of the hot rolled medium thick Al–Zn–Mg–Cu plate after cryogenic-aging treatment was investigated by mechanical properties test, in-situ electrochemical test and microstructure analysis. It was found that the DCT-8 h and 24 h prior to double-stage aging treatment were optimum parameters. Cryogenic-aging treatment prolonged the duration of Al–Zn–Mg–Cu alloy under the coupling of stress and corrosion media. In addition, cryogenic-aging treatment promoted the multiplication of dislocations aggregated on the grain boundary or sub-grain boundary, which provided nucleation sites of precipitates and reduced the width of precipitates-free zone (PFZ). In-situ electrochemical test and microstructure observation were combined to analyze the inhibition mechanism of stress corrosion by cryogenic-aging treatment, which effectively inhibits the rupture of oxide film and the propagation of crack during the initial stage. This study proposes a simple and efficient process to enhance stress corrosion performance, which has important guidance for the application of Al–Zn–Mg–Cu alloys in the aerospace and transportation industries.

Effect of Secondary α Phase on Stress Corrosion Cracking of a Novel Metastable β Titanium Alloy in 3.5% NaCl Solution

The effect of the secondary α phase on stress corrosion cracking of a novel metastable β titanium alloy, Ti-6Mo-5V-3Al-2Fe, in 3.5% NaCl solution was investigated by slow strain rate testing. Fine acicular secondary α phase was obtained by aging at the low temperature of 520 °C, and coarsened rod-like secondary α phase was obtained by aging at the high temperature of 680 °C. The electrochemical measurement results and slow strain rate testing results show that the microstructure contained with fine acicular secondary α phase exhibits better corrosion resistance and less stress corrosion cracking susceptibility. The fracture morphology exhibits a mixed fracture characteristic with shallow and small dimples, as well as tear ridges and flat facets with undulating surfaces. The combination of Absorption Induced Dislocation Emission and Hydrogen Enhanced Localized Plasticity is the main mechanism for stress corrosion cracking. Fine acicular secondary α phase with narrow spacing leads to less accumulated dislocations and smaller localized stress, so that has a beneficial effect on stress corrosion performance.

Influence of Phase Composition on Stress-Corrosion Cracking of Ti-6Mo-5V-3Al-2Fe-2Zr Alloy in 3.5% NaCl Solution

The metastable β titanium alloys used in marine engineering applications suffered from stress-corrosion cracking in seawater. The different phase composition leads to the distinct stress-corrosion cracking behaviors of the alloy. In this work, the influence of the phase composition on the stress-corrosion cracking of a novel metastable β titanium alloy Ti-6Mo-5V-3Al-2Fe-2Zr was investigated. The alloys with different phase compositions were prepared by three types of thermal-mechanical processing, i.e., the single β phase (assigned as M(β)), the β phase plus fine α phase (assigned as M(β+fα)), and the β phase plus coarsened α phase (assigned as M(β+cα)). The electrochemical tests and constant-stress loading tests were performed, and the phase composition and microstructure were analyzed by XRD and SEM. The M(β) alloy exhibits the best corrosion resistance as well as the compact properties of oxide films, followed by the M(β+fα) alloy and the M(β+cα) alloy. Tear ridges and a flat facet with an undulating surface were observed on the stress-corrosion cracking fracture surface, which indicated the occurrence of high-degree dislocations movement and localized plastic deformation. Absorption-induced dislocation emission (AIDE) and hydrogen-enhanced localized plasticity (HELP) are the primary mechanisms for the stress-corrosion cracking of the alloy. The increased amount of β phase has a beneficial effect on stress-corrosion cracking resistance. For the alloy with β and α phases, the α phase with wider spacing has an adverse effect on stress corrosion performance.

The Effect of a Slow Strain Rate on the Stress Corrosion Resistance of Austenitic Stainless Steel Produced by the Wire Laser Additive Manufacturing Process

The wire laser additive manufacturing (WLAM) process is considered a direct-energy deposition method that aims at addressing the need to produce large components having relatively simple geometrics at an affordable cost. This additive manufacturing (AM) process uses wires as raw materials instead of powders and is capable of reaching a deposition rate of up to 3 kg/h, compared with only 0.1 kg/h with common powder bed fusion (PBF) processes. Despite the attractiveness of the WLAM process, there has been only limited research on this technique. In particular, the stress corrosion properties of components produced by this technology have not been the subject of much study. The current study aims at evaluating the effect of a slow strain rate on the stress corrosion resistance of 316L stainless steel produced by the WLAM process in comparison with its counterpart: AISI 316L alloy. Microstructure examination was carried out using optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis, while the mechanical properties were evaluated using tensile strength and hardness measurements. The general corrosion resistance was examined by potentiodynamic polarization and impedance spectroscopy analysis, while the stress corrosion performance was assessed by slow strain rate testing (SSRT) in a 3.5% NaCl solution at ambient temperature. The attained results highlight the inferior mechanical properties, corrosion resistance and stress corrosion performance, especially at a slow strain rate, of the WLAM samples compared with the regular AISI 316L alloy. The differences between the WLAM alloy and AISI 316L alloy were mainly attributed to their dissimilarities in terms of phase compositions, structural morphology and inherent defects.

Stress Corrosion and Corrosion Fatigue of Biodegradable Mg-Zn-Nd-Y-Zr Alloy in In-Vitro Conditions

Mg alloys are attractive as a structural material for biodegradable implants due to their mechanical properties, biocompatibility and degradation capability in physiological environments. However, their accelerated corrosion degradation, coupled with their inherent sensitivity to stress corrosion, can cause premature failure and consequently loss of mechanical integrity. This study aims to evaluate the potential of a Mg-5% Zn alloy with up to 3% Nd as an implant material in terms of stress corrosion performance in in vitro conditions. Stress corrosion behavior was evaluated under static loading conditions using slow strain rate testing (SSRT) analysis and under low cycle corrosion fatigue (LCCF). Both the SSRT analysis and LCCF testing were carried out in a simulated physiological environment in the form of a phosphate-buffered saline (PBS) solution. The obtained results indicate that the addition of up to 3% Nd to Mg-5% Zn alloy did not have any substantial influence on the stress corrosion susceptibility, beyond the inherent different mechanical properties of the tested alloys. This was attributed to the limited effect of the Nd on the passivation layer and due to the fact that the secondary phases produced by the Nd additions—W-phase (Mg3(Nd,Y)2Zn3) and T-phase (Mg4(Nd,Y)Zn2)—did not create any substantial micro-galvanic effect.

The effect of strain rate on stress corrosion performance of Ti6Al4V alloy produced by additive manufacturing process

Ti6Al4V alloy is considered as a favourable material for additive manufacturing (AM) and in particular for selective laser melting (SLM), due to the inherent difficulties relating to casting and plastic forming of this alloy. However, the significantly increased solidification rate associated with the SLM process results in a modified micro-structure and inherent casting imperfections that can have a detrimental effect on the alloy stress corrosion performance. The main objective of this study was to evaluate the effect of strain rate on stress corrosion behavior of Ti6Al4V alloy produced by SLM, as compared to its wrought alloy (Grade 5) counterpart of the same chemical composition. Micro-structure and phase identification were examined by scanning electron microscopy and X-ray diffraction analysis. General corrosion resistance was evaluated in terms of open circuit potential, potentiodynamic polarization analysis and by impedance spectroscopy, while stress corrosion behavior was examined at various strain rates in a 3.5% NaCl solution at ambient temperature. The results obtained revealed that general corrosion resistance and stress corrosion endurance at slow strain rate, in terms of time to failure and ductility of the SLM alloy, were relatively reduced, as compared to the wrought alloy counterpart. This was mainly due to the formation of a strained martensitic matrix in the form of α' phase and the significant reduction of the β phase in the alloy produced by SLM process.

Environmental Behavior of Low Carbon Steel Produced by a Wire Arc Additive Manufacturing Process

Current additive manufacturing (AM) processes are mainly focused on powder bed technologies, such as electron beam melting (EBM) and selective laser melting (SLM). However, the main disadvantages of such techniques are related to the high cost of metal powder, the degree of energy consumption, and the sizes of the components, that are limited by the size of the printing cell. The aim of the present study was to evaluate the environmental behavior of low carbon steel (ER70S-6) produced by a relatively inexpensive AM process using wire feed arc welding. The mechanical properties were examined by tension testing and hardness measurements, while microstructure was assessed by scanning electron microscopy and X-ray diffraction analysis. General corrosion performance was evaluated by salt spray testing, immersion testing, potentiodynamic polarization analysis, and electrochemical impedance spectroscopy. Stress corrosion performance was characterized in terms of slow strain rate testing (SSRT). All corrosion tests were carried out in 3.5% NaCl solution at room temperature. The results indicated that the general corrosion resistance of wire arc additive manufacturing (WAAM) samples were quite similar to those of the counterpart ST-37 steel and the stress corrosion resistance of both alloys was adequate. Altogether, it was clearly evident that the WAAM process did not encounter any deterioration in corrosion performance compared to its conventional wrought alloy counterpart.

Investigation on microstructure and properties of Al18B4O33 whisker reinforced Al[sbnd]Mg[sbnd]Si matrix composite after shot peening

This work investigated the influences of two-step shot peening on the residual stress fields, microstructure, microhardness and corrosion performance of aluminum borate (Al18B4O33) whisker reinforced AlMgSi matrix composite by X-ray stress tester, X-ray diffraction line profile analysis method, transmission electron microscopy (TEM), Vickers analyzer and electrochemical examinations, respectively. The results indicate that shot peening induces considerable compressive residual stress (−151 MPa) and satisfied microstructure refinement into the near surface region. The domain sizes gradually increase from the top surface to the substrate, the microstrain and dislocation density present the contrary variation trends. The maximum microhardness locates at top surface and the value is about 2.5 times that of matrix. Furthermore, shot peening improves the corrosion performance of Al18B4O33 whisker reinforced AlMgSi matrix composite. The sample with a peening intensity 0.40 + 0.08 mmN possesses the best corrosion behavior with maximum polarization resistance (15133 Ω cm2) and lowest corrosion current density (2.202 μA cm−2). The refined domain size and compressive residual stress should account for the improvement of corrosion behavior. However, further increasing shot peening intensity, the corrosion resistance drops, which is considered as a consequence of induced surface defects, increased surface roughness and dislocation density.

The studies on the corrosion behaviors of 316NG and 304NG nitrogen-containing stainless steels made in China

The strength and corrosion properties of austenitic steels could be improved through adding appropriate amount of nitrogen and reducing the amount of carbon, while the plasticity and toughness are not influenced. The corrosion performance of 316NG and 304NG nitrogen-containing stainless steels and 321 stainless steels which used in nuclear plants have been studied, including the uniform corrosion performance, electrochemistry corrosion performance, stress corrosion performance, pitting corrosion performance and salt spray corrosion performance. The results indicated that the corrosion resistance of 316NG and 304NG nitrogen-containing stainless steels was more excellent than the 321 stainless steel, and N and Mo in alloys improved the corrosion behaviors of stainless steels.

Failure analysis of cold drawn prestressing steel wires subjected to stress corrosion cracking

This paper analyzes the stress corrosion performance of cold drawn prestressing steels with different degrees of cold drawing, in the two cases of pure stress corrosion cracking and fracture by hydrogen embrittlement. Results show a progressively anisotropic stress corrosion behaviour with cold drawing, and this anisotropy could be induced by the microstructural orientation. Consequences for engineering design are derived on the basis of the calculation of the transition stress intensity factor (from the stress corrosion subcritical crack growth to the critical cleavage propagation). While in situations of pure stress corrosion cracking such a value is even higher than the fracture toughness of the material in air (due to crack tip blunting), in the case of hydrogen embrittlement there is a marked reduction of stress intensity factor value, which indicates that these steels are highly susceptible to this phenomenon.

Stress Corrosion Cracking of Al-Mg and Mg-Al Alloys

Abstract Al- and Mg-based alloys are being used for reducing the weight of automobiles. For structural applications, they must have adequate stress corrosion resistance, and yet, under some circumstances, stress corrosion cracking can occur in both alloy systems. Precipitation of the Mg-rich β-phase (Al3Mg2) at grain boundaries of Al-Mg alloys and the γ-phase (Mg17Al12) at grain boundaries of the Mg-Al alloys is a critical factor in their stress corrosion performance. In Mg-Al, the γ-phase is cathodic (noble) to the matrix, while in the Al-Mg case, the β-phase is anodic (active) to the matrix. These phases produce localized galvanic-induced corrosion that leads to intergranular stress corrosion cracking and crack growth rates of 350 and 1,800 times faster than the solution-treated condition, for Al-Mg and Mg-Al, respectively.

Improved Fatigue Performance of Friction Stir Welds with Low Plasticity Burnishing: Residual Stress Design and Fatigue Performance Assessment

Although friction stir welding (FSW) produces minimal distortion, residual stresses are created that impact fatigue and stress corrosion performance. X-ray diffraction residual stress and cold work mapping methods used at Lambda Research for FSW studies are described. Post weld surface enhancement processing can be used to place the FSW region in compression to improve fatigue performance. Deep compressive residual stress distributions produced by low plasticity burnishing (LPB) designed to improve fatigue and corrosion fatigue performance in aluminum alloy FSW are described. The LPB tooling and FSW processing are presented. Corrosion fatigue testing used for FSW samples is described and compared to fracture mechanics based fatigue life predictions calculated for the measured residual stress distributions. Residual stress and corrosion fatigue results for aluminum alloy 2219-T8751 are presented.

Metallurgical improvements for enhanced stress corrosion performance of light water reactor structural materials

Incidences of stress corrosion cracking of a wide variety of structural materials used in light water reactors have caused significant forced outages, with associated high costs to utilities and ratepayers for replacement power. This paper focuses on stress corrosion cracking problems in fuel rods and other small core components, piping, steam generator tubes, and turbine discs. These problems have motivated intense research efforts to seek solutions and the resulting material remedies, involving either or both microstructure and alloy chemistry modification, are described.

Stress Corrosion Resistance of Some Copper Base Alloys in Natural Atmospheres

Abstract This paper describes the results of a test program where 25 copper alloys were exposed as stressed U-bends to two industrial atmospheres and one marine atmosphere for times up to 8 years. Many of the alloys have not failed to date. However, a number of zinc containing alloys (>20%), even in the presence of other alloying additions which normally impart resistance to stress corrosion, have failed. The industrial sites are more aggressive than the marine site, resulting in failure of more alloys and shorter stress corrosion life. Alloying effects were found to be extremely important in determining stress corrosion susceptibility and crack morphology. The results are discussed relative to the influence of environment, alloy composition, and structure on stress corrosion performance and the mechanism of stress corrosion cracking (SCC).