Influence of deformation on the corrosion behavior of LZ91 Mg-Li alloy

The effect of rolling and forging on the microstructure and corrosion behavior of LZ91 alloy was investigated using an electron probe micro-analyzer,immersion and electrochemical tests.Results showed that the area fraction of theβ-Li phase remained unchanged,and the grain size of theβ-Li phase decreased after forging.The as-rolled forged alloy(FR-LZ91)exhibited the highest area fraction of theβ-Li phase and the longest grains.The corrosion resistance of the forged LZ91 alloy increased due to grain refinement that prevented further corrosion during the immersion test.Among the experimental alloys,FR-LZ91 showed the highest resistance of corrosion film and charge transfer resistance values due to its protective film caused by the high area fraction of theβ-Li phase.

Corrosion behavior of composite coatings containing hydroxyapatite particles on Mg alloys by plasma electrolytic oxidation: A review

Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their susceptibility to rapid corrosion within the body poses a significant challenge and restricts their applications. To overcome this issue, various surface modification techniques have been developed to enhance the corrosion resistance and bioactivity of Mg-based implants. PEO is a potent technique for producing an oxide film on a surface that significantly minimizes the tendency to corrode. However, the inevitable defects due to discharges and poor biological activity during the coating process remain a concern. Therefore, adding suitable particles during the coating process is a suitable solution. Hydroxyapatite(HAp)has attracted much attention in the development of biomedical applications in the scientific community. HAp shows excellent biocompatibility due to its similarity in chemical composition to the mineral portion of bone. Therefore, its combination with Mg-based implants through PEO has shown significant improvements in their corrosion resistance and bioactivity. This review paper provides a comprehensive overview of the recent advances in the preparation, characterization, corrosion behavior and bioactivity applications of HAp particles on Mg-based implants by PEO.

Impressive strides in amelioration of corrosion behavior of Mg-based alloys through the PEO process combined with surface laser process: A review

The unsatisfactory corrosion properties of Mg-based alloys pose a significant obstacle to their widespread application. Plasma electrolytic oxidation(PEO) is a prevalent and effective coating method that produces a ceramic-like oxide coating on the surface of Mg-based alloys,enhancing their resistance to corrosion. Research has demonstrated that PEO treatment can substantially improve the corrosion performance of alloys based on magnesium in the short term. In an effort to enhance the corrosion resistance of PEO coatings over an extended period of time, researchers have turned their attention to the use of laser processes as both pre-and post-treatments in conjunction with the PEO process. Various laser processes, such as laser shock melting(LSM), laser shock adhesion(LSA), laser shock texturing(LST), and laser shock peening(LSP), have been investigated for their potential to improve PEO coatings on Mg substrates and their alloys. These laser melting processes can homogenize and alter the microstructure of Mg-based alloys while leaving the bulk material unchanged, thereby modifying the substrate surface. However, the porous and rough structure of PEO coatings, with their open and interconnected pore structure, can reduce their long-term corrosion resistance. As such, various laser processes are well-suited for surface modification of these coatings. This study will first examine the PEO process and the various types of laser processes used in this process, before investigating the corrosion behavior of PEO coatings in conjunction with laser pre-and post-treatment processes.

Effect of lithium content on the mechanical and corrosion behaviors of HCP binary Mg–Li alloys

The microstructure,crystallographic texture,mechanical properties and corrosion resistance of as-extruded HCP Mg-x Li(x=1,3,5;in wt%)alloys were investigated.The results indicated that the HCP Mg-5 Li alloy with high lithium content exhibited a low degree of dynamic recrystallization(DRX)compared with Mg-1 Li and Mg-3 Li alloys.Besides,the 45°base(0001)texture of Mg-1 Li alloy could turn into(11–20)and(10–10)prismatic texture of Mg-3 Li and Mg-5 Li alloys with c-axis approximately parallel to transverse direction(TD).As a result,the strong prismatic texture resulted in the mechanical anisotropy of as-extruded Mg-3 Li and Mg-5 Li alloys with higher mechanical strength and low elongation along extrusion direction(ED)(reverse for TD sample).Regarding of corrosion behaviors,filiform corrosion occurred in the three Mg–Li alloys,whilst the high lithium content could mitigate the groove-like corrosion and improve the corrosion resistance of Mg-5 Li alloy,which was ascribed to the refined grains,prismatic texture and surface film.

Influence of grain refinement on the corrosion behavior of metallic materials:A review

Grain refinement can strengthen the mechanical properties of materials according to the classical Hall-Petch relationship but does not always result in better corrosion resistance.During the past few decades,various techniques have been dedicated to refining grain,along with relevant studies on corrosion behavior,including general corrosion,pitting corrosion,and stress corrosion cracking.However,the funda-mental consensus on how grain size influences corrosion behavior has not been reached.This paper reviews existing literature on the beneficial and detrimental effects of grain refinement on corrosion behavior.Moreover,the effects of microstructural changes(i.e.,grain boundary,dislo-cation,texture,residual stress,impurities,and second phase)resulting from grain refinement on corrosion behavior are discussed.The grain re-finement not only has an impact on the corrosion performance,but also results in microstructural changes that have a non-negligible effect on corrosion behavior or even outweigh that of grain refinement.Grain size is not the only factor affecting the corrosion behavior of metallic ma-terials;thus,the overall influence of microstructures on corrosion behavior should be understood.

Effect of rare-earth element Sm on the corrosion behavior of Mg-6Al-1.2Y-0.9Nd alloy

The effect of Sm（0 wt.%-2 wt.%） addition on the corrosion behavior of Mg-6Al-1.2Y-0.9Nd alloy in 3.5 wt.% NaCl solution has been studied by static corrosion tests,corrosion morphology observation,corrosion scale and microstructure analysis.The results show that,with the increasing of Sm content,the corrosion rate of the alloy decreases at first,then increases and reaches the valley at 0.5 wt.% Sm.The reason is that the proper content of Sm addition can refine the precipitates and make the component and microstructure uniform,and therefore,it remarkably improves the corrosion resistance of the alloy.

Effect of microstructure on corrosion behavior of high strength martensite steel-A literature review

The high strength martensite steels are widely used in aerospace,ocean engineering,etc.,due to their high strength,good ductility and acceptable corrosion resistance.This paper provides a review for the influence of microstructure on corrosion behavior of high strength martensite steels.Pitting is the most common corrosion type of high strength stainless steels,which always occurs at weak area of passive film such as inclusions,carbide/intermetallic interfaces.Meanwhile,the chromium carbide precipitations in the martensitic lath/prior austenite boundaries always result in intergranular corrosion.The precipitation,dislocation and grain/lath boundary are also used as crack nucleation and hydrogen traps,leading to hydrogen embrittlement and stress corrosion cracking for high strength martensite steels.Yet,the retained/reversed austenite has beneficial effects on the corrosion resistance and could reduce the sensitivity of stress corrosion cracking for high strength martensite steels.Finally,the corrosion mechanisms of additive manufacturing high strength steels and the ideas for designing new high strength martensite steel are explored.

Microstructure characterization and corrosion behavior of Mg-Y-Zn alloys with different long period stacking ordered structures

Mg-Y-Zn alloys with long period stacking ordered(LPSO)structure have received much attention recently and exhibit great potential in applications such as automotive,aerospace and in bio-medical fields.This paper aimed to investigate the effect of different phase constitution of LPSO structures on corrosion rate of bio-medical Mg-Y-Zn alloys.The results showed that as-cast Mg98.5Y1Zn0.5 alloys containing only 18R structure exhibited the highest corrosion resistance with the corrosion rate of 2.78 mm/year.The precipitation of 14H lamellas within a-Mg grains during solid solution treatment introduced the crystallographic orientation corrosion by accelerating micro-galvanic corrosion.The increase of 18R/14H interfaces deteriorated the corrosion resistance,and the grain boundaries also suffered from severe electrochemical dissolution.This work suggested that Mg-Y-Zn alloys with single LPSO structure(either 18R or 14H)exhibited better corrosion resistance than alloys with co-existence 18R and I4H LPSO structures.

Corrosion behavior of aluminum alloys in Na_2SO_4 solution using the scanning electrochemical microscopy technique

The corrosion behavior of aluminum alloys 1060 and 2A12 in a 10 mM Na2SO4＋5 mM KI solution was investigated by scanning electrochemical microscopy （SECM） and scanning electron microscopy （SEM）. The potential topography and corrosion morphology results show that the potential of the sample surface over the same area changes with the increase of immersion time. The corrosion area becomes large, and the potential becomes more negative. The corrosion potential of the 2A12 alloy surface is lower than that of 1060 aluminum, and 2A12 alloy becomes easily corrosive. This is the reason that preferential dissolution in the boundary region of some intermetallic particles （IMPs） occurs and different dissolution behaviors are associated with different types of IMPs because of different potentials.

Influence of yttrium element on the corrosion behaviors of Mg-Y binary magnesium alloy

The influence of yttrium on the corrosion behavior of Mg–Y alloys has been investigated by electrochemical measurements,scanning electron microscope(SEM)observation,X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS)analysis in NaCl solution.The corrosion resistance decreased with increasing Y content due to increasing Y-rich zone.The solid-dissolved Y improved the chemical activity of the substrate which promoted the corrosion reaction by forming Y2O3.The corrosion resistance was improved by increasing the Y concentration of matrix and proper net Y-rich structure.The sample has the best corrosion resistance when all the Y element was dissolved into the matrix of Mg–5Y in 0.1 M NaCl.

Surface characterization and corrosion behavior of calcium phosphate(Ca-P)base composite layer on Mg and its alloys using plasma electrolytic oxidation(PEO):A review

Magnesium has been known as an appropriate biological material on account of its good biocompatibility and biodegradability properties in addition to advantageous mechanical properties.Mg and its alloys are of poor corrosion resistance.Its high corrosion rate leads to its quick decomposition in the corrosive ambiance and as a result weakening its mechanical properties and before it is repaired,it will vanish.The corrosion and degradation rate must be controlled in the body to advance the usage of Mg and its alloys as implants.Different techniques have been utilized to boost biological properties.Plasma electrolytic oxidation(PEO)can provide porous and biocompatible coatings for implants among various techniques.Biodegradable implants are generally supposed to show enough corrosion resistance and mechanical integrity in the body environment.Much research has been carried out in order to produce PEO coatings containing calcium phosphate compounds.Calcium phosphates are really similar to bone mineral composition and present great biocompatibility.The present study deals with the usage of calcium phosphates as biocompatible coatings applied on Mg and its alloys to study the properties and control the corrosion rate.

Influence of trace As content on the microstructure and corrosion behavior of the AZ91 alloy in different metallurgical conditions

The influence of trace As content(0.04,0.05,0.06 wt%)on the microstructure and corrosion behavior of AZ91 alloy in different metallurgical conditions(as-cast,as-quenched,peak-aged)was firstly investigated.It is found that the corrosion resistance of AZ91 alloy in all conditions is significantly enhanced by As addition,mainly due to cathodic toxication,melt purification and incidence reduction of local corrosion.As alloying leads to the formation of Mg 3 As 2 and makes the β-Mg 17 Al 12 phase less continuous in the as-cast alloys.The alloy containing 0.06 wt%As obtains a higher corrosion rate than those of the alloy containing 0.05 wt%As owing to a more discontinuity of β phase.The β phase is dissolved into the matrix in the as-quenched alloys and reprecipitates along the grain boundaries after aging.The more continuous β phase distribution in the peak-aged alloys contributes to corrosion resistance.The corrosion rates are in the order of as-quenched>as-cast>peak-aged.The lowest corrosion rate(0.67 mm/y)in 3.5 wt%NaCl solution is obtained in the peak-aged AZ91-0.05As alloy,which is over 70%lower than that of as-cast AZ91 alloy(2.22 mm/y).

Effect of cooling temperature on the microstructure and corrosion behavior of X80 pipeline steel

Dual-phase accelerated cooling(DPAC) was applied to X80 pipeline steel to obtain its microstructure with different amounts of bainite and ferrite. The microstructure, hardness, and polarization behaviors of the steel, cooled to different temperatures, were investigated. Results showed that, with decreasing cooling temperature, the amount of polygon ferrite(PF) increased while that of acicular ferrite(AF) decreased. The amount of bainite correspondingly decreased, except when cooled to 760°C. Moreover, the grain size of ferrite increased. The corrosion behaviors of different phases were distinct. Martensite/austenite(M/A) islands presented at the grain boundary of the PF phase caused small pits. Numerous micro-corrosion cells were formed in the AF and bainite phases, where micropores were prone to form. X80 pipeline steel cooled to 700°C had the best corrosion resistance in the simulated seawater. The decreased amount of the PF phase reduced the area of cathode, resulting in slight corrosion. About 40 vol% of the bainite phase provided strength while the PF phase provided adequate ductility to the X80 steel. It was concluded that the appropriate cooling temperature was 700°C for ideal corrosion resistance and mechanical properties.

Corrosion behavior of Mg-Zn-Ca amorphous alloys with Nd addition in simulated body fluids

The effects of Nd addition on corrosion behavior of Mg66Zn30Ca4 amorphous alloys in simulated body f luids(SBF) were studied in this paper. Electrochemical properties of the samples before and after corrosion were determined. Surface morphologies of samples after immersion in SBF at 37℃ for different times were observed under scanning electron microscope(SEM). Results show that the corrosion resistance of Mg-based alloys in SBF is improved with the addition of Nd element. The electrochemical properties indicate that microalloying Nd element to the alloys leads to an ennoblement in the open circuit potentials of the alloys and a decrease in the anodic current density in SBF, especially for the Mg66-xZn30Ca4 Ndx alloys with Nd content of 1.0at.%-1.5at.%. It was observed that the surface morphologies of the alloys immersed in SBF change with the Nd addition. A f lakelike structure parallel to the alloy substrate formed on the surface of 1.0at.% Nd-containing alloy immersed in SBF for 7 days improves the corrosion resistance of the amorphous alloys by blocking the corrosion liquid from attacking the alloys.

Corrosion Behaviors of P110 Steel and Chromium Coating in CO_2-saturated Simulated Oilfield Brine

The protective chromium coating was prepared on P110 steel by employing pack cementation.The corrosion behaviors of P110 steel and the obtained coating in CO2-saturated simulated oilfield brine were studied by static complete immersion tests and electrochemical measurements.The corrosion attacks of the samples were determined by mass loss,corroded surface morphologies,corrosion products,and results of electrochemical measurements.The experimental results showed that the coating was uniform,continuous and compact.The chromium coating was slightly corroded,and the mass loss and corrosion rate of the coating were far lower than those of P110 steel.Chromium coating has higher self-corroding potential and lower corrosion current density than P110 steel in accordance with the electrochemical tests results.Taken as a whole,chromizing treatment has significantly improved the corrosion resistance of P110 steel.

Recent developments on corrosion behaviors of Mg alloys with stacking fault or long period stacking ordered structures

Corrosion is one of the most drawbacks which restricts the wide applications of Mg alloys.In the last decade,the corrosion behaviors of Mg alloys with stacking fault(SF)and/or long period stacking ordered(LPSO)structures have obtained increasing attention.However,the corrosion mechanism of the SF–or LPSO–containing Mg alloys has not been well illustrated and even reverse results have been reported.In this paper,we have reviewed recent reports on corrosion behaviors of SF–or LPSO–containing Mg alloys to better clarify and understand the significance and mechanism.Moreover,some deficiencies are presented and advises are proposed for the development of corrosion resistant Mg alloys with SF or LPSO structures.

Corrosion Behavior of the S136 Mold Steel Fabricated by Selective Laser Melting

The selective laser melting(SLM) method has a great potential for fabricating injection mold with complex structure. However, the microstructure and performance of the SLM molds show significantly di erent from those manufac?tured by traditional technologies. In this study, the microstructure, hardness and especially corrosion behavior of the samples fabricated by SLM and casting were investigated. The XRD results exhibit that the γ?Fe phase is only obtained in the SLM parts, and the α?Fe peak slightly moves to low di raction angle compared with casting counterparts. Due to the rapid cooling rate, the SLM samples have fine cellular microstructures while the casting ones have coarse grains with obvious elements segregation. Besides, the SLM samples show anisotropy, hardness of side view and top view are 48.73 and 50.31 HRC respectively, which are 20% higher than that of casting ones. Corrosion results show that the SLM samples have the better anti?corrosion resistance(in a 6% FeCl3 solution for 48 h) but the deeper corrosion pits than casting ones. Finally, the performance of the SLM molds could meet the requirement of injecting production. Moreover, the molds especially present a significant decrease(20%) of cooling time and increases of cooling uniform?ity due to the customized conformal cooling channels.

Effect of trace yttrium on the microstructure,mechanical property and corrosion behavior of homogenized Mg-2Zn-0.1Mn-0.3Ca-xY biological magnesium alloy

The effects of trace yttrium(Y)element on the microstructure,mechanical properties,and corrosion resistance of Mg-2Zn-0.1Mn-0.3Ca-xY(x=0,0.1,0.2,0.3)biological magnesium alloys are investigated.Results show that grain size decreases from 310 to 144µm when Y content increases from 0wt%to 0.3wt%.At the same time,volume fraction of the second phase increases from 0.4%to 6.0%,yield strength of the alloy continues to increase,and ultimate tensile strength and elongation decrease initially and then increase.When the Y content increases to 0.3wt%,Mg_(3)Zn_(6)Y phase begins to precipitate in the alloy;thus,the alloy exhibits the most excellent mechanical property.At this time,its ultimate tensile strength,yield strength,and elongation are 119 MPa,69 MPa,and 9.1%,respectively.In addition,when the Y content is 0.3wt%,the alloy shows the best corrosion resistance in the simulated body fluid(SBF).This investigation has revealed that the improvement of mechanical properties and corrosion resistance is mainly attributed to the grain refinement and the precipitated Mg_(3)Zn_(6)Y phase.

Effects of trace Ca/Sn addition on corrosion behaviors of biodegradable Mg-4Zn-0.2Mn alloy

The effects of alloying elements of Ca/Sn on corrosion behaviors of the as-cast Mg-4Zn-0.2Mn alloy were investigated by immersion tests and electrochemical methods.The results indicated that the average corrosion rate value of the Mg-4Zn-0.2Mn-Ca alloy was∼0.31 mm/year in Hank’s physiological solution for 40 days,and corrosion resistance increased for the specimens containing Ca element rather than that containing Sn because of the higher breakdown potential value,lower current density and deactivated corrosion rate,which was ascribed to a formation of the uniformly distributed Mg-Zn-Ca ternary phase.

Corrosion behavior of aluminum/steel dissimilar metals friction stir welding joint

The corrosion performance of aluminum/steel contact and aluminum/steel FSW joint in 3.5 wt.%NaCl solution were analyzed using potentiostatic tests.The post-corrosion microstructure of the welding joint was characterized by optical microscope(OM),scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).The results showed that the localized corrosion of FSW joint of Al/steel dissimilar metals mainly initiated at the interface transition zone(ITZ).Precipitation of intermetallic compounds(IMCs)and Fe-rich phase particles in ITZ accelerated the corrosion of the FSW joint.This phenomenon has been attributed to distinct corrosion potentials between IMCs and steel,aluminum base metal.The corrosion resistance sequence of IMCs in ITZ is Fe_(3)Al>FeAl>Fe_(2)Al_(5).