Microstructure, Mechanical Property and Corrosion Resistance Property of Cr26Mo3.5 Super Ferritic Stainless Joints by P-TIG and Laser Welding

The characteristics of microstructure, mechanical property and corrosion behavior of Cr26Mo3.5 super stainless steel joints by pulse tungsten inert gas(P-TIG)welding and laser welding were investigated. The results indicate that the widths of the center equiaxed grain zone(EGZ)and the columnar grain zone(CGZ)increase with the increase of heat input in both welding processes. The precipitates of Nb and Ti carbides and nitrides are formed in the weld metal(WM)and the heat affected zone(HAZ). The joints by laser welding show better tensile and corrosion resistance properties than those by P-TIG welding due to the heat concentration and lower heat input. The tensile strength and elongation increase with the decrease of heat input, and the fracture mode of the joints turns into ductile-brittle mixed fracture from ductile fracture when the welding method turns into P-TIG welding from laser welding. Moreover, the corrosion resistance of all joints declines slightly with the increase of heat input. Hence, laser welding is more suitable for welding Cr26Mo3.5 super stainless steel in engineering applications.

The corrosion behavior and mechanical property of the Mg-7Y-x Nd ternary alloys

The corrosion behavior and mechanical property of Mg-7Y-x Nd(x=0.5,1.0,1.5 wt%)alloys were investigated.The microstructure and precipitations of Mg-7Y-x Nd alloys were studied by scanning electron microscopy,energy-dispersive spectrometry and X-ray Diffraction.The quantities of the Mg_(12)(Y,Nd)phase increased,whereas that of the Mg_(24)(Y,Nd)_(5)phase decreased with increasing Nd-content.The weight loss rate decreased from 17.5020 mg cm^(-2)·d^(-1)(36.7542 mm y^(-1))to 9.3744 mg cm^(-2)·d^(-1)(19.6862 mm y^(-1)).The electrochemical measurement also demonstrated the similar tendency.The loss in mechanical properties after corrosion reaction followed the order Mg-7Y-0.5Nd>Mg-7Y-1.0Nd>Mg-7Y-1.5Nd.The precipitations played dual roles in the corrosion resistance that depended on type and distribution.

Effect of Zn on mechanical property and corrosion property of extruded Mg-Zn-Mn alloy

The effect of Zn on the microstructure, the mechanical property and the corrosion property in simulated body fluid(SBF) of an extruded Mg-Mn alloy was studied. The results indicate that the addition of Zn element can significantly refine the grain size of the extruded Mg-Mn alloy. When Zn content is increased from 0% to 3%, the grain size decreases from 12 μm to 4 μm. Meanwhile, the mechanical properties also increase remarkably with increasing Zn content. When Zn content is 3%, the ultimate tensile strength and the yield strength are increased by 54.7 MPa and 69.7 MPa, respectively. Zn can also improve the anti-corrosion property of the alloy. The best anti-corrosion property is obtained with 1% Zn. However, further increase of Zn content up to 3% deteriorates the corrosion property. Finally, the influence mechanism of Zn on the microstructure, the mechanical property and the corrosion property was discussed.

Evolution of mechanical properties,localized corrosion resistance and microstructure of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging

The evolution of mechanical properties,localized corrosion resistance of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging(NIA)was investigated by hardness test,electrical conductivity test,tensile test,intergranular corrosion test,exfoliation corrosion test,slow strain rate tensile test and electrochemical test,and the mechanism has been discussed based on microstructure examination by optical microscopy,electron back scattered diffraction,scanning electron microscopy and scanning transmission electron microscopy.The NIA treatment includes a heating stage from 40℃to 180℃with a rate of 20℃/h and a cooling stage from 180℃to 40℃with a rate of 10℃/h.The results show that the hardness and strength increase rapidly during the heating stage of NIA since the increasing temperature favors the nucleation and the growth of strengthening precipitates and promotes the transformation of Guinier-Preston(GPI)zones toη'phase.During the cooling stage,the sizes ofη'phase increase with a little change in the number density,leading to a further slight increase of the hardness and strength.As NIA proceeds,the corroded morphology in the alloy changes from a layering feature to a wavy feature,the maximum corrosion depth decreases,and the reason has been analyzed based on the microstructural and microchemical feature of precipitates at grain boundaries and subgrain boundaries.

Synergistic enhancement on mechanical properties and corrosion resistance of biodegradable Mg-Zn-Y alloy via V-microalloying

For the sake of improving the mechanical properties and corrosion resistance of biodegradable Mg alloy synergistically,various content of element V(0,0.05,0.10,0.15,0.20 wt.%)are introduced into an Mg-Zn-Y alloy with long-period stacking ordered(LPSO)structure,and the effects of V on its microstructure,mechanical properties and corrosion resistance are investigated systematically.The results indicate that the grains are effectively refined by V addition,and the primaryα-Mg in Mg-Zn-Y-V0.1 alloy is most significantly refined,with grain size being decreased by 62%.The amount of 18R LPSO structure is increased owing to the V addition.The growth mode of the second phase(W-phase and 18R LPSO structure)is transformed to divorced growth pattern,which ascribes to the thermodynamic drive force of V to promote the nucleation of LPSO phase.Thus,18R LPSO structure presents a continuous distribution.Due to grains refinement and modification of second phase,the tensile strength and strain of alloys are both enhanced effectively.Especially,the ultimate tensile strength and the elongation of V0.1 alloy are 254 MPa and 15.26%,which are 41%and 61%higher than those of V-free alloy,respectively.Owing to the continuously distributed 18R LPSO structure with refined grains and stable product film,the weight loss and hydrogen evolution corrosion rates of V0.1 alloy are 7.1 and 6.2 mmy^(-1),respectively,which are 42.6%and 45.4%lower than those of V-free alloy.

Mechanical properties and damage constitutive model of sandstone after acid corrosion and high temperature treatments

Aiming at the problem of temperature-mechanics-chemical(T-M-C)action encountered by rocks in underground engineering,sandstone was selected as the sample for acid corrosion treatment at pH 1,3,5 and 7,the acid corrosion treated samples were then subjected to high-temperature experiments at 25,300,600,and 900℃,and triaxial compression experiments were conducted in the laboratory.The experimental results show that the superposition of chemical damage and thermal damage has a significant impact on the quality,wave velocity,porosity and compression failure characteristics of the rock.Based on the Lemaitre strain equivalent hypothesis theory,the damage degree of rock material was described by introducing damage variables,and the spatial mobilized plane(SMP)criterion was adopted.The damage constitutive model can well reflect the stress-strain characteristics of the rock triaxial compression process,which verified the rationality and reliability of the model parameters.The experiment and constitutive model analyzed the change law of mechanical properties of rock after chemical corrosion and high temperature thermal damage,which had certain practical significance for rock engineering construction.

Microstructures, mechanical properties, corrosion, and biocompatibility of extruded Mg-Zr-Sr-Ho alloys for biodegradable implant applications

In this study,the microstructures,mechanical properties,corrosion behaviors,and biocompatibility of extruded magnesium-zirconiumstrontium-holmium(Mg-Zr-Sr-Ho)alloys were comprehensively investigated.The effect of different concentrations of Ho on the microstructural characteristics,tensile and compressive properties,corrosion resistance,and biocompatibility were investigated.The microstructures of the extruded Mg-1Zr-0.5Sr-xHo(x=0.5,1.5,and 4 wt.%)alloys consisted ofα-Mg matrix,fineα-Zr particles,and intermetallic phase particles of Mg_(17)Sr_(2) and Ho_(2)Mg mainly distributed at the grain boundaries.Extensive{1012}tensile twins were observed in the partially recrystallized samples of Mg-1Zr-0.5Sr-0.5Ho and Mg-1Zr-0.5Sr-1.5Ho.Further addition of Ho to 4 wt.%resulted in a complete recrystallization due to activation of the particle stimulated nucleation around the Mg_(17)Sr_(2) particles.The evolution of a rare earth(RE)texture was observed with the Ho addition,which resulted in the weakened basal and prismatic textures.Furthermore,a drastic increase of 200%in tensile elongation and 89%in compressive strain was observed with Ho addition increased from 0.5 to 4 wt%,respectively.The tension-compression yield asymmetry was significantly decreased from 0.62 for Mg-1Zr-0.5Sr-0.5Ho to 0.98 for Mg-1Zr-0.5Sr-4Ho due to the weakening of textures.Corrosion analysis of the extruded Mg-Zr-Sr-Ho alloys revealed the presence of pitting corrosion.A minimum corrosion rate of 4.98 mm y^(−1) was observed in Mg-1Zr-0.5Sr-0.5Ho alloy.The enhanced corrosion resistance is observed due to the presence of Ho_(2)O_(3) in the surface film which reduced galvanic effect.The formation of a stabilized surface film due to the Ho_(2)O_(3) was confirmed through the electrical impedance spectroscopy and XPS analysis.An in vitro cytotoxicity assessment revealed good biocompatibility and cell adhesion in relation to SaOS2 cells.

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.

Improvements in mechanical, corrosion, and biocompatibility properties of Mg–Zr–Sr–Dy alloys via extrusion for biodegradable implant applications

In this study,extrusion was performed on Mg-Zr-Sr-Dy alloys for improving their mechanical,corrosion,and biocompatibility properties.Effects of extrusion and alloying elements on the microstructural characteristics,tensile and compressive strengths,corrosion behavior,and biocompatibility were investigated.The Mg-Zr-Sr-Dy alloys were composed of an α-Mg matrix containing {10■2} extension twins and secondary phases of intermetallic compounds Mg_(17)Sr_(2) and Mg_(2)Dy.Evolution of basal and rare earth(RE) textures was observed in the extruded alloys and an increase in Dy content to 2 wt.% resulted in texture randomization and strengthening of the RE component,mainly due to particle-stimulated nucleation and a change from discontinuous dynamic recrystallization to continuous dynamic recrystallization,which also led to an improved tension-compression yield asymmetry of 0.87.Extrusion of the alloys significantly enhanced their tensile and compressive properties due to improved distribution of alloying elements and formation of textures.Corrosion rates tested by hydrogen evolution testing,potentiodynamic polarization,and electrical impedance spectroscopy showed similar trends for each composition,and the lowest corrosion rate of 3.37 mmy^(-1) was observed for the Mg-1Zr-0.5Sr-1Dy in the potentiodynamic polarization testing.Dy_(2)O_(3) was observed in the inner layers of the Mg(OH)_(2) protective films,whose protective efficacy was confirmed by charge-transfer and film resistances.A comparison among the minimum CRs observed in this study and previously studied as-cast Mg-Zr-Sr-Dy and extruded Mg-Zr-Sr alloys,demonstrates that both the extrusion process and addition of Dy in Mg-Zr-Sr improved the CR.Similarly,extruded Mg-Zr-Sr-Dy alloys showed improved cell viability and adhesion of human osteoblast-like SaOS2 cells due to increased corrosion resistance and enhanced Sr distribution within the Mg matrix.

Influence of tool rotational speed on mechanical and corrosion behaviour of friction stir processed AZ31/Al_(2)O_(3)nanocomposite

Nano-sized reinforcements improved the mechanical characteristics efficiently by promoting more implicit particle hardening mechanisms compared to micron-sized reinforcements.Nano-sized particles lessen the critical particle solidification velocity for swamp and thus offers better dispersal.In the present investigation,the friction stir processing(FSP)is utilized to produce AZ31/Al_(2)O_(3)nanocomposites at various tool rotation speeds(i.e.,900,1200,and 1500 rpm)with an optimized 1.5%volume alumina(Al_(2)O_(3))reinforcement ratio.The mechanical and corrosion behavior of AZ31/Al_(2)O_(3)-developed nanocomposites was investigated and compared with that of the AZ31 base alloy.The AZ31 alloy experienced a comprehensive dynamic recrystallization during FSP,causing substantial grain refinement.Grain-size strengthening is the primary factor contributed to the enhancement in the strength of the fabricated nanocomposite.Tensile strength and yield strength values were lower than those for the base metal matrix,although an upward trend in both values has been observed with an increase in tool rotation speed.An 19.72%increase in hardness along with superior corrosion resistance was achieved compared to the base alloy at a tool rotational speed of 1500 rpm.The corrosion currents(Jcorr)of all samples dropped with increase in the rotational speed,in contrast to the corrosion potentials(Ecorr),which increased.The values of Jcorr of AZ31/Al_(2)O_(3)were 42.3%,56.8%,and 65.5%lower than those of AZ31 alloy at the chosen rotating speeds of 900,1200,and 1500 rpm,respectively.The corrosion behavior of friction stir processed nanocomposites have been addressed in this manuscript which has not been given sufficient attention in the existing literature.Further,this work offers an effective choice for the quality assurance of the FSP process of AZ31/Al_(2)O_(3)nanocomposites.The obtained results are relevant to the development of lightweight automobile and aerospace structures and components.

Effects of cooling rate on microstructure,mechanical and corrosion properties of Mg-Zn-Ca alloy

Mg69Zn27Ca4 alloys with diameters of 1.5, 2 and 3 mm were fabricated using copper mold injection casting method. Microstructural analysis reveals that the alloy with a diameter of 1.5 mm is almost completely composed of amorphous phase. However, with the cooling rate decline, a little α-Mg and MgZn dendrites can be found in the amorphous matrix. Based on the microstructural and tensile results, the ductile dendrites are conceived to be highly responsible for the enhanced compressive strain from 1.3% to 3.1% by increasing the sample diameter from 1.5 mm to 3 mm. In addition, the Mg69Zn27Ca4 alloy with 1.5 mm diameter has the best corrosion properties. The current Mg-based alloys show much better corrosion resistance than the traditionally commercial wrought magnesium alloy ZK60 in simulated sea-water.

Effect of Ti on microstructure,mechanical and corrosion properties of (Zr_(0.55)Al_(0.1)Ni_(0.05)Cu_(0.3))_(100-x)Ti_x bulk metallic glasses

The（Zr_（0.55）Al_（0.1）Ni_（0.05）Cu_（0.3））_（100-x）Ti_x alloys were prepared using an in-situ suck-casting method in a copper mold. The effects of Ti addition on the microstructure, mechanical and corrosion properties of the（Zr_（0.55）Al_（0.1）Ni_（0.05）Cu_（0.3））_（100-x）Ti_x alloys were investigated by X-ray diffraction, scanning electron microscopy, compressive tests and corrosion tests. It has been found that the addition of Ti higher than 4%（mole fraction） causes the formation of many crystalline phases in the alloy. The alloys with 1%-3% Ti display an obvious yield stage on their compressive stress-strain curves. An appropriate addition of Ti can improve the strength and ductility of the alloys. All the alloys have high corrosion resistance in 1 mol/L Na OH solution, and are corroded in 1 mol/L HCl solution. However, the appropriate addition of Ti can significantly improve the corrosion resistance of the alloys in HCl solution.

Mechanical properties and stress corrosion cracking behaviour of AZ31 magnesium alloy laser weldments

An AZ31 HP magnesium alloy was laser beam welded in autogenous mode with AZ61 filler using Nd-YAG laser system.Microstructural examination revealed that the laser beam weld metals obtained with or without filler material had an average grain size of about 12 μm.The microhardness and the tensile strength of the weldments were similar to those of the parent alloy.However,the stress corrosion cracking （SCC） behaviour of both the weldments assessed by slow strain rate tensile （SSRT） tests in ASTM D1384 solution was found to be slightly inferior to that of the parent alloy.It was observed that the stress corrosion cracks originated in the weld metal and propagated through the weld metal-HAZ regions in the autogenous weldment.On the other hand,in the weldment obtained with AZ61 filler material,the crack initiation and propagation was in the HAZ region.The localized damage of the magnesium hydroxide/oxide film formed on the surface of the specimens due to the exposure to the corrosive environment during the SSRT tests was found to be responsible for the SCC.

Effects of interrupted ageing and asymmetric rolling on microstructures, mechanical properties, and intergranular corrosion behavior of Al-Mg-Si-Zn alloy

Effects of interrupted ageing(T6I6) and asymmetric rolling on microstructures, mechanical properties, and intergranular corrosion(IGC) behaviors of Al-Mg-Si-Zn alloy were investigated. Results showed that the T6 alloy has the lowest strength and the worst IGC resistance, while the T6I6 alloy has higher strength and better IGC resistance.What’ s more, the alloy treated by pre-rolling deformation has higher strength and better IGC resistance;and the alloy treated by the pre-asymmetry rolling achieves the highest strength, the best IGC resistance and lower elongation. The mechanical properties depend on microstructures such as the grain size, texture, dislocation density and precipitation, the grain boundary misorientation and grain boundary microstructure are responsible for the IGC resistance.

Effect of Scandium and Zirconium on Mechanical and Exfoliation Corrosion Properties of Al-Mg-Mn Alloys

To quest for the best combination of mechanical properties and exfoliation corrosion resisting property of Al-Mg-Mn base alloys, and to seek after the effect of Sc and Zr on mechanical and exfoliation corrosion properties of Al-Mg-Mn alloys, comparative research technique was used, the mechanical properties of Al-Mg-Mn alloys with and without minor Sc and Zr treated by different annealing were measured, the degrees of exfoliation corrosion for these alloys through accelerated exfoliation corrosion test were evaluated, and polarization curves of these alloys were measured, too. The micro-morphologies of corrosion specimens were observed by SEM and the corrosion product was analyzed using EDS. Optical microscope and TEM were used, the relationship between their microstruc-tures and mechanical properties, exfoliation corrosion resisting property was investigated, and the results show that the addition of minor Sc and Zr can enhance the strength greatly and also improve the combination of strength and plasticity. Moreover, the addition of minor Sc, Zr does not cause appreciable decrease of exfoliation corrosion resisting property, the Al-Mg-Mn-Sc-Zr alloy annealed at 350 ℃ for 1 h has excellent combination of mechanical properties and exfoliation corrosion resisting property, the satisfied combination of mechanical properties nad exfoliation corrosion resisting property can be obtained by means of adding minor Sc and Zr, decreasing the content of Mn, and adopting reasonable annealing practice.

Effects of ECAE processing temperature on the microstructure, mechanical properties, and corrosion behavior of pure Mg

A two-step equal channel angular extrusion（ECAE） procedure was used to process pure Mg. The effects of ECAE processing temperature on the microstructure, mechanical properties, and corrosion behavior of pure Mg were studied. The results show that the average grain size of pure Mg decreases with decreasing extrusion temperature. After ECAE processing at 473 K, fine and equiaxed grains（~9 μm） are obtained. The sample processed at 473 K exhibits the excellent mechanical properties, whereas the sample processed at 633 K has the lowest corrosion rate. The improved corrosion resistance and mechanical properties of pure Mg by ECAE are ascribed to grain refinement and microstructural modification.

Microstructure, mechanical, and corrosion properties of extruded low-alloyed Mg–xZn–0.2Ca alloys

The microstructure, mechanical, and corrosion properties of extruded low-alloyed Mg xZn 0.2Ca (x=0, 1.0, 2.0, 3.0) alloys were investigated in this study. Findings from scanning electron microscope, X-ray diffraction and transmission electron microscopy results indicate that the amount of ternary Ca2Mg6Zn3 phase, as the only secondary phase in 1.0Zn, 2.0Zn, and 3.0Zn alloys, gradually increases with the addition of Zn, while the Mg2Ca phase was observed in the Mg 0.2Ca alloy only. Zn has a strong effect on the orientation and intensity of textures, which also influence mechanical behaviors, as revealed by electron back-scatter diffraction. Among all the alloys, the Mg 2.0Zn 0.2Ca alloy obtains the maximum tensile strength (278 MPa) and yield strength (230 MPa). Moreover, Zn addition has an evident influence on the corrosion properties of Mg xZn 0.2Ca alloy, and Mg 1.0Zn 0.2Ca alloy exhibits the minimum corrosion rate. This paper provides a novel low-alloyed magnesium alloy as a potential biodegradable material.

Effects of small additions of Zn on the microstructure, mechanical properties and corrosion resistance of WE43B Mg alloys

Zn is a commonly used alloying element for Mg alloys owing to its beneficial effects on mechanical properties. To improve the mechanical and corrosion properties of WE43B Mg alloys, the effects of 0–0.7wt% Zn addition on the microstructure and properties of sample alloys were investigated. Addition of Zn to as-cast WE43B alloy promoted the formation of the Mg12Nd phase;by contrast, after T6 heat treatment, the phase composition of WE43B alloys with and without Zn addition remained mostly the same. A long-period stacking ordered phase was predicted by CALPHAD calculation, but this phase was not observed in either the as-cast or heat-treated Zn-containing WE43B alloys. The optimum temperature and duration of T6 heat treatment were obtained using CALPHAD calculations and hardness measurements. Addition of Zn resulted in a slight reduction in the average grain size of the as-cast and T6 heat-treated WE43B alloys and endowed them with increased corrosion resistance with little effect on their mechanical properties.

Effects of Zn content on the microstructure and the mechanical and corrosion properties of as-cast low-alloyed Mg–Zn–Ca alloys

The effects of Zn content on the microstxucture and the mechanical and corrosion properties of as-cast low-alloyed Mg-xZn~.2Ca alloys （x = 0.6wt%, 2.0wt%, 2.5wt%, hereafter denoted as 0.6Zn, 2.0Zn, and 2.5Zn alloys, respectively） axe investigated. The results show that the Zn content not only influences grain refinement but also induces different phase precipitation behaviors. The as-cast microstxucture of the 0.6Zn alloy is composed of ct-Mg, Mg2Ca, and Ca2Mg6Zn3 phases, whereas 2.0Zn and 2.5Zn alloys only contain ct-Mg and Ca2Mg6Zn3 phases, as revealed by X-ray diffraction （XRD） and txonsmission electron microscopy （TEM） analyses. Moreover, with in- creasing Zn content, both the ultimate tensile strength （UTS） and the elongation to fracture first increase and then decrease. Among the three investigated alloys, the largest UTS （178 MPa） and the highest elongation to fracture （6.5%） are obtained for the 2.0Zn alloy. In addition, the corrosion rate increases with increasing Zn content. This paper provides on updated investigation of the alloy composi- tion-microstxucture-property relationships of different Zn-containing Mg-Zn-Ca alloys.

Anisotropy in mechanical properties and corrosion resistance of 316L stainless steel fabricated by selective laser melting

The corrosion behavior and mechanical properties of 316 L stainless steel(SS) fabricated via selective laser melting(SLM) were clarified by potentiodynamic polarization measurements, immersion tests, and tensile experiments. The microstructural anisotropy of SLMed 316 L SS was also investigated by electron back-scattered diffraction and transmission electron microscopy. The grain sizes of the SLMed 316 L SS in the XOZ plane were smaller than those of the SLMed 316 L SS in the XOY plane, and a greater number of low-angle boundaries were present in the XOY plane, resulting in lower elongation for the XOY plane than for the XOZ plane. The SLMed 316 L was expected to exhibit higher strength but lower ductility than the wrought 316 L, which was attributed to the high density of dislocations. The pitting potentials of the SLMed 316 L samples were universally higher than those of the wrought sample in chloride solutions because of the annihilation of MnS or(Ca,Al)-oxides during the rapid solidification. However, the molten pool boundaries preferentially dissolved in aggressive solutions and the damage of the SLMed 316 L in FeCl3 solution was more serious after long-term service, indicating poor durability.