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High-purity magnesia refractories were fabricated by brine magnesium hydroxide from the salt-lake brine (Qinghai Salt Lake) and Y 2 O 3 as an additive at 1780 °C. It avoided the substantial CO 2 emissions and ultra high temperature sintering process (＞1900 °C) when compared with the conventional magnesite-calcination technical approach. The results confirmed that Y 2 O 3 was dispersed on the MgO grains boundaries in the fabricated MgO aggregates, resulting in a decrease in apparent porosity and enhancing the grains' boundaries. With 3 wt% addition of Y 2 O 3 , the apparent porosity and bulk density of the sample reached to 15.9 % and 3.10 g/cm3 from 37.9 % to 2.30 g/cm3 of blank control group, respectively. Compared to the blank control without Y 2 O 3 -adding, the sample with 5 wt% Y 2 O 3 exhibited a 54.17 % increase in the resistance to molten slag. SEM results indicated that the incorporation of Y 2 O 3 in samples increased the porosity of small pores and enhanced grains boundaries, thereby suppressing slag's penetration. Furthermore, the Y 2 O 3 -adding was employed to disperse the MgO grains boundaries and existed as separate phases for grains boundaries enhancement. The slag attack of the fabricated MgO–Y 2 O 3 refractory raw materials were controlled by an inter-crystalline corrosion process. [ABSTRACT FROM AUTHOR]

The bio-corrosion behavior and bio-compatibility of TiNbZrTa and TiNbZrTaMo high entropy alloys (HEAs) are crucial for their efficient maintenance during biological implantation. In this work, TiNbZrTa and TiNbZrTaMo HEAs were successfully prepared via vacuum melting, with a β-type titanium alloy Ti35Nb7Zr5Ta, exhibiting good biocompatibility used as a comparison. Due to the high entropy effect of equal atomic ratios, both TiNbZrTa and TiNbZrTaMo HEAs exhibit body-centered cubic (BCC) structure and lattice distortion compared to the β titanium alloy Ti35Nb7Zr5Ta. Mo elements contribute to the formation of a new BCC phase, resulting in a white matrix rich in Ta and Mo, and a dark second phase rich in Ti, Zr, and Nb. Electrochemical test results at 37 °C shown that TiNbZrTa has a wider and more stable passivation area than TiNbZrTaMo. The XPS results shown that formation of the passive film is related to the main elements added. Ti, Nb, Ta and Mo formed oxides via the solid-liquid interface and migrate inward, while Zr is formed at the passivation film/metal substrate interface and migrates outward, finally forming the layered structure of the passivation film. Additionally, the cytotoxicity test of mouse fiber cells was carried out to evaluate the biocompatibility of the HEAs. The results shown that the cell proliferation rate of TiNbZrTa and TiNbZrTaMo HEAs reached 0 and 1, respectively, with TiNbZrTa exhibiting better biocompatibility, as adding Mo reduced the cell proliferation rate. These findings may provide a method for predicting the bio-corrosion behavior and bio-compatibility of HEAs used for biological implantation.

Effects of pre-treatment (either pre-deformation or composed of pre-aging and pre-deformation prior to aging) on the dislocation morphologies and subsequent precipitation, corrosion behaviors, and mechanical properties of a novel Al-8.26Zn-1.95Mg-1.89Cu-0.08Sc-0.17Zr (wt.%) alloy were investigated. Pre-existing Al3(Sc, Zr) dispersoids can pin dislocations induced by pre-deformation before aging to form dislocation cells and cell walls. As a result, bimodal microstructures are formed during the subsequent aging process, with coarse precipitates dispersed along dislocation walls and fine precipitates inside dislocation cells. Meanwhile, dislocations pinned by Al3(Sc, Zr) dispersoids nearby grain boundaries inhibit the diffusion of solutes towards grain boundaries, which can modify grain boundary features by decreasing the potential difference between grain boundaries and grain interiors, and reducing precipitation-free zone width and grain boundary precipitate size. In particular, pre-aging prior to pre-deformation makes the dislocation distribution more uniform, which increases the volume fraction of nanoprecipitates without significant coarsening and further improves the grain boundary characteristics. Compared with the traditional T74 treated sample, these multiple microstructures significantly enhance the corrosion resistance of the alloy with less strength degradation. This study offers novel insights into the strengthening and corrosion mechanisms of pre-treated Al–Zn–Mg–Cu alloys with Zr and Sc microalloying.

In this study, to reactivate the oxide film and to secure biocompatibility, plasma electrolytic oxidation (PEO) treatment and hydroxyapatite (HA) deposition via mechanical coating (MC) processes were investigated. This experimental approach involved subjecting the Ti–6Al–4V alloy specimens to PEO treatment, followed by MC with HA powder for different hours as HA has the potential to increase bioactivity and surface characteristics due to its chemical composition and structural properties similar to natural bone. Therefore, the study aimed to examine the effects of MC with HA powder for 0, 1, 3, 5, 7, and 9 h on PEO-coated Ti–6Al–4V alloy discs for analyzing the surface characterization, phase analysis, surface roughness, wettability, adhesion strength, hardness, corrosion behavior, and cell proliferation properties for dental implant use. The findings demonstrate that prolonged HA milling enhances the substrate's mechanical strength, corrosion resistance, and adhesion properties. The presence of prominent anatase and HA peaks, particularly in the 5 MC-PEO, 7MC-PEO, and 9 MC-PEO samples, validates the synergistic impact of the PEO oxide layer and HA milling, resulting in outstanding corrosion resistance and biocompatibility. Cell culture analysis reveals a positive correlation between increased milling time and enhanced cell proliferation, particularly towards small-sized HA particles. [Display omitted] [ABSTRACT FROM AUTHOR]

Biodegradable suture anchors based on Mg-Nd-Zn-Zr alloy were developed for ligament-to-bone fixation in rotator cuff surgeries. The Mg alloy anchors were designed with structural features of narrow tooth and wide tooth, and simulated through finite element analysis (FEA). Meanwhile, the corrosion behaviors of the Mg alloy anchors were studied by immersion test and the mechanical properties were investigated by measuring the maximum torque and pull-out force. The simulation result showed that the wide-tooth anchor exhibited more a uniform stress distribution and lower shear stress in the torsion process, suggesting a satisfactory torsional resistance of this structure. Meanwhile, the wide-tooth anchor exhibited a lower Von-Mises stress after applying the same pull-out force in the simulation, indicating a higher resistance to pull-out failure of the anchor. The result of the immersion test indicated that the wide-tooth anchor exhibited a slightly slower corrosion rate in Hank's solution after 14-day immersion, which was beneficial to enhance the structural and mechanical stability of the biodegradable suture anchor. Furthermore, the results of the mechanical properties test demonstrated that the wide-tooth anchor showed superior performance with higher maximum torques and axial pull-out forces before and after corrosion. More importantly, the axial pull-out force and maximum torque for the wide-tooth anchor decreased by 5.86% and 8.64% after corrosion, which were significantly less than those for the narrow-tooth anchor. Therefore, the wide-tooth suture anchor with lower corrosion rate, higher mechanical properties and structural stability is a promising candidate for ligament-bone fixation in the repair of rotator cuff injuries. [ABSTRACT FROM AUTHOR]

In this work, Fe-20Cr-20Mn-0.75N (wt.%) high-nitrogen stainless steel (HNSS) was studied using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electrochemical testing. The corrosion behaviors of Fe-20Cr-20Mn-0.75N HNSS with different concentrations of NaCl were studied. The composition of a passive film on Fe-20Cr-20Mn-0.75N HNSS was analyzed using X-ray photoelectron spectroscopy (XPS) at an applied potential of 0.2VSCE. The results showed that, with the increase in Cl− concentration, the corrosion tendency and corrosion rate of Fe-20Cr-20Mn-0.75N HNSS get higher. In the solution of a low Cl− concentration, the fraction of Fe and Cr oxides in the passive film is higher, and the passive film is thicker and more stable. By increasing the stability of the passive film and preventing its rupture, the elevated NH4+ concentration can enhance the corrosion resistance of Fe-20Cr-20Mn-0.75N HNSS in a NaCl solution. [ABSTRACT FROM AUTHOR]

This review provides an overview of Cu–Ni–Sn alloys, which have great advantages as a potential substitute for beryllium bronze. The characteristics of spinodal decomposition in Cu–Ni–Sn alloys are thoroughly discussed by conducting a comprehensive analysis of thermodynamics and the phase diagram. The traditional casting process for Cu–Ni–Sn alloys is subject to several limitations, including segregation during solidification as a primary constraint. Another significant limitation is the occurrence of discontinuous precipitation during aging. Thus, the strategies to overcome these limitations are further elaborated. Commonly used methods include thermal-mechanical processing and composition design. Finally, the application of Cu–Ni–Sn alloys in friction and corrosion is discussed. The purpose of this review is to provide a comprehensive summary of the research progress and significant limitations encountered in Cu–Ni–Sn spinodal alloys. This includes a discussion of traditional casting methods as well as novel preparation techniques. The aim is to serve as a valuable reference for the development of new manufacturing methods and the future advancement of Cu–Ni–Sn spinodal alloys.

A novel low-alloyed Mg–1Bi–1Zn–1Ag alloy system was developed by extrusion at different extrusion ratios to achieve a bimodal grain structure. The dependence of the corrosion behavior and tensile properties on the grain structure was analyzed. The sample obtained at the extrusion ratio of 9 (BZQ111-R9) displayed a bimodal grain microstructure. In addition, its dominant corrosion mode was filiform with intergranular corrosion at a low corrosion rate of 0.06 mm/a. An improved synergy between strength (tensile yield strength of 207.1 MPa) and ductility (elongation of 35.9%) was realized in the BZQ111-R9 sample. Thus, the proposed approach can develop low-alloyed Mg–Bi-based alloys with excellent synergy between the corrosion resistance and tensile properties based on the control of the bimodal grain structure.

The Mg–Er–Ni alloy with comparable strength and solubility was prepared by controlling the Ni content. The mechanical properties and corrosion mechanism of alloys with long-period stacking ordered (LPSO) phase, as well as those with both LPSO and γʹ phases, were investigated and clarified. This study focused on investigating the underlying reasons for the high mechanical strength and fast corrosion rate of the Mg–13Er–3Ni alloy with LPSO and γʹ phases. The highest corrosion rate of the Mg–13Er–3Ni (wt.%) alloy is not only associated with the high volume fraction of the LPSO phase, which provides a larger zone for the corrosion cathode rather than forming a corrosion barrier, but also linked to the introduction of the γʹ phase that forms new sites for galvanic corrosion and avoids the formation the Er2O3 corrosion product film with corrosion-resistant. Moreover, The high mechanical properties of Mg–13Er–3Ni alloy are mainly attributed to the texture strengthening, dislocation strengthening and the second phase reinforcement that were caused by high volume fraction of LPSO phase and the precipitation of lamellar γʹ phase in Mg matrix. Generally, Compared to the Mg–13Er-1.5Ni (wt.%) alloy, the corrosion rates and mechanical strength of Mg–13Er–3Ni (wt.%) alloy were increased significantly by 302.8% and 50.3%, respectively, by coupling the LPSO and γʹ phases. Its ultimate tensile strength of 445 MPa and corrosion rare of 128.5 mg cm−2 h−1, which provides a new high strength and rapid corrosion Mg alloy materials for fracturing tools application.

Refill friction stir spot welding (RFSSW) of high strength aluminum alloy has a wide application prospect. However, there are few studies between the microstructure and macroscopic corrosion behavior, causing a significant impediment in corrosion protection of the joint. Therefore, the microstructure and corrosion behavior of 7050 aluminum alloy RFSSW joint was investigated in this paper. Due to the difference of microstructure, the joint can be divided into five zones, namely stir zone (SZ), thermo-mechanically affected zone (TMAZ), heat affected zone-I (HAZ-I), heat affected zone-II (HAZ-II) and base metal (BM). Therein, the grain size and the micron-sized second phase particles of SZ were fine, while other areas were coarse. And they were mainly Al2CuMg and Al7Cu2Fe. After intergranular corrosion and exfoliation corrosion tests, it was indicated that the grain morphology and second phase particles did not significantly affect the corrosion susceptibility, but the continuous degree of intergranular nano-precipitates was the key factor. A coefficient r was defined to quantitatively characterize the continuous degree of intergranular nano-precipitates. The HAZ-II and TMAZ exhibited high corrosion sensitivity with a high value of r, while HAZ-I and SZ exhibited low corrosion sensitivity with a low r. The corrosion mechanism was also briefly discussed.

The demand for soluble magnesium alloys with high plasticity used for sealing tools in petroleum field is increasing. Here, the effects of Ni content (0.1, 0.2 and 0.5wt.%) on microstructure, mechanical properties and corrosion rate of Mg-2Gd alloy were studied. The volume fraction of LPSO phases and the average grain size (α-Mg) increased and decreased with the increase of Ni content, respectively. After adding Ni, the texture changed from the rare earth texture to the basal fiber texture, and the strength, hardness and corrosion rate were increased with an acceptable decrease in elongation: the ultimate tensile strength/elongation/corrosion rate of the Mg-2Gd alloy and Mg-2Gd-0.5Ni alloy were 191 MPa/23.1%/15.2 mm·y-1, 287 MPa/18.1%/499.9 mm·y-1, respectively. Therefore, the addition of Ni effectively improved the strength and degradation rate of the Mg-2Gd alloy, which was mainly due to the grain refinement, the enhancement of basal fiber texture and the appearance of LPSO phases.

Biodegradable suture anchors based on Mg-Nd-Zn-Zr alloy were developed for ligament-to-bone fixation in rotator cuff surgeries. The Mg alloy anchors were designed with structural features of narrow tooth and wide tooth, and simulated through finite element analysis (FEA). Meanwhile, the corrosion behaviors of the Mg alloy anchors were studied by immersion test and the mechanical properties were investigated by measuring the maximum torque and pull-out force. The simulation result showed that the wide-tooth anchor exhibited more a uniform stress distribution and lower shear stress in the torsion process, suggesting a satisfactory torsional resistance of this structure. Meanwhile, the wide-tooth anchor exhibited a lower Von-Mises stress after applying the same pull-out force in the simulation, indicating a higher resistance to pull-out failure of the anchor. The result of the immersion test indicated that the wide-tooth anchor exhibited a slightly slower corrosion rate in Hank’s solution after 14-day immersion, which was beneficial to enhance the structural and mechanical stability of the biodegradable suture anchor. Furthermore, the results of the mechanical properties test demonstrated that the wide-tooth anchor showed superior performance with higher maximum torques and axial pull-out forces before and after corrosion. More importantly, the axial pull-out force and maximum torque for the wide-tooth anchor decreased by 5.86% and 8.64% after corrosion, which were significantly less than those for the narrow-tooth anchor. Therefore, the wide-tooth suture anchor with lower corrosion rate, higher mechanical properties and structural stability is a promising candidate for ligament-bone fixation in the repair of rotator cuff injuries.

The Selective Laser Melting (SLM) is an effective method to produce highly corrosion resistant Oral Alveolar Implants (OAI) by changing the scanning speed. Nevertheless, the long-term corrosion behavior of SLM 316L orthodontic bracket alloys in artificial saliva is overlooked in previous studies. In this study, 316L SS samples fabricated by SLM at different scanning speeds (800 mm/s, 1200 mm/s, and 1600 mm/s) were conducted a long-term (90 days) immersion test by being put into artificial saliva with three different pH values (pH 1.5, pH 4, and pH 6). The morphology, XRD and especially corrosion behavior of the samples fabricated by SLM and forging were investigated. The XRD results exhibit that high-speed scanning accelerates the cooling rate and inhibits the δ → γ phase transformation proceeding. Corrosion results show that the corrosion attack induced by pre-existing pores will expand through the crevices and break down the surface structure around the pores, leading to corrosion damage area to expand to several times of the original pore area. Besides, the mean corrosion rate of the sample at a scanning speed of 800 mm/s shows better corrosion resistance in artificial saliva of pH 4 and pH 6. Compared with wrought 316L SS samples, the SLM 316L SS samples had an obvious difference in the performance of corrosion rate and corrosion behaviors.

Fracturing tools for oil and gas exploitation require high mechanical properties and degradability. Zn alloys are possible to have good mechanical properties and much lower cost than widely used rare-earth Mg alloys, so it is worthy to develop Zn alloys as alternative materials. In this paper, a novel shell-like microstructure of Zn-5Mn alloy has been realized by bottom circulating water cooling. MnZn 9 phase appears by the first time in Zn-Mn alloys with Mn < 6.4 wt%. This phase leads to the formation of hard MnZn 9 /MnZn 13 core/shell structure with a high volume fraction of 76 %, dispersed uniformly in soft Zn phase. The alloy has excellent compressive properties without fracture even when stress and strain reach 2776 MPa and 80 %, respectively. Its ultimate uniform compressive stress and strain are 865 MPa and 56 % respectively, beyond widely used dissoluble Mg alloys. Weight loss rate of the Zn-5Mn alloy is two times that of pure Zn, immersed in 3 wt% KCl solution at 93°C. The shell-like Zn-5Mn alloy provides guiding significance of applying Zn alloys in fracturing tools for oil and gas exploitation. [Display omitted] • MnZn 9 phase appears by the first time in Zn-Mn alloys with Mn < 6.4 wt%. • A novel MnZn 9 /MnZn 13 core/shell structure is dispersed uniformly in Zn phase. • Zn-5Mn alloy has the best compressive mechanical properties in degradable materials. • Weight loss rate of the alloy in 3 wt% KCl at 93°C is twice that of pure Zn. [ABSTRACT FROM AUTHOR]

The microstructure, corrosion behavior, and electrochemical behavior of as-cast Mg-4Y-xZn (x=1,2,3,4 wt.%) are studied by SEM, weight loss and electrochemical tests. Mg12YZn (X), Mg3Y2Zn3 (W) and Mg24Y5 constitute the phase composition system of the alloy. When Zn content is 1 wt.%, all tests reveal that alloy has the optimal corrosion performance. The second phase in these alloys, due to their nobler nature than α-Mg, exists as a cathode during the corrosion process, so that α-Mg preferentially occurs corrosion to accelerate the formation of corrosion pits. After soaking in 3.5 wt.% NaCl solution for some time, the stability of the W phase changed, and gradually dissolved, which was finally removed by chromic acid used for removal of corrosion products. In addition, X phase can be used as an anode in the micro-galvanic cells formed with W phase to reduce the corrosion rate of α-Mg and thus improve the corrosion performance of the alloy.

A series of Mg–Ti composites are fabricated by high-pressure solid-state sintering (HPSSS) technique developed in our lab. The correlation between microstructures and corrosion behaviors is comparatively studied. It is shown that the Mg/Ti interface primarily determines the corrosion resistance of the composites, and the corrosion process is a comprehensive action of material composition, interface content, corrosion potential and interfacial oxide. Besides, the present semi-degradable Mg–Ti composites retain superior structure stability after Mg degradation due to the strong interfacial bonding obtained by the high-pressure solid-state sintering. All of the derived porous Ti exhibits a superior compressive plasticity, and the mechanical properties of the porous Ti can be readily adjusted by tuning the porosity. With superior mechanical properties, low Young's modulus and favourable pore size, the present porous Ti offers superior mechanical compatibility, demonstrating promising prospect in the load bearing biomedical applications.

Magnesium alloys, a novel functional material for the fabrication of fracturing tools, are being paid more and more attentions recently due to their relatively high mechanical properties and fast dissolubility ability after fracturing. In this study, the novel extruded Mg–10Gd–3Y–0.3Zr–xNi alloys will be reported and their microstructure, mechanical and corrosion behaviors will be also studied. The results show that Ni contents influence phase precipitation behaviors. With adding 0.2 wt% Ni, a large amount of Zr7Ni10 phases will be precipitated insides α-Mg matrix, directly leading to degradation of strength and large corrosion rate. With further increasing Ni contents, the precipitation phases can be changed from Mg5RE to 18R-LPSO structure, resulting in higher mechanical properties and faster corrosion rate. Moreover, adding Ni element also change the texture orientation by influencing the precipitation behavior of the alloys. The alloys invented in this paper have attained the highest compressive and tensile properties among all the reported dissoluble magnesium alloys. This work is beneficial in understanding the role of Ni in the magnesium alloys and provides more materials alternatives for the fabrication of dissoluble fracturing tools.

AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) has attracted significant interest among researchers due to unprecedented mechanical properties compared with single-phase solid solution high entropy alloys; however, the high content of cobalt element limits its engineering applications. In this paper, the mechanical and corrosion behaviors of cost-effective AlCrFeNi3.1 and AlCrFe2Ni2.1 HEAs were systematically studied by tensile tests and electrochemical methods; meanwhile, the results were compared with AlCoCrFeNi2.1 EHEA. The results indicated that all the studied HEAs showed dual phase microstructure composed of FCC and BCC/B2 phases. Due to the hetero-deformation induced strengthening, all the studied HEAs showed an excellent combination of strength and ductility with fracture strength over 1 GPa and fracture strain exceeding 17%, indicating that substituting the cobalt element of AlCoCrFeNi2.1 EHEA by nickel or iron element is feasible from the perspective of mechanical properties. As for the corrosion behaviors in 3.5 wt.% NaCl solution, AlCrFeNi3.1 HEA exhibited the best corrosion resistance due to the high volume fraction of the corrosion resistant FCC phases and low Al/Cr ratio of BCC/B2 phases, while AlCrFe2Ni2.1 HEA showed the worst corrosion resistance owing to the high Al/Cr ratio of BCC/B2 phases. [ABSTRACT FROM AUTHOR]

Dissoluble magnesium alloys for fabrication of fracturing tools have received increasing attention in recent years. However, most of the existing research is focused on the small-sized samples prepared in the laboratory, and there is almost no report on the industrial dissoluble magnesium alloys. In this study, large-scale Mg-Al-Zn-Mn-Ca-Ni alloys with a diameter of 110 mm were prepared by a semi-continuous casting and two-step extrusion method, and the corresponding microstructure and mechanical and corrosion properties were also investigated. It was found that after two-step extrusion, the mainly precipitate phases in the Mg-Al-Zn-Mn-Ca-Ni alloy are bulk-like AlMnNi, strip-like Al3Ni, and granular-like and lamellar-like Mg17Al12 phases. Due to the combined effects of grain refinement and precipitation strengthening, the Mg-Al-Zn-Mn-Ca-Ni alloy obtained excellent mechanical properties after two-step extrusion, and its ultimate tensile strength, yield strength, and elongation were 314.6 MPa, 191.2 MPa, and 13.1%, respectively. Moreover, the corrosion rate of the alloy in 3 wt.% KCl at 93 °C was as high as 97.61 mg·cm−2·h−1. This work provides a high-performance, low-cost, and large-scale alloy product for the fabrication of dissoluble fracturing tools. [ABSTRACT FROM AUTHOR]

The influence of various Ag contents on the microstructure, mechanical properties, and corrosion behavior of extruded Al-4.0Cu-1.1Li-0.4Mg-xAg-0.2Mn-0.2Zr (x = 0.4 and 0.9, wt.%) alloys was investigated. The alloy with 0.9 Ag content contains higher number density of slender T1 (Al2CuLi) precipitates along with some θ' (Al2Cu) phases in the matrix than the alloy with 0.4 Ag content, which is associated with a more rapid hardening response and higher mechanical properties and corrosion resistance, particularly for aging at 130 °C. When aging at high temperatures (above 160 °C), the increase of Ag content mitigates hardness loss by preventing the T1 precipitates from coarsening, and makes the alloy decorate more coarse precipitates at grain boundaries, which leads to the fracture morphology mainly occupied by intergranular fracture. Furthermore, due to the simultaneous promotion of T1 precipitates at grain boundaries and in grain interiors, the 0.9 Ag-containing Al-Cu-Li-Mg-Ag alloy has almost no improvement in corrosion resistance. [ABSTRACT FROM AUTHOR]

For the development of biological ZrTi alloys with excellent properties, microstructure evolution, mechanical properties and corrosion behaviors of a novel Zr–40Ti–4.5Al–4.5 V (Z40T, wt.%) alloy resulted from different cooling rates have been investigated. Variations in the phase composition and microstructure are observed with X-ray diffraction, metallography, scanning and transmission electron microscopy analyses. The results demonstrate that α'' martensite can be formed through a nondiffusive phase transformation of the β phase during rapid cooling. However, slow cooling rates provide a stable α phase due to atomic diffusion and rearrangement. Furthermore, the grain size of each phase also changes as a result of different cooling rates. Moreover, the mechanical properties and corrosion behaviors are determined with uniaxial tensile testing and potentiodynamic polarization testing in NaCl solution. The mechanical properties and corrosion behaviors of the Z40T alloy are closely related to the phase composition and microstructure. The sample strength and fracture elongation changes obviously as the cooling rates change from water cooling to slow cooling. Analysis of potentiodynamic potential curves indicates that corrosion potential increases and corrosion current density decreases as the cooling rate is increased from slow cooling to water cooling. The variation in the mechanical properties and corrosion behaviors of the Z40T alloy are ascribed to the differences in the crystal structure and grain size of the constituent phase.

Because the CMAS corrosion and phase transformation at elevated temperatures above 1250 °C have limited the applications of traditional YSZ, the design of novel thermal barrier materials is a hotspot. GdTaO 4 is considered as a type of potential novel thermal barrier material owing to its low thermal conductivity. In this study, the mechanical and thermal properties, CMAS corrosion resistance, and the wettability of the GdTaO 4 were studied and compared with that of YSZ. The results show that the coefficient of thermal expansion and hardness of GdTaO 4 are 14.1 × 10−6 K−1 (1350 °C) and 534.2 Hv 0.3 respectively. The thickness of CMAS reaction layer of GdTaO 4 is ~30.8 μm after 24 h reaction at 1350 °C, which is thinner than that of YSZ. After corrosion reaction, the CMAS glass aggregated instead of completely disappearing or continuously extending over the surface of GdTaO 4. The main reaction product is Ca 2 Ta 2 O 7 , and the anorthite phase may not be detected, which is similar to YTaO 4. By comparison, the dense substrate of YSZ became porous and CMAS glass has disappeared after 10 h. CMAS corrosion at 1350 °C. The on-line contact angle results show that the wettability of CMAS on GdTaO 4 is worse than that on YSZ at 1350 °C, while the opposite of the work of adhesion, which indicates that GdTaO 4 can remove liquid CMAS more easily than YSZ TBCs during the service. Furthermore, the corrosion depth and areas of GdTaO 4 are smaller than those of YSZ in the same situation. These findings suggest that GdTaO 4 possesses better high-temperature properties and CMAS corrosion resistance than YSZ as a kind of potential of thermal barrier material. [ABSTRACT FROM AUTHOR]

Magnesium alloys, a novel functional material for the fabrication of fracturing tools, are being paid more and more attentions recently due to their relatively high mechanical properties and fast dissolubility ability after fracturing. In this study, the novel extruded Mg–10Gd–3Y–0.3Zr–xNi alloys will be reported and their microstructure, mechanical and corrosion behaviors will be also studied. The results show that Ni contents influence phase precipitation behaviors. With adding 0.2 wt% Ni, a large amount of Zr 7 Ni 10 phases will be precipitated insides α-Mg matrix, directly leading to degradation of strength and large corrosion rate. With further increasing Ni contents, the precipitation phases can be changed from Mg 5 RE to 18R-LPSO structure, resulting in higher mechanical properties and faster corrosion rate. Moreover, adding Ni element also change the texture orientation by influencing the precipitation behavior of the alloys. The alloys invented in this paper have attained the highest compressive and tensile properties among all the reported dissoluble magnesium alloys. This work is beneficial in understanding the role of Ni in the magnesium alloys and provides more materials alternatives for the fabrication of dissoluble fracturing tools. [ABSTRACT FROM AUTHOR]

Dissoluble magnesium alloys for fabrication of fracturing tools have received increasing attention in recent years. However, most of the existing research is focused on the small-sized samples prepared in the laboratory, and there is almost no report on the industrial dissoluble magnesium alloys. In this study, large-scale Mg-Al-Zn-Mn-Ca-Ni alloys with a diameter of 110 mm were prepared by a semi-continuous casting and two-step extrusion method, and the corresponding microstructure and mechanical and corrosion properties were also investigated. It was found that after two-step extrusion, the mainly precipitate phases in the Mg-Al-Zn-Mn-Ca-Ni alloy are bulk-like AlMnNi, strip-like Al3Ni, and granular-like and lamellar-like Mg17Al12 phases. Due to the combined effects of grain refinement and precipitation strengthening, the Mg-Al-Zn-Mn-Ca-Ni alloy obtained excellent mechanical properties after two-step extrusion, and its ultimate tensile strength, yield strength, and elongation were 314.6 MPa, 191.2 MPa, and 13.1%, respectively. Moreover, the corrosion rate of the alloy in 3 wt.% KCl at 93 °C was as high as 97.61 mg·cm−2·h−1. This work provides a high-performance, low-cost, and large-scale alloy product for the fabrication of dissoluble fracturing tools.

The effect of the Ca2Mg6Zn3 phase on the corrosion behavior of biodegradable Mg-4.0Zn-0.2Mn-xCa (ZM-xCa, x = 0.1, 0.3, 0.5 and 1.0 wt.%) alloys in Hank’s solution was investigated with respect to phase spacing, morphology, distribution and volume fraction. With the increase in Ca addition, the volume fraction of the Ca2Mg6Zn3 phase increased from 2.5% to 7.6%, while its spacing declined monotonically from 43 μm to 30 μm. The Volta potentials of secondary phases relative to the Mg matrix were measured by using scanning kelvin probe force microscopy (SKPFM). The results show that the Volta potential of the intragranular spherical Ca2Mg6Zn3 phase (+109 mV) was higher than that of the dendritic Ca2Mg6Zn3 phase (+80 mV). It is suggested that the Ca2Mg6Zn3 acted as a cathode to accelerate the corrosion process due to the micro-galvanic effect. The corrosion preferred to occur around the spherical Ca2Mg6Zn3 phase at the early stage and developed into the intragranular region. The corrosion rate increased slightly with increasing Ca content from 0.1 wt.% to 0.5 wt.% because of the enhanced micro-galvanic corrosion effect. The decrease in the phase spacing and sharp increase in the secondary phase content resulted in a dramatic increase in the corrosion rate of the ZM-1.0Ca alloy.

The influence of various Ag contents on the microstructure, mechanical properties, and corrosion behavior of extruded Al-4.0Cu-1.1Li-0.4Mg-xAg-0.2Mn-0.2Zr (x = 0.4 and 0.9, wt.%) alloys was investigated. The alloy with 0.9 Ag content contains higher number density of slender T1 (Al2CuLi) precipitates along with some θ’ (Al2Cu) phases in the matrix than the alloy with 0.4 Ag content, which is associated with a more rapid hardening response and higher mechanical properties and corrosion resistance, particularly for aging at 130 °C. When aging at high temperatures (above 160 °C), the increase of Ag content mitigates hardness loss by preventing the T1 precipitates from coarsening, and makes the alloy decorate more coarse precipitates at grain boundaries, which leads to the fracture morphology mainly occupied by intergranular fracture. Furthermore, due to the simultaneous promotion of T1 precipitates at grain boundaries and in grain interiors, the 0.9 Ag-containing Al-Cu-Li-Mg-Ag alloy has almost no improvement in corrosion resistance.

The 2024 aluminum alloy has excellent mechanical and low corrosion due to the existence of the high Cu levels, which shortens its service life. In this paper, we have systematically investigated the mechanism of the influence of three elements (Sc, Zr, and Ag) on the microstructure and corrosion behavior of 2024 aluminum alloy after microalloying. The results showed that microalloying treatment of 2024 aluminum alloy reduced the dendritic spacing of cast aluminum alloy; decreased the sizes of Cu-rich intermetallic particles (Cu-IMPs) within the peak aging of the T6 alloy to make their distribution more uniform; and changed the grain boundary phases (GBPs) and precipitate-free zones (PFZs) width of the T6 alloy. Microalloying treatment significantly changed the corrosion resistance of the alloy. Both Zr and Ag elements significantly improved the corrosion resistance of the alloy and reduced IGC depth and electrochemical corrosion rate, however, the Sc elements deteriorated the corrosion resistance of the alloy. Moreover, the corrosion mechanism of the alloy was also discussed in detail. • The PFZ of 2024 aluminum alloy can be narrowed by microalloying Zr and Ag elements, while the PFZ can be broadened by Sc elements. • Microalloying of Al-Cu-Mg alloy with Zr and Ag elements can reduce the corrosion susceptibility of the alloy. • The aggregate of Zr elements near the GBs forms Al 3 Zr particles, which prevent the formation of GBP of 2024Z alloy. [ABSTRACT FROM AUTHOR]

This study delved into the influence of Mg content on the microstructure and corrosion behavior of homogenized Al-Zn-Mg-Cu alloys. The findings unveiled that alloys featuring a moderate Mg content showcased an exceptionally low immersion corrosion rate of 0.0789 mm/a. A notable 22.3 % reduction in average grain size led to a significant 57.2 % drop in immersion corrosion rate. Furthermore, the augmentation of the Mg(Zn, Al, Cu) 2 phase within the grains contributed to a decrease in the maximum immersion corrosion depth of the alloy. These novel findings offer fresh insights and hold potential for enhancing the corrosion resistance of homogenized Al-Zn-Mg-Cu alloys. [Display omitted] • Alloys featuring a moderate Mg content showcased an exceptionally low immersion corrosion rate of 0.0789 mm/a. • A notable 22.3 % reduction in average grain size led to a significant 57.2 % drop in immersion corrosion rate. • The augmentation of the Mg(Zn, Al, Cu) 2 phase contributed to a decrease in the maximum immersion corrosion depth. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) is an ideal method to directly fabricate products with high geometrical complexity. With low density and good corrosion resistance, aluminum alloys are widely used as important structural materials. Microstructures and mechanical properties of SLMed aluminum alloys have been recently widely studied. Corrosion behavior as a vital concern during the service of SLMed aluminum alloy parts has also drawn many attentions. Previous studies have found that SLM-processed aluminum alloys exhibit better corrosion resistance compared to the casted and wrought counterparts for both Al-Si alloys and high strength 2xxx Al alloys, which is mainly due to the unique microstructure features of SLMed Al alloys. For Al-Si alloys, with different shapes of Si networks, the different building planes show discrepant corrosion behaviors. Owing to the rougher surface with relatively larger numbers of defects, the as-printed surface is vulnerable to corrosion than the polished. Heat treatment has a negative effect on corrosion resistance due to the breakup of Si networks. The microstructure features correlated with the corrosion behaviors were also reviewed in this paper. Some suggestions on the future study of corrosion behaviors of SLMed Al alloys were put forward.

The microstructure, mechanical properties and corrosion behaviors of as-cast ternary Mg-2Zn-xCa (x=0, 0.2, 0.4, 0.8) alloys have been investigated in this study. Results indicate that the microstructure of Mg-Zn-Ca alloys can be significantly refined with increasing Ca concentration. Moreover, the alloys with different contents of Ca exhibit the different phases formation behaviors, i.e. a-Mg + Ca2Mg6Zn3 phases for Mg-2Zn-0.2Ca and Mg-2Zn- 0.4Ca alloys, and a-Mg + Ca2Mg6Zn3 + Mg2Ca phases for Mg-2Zn-0.8Ca alloy, respectively. Among all the alloys, the maximum ultimate tensile strength and elongation (161 MPa and 9.1%) can be attained for the Mg-2Zn-0.2Ca alloy. Corrosion tests in Hanks' balanced salt solution indicated that Ca addition is detrimental to corrosion resistance of Mg-2Zn alloy. The relationship between as-cast microstructure and properties for different Ca-containing alloys is also discussed in detail. [ABSTRACT FROM AUTHOR]

Both high corrosion resistance and electrical conductivity are required for the surface coatings of the magnesium alloys as used in electronics or aerospace applications. In this study, anticorrosive yet conductive Hf/HfN multilayer coatings are deposited on magnesium alloys via magnetron sputtering. The microstructural characterizations reveal that the growth of nano-scale pinholes along with the columnar structure of Hf sublayers have been completely suppressed by introducing the nanocrystalline HfN sublayers. The optimized Hf/HfN multilayer coated magnesium alloy exhibits a positive corrosion potential of − 0.51 V vs SCE and low corrosion current density of 0.01 μA/cm 2 in electrochemical system, and few corrosion pits after 48 h salt spray test, while maintaining the fine electronic conductivity similar to magnesium alloy. The desirable performance was attributed to the multilayer structure induced by nanocrystalline HfN interlayer, which resulted in decreased coating porosity, confined pathway and increased energy barrier for corrosion media. [ABSTRACT FROM AUTHOR]

The study of the corrosion behaviors of structural materials exposed to liquid lithium (Li) is very important for the application of liquid Li as a potential plasma-facing or blanket material in future fusion device. It was demonstrated that the temperature plays an important role in the corrosion process. The corrosion behaviors of 304 stainless steel (304SS) in static liquid Li at 600 K and 640 K for 1320 h under high vacuum have been compared in the present work. The results show that the weight loss and corrosion depth of the 304SS specimens in static liquid Li at 640 K are about 3 times more than those at 600 K. After exposure to liquid Li, all the surfaces produce non-uniform damage which includes pitting and grain boundary corrosion. The surface damage of 304SS specimens at 640 K is more serious than that at 600 K. The corrosion mechanisms include physical dissolution and chemical corrosion; the effect of the latter on the corrosion behavior at 640 K is much more than that at 600 K. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Dissolvable functional magnesium alloys are attracting strong attention due to the prominent advantages of high strength and suitable dissolution rate. Here, the effect of Cu micro-alloying (0, 0.4, 0.8 wt%) on the microstructure, mechanical and corrosion properties of Mg-9.5Gd-2.7Y-0.9Zn alloys are investigated. With the increase of Cu contents, the block 14 H long-period stacking ordered (LPSO) phase gradually increases, which promotes the nucleation of dynamic recrystallized (DRXed) grains. However, the migration of the sub-structure is inhibited caused by the plate LPSO phase and the growth of DRXed grains is suppressed. Eventually, the grain size of DRXed grains decreased. The alloy with 0.8 wt% Cu obtains higher yield strength compared with Cu-free alloys, which is mainly ascribed to multiple strengthening contributions containing second phase, dislocation, grain boundary and solid solution. Due to the potential difference between the LPSO phase and the Mg matrix in the investigated alloys, the LPSO phase acts as cathodic to accelerate corrosion. The 0.8Cu alloy exhibits the highest corrosion rate, which is the synergistic effect of the second phase (its larger volta potential compared with 0Cu and its higher fraction of LPSO phase), dislocation density, grain size and crystal orientation. Ultimately, the Mg-9.5Gd-2.7Y-0.9Zn-0.8Cu alloy exhibits an ultimate tensile strength of 380 MPa, tensile yield strength of 331 MPa, and decent corrosion rate (16.8 mg·cm−2·h−1 at 93 °C in 3 wt% KCl solution). This work strengthens understanding the Cu role in designing high-strength dissolvable Mg-RE alloys. [Display omitted] • The effect of Cu micro-alloying on the microstructure and properties of Mg-Gd-Y-Zn alloys were investigated. • The Cu-added affects the formation of LPSO phase, which influences the DRXed behaviors. • The excellent strength for 0.8Cu alloy was ascribed to multiple strengthening contributions. • The 0.8Cu alloy with highest corrosion rate originated from the second phase, dislocation density, grain size and crystal orientation. [ABSTRACT FROM AUTHOR]

The microstructure, mechanical properties, and corrosion behaviors of solution-treated AM60-2%RE magnesium alloy containing 0.2-0.8% wt.% Zn were investigated. With the increase of Zn, the volume fraction of dispersed rod-like AlRE and granular-like AlRE phases of solution-treated AM60-2%RE + x%Zn increased, which improved the mechanical properties by dispersion strengthening. With increasing Zn content, the corrosion current density decreased, and the corrosion potential and electrochemical impedance of the alloys increased, and the corrosion resistance of solution-treated AM60-2%RE + x%Zn was improved. With the increase of Zn content, the leaf-like corrosion products of the alloy became smaller and more compact, and the content of Zn, Al, Ce, and La in corrosion products increased, which was beneficial to inhibit the corrosion progress. [ABSTRACT FROM AUTHOR]

Mg alloys are widely used in the fields of aerospace, automotive, and electronic communication equipment. Understanding the corrosion behavior of Mg alloys is critical to prevent their catastrophic failures from the acid rain corrosion. The influences of heat treatment on corrosion behaviors of Mg-4Nd alloy in acid rains were investigated. The corrosion mechanisms of Mg-4Nd alloy are dominated by electrochemical and chemical corrosion, and the corrosion behaviors of Mg-4Nd alloy are affected by the concentrations of acid rain and heat-treated temperatures. Furthermore, Nd 2 O 3 are derived from the oxidation of exposed Nd atoms at the edge of precipitates and solid-solution atoms. [Display omitted] • The corrosion behaviors of Mg alloy in acid rain are affected by pH and precipitates. • Corrosion behaviors of Mg alloy in acid rain are dominated by electrochemical and chemical corrosion. • The micro-galvanic corrosion occurs between Mg 41 Nd 5 and Mg 12 Nd. • Nd 2 O 3 comes from the oxidation of precipitates and solid-solution atoms in the corrosion process. • The Nd 2 O 3 embedded in corrosion product films prevents the attack of corrosive ions. [ABSTRACT FROM AUTHOR]

Three Mg–Y–Zn–Zr alloys have been designed with specific Y/Zn mole ratios around 1.32 for the purpose of high performance. Microstructures, mechanical properties and corrosion behaviors of the alloys have been studied. A wide distribution of compact and thick X-phase could promote the mechanical properties and corrosion resistance drastically. Moreover, a solidification behavior was proposed to understand the alternant distribution of X-phase (Mg 12 YZn) and W-phase (MgY 2 Zn 3 ). After hot extrusion, the corrosion resistance and mechanical properties of the alloys are strongly improved, due to the grain refinement and dispersive distribution of X-phase. Among the designed alloys, a high performance MgY 3.8 Zn 3 Zr 0.18 alloy was prepared by conventional casting and subsequent hot extrusion process. It owns an ultimate and yield strength of 420 MPa and 300 MPa, respectively, as well as the best corrosion resistance. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cu–Hf–Al amorphous thin films were synthesized using DC magnetron sputtering method. [•] Cu–Hf–Al amorphous thin film exhibited high Young’s modulus and hardness. [•] Cu–Hf–Al amorphous thin film has a high corrosion resistance in H+ or Na+ solutions. [ABSTRACT FROM AUTHOR]

The effects of heat treatments on the microstructures and corrosion behaviors of extruded Mg-2Nd-2Zn alloys in 3.5% NaCl electrolyte were investigated. It was found that the average corrosion rate of solid solution Mg-2Nd-2Zn alloy is 45.86 mm/y, which is much lower than that of the as-extruded and solution-aged Mg alloys. The nano-scale oxides were formed by the oxidation of solid solution atoms during the corrosion process and filled into the porous corrosion product film, which was conducive to reducing the corrosion rates of Mg alloys. Therefore, the solid solution treatment remarkably improved the corrosion rate of Mg alloys. • Heat treatments remarkably increase the grain sizes of Mg alloys and reduce grain boundary corrosion. • The corrosion products of Mg-2Nd-2Zn alloy are mainly composed of Mg(OH) 2 and Mg 2 Cl (OH) 3 ·4H 2 O. • Cl- attacks Mg(OH) 2 to form loose Mg 2 Cl(OH) 3 ·4H 2 O, resulting in a poor corrosion resistance of Mg alloys in Cl- solution. • Nano-scale oxides of solute atomic embedded in corrosion product film improves the corrosion resistance of Mg alloys. [ABSTRACT FROM AUTHOR]

Abstract: The corrosion behaviors of Mg–7Gd–5Y–1Nd–0.5Zr alloys after T5 treatment under (NH4)2SO4, NaCl and Ca(NO3)2 salt spray condition were investigated by weight loss rates, residual mechanical properties, scanning electron microscope (SEM), X-ray Diffraction (XRD) and potentiodynamic polarization tests. The corrosion degree of Mg–7Gd–5Y–1Nd–0.5Zr alloys in Ca(NO3)2 salt spray was very shallow by corrosion morphology and the corrosion route was extended along the surface in texture-like shape, while the alloy in NaCl and (NH4)2SO4 salt spray were major local corrosion and there were serious corrosion pits on the surface. The weight loss rates in (NH4)2SO4, NaCl and Ca(NO3)2 salt spray was respectively 0.4147, 0.1618 and 0.0725 mg/(cm2 d−1). The results of residual mechanical properties indicated that the corrosion order in salts spray of Mg–7Gd–5Y–1Nd–0.5Zr alloys is NH4SO4 > NaCl > Ca(NO3)2, which was consistent with the results of potentiodynamic polarization tests. The type of the salts will play a vital role in the initiation of the corrosion of EW75 alloy when they are used in the atmosphere environments. Inorganic salts with the smaller PH value after dissolution will have a stronger impact on the corrosion of EW75 magnesium alloys. [Copyright &y& Elsevier]

The effects of annealing and cryogenic thermal cycling treated on hydrophobic properties of Zr-based bulk metallic glasses surfaces fabricated by electrochemical etching were studied. The cryogenic thermal cycling on leads to poor corrosion performance for heat-treated metallic samples, while the annealing treatment induces the improved corrosion performance. Under the same electrochemical etching process, the etched sample surface is covered by dense coral-like micro-nano composite structures after cryogenic thermal cycling treatment for 30 cycles, and achieves superhydrophobic. However, there almost no nanoscale structures appear on the sample surface heat-treated at 702 K which results in the poor hydrophobic properties. Superhydrophobic film can generate a corrosion protection due to the existence of micro-nano composite structures in the samples. The effects of annealing and cryogenic thermal cycling treated on hydrophobic properties of Zr-based bulk metallic glasses surfaces fabricated by electrochemical etching were studied. After cryogenic thermal cycling treatment for 30 cycles, the sample achieves superhydrophobic due to the uperhydrophobic film can generate a corrosion protection due to the existence of micro-nano composite structures in the samples. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The corrosion behavior of 28Cr–7Ni–O–0.34N duplex stainless steels in air-saturated 3.5-wt% NaCl solution at pH 2, 7, 10 and 27 °C was studied by the potentiodynamic method. Two types of microstructures were investigated: the as-forged duplex and microduplex (average austenite grain size 5–16 μm) structures. The austenite volume fractions of the tested steels were between 0.35 and 0.64. The nitrogen effect on corrosion behaviors of both duplex and microduplex stainless steels were the same. At pH 2, the corrosion potential increased when the nitrogen content increased, however, corrosion current density as well as corrosion rate decreased. At pH 7 and 10, the effect of nitrogen on corrosion potential and corrosion rate could not be observed. Corrosion potential at pH 10 was lower than at pH 7. Pitting potential increased when the nitrogen content in the tested steels increased at all tested pH. For the nitrogen effect on the passive current density, it seemed that only at pH 2, the average passive current densities reduced when the nitrogen content increased. Nitrogen may have participated in the passive film or has been involved in the reaction to build up passive film. The ammonium formation and nitrogen enrichment at the interface metal/passive film with adsorption mechanism were discussed. The dissolute nitrogen might have combined with the hydrogen ions in solution to form ammonium ions, resulting in increasing solution pH. The steel could then easily repassivate, hence the corrosion potential and pitting potential would increase. However, the ammonium formation mechanism could not explain the decrease of corrosion potential in basic solution. Nitrogen enrichment at the metal/passive film interface with adsorption mechanism seemed to be an applicable consideration in increasing pitting potential. However, this mechanism did not involve the ammonium ion formation. In general, for the duplex and microduplex stainless steels tested, nitrogen increased the general corrosion resistances in acid solution and pitting corrosion resistance at all solution pH. Metallographic observation in both tested duplex and microduplex steels after pitting corrosion at all tested pH revealed that, the corroded structure in the tested steels without nitrogen alloying was austenite, but those with nitrogen alloying was ferrite. Even though ferrite had a higher chromium content than austenite but higher dissolved nitrogen in austenite than in ferrite may have increased the pitting resistance equivalent number (PRE) of austenite to be higher than that of ferrite. [Copyright &y& Elsevier]

The effects of alloying elements on the microstructure, mechanical properties, and corrosion behaviors of duplex stainless steels (DSSs) have been investigated in this study. Experimental alloys were prepared by varying the concentrations of the constituent elements in DSSs. Hot ductility test, tensile test, charpy impact test, and corrosion test were performed to evaluate the properties of the experimental alloys. The results showed that the extent of edge cracking of DSSs increased with the increasing value of the crack sensitivity index (CSI). The higher the hot ductility index (HDI) was, the better the hot ductility of DSSs achieved. Austenite ( γ) stabilizer generally caused a decrease in the strength and an increase in the charpy impact absorbed energy of the stainless steel. On the contrary, ferrite ( α) former exerted its beneficial effect on the strength but became detrimental to the toughness of DSSs. The presences of sulfur and boron also caused a decrease in the impact energy, but nitrogen and carbon hardly affected the toughness within the concentration range tested in this study. The value of pitting nucleation potential ( E np ) of different nitrogen contents in 3.5 wt.% NaCl solution at room temperature was almost the same, but the value of pitting protection potential ( E pp ) among these alloys was increased with increasing the content of nitrogen. The susceptibility to stress corrosion cracking (SCC) of DSSs was high when tested in boiling 45 wt.% MgCl2 solution. On the other hand, the time to failure of the experimental steels in 40 wt.% CaCl2 solution at 100 °C was longer than that in MgCl2 solution. Nitrogen could affect the SCC behavior of DSSs in CaCl2 solution through the combinative effects by varying the pitting resistance and the slip step dissolution. An optimum nitrogen (N) content of 0.15 wt.% was found where the highest SCC resistance could be obtained. Although γ phase exhibited better resistance to SCC, cracks were found to penetrate through α and γ grains or to propagate along the α/γ interface. As a result, a mixed transgranular plus intergranular mode of fracture surface was observed. [ABSTRACT FROM AUTHOR]