Loss In Ultimate Tensile Strength Research Articles

Microstructure, mechanical properties and corrosion resistance of direct energy deposited AlCu0.25CoCrFeNi2.1 high entropy alloy: Tailored by annealing heat treatment

In this study, a novel high entropy alloy AlCu0.25CoCrFeNi2.1 is additively manufactured by laser direct energy deposition process. The microstructure, mechanical properties and corrosion resistance of the prepared AlCu0.25CoCrFeNi2.1 high entropy alloy are investigated and tailored by annealing heat treatment. The results indicate the alloy exhibits a dual-phase microstructure with face-centered cubic (FCC) columnar dendrites and body-centered cubic (BCC) interdendritic structures. The annealing heat treatment facilitates the precipitation and coarsening of Cu-rich short rod-like B2 phase within the incipient FCC phase and the dissolution of incipient BCC phase, synergistically varying the proportion of FCC/BCC + B2 contents and tailoring the properties. The hardness of microstructure fluctuates under the coupling effect of precipitation strengthening and lattice distortion reduction and shows an overall downward trend with the increase of annealing time. The tensile properties are noteworthily improved within 6-h annealing and achieve a maximum ultimate tensile strength of 1156.4 MPa. After 8-h annealing, the ductility of the alloy obtains a maximum value of 30.3% with minor loss of ultimate tensile strength. The corrosion resistance is dramatically enhanced and obtains the best value after 2-h annealing, and then gradually deteriorates with the destroying of FCC matrix passive film phase by coarsened B2 phases. These results are of great importance in rapidly designing/manufacturing novel high entropy alloys by laser direct energy deposition process and tailoring microstructure, mechanical properties and corrosion resistance by annealing heat treatment.

Mitigation of Desulfovibrio ferrophilus IS5 degradation of X80 carbon steel mechanical properties using a green biocide.

Most microbiologically influenced corrosion (MIC) studies focus on the threat of pinhole leaks caused by MIC pitting. However, microbes can also lead to structural failures. Tetrakis hydroxymethyl phosphonium sulfate (THPS) biocide mitigated the microbial degradation of mechanical properties of X80 steel pipeline by Desulfovibrio ferrophilus (IS5 strain), a very corrosive sulfate reducing bacterium. It was found that 100 ppm (w/w) THPS added to the enriched artificial seawater (EASW) culture medium before incubation resulted in 2.8-log reduction in sessile cell count after a 7-d incubation at 28 °C under anaerobic conditions, leading to 94% uniform corrosion rate reduction (from 1.3to 0.07mm/a), and 84% pitting corrosion rate reduction (from 0.70to 0.11mm/a). The X80 dogbone coupon incubated with 100 ppm THPS for 7 d suffered 3% loss in ultimate tensile strain and 0% loss in ultimate tensile strength compared with the abiotic control in EASW. In comparison, the no-treatment X80 dogbone coupon suffered losses of 13% in ultimate tensile strain and 6% in ultimate tensile stress, demonstrating very good THPS efficacy.

Carbon Source Starvation of a Sulfate-Reducing Bacterium–Elevated MIC Deterioration of Tensile Strength and Strain of X80 Pipeline Steel

It is known that starved sulfate-reducing bacterial biofilms corrode carbon steel more aggressively because they use electrons from elemental iron oxidation as an alternative source of energy. This work used carbon source starvation to vary MIC (microbiologically influenced corrosion) severity for studying subsequent MIC impacts on the degradation of X80 carbon steel mechanical properties. X80 square coupons and dogbone coupons were immersed in ATCC 1249 culture medium (200 ml in 450-ml anaerobic bottles) inoculated with Desulfovibrio vulgaris for 3-day pre-growth and then for an additional 14 days in fresh media with adjusted carbon source levels for starvation testing. After the starvation test, the sessile cell counts (cells/cm2) on the dogbone coupons in the bottles with carbon source levels of 0, 10, 50, and 100% (vs that in the full-strength medium) were 8.1 × 106, 3.2 × 107, 8.3 × 107, and 1.3 × 108, respectively. The pit depths from the X80 dogbone coupons were 1.9 μm (0%), 4.9 μm (10%), 9.1 μm (50%), and 6.4 μm (100%). The corresponding weight losses (mg/cm2) from the square coupons were 1.9 (0%), 3.3 (10%), 4.4 (50%), and 3.7 (100%). The 50% carbon source level had the combination of carbon starvation without suffering too much sessile cell loss. Thus, both its pit depth and weight loss were the highest. The electrochemical tests corroborated the pit depth and weight loss trends. The tensile tests of the dogbone coupons after the starvation incubation indicated that sulfate-reducing bacteria (SRB) made X80 more brittle and weaker. Compared with the fresh (no-SRB-exposure) X80 dogbone coupon’s ultimate tensile strain of 13.6% and ultimate tensile stress of 860 MPa, the 50% carbon source level led to the lowest ultimate tensile strain of 10.3% (24% loss when compared with the fresh dogbone) and ultimate tensile stress of 672 MPa (22% loss). The 100% carbon source level had a smaller loss in ultimate tensile strain than the 50% carbon source level, followed by 10% and then 0%. Moreover, the 100% carbon source level had a smaller loss in ultimate tensile strength than the 50%, followed by 10% and 0% in a tie. This outcome shows that even in the 17-day short-term test, significant degradation of the mechanical properties occurred and more severe MIC pitting caused more severe degradation.

In vitro oxidative stability of high strength siloxane poly(urethane-urea) elastomers based on linked-macrodiol.

In vitro oxidative stability of two siloxane poly(urethane urea)s synthesized using 4,4'-methylenediphenyl diisocyanate (in SiPUU-1) and Isophorone diisocyanate (in SiPUU-2) linked soft segment was evaluated using 20% H2 O2 and 0.1 mol/L CoCl2 solution at 37°C under 150% strain. Commercially available siloxane polyurethane (Elast-Eon™ 2A) and polyether polyurethane (ChronoThane P™ 80A) were used as negative and positive controls, respectively. ChronoSil™ 80A was included as another commercially available polycarbonate polyurethane. Scanning electron microscopic (SEM) examinations, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and molecular weight reduction revealed the extensive degradation of ChronoThane P™ 80A after 90 days while SiPUU-1, SiPUU-2 and Elast-Eon™ 2A showed no noticeable surface degradation. ChronoSil™ 80A showed degradation in both soft and hard segments. Tensile testing was carried out only on unstrained polyurethanes for 90 days. ChronoThane P™ 80A showed 35% loss in ultimate tensile strength and it was only 13-14% for SiPUU-1 and Elast-Eon™ 2A. However, the tensile strength of ChronoSil™ 80A was not significantly affected. The results of this study proved that SiPUU-1 possess oxidative stability comparable with Elast-Eon™ 2A. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2557-2565, 2019.

Degradation behaviors of geometric cues and mechanical properties in a 3D scaffold for tendon repair.

A three-dimensional (3D) scaffold fabricated via electrohydrodynamic jet printing (E-jetting) and thermally uniaxial stretching, has been developed for tendon tissue regeneration in our previous study. In this study, more in-depth biological test showed that the aligned cell morphology guided by the anisotropic geometries of the 3D tendon scaffolds, leading to up-regulated tendious gene expression including collagen type I, decorin, tenascin-C, and biglycan, as compared to the electrospun scaffolds. Given the importance of geometric cues to the biological function of the scaffolds, the degradation behaviors of the 3D scaffolds were investigated. Results from accelerated hydrolysis showed that the E-jetted portion followed bulk-controlled erosion, while the unaixially stretched portion followed surface-controlled erosion. The 3D tendon scaffold exhibited consistency between the weight loss and the decline of mechanical properties, which indicated by a 65% decrease in mass with a corresponding 56% loss in ultimate tensile strength after degradation. This study not only reveals that the anisotropic geometries of 3D tendon scaffold could affect cell morphology and lead to desired gene expression toward tendon tissue but also gives an insight into how the degradation impacts geometric cues and mechanical properties of the as-fabricated scaffold. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1138-1149, 2017.

Effect of Corrosion in Alkaline Solution to the Microstructure and Mechanical Properties of Cu/Sn-9Zn/Cu

Corrosion resistance performance of binary eutectic tin-zinc (Sn-9Zn) solder was investigated in 6 M potassium hydroxide. The corrosion resistance performance of the solder was studied through potentiodynamic polarization. Double dissolution peaks were seen during polarization, indicating preferential dissolution of elements from this solder. Tensile strength measurement shows substantial loss of ultimate tensile strength (UTS) of the joint made after polarization. Microstructure characterization proved that weak spots were introduced as active elements removed during polarization. This showed that microstructure alteration contributed to the loss of UTS after polarization.

Influence of direct rolling below β transus and annealing on microstructure and room temperature tensile properties of Ti–6Al–4V plates fabricated by electron-beam melting (EBM)

Abstract

Influence of fouling assemblage on the corrosion behaviour of mild steel in the coastal waters of the Gulf of Mannar, India

Corrosion behaviour and biofouling characteristics of mild steel in three different coastal locations in the Gulf of Mannar, India have been studied over a period of 24 months. Oyster fouling was predominant at Open sea — Tuticorin, while barnacle fouling was dominant at both Mandapam and Harbour — Tuticorin. The rate of corrosion for 24 months exposure period was highest at Mandapam, where fouling was minimal. The surface of the mild steel was characterized by etchings & crevices beneath the hard foulers attached on it, at all the test locations. The depth of crevice caused by hard foulers was higher at Open sea — Tuticorin followed by Harbour — Tuticorin and Mandapam. The loss in ultimate tensile strength was more in Open sea — Tuticorin than the other two locations. Corrosion behaviour of mild steel is discussed based on the variation in the biofouling assemblage at the three test locations.

Quercetin-crosslinked porcine heart valve matrix: Mechanical properties, stability, anticalcification and cytocompatibility

Bioprosthetic heart valves, prepared by glutaraldehyde (GA) crosslinking, have some limitations due to poor durability, calcification and immunogenic reactions. The aim of this study was to evaluate the crosslinking effect of a natural product, quercetin, on decellularized porcine heart valve extracellular matrix (ECM). After crosslinking, the mechanical properties, stability, anticalcification and cytocompatibility were examined. The results showed that the tensile strength of quercetin-crosslinked ECM was higher than that of GA-crosslinked ECM. After crosslinking with quercetin, the thermal denaturation temperature of ECM was clearly increased. Quercetin-crosslinked ECM could be stored in D-Hanks solution for at least 30 days without any loss of ultimate tensile strength and elasticity. After soaking in D-Hanks solution for 36 days, there was only 11.55% non-crosslinked excess quercetin released and no further release thereafter. Cell culture study shows that no inhibition on proliferation of vascular endothelial cells occurred when the quercetin concentration was lower than 1 μg ml −1. This non-cytotoxic concentration was 100 times higher than that of GA. The resistibility of quercetin-crosslinked ECM to in vitro enzymatic hydrolysis was comparable to that of GA-crosslinked ECM. An in vitro anticalcification experiment showed that quercetin crosslinking could protect ECM from deposition of minerals in simulated body fluid. The present study demonstrated that quercetin can crosslink porcine heart valve ECM effectively, which suggests that quercetin might be a new crosslinking reagent for the preparation of bioprosthetic heart valve xenografts and scaffolds for heart valve tissue engineering.

Notch tensile response of mini-regions in AA2024 and AA2524 friction stir welds

For the first time, experiments are conducted on solid-state FSW joints in a pair of aerospace alloys to determine how the process affects notch–strength and notch sensitivity. In this study, AA2524 and AA2024 FSW welds using notched tensile specimens are used to evaluate the notch tensile strength (NTS) of specific regions with different hardness values in the weld process zone. For the FSW process parameters used in this study, the response of the unnotched weld nugget specimen incurs a 4% loss in ultimate tensile strength (UTS) while retaining good ductility in comparison to the base metal. However, when a notch is introduced, the nugget experiences a reduction of ∼13% in the NTS while notch fracture strain (NFE) decreased by 40%. Fractographic results show that the existence of a banded microstructure in the nugget region is a primary factor affecting the reduction in NTS and NFE in the weld nugget. For notched specimens located at both the nugget–HAZ boundary and at the minimum hardness (HAZ), the measured reduction in NTS is directly correlated to a greater amount of inter-granular fracture in these regions due to over-aging in the welding process. Finally, when comparing local mechanical properties for both notched and unnotched specimens, the notch–strength ratio for all FSW zones in the AA2024 and AA2524 FSW joints, NSR FSW zone = (NTS/UTS) FSW zone > 1.00, demonstrating that the entire FSW process zone in AA2024 and AA2524 is notch insensitive.

Investigation of installation damage of some geogrids using laboratory tests

A series of laboratory tests simulating installation damage was carried out on four types of woven geogrid. Relationships between index properties of the geogrids and the loss in ultimate tensile strength, strain at failure and tensile stiffness of the geogrids are presented. For the geogrids investigated, the ratio of volume of coating material to the mass of yarn (V-M ratio) plays a major role in evaluating the loss of ultimate tensile strength; that is, the amount of ultimate strength loss decreases with an increase in V-M ratio. The V-M ratio also plays a part in the stress—strain characteristics of the damaged geogrids: for a regularly coated geogrid (PET yarn + PVC coating with a relatively low V-M ratio), similar amounts of ultimate strength and strain losses were found; for a similar geogrid with a relatively high V-M ratio, the amount of ultimate strain loss was only about 50% of the ultimate strength loss. The experimental results also indicate that the losses of tensile stiffness at 2% and 5% strains seem to be governed by the types of yarn and coating material, regardless of their V-M ratio.

The effect of virtual cross linking on the oxidative stability and lipid uptake of aliphatic poly(urethane urea)

In vitro oxidative degradation and lipid sorption of aliphatic, low elastic modulus and virtually cross-linked poly(urethane urea)s based on 4,4′ methylene bis(cyclohexyl isocyanate), hydroxy terminated poly butadiene and hexamethylene diamine were evaluated. The aged samples revealed no weight loss in the oxidation medium. The IR spectral analyses revealed the stability of unsaturated double bonds at 964 cm −1 (characteristic for polybutadiene soft segment) with no change in peak intensity. The poly(tetramethylene glycol) (PTMG)–added poly(ether urethane urea) polymer also revealed no disappearance of IR peaks for ether and unsaturated double bonds in samples aged in vitro oxidation medium. All the polymers have shown increase in weight due to lipid up take in lipid-rich medium (palm oil) but it was rather low in Dulbecco's modified eagle medium (DMEM) cholesterol. The slight change in mechanical properties of the present polymers in oxidation and DMEM is due to the rearrangement of molecular structure with virtual cross links of hydrogen bonding (physical cross linking) without degradation and plasticization effect of lipid. The influence of these media on the rearrangement of virtual cross links has been observed. Higher the virtual cross-link density, lesser is the loss of tensile properties of poly(urethane urea)s in the oxidation medium and vice versa. On the other hand, higher the virtual cross-link density of poly(urethane urea), higher is the loss of ultimate tensile strength and stress at 100% strain and vice versa in DMEM medium.

An Evaluation of the Mechanical Properties of Mn-Mo and Mn-Mo-Ni Steels

A study of the effects of normalizing and austenitizing on the mechanical properties of Mn-Mo and Mn-Mo-Ni steels is presented. It is shown that the quenched and tempered condition has superior notch toughness, elevated temperature tensile properties, and creep ductility than the normalized and tempered condition. The basis of comparison used for strength is the percentage of the room temperature strength. The creep strength and rupture resistance of the normalized and tempered condition are better than those of the quenched and tempered condition. Also, a comparison of the properties of the steels is made to evaluate the effects of a 0.5 percent Ni addition. While it improves hardenability, Ni tends to impair the elevated temperature creep strength and rupture resistance. Significant effects of Ni are seen on the elevated temperature tensile properties. The loss in ultimate tensile strength with increasing temperature is greater for the Ni modified grade than for the unmodified Mn-Mo. In the quenched and tempered condition, both yield strength and ultimate tensile strength are less affected by temperature when no Ni is added.