MPa Ultimate Tensile Strength Research Articles

Effects of Li content on microstructure evolution and mechanical properties of squeeze-cast Al-5Cu-xLi alloy assisted with ultrasonic treatment

In this study, a new squeeze-cast Al-5Cu-xLi-0.5Mn-0.3Mg-0.15Ti (x = 0.3, 0.6, 0.9, 1.2 wt%) alloy (Al-5Cu-xLi alloy for short) was prepared with ultrasonic treatment (UT), and the effects of UT and Li content on the microstructure evolution and mechanical properties of Al-5Cu-xLi alloy were investigated. Unlike other aluminum alloys, UT applied to aluminum-lithium alloys can bring about significant degassing effects in addition to grain refinement and homogenization, which is beneficial for the high strength and toughness of Al-5Cu-xLi alloy. With the increase of Li content from 0.3 wt% to 1.2 wt%, the average grain size remains unchanged at first, and then increases significantly. Interestingly, the average size of α-Al grains is 30% smaller than that of Al-5Cu-0Li alloy (without Li element) after adding only 0.3 wt% of Li element, while the ultimate tensile strength (UTS), yield strength (YS) and elongation are increased by 11.3%, 15.6% and 26.9%, respectively. The optimal comprehensive mechanical properties are obtained in Al-5Cu-0.6Li alloy, which exhibits 300 MPa in UTS, 190 MPa in YS and 16.7% in elongation. However, by further increasing the Li content, the strength of the Al-5Cu-xLi alloy remains almost unchanged, while its elongation decreases significantly (but still more than 13.5%), due to grain coarsening and slight compositional segregation.

Insights into the relationship between γ/α transformation and strength-ductility of auto-steel with 980 MPa grade based on experiments and theoretical calculations

Two novel dual-phase steels with high ductility (DH steel) were designed to satisfy the rising demand and stringent requirements for automotive steel. In order to improve mechanical properties, water quenching and isothermal bainite treatment (IBT) were applied after intercritical annealing (IA) respectively. Three-dimensional atom probe (3DAP) observation and kinetic simulation showed that the intercritical austenite formation was mainly controlled by the partitioning of C during intercritical austenite and ferrite (γ/α) transformation. The steels after water quenching were characterized by martensite and ferrite, and the enrichment of C in the martensite could enhance the strength, while a higher ferrite content could improve plasticity. After IBT treatment, the steels exhibited superiorly comprehensive mechanical properties, exhibiting more than 1000 MPa ultimate tensile strength (UTS) and total elongation (TEL) of about 22%. The matrix microstructure composition of ferrite, bainite and retained austenite (RA) was affected by the IA transformation. The higher content of intercritical austenite led to higher levels of bainite and RA, but the stability of RA was low. The bainite could lead to higher strength of the sample, while the unstable RA transformed into martensite before reaching the yield stress, exhibiting weaker transformation-induced plasticity (TRIP) effect and lower plasticity.

Effects of Heterogenization Treatment on the Hot-Working Temperature and Mechanical Properties of Al-Cu-Mg-Mn-(Zr) Alloys.

This study investigated the effects of a minor Zr addition (0.15 wt%) and heterogenization treatment (one-stage/two-stage) on the hot-working temperature and mechanical properties in Al-4.9Cu-1.2Mg-0.9Mn alloy. The results indicated that the eutectic phases (α-Al + θ-Al2Cu + S-Al2CuMg) dissolved after heterogenization, retaining θ-Al2Cu and τ1-Al29Cu4Mn6 phases, while the onset melting temperature increased to approximately 17 °C. A change in the onset melting temperature and evolution of the microstructure is used to assess an improvement in hot-working behavior. With the minor Zr addition, the alloy exhibited enhanced mechanical properties due to grain growth inhibition. Zr-added alloys show 490 ± 3 MPa ultimate tensile strength and 77.5 ± 0.7 HRB hardness after T4 tempering, compared to 460 ± 2.2 MPa and 73.7 ± 0.4 HRB for un-added alloys. Additionally, combining minor Zr addition and two-stage heterogenization resulted in finer Al3Zr dispersoids. Two-stage heterogenized alloys had an average Al3Zr size of 15 ± 5 nm, while one-stage heterogenized alloys had an average size of 25 ± 8 nm. A partial decrease in the mechanical properties of the Zr-free alloy was observed after two-stage heterogenization. The one-stage heterogenized alloy had 75.4 ± 0.4 HRB hardness after being T4-tempered, whereas the two-stage heterogenized alloy had 73.7 ± 0.4 HRB hardness after being T4-tempered.

Development of low-temperature impact-damage tolerant high entropy alloy with sequential multi-deformation mechanisms

Metals often lose their ductility at cryogenic temperatures owing to the decreased mobility of dislocations. TRansformation-induced plasticity (TRIP), a toughening mechanism at room temperature, can increase damage susceptibility at low temperatures, as the resultant martensite phases can become more brittle than the parent phases. Herein, we develop a high-entropy alloy (HEA) with an improved low-temperature impact-damage tolerance through a sequential plasticity mechanism. We design a trip-assisted dual-phase HEA (TADP HEA) and investigate the effects of Al addition on its mechanical properties upon deformation at different temperatures, depending on stacking fault energy (SFE). Our analysis shows that a senary (Cr20Mn6Fe34Co34Ni6)98Al2 HEA exhibits superior mechanical properties, including a 641 MPa yield strength (σy), 964 MPa ultimate tensile strength (σUTS), and 40% uniform elongation (ɛUTS) at ambient temperature (25 °C), and a 1 GPa σy, 1.5 GPa σUTS, and 36% ɛUTS at −100 °C. Notably, despite the presence of hexagonal-close packed martensite, the HEA exhibits a higher Charpy impact energy (406 J) than Cantor HEA (344 J) at −100 °C. We attribute this improvement to the sequential deformation mechanism of mechanical twinning and martensitic transformation in the HEA at −100 °C, which results in sustainable steady strain-hardening during deformation. We suggest that optimizing the sequential deformation mechanism by manipulating SFE in multi-component alloys can be an effective route for improving the damage tolerance of metals at cryogenic temperatures.

Simultaneous densification and improvement of cold spray additively manufactured Ti-6Al-4 V properties via electro-plastic treatment

Large-scale industrial application of additively manufactured (AM) components in general, and specifically cold sprayed additive manufactured (CSAM), is limited due to the nature of this technology and the resulting product’s porosity and embrittlement. To improve the final properties of additively manufactured material, many lengthy, complex, or expensive post-treatments have been proposed. Reducing the environmental impact, cost, and time required for additive manufacturing will allow for greater use in industrial applications. A novel thermomechanical treatment known as in situ electro-plastic treatment (ISEPT) is used in this study to treat CSAM Ti-6Al-4 V alloy known as grade 5 titanium. The Ti-6Al-4 V alloy has approximately three times the strength and hardness of commercial purity titanium (CP-Ti) with lower ductility and a dual-phase (α + β) microstructure that poses challenges during the CSAM process. Compared to CP-Ti, the results showed that CSAM Ti-6Al-4 V presented double the porosity and triple the number of ISEPT passes that presented ~ 2 µm ultra-fine grain microstructure. The ultimate tensile strength (UTS) of the ISEPT material was superior to that of CSAM Ti-6Al-4 V and increased from 184 to 1096 MPa with improved ductility rise from 1.1 up to 8.8%. Six ISEPT passes in air resulted in a slight increase in oxygen from 0.2% in the as-CSAM condition to 0.35%. Tensile properties of the ISEPT material were comparable to wrought Ti-6Al-4 V with 989 MPa UTS and 8.3% elongation. The ISEPT passes consolidated the CSAM (α + β) dual-phase Ti-6Al-4 V and allowed for the nucleation of equiaxed grains at the vicinity of former CSAM splat boundaries. The formation of lamellar colonies within the splat’s inner regions was observed. The role of ISEPT conditions on the rapid elimination of porosity and the evolution of cold spray splat boundaries via dynamic recrystallization were discussed.

Friction Stir Welding of Dissimilar Materials with Reinforcement of Copper Particulates

In this study, the controlled input parameters namely welding speed and spindle speed were optimized by Taguchi method for reinforcement of copper particulates in aluminium alloy (AA6061-AA6063-T6). High carbon and high chromium steel i.e. tool steel D2 type material is used as a friction stir welding tool. Subsequently, the effects of the process parameters were investigated. The signal-to-noise ratios and analysis of variance were applied for statistical analysis. The outcome shows welding speed is the significant parameter than spindle speed. Under the optimum process parameters, 1400 rpm with 16 mm/min were shown best values such as 61.60 MPa for ultimate tensile strength and 91 hardness values. It means moderate spindle speed and lower welding speed develop higher heat. Subsequently, it is also shown that the feasibility of signal-to-noise ratio is responsible to improve welding quality after reinforcement.

Knowledge-aware design of high-strength aviation aluminum alloys via machine learning

The development of the aviation industry is accompanied by the continuous research of high-performance aviation aluminum alloys. Stuck in vast untapped composition space and the routine trial-and-error method, efficiently discovering high-strength aluminum alloys remains a significant challenge. To address this issue, we proposed a knowledge-aware design system (KADS) using machine learning (ML) methods to facilitate the rational design of high-strength aviation aluminum alloys. An aviation aluminum alloy database containing 5113 samples was built based on Al–Zn–Mg–Cu, Al–Cu, and Al–Li series aluminum alloys. Notably, guided by the material knowledge, we constructed a feature pool (23 descriptors) to improve the interpretability and accuracy of ML models. Taking key knowledge-aware features as input, we realized the transformation from “element content to property” to “material knowledge to property” in ML modeling, which is the first time proposed in aviation aluminum alloys design. According to the predictive results, we experimentally fabricated a KADS-designed aluminum alloy (KADS-Sc) with superior mechanical strength (812 MPa for ultimate tensile strength and 792 MPa for yield strength). Furthermore, the strengthening mechanisms in KADS-Sc alloy were established quantitatively. The calculations confirmed that the precipitation strengthening (≈ 439 MPa) was most critical in the final strength increment, agreeing with the microstructure analysis.

Novel insights into the contribution of pretreatment on mechanical properties of high nitrogen martensitic bearing steels

The significance of pretreatment on the microstructure and mechanical properties of high nitrogen martensitic bearing steel was investigated via multiscale characterization. The specimen undergoing spheroidizing and normalizing possessed ultrahigh strength and improved plasticity (2303 MPa ultimate tensile strength, 4.8 % elongation), which were attributed to the elimination of cementite networks, the better distribution of carbides/nitrides through spheroidizing and the refined prior austenite grains by normalizing. The growth of martensite blocks was correspondingly limited due to the heredity characteristic of martensite microstructure from austenite. The fine retained austenite (RA) grains dispersed evenly in the martensite which undertook an important proportion of plastic strain and helped to coordinate the local stress concentration.

A New Kind of Biomedical Ti–Mn–Nb Alloy

Titanium and its alloys are widely used as implant biomaterials due to their well mechanical properties and biological compatibilities. Nb and Mn are well‐known alloying elements with biological potential. Herein, the Ti–Mn–Nb phase equilibria at 900 °C (Ti‐rich region) is determined and published. According to the β single‐phase field in this phase diagram (at 900 °C), Ti–xMn–yNb (x = 4, 10, 16; y = 2, 8, 14, at%) alloys are selected and fabricated which are suited for solution heat treatment. The Ti–Mn–Nb alloys are investigated by optical microscopy (OM), X‐ray diffraction (XRD), and mechanical testing. A unique diffraction pattern (interpreted as occurrence of a transition phase) is observed by transmission electron microscopy (TEM) in Ti–10Mn–2Nb. In the in vitro evaluation, the human osteoblasts (MG63) adhere well and proliferate on the surface of Ti–xMn–yNb (x = 4, 10; y = 2, 8, 14, at%). According to cell culture experiments, the alloys are nontoxic to human osteosarcoma cells in comparison with pure titanium. Based on a performed screening study, different titanium alloys Ti–4Mn–yNb (y = 2, 8, 14) appear as the biomaterial with the highest potential around 700 MPa ultimate tensile strength and 9–10% elongation.

An improved combination of tensile strength and ductility in titanium alloys via oxygen ordering

Oxygen content has always been limited in commercial titanium and titanium alloys due to its propensity to induce a severe ductility loss. Yet, its effect on the macroscopical behavior has never been clearly understood and is still rather unclear considering the wide variability in the literature results. Here, we investigate the tensile properties of α-titanium with oxygen contents ranging from 0.15 to 0.80 weight percent (wt%). While the strain-hardening ability of oxygen is maintained, no ductility drop is observed up to 0.60 wt% of oxygen, thus allowing exceptional combinations of mechanical properties with an ultimate tensile strength (UTS) of 800 MPa and 29% of elongation at fracture for the Ti-0.6O alloy. Both high strength and ductility of these alloys result from the dislocations/precipitate's interactions. It is proposed that these interactions induce an important cross-slip activity responsible for a dislocation multiplication and a high work-hardening rate. With the addition of Zr, alloys exhibit an even more promising combination of mechanical properties, achieving 1,075 MPa of UTS and 28% of elongation at fracture for the Ti-4.5Zr-0.8O alloy. The mechanical properties of TiO and TiZrO alloys brought out in this study surpass those of Ti–6Al–4V alloy and open significant prospects for developing a new generation of oxygen-tolerant titanium alloys.

Additive Manufacturing for Bioinspired Structures: Experimental Study to Improve the Multimaterial Adhesion Between Soft and Stiff Materials.

The fabrication of bioinspired structures has recently gained an increasing popularity: mimicking the way in which nature develops structures is a vital prerequisite in soft robotics to achieve multiple benefits. Stiff structures connected by soft joints (recalling, for instance, human bones connected by cartilage) are highly appealing: several prototypes have been manufactured and tested, demonstrating their full potential. In the present research, the material extrusion (MEX) additive manufacturing technology has been used to manufacture stiff-soft bioinspired structures activated by shape memory alloy (SMA) actuators. First, three commercially available stiff composite plastic materials were investigated and linked to different 3D printing infills. Surprisingly, we found that the "gyroid" infill was correlated to the mechanical properties, demonstrating that it produces better results in terms of Young's modulus and ultimate tensile strength (UTS) than the widely studied "lines" infill. The primary focus of the research is an experimental study aimed at improving the adhesion at the interface between stiff and soft materials using an inexpensive method (i.e., MEX). Three different variables that have significant effects on the interface bonding were studied: (1) the interface geometry between stiff and soft parts, (2) the mesh overlapping process parameter, and (3) the annealing post-treatment. By optimizing the three variables, a Young's modulus of 48.8 MPa and a UTS of 3.8 MPa were achieved, when nylon+glass fiber (a stiff material) and thermoplastic polyurethane (a soft material) were 3D printed together. In particular, the 3.8 MPa UTS is 48% higher than the highest adhesion between the soft and stiff material (thermoplastic polyurethane [TPU] and acrylonitrile butadiene styrene) reported in literature. Finally, taking advantage of the improved stiff-soft adhesion, a bioinspired robotic finger has been fabricated and tested using an SMA actuator, showing an enormous potential for the proposed additive manufacturing approach in realizing bioinspired systems.

Effect of the processing route on the microstructure and mechanical behavior of superlight Mg-9Li-1Zn alloy via friction stir processing

In this study, the effect of the processing route using a friction stir processing (FSP) method on the microstructure and mechanical behavior of a Mg-9Li-1 Zn alloy was systematically investigated. In the FSP method, the odd-numbered (1st and 3rd) process directions and even-numbered (2nd and 4th) passes were alternated to distribute the strain throughout the whole processed zone uniformly. Consequently, the processed zone had a much more uniform microstructure and hardness distribution than the processed zone obtained using the conventional FSP method. Using this method, the grain size of a Mg-9Li-1 Zn sheet alloy was refined from ∼31 μm to ∼0.21 μm with uniformly distributed α and β phases. The processed alloy exhibited a high strength-ductility synergy with an ultimate tensile strength (UTS) of 220.1 MPa and total elongation of 70.0% at a strain rate of 10 −3 s − 1 , overwhelmingly higher than those of the base metal, 155.6 MPa in UTS and 36.0% in elongation. The in-situ SEM-DIC analysis and TEM observation demonstrated that such an outstanding ductility with moderate strength is caused by grain boundary sliding, the dominant deformation mechanism of the ultra-fine-grained sample after FSP. The processing route with reverse processing direction was proven to be efficient in producing the ultrafine grain size microstructure and improving the mechanical properties of superlight Mg-9Li-1 Zn alloy.

Fabrication, microstructure characterization and mechanical properties of B4C microparticles and SiC nanowires hybrid reinforced aluminum matrix composites

Due to the high modulus, high strength, low density, excellent wear resistance and good neutron absorption, the boron carbide (B 4 C) particle reinforced aluminum (Al) matrix composites have been widely applied in the aerospace, weaponry, transportation and neutron shielding fields. In response to the increasing requirement of better strength -ductility matching of B 4 C/Al composites, introducing a nano-scale reinforcement into the B 4 C/Al composites becomes an attractive research focus. In this work, the SiC nanowires were ball-milled with Al powders, and then the SiC/Al composite powders were mixed with B 4 C microparticles. Thus, the 15vol. % B 4 C/SiC/Al composites with different volume fractions of SiC nanowires were fabricated by hot-pressing sintering and hot extrusion. B 4 C microparticles and SiC nanowires are uniformly dispersed in the B 4 C/SiC/Al composites, while the introduced SiC nanowires effectively decrease the Al matrix grain sizes. B 4 C/SiC/Al composites produce the better strength-ductility matching than that of B 4 C/Al composites, while the 15vol. % B 4 C/SiC/Al composite with 1vol. % SiC nanowires achieved the best strength-ductility matching. It generates the 281.7 ± 2.7 MPa in yield strength, 351.2 ± 0.1 MPa in ultimate tensile strength and 5.9 ± 0.7% in failure elongation, which are increased by 18.2%, 15.1% and 13.5% compared to the B 4 C/Al composites. Uniformly dispersed B 4 C microparticles and SiC nanowires largely block the dislocation motions and improve the dislocation storage capacity, which results in a more significant hetero-deformation induced (HDI) hardening effect in the B 4 C/SiC/Al composites. Moreover, the B 4 C/Al interfacial transition regions with the added SiC nanowires becomes stronger, which can enhance the load transfer efficiency of the B 4 C/Al interfaces as a result of the existing dislocation hardening zones. In conclusion, it is a good strategy to combine the synergistic strengthening effect of micro-scale and nano-scale reinforcements in the metal matrix composites. • The hybrid reinforcements of B 4 C microparticles and SiC nanowires generate a synergistic strengthening effect on the mechanical properties of B 4 C/SiC/Al composites. • The yield strength, ultimate tensile strength and failure elongation of B 4 C/SiC/Al composites with 1vol. % SiC nanowires are increased by 18.2%, 15.1% and 13.5% respectively compared to those of the B 4 C/Al composites. • SiC nanowires increase the geometrically necessary dislocations densities in the B 4 C/SiC/Al composites, which contribute to the heteto-deformation induced hardening effect and load transfer efficiency of the B 4 C/Al interface.

A low-cost and high-performance casted titanium matrix composite with Cr3C2 additions

A low-cost, high performance TiC reinforced titanium matrix composite was successfully fabricated using an in situ reaction casting method. The results showed that the morphology and distribution of TiC in the microstructure were the more important factors affecting the properties of composites. And due to the second phase strengthening of the TiC and the Cr element solid solution strengthening for titanium matrix, it provides exceptionally high strength and toughness (1034.5 MPa ultimate tensile strength and 9.0 % elongation) for titanium structural components and increases extremely high hardness (50.4HRC) for titanium wear-resistant components. This study provides additional options for the application of low-cost titanium components.

Effect of rotating magnetic field on NiAl(Si) phase evolution and mechanical properties of special nickel brass

The rotating magnetic field (RMF) has been proven as one of effective method and widely used for solidification controlling of metallics materials. In this present study, a rotating magnetic field was applied during the solidification of special nickel brass, and corresponding effect on solidification microstructure and mechanical properties were investigated and revealed. Results demonstrated that the application of RMF greatly affects the lattice parameters of the synthesized NiAl(Si) phase. It also can be determined that the applied RMF can effectively eliminate the aggregation of the NiAl(Si) phase at grain boundaries, which is favorable and beneficial for homogenous distribution of NiAl(Si) phase. Additionally, the applied RMF also refines the brass matrix and induces the morphology evolution of the NiAl(Si) phase changing from bulk to spherical morphology. Accordingly, the enhanced mechanical properties with 627 MPa in ultimate tensile strength (UTS), 518 MPa in yield strength (YS) and 3.6% in elongation (EL) can be obtained under the RMF with optimal current intensity of 30 A, corresponding to the improvement of about 6.1%, 5.0% and 33.3% over the respective properties of the special nickel brass without applied RMF. In addition, underlying mechanisms for the effect of RMF on the solidification process of special nickel brass and evolution of NiAl(Si) phase, as well as the resultant mechanical properties was discussed and clarified. It is anticipated that this present study would provide a feasible and effective approach to tailor the solidification microstructure and mechanical properties of the commercial brass for industrial application.

Optimization of biocorrosion resistance and mechanical properties of PM Ti–XAl–2Fe–3Cu alloys by response surface methodology

In the current study, the biocorrosion resistance and mechanical properties of the Ti–XAl–2Fe–3Cu (wt%) (X = 6, 4, 2 wt%) alloy produced by powder compact extrusion of blended elemental powders were optimized by using the response surface methodology in order to gain the best combination of processing parameters. To run the optimization process, central composite design with three equal levels of oxygen, hydrogen and aluminum was used and, by employing ANOVA, the analysis of variance was implemented. The results showed that the content of aluminum has a significant effect on the microstructure, mechanical properties, biocorrosion resistance and fracture behavior of the extruded rods. The highest aluminum content corresponds to the highest alloy strength and biocorrosion resistance. This was due to the reduction of the lamella thickness and of the material colonies as the aluminum content increases. Also, by running the experimental and optimization tests, the mechanical properties resulted 1245 MPa in yield strength and 1340 MPa in ultimate tensile strength with 0.1 µAcm−2 in corrosion current.

Mechanical properties and biocorrosion behaviour of as-cast Zn-xCu-Sr alloys for cardiovascular bioabsorbable devices

ABSTRACT In this study, the mechanical and biocorrosion behavior of as-cast Zn-xCu-0.1Sr (x = 1, 2, and 3wt%) alloys for potential application was studied. The microstructure, mechanical properties, and in vitro degradation of Zn-xCu-0.1Sr alloys were investigated. The results show that as Cu content increased from 1.0 to 3.0wt%, the number of CuZn5 phases increased and the average grain size of CuZn5 phases increased from 6.96 μm to 10.92 μm. The 2wt% addition of Cu resulted in the best mechanical properties with 129.4 MPa in ultimate tensile strength and 108.4 MPa in yield strength. Furthermore, the higher corrosion rate was experienced in the alloys with higher Cu content after immersion. Zn-xCu-0.1Sr alloys all presented appropriate in vitro degradation rates in a basically uniform degradation mode. The strength, ductility and biocorrosion property exhibited by the Zn-2Cu-0.1Sr alloy compositions make it a promising candidate for cardiovascular stent applications.

A Novel Hydroforming Process by Combining Internal and External Pressures for High-Strength Steel Wheel Rims.

As one of the key safety components in motor vehicles, the steel wheel rim is commonly fabricated with the roll forming process. However, due to the varied cross-sections of the rim and the low formability of high-strength steel, it is difficult to produce thin-wall and defect-free wheel rims to realize the purpose of light weight. To solve these problems, a novel hydroforming process by combining internal and external pressures (HIEP) was proposed to produce thin-wall wheel rims in the current study. The designed initial tube with diameter between the maximum and minimum diameter of the wheel rim ensures dispersed deformation and effectively avoids local excessive thinning. During HIEP, a hydroforming process was performed with two successive stages: the external pressure and internal pressure stages. Theoretical analysis and finite element method (FEM) were jointly used to investigate the effect of process parameters on the wrinkling and thinning. With the optimized parameters for internal and external pressure, the wrinkling of wheel rims is prevented under compressive state during the external pressure forming stage. Additionally, HIEP was experimentally carried out with high-strength steel rims of 650 MPa ultimate tensile strength (UTS). Finally, wheel rims with weight reduction of 13% were produced successfully, which shows a uniform thickness distribution with a local maximum thinning ratio of 11.4%.

Microstructure, mechanical and corrosion properties of biodegradable Zn-Mg-Zr alloys for biomedical applications

• Biodegradable HR Zn-1Mg-xZr alloys are fabricated via alloying and hot-rolling. • HR Zn-1Mg-0.05Zr alloy shows YS of 218.0 MPa, UTS of 263.2 MPa, and EL of 12.1% • Hot-rolling enhances the YS, UTS, and EL due to the dynamic recrystallization. • HR Zn-1Mg-0.05Zr alloy possesses a degradation rate of 71 μm/y in Hanks’ solution. Zn-1Mg-xZr alloys were prepared via alloying with different Zr contents and hot-rolling, and their microstructures, mechanical properties, and corrosion behaviors were assessed systematically. The results indicated that the mechanical strength of as-cast and hot-rolled (HR) samples initially increased and subsequently decreased with increasing Zr addition. HR samples showed a substantial increase in yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) compared with their as-cast counterparts. HR Zn-1Mg-0.05Zr alloy showed higher mechanical property matching (218.0 MPa for YS, 263.2 MPa for UTS, 12.1% for EL) and an appropriate corrosion rate of 455 μm/y in Hanks’ solution among the Zn-1Mg-xZr alloys for biomedical applications.

Optimization of matrix viscosity improves polypropylene fiber dispersion and properties of engineered cementitious composites

• PP fiber dispersion can be improved by tailoring ECC matrix viscosity using VMA. • At optimal state, PP-ECC attains 7 % tensile strain and 3.5 MPa tensile strength. • Adding VMA beyond optimal state lowers ECC’s tensile strength and ductility. Engineered cementitious composites (ECC) is a durable cementitious material with high tensile ductility and strain-hardening characteristics. Although considered as a cost-effective fiber for ECC, polypropylene (PP) fiber is reportedly difficult to disperse in mortar matrix due to its high aspect ratio and hydrophobicity. In this study, the matrix viscosity of a low-carbon ECC based on limestone calcined clay cement was tailored as a variable to improve PP fiber dispersion under a pre-determined mixing protocol. The effect of matrix viscosity on the composite fresh and hardened properties was investigated experimentally. Results suggested an optimal range of matrix viscosity (10.3–11.5 Pa‧s) favors the composite tensile strength and strain capacity at 28 days. At the optimal state with a 0.1 % viscosity modifying admixture (VMA)-to-binder mass ratio, PP-ECC achieved 7.0 % tensile strain capacity and 3.5 MPa ultimate tensile strength. When matrix viscosity falls outside the desired range, both ultimate tensile strength and strain capacity were diminished. By tailoring the VMA dosage, the matrix viscosity can be adjusted for desired fiber dispersion, workability, and mechanical properties. The findings of this study provide a technical reference for the practical design and application of PP-ECC.