Sn-free Alloy Research Articles

Effect of Sn addition on the microstructure and corrosion behavior of dilute wrought Mg-Zn-Ca series alloys

The effect of Sn alloying (0.5, 1.0, 2.0 wt%) on microstructure and corrosion behavior of dilute Mg-2Zn-xSn-0.5Ca rolled sheets is illuminated. The corrosion resistance first increases and then decreases with raising Sn content. The alloy with 1 wt% Sn shows the lowest corrosion rate of ∼2.1 mm/y, decreased by ∼63 % compared with Sn-free alloy. Although nobler MgSnCa phase is formed after alloying, more protective oxide film containing SnO2 is also formed, which effectively hinders localized corrosion. However, at 2 wt% Sn addition, detrimental effect of MgSnCa overwhelms positive effect of Sn on film, thus deteriorating corrosion resistance.

Enhanced age-hardening response and creep resistance of an Al-0.5Mn-0.3Si (at.%) alloy by Sn inoculation

Precipitation-strengthening at ambient and high temperatures is examined in Al-0.5Mn-0.3Si (at.%) alloys with and without 0.02 at.% Sn micro-additions. Isochronal aging experiments reveal that Sn inoculation results in a pronounced age-hardening response: a hardening increment of 125 MPa is achieved at peak-aging (475 °C), which is five times greater than that of a Sn-free alloy. Scanning electron microscopy and synchrotron x-ray diffraction analyses demonstrate that, while the structure of the α-Al(Mn,Fe)Si precipitates formed in the peak-aged alloys is identical, their mean radius is smaller (R ∼ 25 vs. 100–500 nm) and their number density is greater (∼1021 vs. ∼1019–20m− 3) in the Sn-modified alloy. Atom-probe tomography analyses reveal that the enhanced dispersion of the α-precipitates is related primarily to the formation of Sn-rich nanoprecipitates at intermediate temperatures, which act as nucleation sites for Mn-Si-rich nanoprecipitates. High-resolution transmission electron microscopy analyses demonstrate that these Mn-Si-rich nanoprecipitates exhibit icosahedral quasicrystal ordering (I-phase), which transform into the cubic-approximant α-phase upon peak aging. Significant Sn segregation at the semi-coherent interfaces of the α-precipitates in the peak-aged Sn-modified alloy is observed via APT, which promotes homogeneous nucleation of the I/α-precipitates at aging temperatures > 400 °C. At 300 °C, creep threshold stresses are observed in both alloys in the peak-aged state, which increases from ∼30 MPa in the Sn-free alloy to ∼52 MPa in the Sn-modified alloy. This boost in creep resistance is consistent with the enhanced aging response (higher Orowan stress).

Characterization of structure and hardness at aging of the A319 type aluminum alloy with Sn trace addition

The effect of 0.1 wt% (0.02 at%) Sn trace addition on the structure and phase composition of Al-Si-Cu based alloy has been studied using thermodynamic calculations (Thermo-Calc software) and experimental techniques (transmission electron microscopy (TEM), atom probe tomography (APT), hardness and specific electrical conductivity measurements). The Vickers hardness measurement made after aging at 175 °C revealed that the peak hardness of the Sn-containing alloy is about 22% higher than that of the Sn-free alloy (135 HV vs 115 HV). Moreover, the peak hardness is achieved in a much shorter aging time (4 h vs 16 h). Considerably finer precipitates of the θ′ phase (average length less than 60 nm and thickness 3–5 nm) with a substantially higher number density are observed in the Sn-containing alloy. Tiny, rounded particles most of which are associated with the θ′ phase precipitates are also observed. Atom probe tomography analysis confirmed that the observed nanoparticles consist of tin. Quantitative APT analysis revealed that the number density of the copper-containing precipitates is at least twice that of the tin-containing ones (7.6·104 vs 3·104 µm-3). APT data also revealed a clear evidence of noticeable dissolution of Sn (average concentration from 0.05 to 0.10 at%) and silicon (average concentration from 2.2 to 2.8 at%) at the core of the θ′ phase precipitates, which is consistent with the fact that Sn and to a lesser extent Si act as catalysts in the nucleation of this phase. The data obtained using the proxigram technique suggest that Sn atoms show no tendency to segregate at the coherent θ′/(Al) heterophase interface upon aging, whereas localized Sn segregation is observed at the semi-coherent interface. Both Sn-free and Sn-containing alloys in their peak aged states have been subjected to uniaxial compression tests at an elevated temperature of 250 °С. The results suggest that the yield strength of the Sn-containing alloy is about 1.5 times that of the Sn-free alloy (250 MPa vs 175 MPa). The revealed difference is very big and testifies to a high potential of the new alloys as materials for new-generation engine parts.

Combined effect of Sn addition and pre-ageing on natural secondary and artificial ageing of Al\u2013Mg\u2013Si alloys

Both Sn addition and pre-ageing are known to be effective in maintaining the artificial ageing potential after natural ageing of Al–Mg–Si alloys. In this study, the combined effects of Sn addition and pre-ageing at 100 °C or 180 °C on natural secondary ageing and subsequent artificial ageing of an alloy AA6014 were investigated using hardness, electrical resistivity, differential scanning calorimetry and transmission electron microscopy characterizations. It is found that pre-ageing can suppress natural secondary ageing and improve the artificial ageing hardening kinetics and response after 1 week of natural secondary ageing in both alloys with and without Sn addition. The effect of pre-ageing at 100 °C is more pronounced in the Sn-free alloy while the combination of pre-ageing at 180 °C and adding Sn shows superiority in suppressing natural secondary ageing and thus avoiding the undesired hardening before artificial ageing. Moreover, when natural ageing steps up to 8 h are applied before pre-ageing at 100 °C, the effect of pre-ageing in Sn-added alloy can be further improved. The influence of Sn on vacancies at different ageing temperatures is discussed to explain the observed phenomena.Graphical abstract

Hardening and precipitation behavior of as-quenched Al–0.4Mg–1.0Si alloy with minor Sn addition at different aging temperatures

The effect of Sn on the hardening and corresponding precipitation behavior of as-quenched Al–0.4Mg–1.0Si alloy at different aging temperatures was investigated with hardness tests, differential scanning calorimetry analysis, and transmission electron microscopy. The hardness of the Sn-free alloy was higher than that of the Sn-added alloys during under-aging, but the tendency is reversed during over-aging. The effect of Sn on the hardening behavior of these alloys is not substantially affected by the aging temperature, i.e., the addition of Sn can improve resistance to over-aging softening at different aging temperatures. The reason for the resistance to over-aging softening by the addition of Sn is related to the increase in the number density of precipitates during under-aging and the decrease in precipitates size during over-aging.

High-temperature age-hardening behavior of Al–Mg–Si alloys with varying Sn contents

The effects of Sn content on the age-hardening behavior and peak aging precipitates of Al–Mg–Si alloys at 250 °C were investigated by hardness testing, scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The results indicated that the peak hardness of the experimental alloys initially increased and then decreased with Sn content increasing from 0 to 0.15 wt.%, and it reached a maximum value of 108 HV in the alloy containing 0.1 wt.% Sn. All the Sn-added alloys exhibited higher peak hardness than the Sn-free alloy. Microstructure observations revealed that the enhanced peak hardness of the Sn-added alloys derived from the refinement of precipitates and their increase in number density. The underlying mechanisms of varying Sn addition contents on the precipitate microstructure were discussed.

Study of α”-Martensitic Transformation in Ti35NbxSn Alloys Subjected to Cryogenic Heat Treatment

TiNbSn alloys have been extensively researched due to several properties they exhibit, including high mechanical strength, low elastic modulus, superelasticity, shape memory effect, biocompatibility. The present study evaluated the cryogenic heat treatment in the Ti35NbxSn alloys (x = 0.0; 2.5; 5.0; 7.5). The alloys were arc melted, cold formed and quenched in both water and liquid nitrogen at-198° C. The Ti35Nb2.5Sn alloy was also aged after exposed to both quenching medium. Microstructure and microhardness analyses were performed. Cryogenic treatment was not enough for transformation of primary β phase into martensitic α” in alloys containing 5 and 7.5% Sn. Cryogenic treatment provided β to α” transformation in alloys containing 0 and 2.5% Sn. The Sn-free alloy was more likely to α" transformation in both quenching medium. The alloys microhardness increased with decrease of both quenching temperature and Sn content. The increase of α" is also related to the increase of the alloy microhardness after aging.

Effect of Sn addition on the high-temperature oxidation behavior of high Nb-containing TiAl alloys

The effect of Sn addition on the oxidation behavior of high-Nb containing TiAl alloys was investigated with isothermal oxidation tests conducted in static air at 1000 °C. Sn addition can improve the high-temperature oxidation resistance of TiAl alloys by forming a protective Ti3Sn layer to diminish the inward oxygen diffusion. Moreover, the generated Al2O3 oxide pegs provide a mechanical locking to enhance the spallation resistance. The alloy containing 3 at.% Sn exhibits superior oxidation resistance, with no spallation occurring. The lowest mass gain after being oxidized for 100 h was 3.29 mg/cm2, which is 42.1 % lower than the Sn-free alloy.

Effect of Sn-addition on the properties of the biomedical Ti-17Nb-6Ta alloy.

The effect of Sn-addition (0, 1.5, and 3 Sn, at.%) to the biomedical Ti-17Nb-6Ta alloy has been investigated in this study. The three alloys were proved using XRD analysis to be β-type alloys. Microstructural analysis using optical microscope showed martensite lathes in all alloys and proved that Sn addition stabilized β phase and suppresses the martensite formation during quenching. Micro-hardness results showed a slight increase with 1.5% Sn adding but superior addition of Sn with 3% at. has negligible effect on the hardness compared to Sn-free alloy. The compressive yield stress for the three alloys located between 400 to 500 MPa, and the stain values increased with the increasing of Sn percentages in the TNT alloy.

Effect of Sn Content on Heat Resistance of Mg-3%Al-1%Si Alloy for Casting

Magnesium alloys have the characteristic with high specific strength and lightweight property, it is widely used for auto mobile industry. Heat-resistant magnesium alloy is focused as a suitable material for weight reduction of the engine and power train parts in automotive field. In this study, microstructure and heat-resistant property in Mg-3mass%Al-1mass%Si (Mg-3%Al-1%Si) alloy with containing large amount of Sn (tin) were investigated. The alloys produced by permanent mold casting were investigated by optical microscope (OM), scanning electron microscopy (SEM) and measuring of bolt load retention at 423K. The heat-resistant property of Mg-3mass % Al-1mass % Si alloy with containing 6-13masss%Sn was higher compared with Sn free alloy and conventional Magnesium alloys (e.g. AZ91 and AM60 alloys).

Effect of Sn element on the formation of LPSO phase and mechanical properties of Mg-6Y-2Zn alloy

The long period stacking ordered (LPSO) phase is a key strengthening precipitate phase in the Mg-Y-Zn based alloys. Fully controlled by the chemical ordering and stacking faults, the LPSO phase could be strongly modified by alloying elements. This work explored the effect of trace Sn addition on the Mg-6Y-2Zn alloy, with an emphasis on the LPSO phase and corresponding changes of mechanical properties in the as-cast, as-annealed and as-extruded states. Results show that the 18R LPSO phase forms as needles and distributes at grain boundaries. Meanwhile, its length and density are stimulated dramatically by the Sn addition in the as-cast state. After annealing, the content of the 18R increases accompanied by the change of morphology shapes from needle to block. Additionally, fine 14H LPSO lamellas are precipitated both in grains and between 18R phases. In contrast to the as-annealed Sn-free alloy, the area fraction of 18R phase in the Sn-containing Mg alloy increases from 35% to 58%, the 14H is also promoted to a certain extent. Tensile tests conducted on as-extruded state revealed remarkable mechanical properties improvement in the Sn-containing alloy over its ternary equivalents. The relevant mechanisms are also investigated in detail.

INFLUENCE OF TRACES ADDITION OF TIN ON THE GROWTH AND ON THE COARSENING OF THE GUINIER-PRESTON ZONES IN Al-10% at.Ag ALLOY

The formation of the Guinier-Preston zones in aluminium alloys is closely linked with the excess vacancies. Traces of tin added to an Al-Ag alloy exert an influence on the Guinier-Preston zones precipitation. Due to their high binding energy with vacancies, tin atoms trap some of these available to promote the diffusion of silver atoms for the formation of the Guinier-Preston zones. At 125°C, tin microalloying slows down the reaction of the Guinier-Preston zones precipitation. The diffusion coefficient of the solute atoms in the Sn free alloy and in the Sn added alloy are determined during the coarsening regime which obeys to the Lifshitz, Slyosov and Wagner theory.

Effects of Sn Addition on Clustering and Age-Hardening Behavior in a Pre-Aged Al-Mg-Si Alloy

The effects of Sn addition on clustering and age-hardening behavior in an Al-0.6Mg-1.0Si (mass %) alloy were investigated. Addition of Sn delayed the age-hardening in single aging at 170 ̊C. On the other hand, Sn promoted the age-hardening response in 3-step aging process which comprises a pre-aging (PA) at 90 ̊C for 18ks followed by natural aging (NA) for 604.8ks and artificial aging (AA) at 170 ̊C. The characteristics of clusters formed during PA and NA were evaluated by differential scanning calorimetry (DSC) analysis and atom probe tomography (APT). The DSC results show that the endothermic peak at around 160 ̊C to 200 ̊C was observed in the Sn-free alloy. On the other hand, in the Sn-added alloy, endothermic peak was not observed. It is suggested that Sn addition suppresses the formation of the clusters formed during NA. The APT results show that the Sn addition decreases the number density of clusters, especially smaller clusters. No Sn precipitates were found in Mg-Si precipitates formed during AA at 170 ̊C for 3.6ks. It is speculated that suppression of smaller cluster formation by addition of Sn promotes the age-hardening response

용체화처리한 AZ91-X%Sn 마그네슘 합금의 부식 저항성 변화

The effects of Sn addition and solution treatment on corrosion behavior were studied in AZ91 magnesium casting alloy. The addition of 5%Sn contributed to the introduction of phase, to the reduction in dendritic cell size and to the increase in the amount of secondary phases. After the solution treatment, trace amount of particles were observed in the -(Mg) matrix for the AZ91 alloy, while phase with high thermal stability was additionally found in the AZ91-5%Sn alloy. Before the solution treatment, the AZ91-5%Sn alloy had better corrosion resistance than the Sn-free alloy, which is caused by the enhanced barrier effect of the () phases formed more continuously along the dendritic cell boundaries. It is interesting to note that after the solution treatment, the corrosion rate of both alloys became increased, but the Sn-added alloy showed higher corrosion rate than the Sn-free alloy. The microstructural examination on the corroded surfaces revealed that the remaining particles in the solution-treated AZ91-5%Sn alloy play a role in accelerating corrosion by galvanic coupling with the -(Mg) matrix.

The effect of Sn concentration on oxide texture and microstructure formation in zirconium alloys

The development of oxide texture and microstructure formed on two zirconium alloys with differing Sn contents (Zr–1Nb–1Sn–0.1Fe, i.e. ZIRLO™ and Zr–1.0Nb–0.1Fe) has been investigated using transmission Kikuchi diffraction (TKD) in the scanning electron microscope (SEM) and automated crystal orientation mapping in the transmission electron microscope (TEM). Bulk texture measurements were also performed using electron backscatter diffraction (EBSD) in order to quantify and compare the oxide macrotexture development. The Sn-free alloy showed significantly improved corrosion performance by delay of the transition region and reduced levels of hydrogen pickup. The macroscopic texture and grain misorientation analysis of the oxide films showed that the improved corrosion performance and reduced hydrogen pick up can be correlated with increased oxide texture strength, the improved oxide grain alignment resulting in longer, more protective columnar grain growth. A lower tetragonal phase fraction is also observed in the Sn-free alloy. This results in less transformation to the stable monoclinic phase during oxide growth, which leads to reduced cracking and interconnected porosity and also to the formation of larger, well-aligned monoclinic grains. It is concluded that the Zr–1.0Nb–0.1Fe alloy is more resistant to hydrogen pickup due the formation of a denser oxide with a larger columnar grain structure.

Effects of Sn Addition on the Microstructures and Mechanical Properties of Mg-6Zn-3Cu-xSn Magnesium Alloys

In this paper, Mg-6Zn-3Cu-xSn (ZC63-xSn) magnesium alloys with different Sn contents (0, 1, 2, 4 wt pct) were fabricated and subjected to different heat treatments. The microstructures and mechanical properties of the obtained ZC63-xSn samples were investigated by optical microscopy, X-ray diffraction, scanning electron microscopy, Vickers hardness testing, and tensile testing. It was found that the As-cast Mg-6Zn-3Cu (ZC63) magnesium alloy mainly contained α-Mg grains and Mg(Zn,Cu) particles. Sn dissolved in α-Mg grains when Sn content was below 2 wt pct while Mg2Sn phase forms in the case of Sn content was above 4 wt pct. Addition of Sn refined both α-Mg grains and Mg(Zn,Cu) particles, and increased the volume fraction of Mg(Zn,Cu) particles. Compared with the Sn-free alloy, the microhardness of Sn-containing alloys increased greatly and that of As-extrude ZC63-4Sn sample achieved the highest value. The strength of ZC63 magnesium alloy was significantly enhanced because of Sn addition, which was attributed to grain refinement strengthening, solid solution strengthening, and precipitation strengthening. Furthermore, the ultimate yield stress, yield strength, and elongation of ZC63-xSn magnesium alloys were increased owing to the deceasing grain size induced by extrusion process.

미량 Sn을 함유한 AZ91 마그네슘 합금의 미세조직 및 기계적 특성

Microstructural features were comparatively investigated in AZ91 (Mg-9%Al-1%Zn) and AZ91-0.5%Sn alloys, in order to clarify the reason for the enhancement in room temperature tensile properties by the addition of small amount of Sn in Mg-Al-based alloy. In as-cast state, the Sn-containing alloy showed increased YS, UTS and elongation than the Sn-free alloy. The microstructural examination revealed that various factors including finer cell size, reduction of lamellar (<TEX>${\alpha}+{\beta}$</TEX>) phase and morphological change of bulky <TEX>${\beta}$</TEX> phase from partially divorced shape to fully divorced shape, are likely to be responsible for the improvement in tensile properties for the Sn-containing alloy. It is noted that two alloys showed similar tensile properties after solution treatment. This implies that microstructural evolution related to the <TEX>${\beta}$</TEX> phase plays a key role in better tensile properties in the Sn-containing alloy.

Effects of Sn addition on the microstructure and mechanical properties of as-cast, rolled and annealed Mg–4Zn alloys

The effects of Sn addition on the microstructure and mechanical properties of as-cast, as rolled and subsequent isothermal annealed Mg–4Zn alloys are investigated. Tensile and Rockwell hardness tests are conducted to evaluate the mechanical properties of the as-cast alloys. Improvements of the mechanical properties in Sn-containing alloys are attributed to the increasing volume fraction of secondary phases and modifying the type of intermetallic phases. Additions of Sn increase the twinning density and modify the annealing texture in as-rolled Mg–4Zn alloys. In comparing rolled-annealed Mg–4Zn to Mg–4Zn–3Sn alloy, numerous small particles are dispersed in the matrix of rolled-annealed Mg–4Zn–3Sn alloy. The particles exhibit two different morphologies and sizes: nanosized Zn-rich particles and rectangular-shaped Mg2Sn particles with a size of about 175nm. The rolled-annealed Mg–4Zn–3Sn alloy exhibits high ultimate tensile strength, yield strength and elongation of 273MPa, 159MPa and 16.2%, respectively. The UTS and YS are about 16% and 53% higher than Sn-free alloy.

The magic thicknesses of θ′ precipitates in Sn-microalloyed Al–Cu

θ′ is an effective strengthening precipitate phase in high-strength Al alloys; unfortunately its nucleation is difficult and usually requires assistance, such as that provided by Sn in Sn-microalloyed Al–Cu. In order to clarify the mechanisms by which Sn promotes the nucleation of θ′, we investigated the structure and thickness of θ′ precipitates in a Al–1.7 at.% Cu alloy with trace additions of Sn (0.01 at.%). Scanning transmission electron microscopy imaging reveals that θ′ platelets recently nucleated at 160 and 200 °C exhibit a discrete distribution of specific, or “magic”, thicknesses, corresponding to minima in the residual volumetric and shape misfit strain. This observation is unique to the Sn-assisted nucleation of θ′: θ′ platelets that undergo growth or form in the Sn-free alloy do not display this discrete distribution, although preference for the magic thicknesses persists. Direct evidence is presented that Sn does not accommodate volumetric misfit strain. Instead, it is shown that Sn in its solute form reduces either the interfacial energy of θ′ and/or the transformation shape strain associated with thicknesses intermediate to the magic thicknesses.

A new Ti–Zr–Hf–Cu–Ni–Si–Sn bulk amorphous alloy with high glass-forming ability

The effect of Sn substitution for Cu on the glass-forming ability was investigated in Ti 41.5Zr 2.5Hf 5Cu 42.5− x Ni 7.5Si 1Sn x ( x = 0, 1, 3, 5, 7) alloys by using differential scanning calorimetry (DSC) and X-ray diffractometry. The alloy containing 5% Sn shows the highest glass-forming ability (GFA) among the Ti–Zr–Hf–Cu–Ni–Si–Sn system. Fully amorphous rod sample with diameters up to 6 mm could be successfully fabricated by the copper mold casting Ti 41.5Zr 2.5Hf 5Cu 37.5Ni 7.5Si 1Sn 5 alloy. The activation energies for glass transition and crystallization for Ti 41.5Zr 2.5Hf 5Cu 37.5Ni 7.5Si 1Sn 5 amorphous alloy are both larger than those values for the Sn-free alloy. The enhancement in GFA and thermal stability after the partial replacement of Cu by Sn may be contributed to the strong atomic bonding nature between Ti and Sn and the increasing of atomic packing density. The amorphous Ti 41.5Zr 2.5Hf 5Cu 37.5Ni 7.5Si 1Sn 5 alloy also possesses superior mechanical properties.