Zn-containing Alloys Research Articles

Effect of Zn addition on microstructure and mechanical properties of Mg–9Gd–3Y–0.5Zr alloy

Abstract

Precipitation priority in 5083 Al-alloys containing small amounts of Cu or Zn

ABSTRACTThis study investigated the precipitation priority in Al–Mg alloys modified by the addition of 0.8 wt-% Cu or Zn, revealing that both these alloys exhibit increased hardness and decreased corrosion resistance. Scanning electron microscopy, transmission electron microscopy, and high-angle annular dark field imaging show that the precipitation priority changed the main second-phase particles of Cu- and Zn-containing alloys. Additionally, thermodynamic data of these phases were calculated using a semi-empirical model, showing good agreement with the experimental results.This paper is part of a thematic issue on Light Alloys.

Microstructure and mechanical properties of Mg–3.0Y–2.5Nd–1.0Gd–xZn–0.5Zr alloys produced by metallic and sand mold casting

Abstract

Influence of Sc on Microstructure and Mechanical Properties of High Zn-Containing Mg Alloy

Microstructures and mechanical properties of Mg-11Zn and Mg-11Zn-1Sc (wt%) alloys were investigated. The main secondary phase of Mg-11Zn and Mg-11Zn-1Sc alloys is MgZn2phase. Rare earth Sc element is an effective grain refiner and the grain size of Mg-11Zn-1Sc alloy is greatly refined. The mechanical properties of the Mg-11Zn alloy were greatly improved with incorporation of 1 wt% Sc, especially for the elevated temperature strength. Such mechanical property enhancement is ascribed to the refinement and pinning mechanism of high heat-resistant Sc and Sc-containing intermetallic particles in Mg alloy.

Indentation creep of lead-free Sn–3.5Ag solder alloy: Effects of cooling rate and Zn/Sb addition

The effect of cooling rate and separate additions of 1.5wt% Zn and 1.5wt% Sb on the creep behavior of Sn–3.5wt% Ag lead-free solder alloy was investigated by indentation creep testing at 298 and 370K. All three alloys were prepared at two different cooling rates of 0.01Ks−1 and 8Ks−1, in order to examine the influence of cooling rate on their creep resistances. This affected the microstructure and thus, the creep behavior of the materials. Fast cooling enhanced the creep resistance by refining the coarse plate-like Ag3Sn particles. Both the ternary alloys showed creep resistances higher than that of the eutectic binary Sn–3.5Ag alloy. The higher creep resistance of the Zn-containing alloy is attributed to the refinement of the Ag3Sn precipitates, while solid solution hardening of Sb in the Sn matrix is responsible for the superior creep behavior of the Sb-containing alloy. The higher creep resistance of the ternary alloys is more pronounced at higher temperatures, where the binary base alloy weakens more readily. The stress exponents were found to be in the range 6.6–9.8 and 7.1–10.2 for the slowly cooled (SC) and the fast cooled (FC) conditions, respectively. These are in agreement with those determined by room temperature conventional creep and other creep testing methods of the same materials reported in the literature. The high stress exponents together with the activation energy of about 80kJ/mol may suggest that the dominant creep mechanism is dislocation creep.

Influence of Zn Content on the Microstructure and Properties of As-Annealed Al-Mn-Si Alloys

The effect of Zn addition on the microstructure, tensile properties and electrochemical properties of as-annealed Al-Mn-Si alloy was investigated through TEM observations, anodization metallography, tensile tests and Tafel polarization analysis. High density precipitates were found in the Zn-containing alloys and the alloy with 1.5 % Zn had the most uniform precipitation. The Zn element could restrain recrystallization of the alloy. Tensile test results indicated that Zn has a great effect on tensile strength of Al-Mn-Si alloy. The alloy with 1.8 % Zn addition had the highest ultimate tensile strength. The electrochemical testing results indicated that Zn element had great impact on the corrosion potential of the as-annealed alloys tested in 0.5% NaCl solutions. Alloying with Zn element could make the corrosion potential shift to negative direction but increase the resistance to pitting corrosion

Comparative studies on as-cast microstructures and mechanical properties between Mg—3Ce—1.2Mn—0.9Sc and Mg—3Ce—1.2Mn—1Zn magnesium alloys

The as-cast microstructures and mechanical properties of Mg—3Ce—1.2Mn—0.9Sc and Mg—3Ce—1.2Mn—1Zn magnesium alloys were investigated and compared. The results indicate that the Sc-containing alloy mainly consists of α-Mg, Mg12Ce and Mn2Sc phases, and the Zn-containing alloy is mainly composed of α-Mg and Mg12Ce phases. The morphologies of the Mg12Ce phases in the two as-cast alloys are different. The Mg12Ce phases in the Sc- and Zn-containing alloys mainly exhibit particle-like shapes and continuous and/or quasti-continuous nets, respectively. Furthermore, the grains of the Sc-containing alloy are finer than those of the Zn-containing alloy. In addition, the Sc- and Zn-containing alloys have similar as-cast tensile properties at room temperature and 300°C. However, the Sc-containing alloy exhibits higher creep-resistant properties at 300°C and 30 MPa for 100 h than the Zn-containing alloy.

Comparison about as-cast microstructures and mechanical properties of Mg–4Y–1.2Mn–0.9Sc and Mg–4Y–1.2Mn–1Zn (wt%) magnesium alloys

In this article, the as-cast microstructures and mechanical properties of the Mg–4Y–1.2Mn–0.9Sc and Mg–4Y–1.2Mn–1Zn (wt%) magnesium alloys are investigated and compared. The results indicate that the Sc-containing alloy is mainly composed of α-Mg and fine particle-like Mg24Y5, Mn12Y, and Mn2Sc phases, while the Zn-containing alloy mainly consists of α-Mg and coarse Mg12YZn phases with a continuous network. Furthermore, the grains of the Zn-containing alloy are relatively finer than those of the Sc-containing alloy. In addition, the Sc-containing alloy exhibits relatively higher tensile properties at room temperature and 300 °C than the Zn-containing alloy. However, the creep properties at 300 °C and 30 MPa for 100 h for the Sc-containing alloy are relatively lower than those for the Zn-containing alloy.

Effect of Zn content on tensile and electrochemical properties of 3003 Al alloy

The effect of Zn addition on the microstructure, tensile properties and electrochemical properties of as-annealed 3003 Al alloy was investigated through TEM observations, tensile tests and Tafel polarization analysis. High density precipitates are observed in the Zn-containing alloys and the alloy with 1.8% Zn addition also has rod-like precipitates. Tensile test results indicate that Zn has a great effect on tensile strength of 3003 Al alloy. The alloy with 1.5% Zn addition has the highest ultimate tensile strength. The electrochemical results indicate that Zn addition to 3003 Al alloy also has great impact on the corrosion potential of the 3003 Al alloy in 0.5% NaCl solution and ethylene glycol-water solution. The corrosion potential varies with the Zn content and shifts negatively.

High Temperature Deformation of Wrought Zn-Containing Magnesium Alloys

The high temperature response in torsion and creep of two extruded Mg-Zn alloys was investigated in the present study. The alloy 0 (Mg-2Zn-1Mn) was found to exhibit a lower strength than the alloy 2 (Mg-0.55Zn-0.79Mn-0.75Al-0.17Ca), even if the activation energy for creep was similar for both materials (170-180 kJ/mol). The difference in flow stress was here preliminarily attributed to the precipitation of fine Al2Ca particles.

Effect of the long periodic stacking structure and W-phase on the microstructures and mechanical properties of the Mg–8Gd– xZn–0.4Zr alloys

Microstructures and mechanical properties of the Mg–8Gd– xZn–0.4Zr ( x = 0, 1 and 3 wt.%) alloys, in the as-cast condition and the as-extruded condition, have been investigated. The results show that both the 14H long periodic stacking structure and the W-phase coexist together in the cast Zn-containing alloys. The volume fraction of the W-phase increases with increasing the addition of Zn. This phase is the crack source of the fracture. The 6H long periodic stacking structure is observed in the extruded Zn-containing alloys. The Mg–8Gd–1Zn–0.4Zr alloy exhibits the highest elongation, and the value of its elongation is 130% at 300 °C due to the refined microstructure. The W-phase plays an important role in improving the mechanical properties via pinning the movement of the grains at elevated temperature.

Influence of Zn content on the microstructure and mechanical properties of extruded Mg–5Y–4Gd–0.4Zr alloy

Microstructures and mechanical properties of the Mg–5Y–4Gd– xZn–0.4Zr alloys have been investigated. These results show that the Mg–5Y–4Gd–0.5Zn–0.4Zr alloy in the peak-aged condition exhibits the highest tensile strength, and the values of the ultimate tensile strength and yield tensile strength are 370 and 300 MPa, respectively. It is suggested that addition of 0.5% Zn has a great effect on age hardening response. The long periodic stacking structure has been found in these Zn-containing alloys, and the volume fraction of this phase increases with increasing Zn addition. This phase plays an important role in improvement of the mechanical properties, especially for the elongations. The β′ phase precipitates during the ageing process are responsible for the improvement of the mechanical properties of the alloys in the peak-aged condition.

Effect of Sc and Zn Additions on Microstructure and Hot Formability of Al-Mg Sheet Alloys

Trace elements of Sc or Zn were added to Al-Mg sheet alloys. Microstructural examination showed that the Sc addition greatly refined the grain size, especially in the Zn-containing alloy where large amounts of subgrains and fine grains were formed. Meanwhile, a number of large primary intermetallic particles formed in the Sc-adding alloys. In order to evaluate the high-temperature formability, warm tensile tests were carried out at temperatures ranging from 275 °C to 350 °C and at strain rates of 0.015 to 1.5 s−1. The test results showed that, in the alloys with the single addition of Zn or Sc, Zn slightly increased the flow stress but decreased the ductility and Sc worsened both the flow stress and the ductility. However, in the alloy with the combined addition of Zn and Sc, the flow stress was significantly increased at almost all testing conditions and the ductility was also increased at a higher temperature of 350 °C and lower strain rate of 0.015 s−1. The results of superplastic tensile tests and biaxial stretch tests demonstrated that the alloy with both Zn and Sc additions exhibited good high-temperature formability. The effect of Zn and Sc additions on the microstructure and the hot formability is discussed.

Effect of reaction time on mechanical strength of the interface formed between the Sn-Zn(-Bi) solder and the Au/Ni/Cu bond pad

In this work, the shear strengths and the interfacial reactions of Sn-9Zn, Sn-8Zn-1Bi, and Sn-8Zn-3Bi (wt.%) solders with Au/Ni/Cu ball grid array (BGA) pad metallization were systematically investigated after extended reflows. Zn-containing Pb-free solder alloys were kept in molten condition (240°C) on the Au/electrolytic Ni/Cu bond pads for different time periods ranging from 1 min. to 60 min. to render the ultimate interfacial reaction and to observe the consecutive shear strength. After the shear test, fracture surfaces were investigated by scanning electron microscopy equipped with an energy dispersive x-ray spectrometer. Cross-sectional studies of the interfaces were also conducted to correlate with the fracture surfaces. The solder ball shear load for all the solders during extended reflow increased with the increase of reflow time up to a certain stage and then decreased. It was found that the formation of thick Ni-Zn intermetallic compound (IMC) layers at the solder interface of the Au/electrolytic Ni/Cu bond pad with Sn-Zn(-Bi) alloys deteriorated the mechanical strength of the joints. It was also noticed that the Ni-Zn IMC layer was larger in the Sn-Zn solder system than that in the other two Bi-containing solder systems.

Effect of Zn addition, strain rate and deformation temperature on the tensile properties of Sn–3.3 wt.% Ag solder alloy

Stress–strain characteristics of the binary Sn–3.3 wt.% Ag and the tertiary Sn–3.3 wt.% Ag–1 wt.% Zn solder alloys were investigated at various strain rates (SR, ε ·) from 2.6 × 10 − 4 to 1.0 × 10 − 2 s − 1 and deformation temperatures from 300 to 373 K. Addition of 1 wt.% Zn to the binary alloy increased the yield stress σ y and the ultimate tensile stress σ UTS while a decrease of ductility (total elongation ε T) was observed. Increasing the strain rate ( ε ·) increased both σ y and σ UTS according to the power law σ = C ε · m . A normal decrease of ε T with strain rate was observed according to an empirical equation of the form ε T = A exp (− λε ·); A and λ are constants. Increasing the deformation temperature decreased both σ y and σ UTS in both alloys, and decreased the total elongation ε T in the Zn-free binary alloy, whereas ε T was increased in the Zn-containing alloy. The activation energy was determined as 41 and 20 kJ mol − 1 for these alloys, respectively. The results obtained were interpreted in terms of the variation of the internal microstructure in both alloys. The internal microstructural variations in the present study were evaluated by optical microscopy, electron microscopy and X-ray diffraction. The results show the importance of Zn addition in enhancing the mechanical strength of the Sn–3.3 wt.% Ag base alloy.

New Pb-free solder alloy with superior mechanical properties

New high-strength Pb-free solder alloys, based on the Sn-Ag-Zn system, have been developed. A relatively small addition of Zn significantly improves the mechanical strength of Sn-3.5% Ag eutectic solders while maintaining the same level of ductility. The observed increase in strength is as much as 48% over that of the Zn-free alloy. This strengthening from the Zn additions is attributed to a substantial refinement of the precipitates in the solidification microstructure. The problems of nonuniformity in solidification dendrite structure and solder surface roughness often observed in the Sn-Ag binary alloys are also alleviated by the Zn addition. It is found that essentially all of the added Zn resides in the more corrosion-resistant, Ag-based, intermetallic precipitates, leaving the Sn-rich matrix primarily free of Zn in solid solution. High-temperature creep tests indicate that the new Zn-containing alloys exhibit a remarkably improved creep resistance of more than an order of magnitude.