Effect of volume fraction of LPSO phases on corrosion and mechanical properties of Mg-Zn-Y alloys

Li, C.Q.; Xu, Daokui; Zeng, Zhuoran; Wang, B.J.; Sheng, Liyuan; Chen, Xiaobo; Han, En‐Hou

doi:10.1016/j.matdes.2017.02.078

Cited by 163 publications

(49 citation statements)

References 43 publications

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“…According to the recent researches [23,40], the mechanical properties of alloy is related with the microstructue greatly. The matrix with fine microstructure and well distributed strengthening phase would increase the strength and ductility simultaneously.…”

Section: Resultsmentioning

confidence: 99%

“…Though the grain coarsening during heat treatment influences the mechanical properties, the heat treated alloy is still possesses better strength and ductility than the as cast alloy. In the hot extruded alloy, the extrusion refines the microstructure and the strengthening phase significantly, which contributes to the strength and ductility simultaneously [40,41]. Though the strengthening phases still prefer to segregate along grain boundary, their small size could exert little influence on the synergistically deformability of the alloy.…”

Section: Resultsmentioning

confidence: 99%

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Influence of heat treatment and hot extrusion on the microstructure and tensile properties of rare earth modified Mg-Zn based alloy

Sheng

Wang

et al. 2018

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. In the present paper, the Mg-Zn-Y-Nd alloy was prepared by casting, heat treatment and hot extrusion. The microstructure and mechanical properties of the alloys were tested by OM, SEM, TEM and tensile test. The results showed that the Mg 3 Zn 2 Y 3 phase is the main strengthening phase and forms the eutectic structure with α-Mg matrix in the as cast alloy. The strengthening phases semi-continuously connect and separate the α-Mg matrix into cell structure. The average grain size of the as cast alloy is about 60 μm. The heat treatment promotes the solid solution of the strengthening phase and precipitation of small particles inside grain.Compared with the as cast alloy, the heat treatment increases grain size a little and mechanical properties more than 30%. The hot extrusion refines the grain and strengthening phase, which increase the mechanical properties significantly. Moreover, the great deformation by the hot extrusion results in the ultrafine structure and abundant of crystal defects. The intersection of micro-twins lead to the special region with nanometer size. IntroductionMagnesium (Mg) alloys have attracted great attention as the light weight structural materials owing to their high specific strength, low density, ease of recycling and good damping, which can be applied in many fields, including implants, hand tools, sports equipment, automobiles, aerospace applications and electronic equipment [1][2][3][4]. Moreover, the recent research exhibited that the clinic trial of coronary stent made by rare earth doped Mg alloy exhibited good therapeutic effect without thrombosis, which demonstrated the good application prospect of Mg based implant [5]. However, the hexagonal closepacked (HCP) crystal structure of Mg limited the number of initiation slip systems during deformation at relative low temperature, which resulted in the poor deformability of Mg alloy [6]. The poor ductility and low strength of Mg alloy handicapped its wide application. To conquer these shortcomings of Mg alloy, many methods had been applied [7][8][9]. Alloying and thermal processing had been thought as the efficient method to improve the mechanical properties of Mg alloy at room and high temperature.Recently, the investigations [10-12] on biomedical magnesium alloys revealed that the addition of Zn could improve its mechanical properties and corrosion resistance with little influence on its biocompatibility, because the Zn is the essential element of the human body. Then a series of new magnesium alloys for biomedical application were developed [13][14][15]. The research of Zhang et al. [10] exhibited that Zn addition in Mg could increases the mechanical performance and biocompatibility, and the Mg-6Zn (wt.%) alloy was the best choice. But the mechanical properties of Mg-Zn alloy is not

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Influence of heat treatment and hot extrusion on the microstructure and tensile properties of rare earth modified Mg-Zn based alloy

Sheng

Wang

et al. 2018

IOP Conf. Ser.: Mater. Sci. Eng.

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“…Microstructure As shown in figure 1, SEM morphology of four as-cast alloys. It can be seen that the tissues of the four as-cast alloys are all composed of a black -Mg matrix and a second phase of a bright white lamellar, and the bright white lamellar phase is LPSO [17]. The LPSO phase in the alloy is distributed in a network along the grain boundary.…”

Section: Methodsmentioning

confidence: 97%

“…However, it has also been reported [15] that LPSO in extruded alloys accelerated the corrosion of the alloy, and with the increase of LPSO phase volume fraction, the degradation rate of the alloy accelerated. In addition, Li et al [16] found that the corrosion resistance of magnesium alloys weakened first and then increased with the increase of LPSO phase volume fraction. It can be seen that the influence of corrosion behavior of LPSO on magnesium alloy has not been universally recognized.…”

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confidence: 99%

Effect of Y/Zn ratio on microstructure and properties of as-extruded Mg-Y-Zn alloys

Liu

Yang

Wang

et al. 2020

Mater. Res. Express

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In this work, four Mg-Y-Zn alloys with specific Y/Zn (wt%) ratio have been prepared. The effects of Y/Zn (wt%) on the microstructure of extruded Mg-Y-Zn alloy were investigated by SEM and TEM. The mechanical properties and corrosion behavior of extruded Mg-Y-Zn alloy were also studied by tensile test, electrochemical and immersion measurements. The corrosion mechanism was studied by SEM observation of the surface morphology of the samples after immersion corrosion. The result indicates that the as-extruded Mg-6Y-3Zn alloy consists of α-Mg, W phase and long-period stacking ordered structure (LPSO) phases. Two types of LPSO structure (18 R and 14 H) appear in the asextruded alloys. The volume fraction of LSPO increases with the increase of Y and Zn atoms witht the same Y/Zn mass ratio. Mg-9Y-3Zn alloy has the best comprehensive mechanical properties. Its yield strength, ultimate tensile strength and elongation are 230 MPa, 327mpa and 23% respectively, because the volume fraction of LSPO phase in the alloy is the highest. In addition, the higher volume fraction of LPSO is beneficial to enhance the corrosion resistance of Mg-9Y-3Zn alloy.Magnesium alloys have a series of performance advantages, such as low density, good specific strength and stiffness, good casting performance and processing performance, and also has low elastic modulus, vibration and noise reduction, etc, which have been widely applied in 3 C, aerospace and automobile fields [1-3]. However, the unavoidable problem is the low strength and poor corrosion resistance of magnesium alloys [4][5][6]. Therefore, researchers have done a lot of research on the strengthening and corrosion behavior of magnesium alloys [7][8][9][10].In improving the strength of magnesium alloys, magnesium rare earth alloys are the most successful systems. Recent studies have found that adding a small amount of Zn to certain Mg-RE alloys can generate a novel longperiod stacking ordered structure (referred to as long-period structure, LPSO structure) under appropriate addition amounts and process conditions. In-depth research shows that there are three types of ternary equilibrium phases in Mg-Zn-Y alloys, which are Mg 3 YZn 6 (I-phase icosahedral quasi-crystal structure and quasi-periodic order), Mg 3 Y 2 Zn 3 (W-phase face-centered cubic structure) and Mg 12 ZnY (X-phase long period stacked ordered structure, including 6 H, 14 H and 18 R) [8]. At the same time, it is generally believed that the phase composition of the alloy depends on the Y/Zn molar ratio [9]. It is reported that LSPO is an important strengthening phase in Mg-Y-Zn alloy, and the common structures are 18 R and 14 H [10]. After heat treatment at 350°C-500°C, 18 R structure will be transformed into 14 H LPSO structure [11]. Wang J F et al reported that the LPSO structural phase can improve the mechanical properties of magnesium alloys while maintaining the good damping capacity of the alloys, and the LPSO phase arranged along the extrusion direction can act as the hardening phase [12]. It is known that hot extrusi...

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“…In the Mg–Zn–Y alloys, the LPSO phase of 18R structure was obtained in the cast state which usually appeared in the crystal boundary, and turned to a 14H structure after heat treatment, which appeared laminated in the crystal. The corrosion rates of the as-cast Mg–Zn–Y alloys was a function of the volume fraction of LPSO phases due to their nobler nature than that of α-Mg matrix [15]. Most corrosion pits preferentially formed at the LPSO-phase/α-Mg interface and gradually developed along the direction of the LPSO phases.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Rod-Shaped Long-Period Stacking Ordered Phases Evolution on Corrosion Behavior of Mg95.33Zn2Y2.67 Alloy

et al. 2018

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The morphology evolution of long-period stacking ordered (LPSO) phases on corrosion behavior of Mg95.33Zn2Y2.67 alloy is investigated systematically during as-cast, pre-extrusion heat-treated, as-extruded and post-extrusion heat-treated conditions. The second phases in the as-cast alloy are only LPSO phases with a few Y particles. The pre-extrusion heat treatment changed LPSO phases from blocks into a rudimentary rod shape with lamellar structure, subsequently into fine fragments by extrusion, and then into a regular rod shape with lamellar structure followed by post-extrusion heat treatment. Immersion tests and electrochemical measurements in 3.5 wt % NaCl solution reveal that the post-extrusion heat-treated alloy has the best corrosion resistance with the lowest corrosion rate. This is attributed to the rod-shaped LPSO phases, which could hinder corrosion proceeding, and result in corrosion orientated along the direction of rods and forming relatively dense long-strip corrosion products. Our findings demonstrate that the improved corrosion resistance of magnesium alloys with LPSO phases can be tailored effectively by the proceeding technology and post-heat treatment.

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Effect of volume fraction of LPSO phases on corrosion and mechanical properties of Mg-Zn-Y alloys

Cited by 163 publications

References 43 publications

Influence of heat treatment and hot extrusion on the microstructure and tensile properties of rare earth modified Mg-Zn based alloy

Influence of heat treatment and hot extrusion on the microstructure and tensile properties of rare earth modified Mg-Zn based alloy

Effect of Y/Zn ratio on microstructure and properties of as-extruded Mg-Y-Zn alloys

The Effect of Rod-Shaped Long-Period Stacking Ordered Phases Evolution on Corrosion Behavior of Mg95.33Zn2Y2.67 Alloy

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