The damping and mechanical properties of magnesium alloys balanced by aluminum addition

Accepted Manuscript The damping and mechanical properties of magnesium alloys balanced by aluminum addition Diqing Wan, Houbin Wang, Shuting Ye, Yinglin Hu, Lili Li PII:

S0925-8388(18)34525-0

DOI:

https://doi.org/10.1016/j.jallcom.2018.11.393

Reference:

JALCOM 48619

To appear in:

Journal of Alloys and Compounds

Received Date: 9 September 2018 Revised Date:

27 November 2018

Accepted Date: 29 November 2018

Please cite this article as: D. Wan, H. Wang, S. Ye, Y. Hu, L. Li, The damping and mechanical properties of magnesium alloys balanced by aluminum addition, Journal of Alloys and Compounds (2019), doi: https://doi.org/10.1016/j.jallcom.2018.11.393. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT The Damping and Mechanical Properties of Magnesium Alloys Balanced by Aluminum Addition Wan Diqing∗,Wang Houbin, Ye Shuting, Hu Yinglin, Li lili

RI PT

School of Materials Science and Engineering, East China Jiaotong University, Nanchang 330013, China

Abstract In this study, high-strength Mg97Zn1Y2 alloy was chosen as the matrix material. The damping properties of Mg97Zn1Y2 alloy were influenced by adding an

SC

Al element, but the comprehensive improvement of mechanical properties and damping properties of Mg97Zn1Y2 alloy was achieved by Al addition. Besides, the

M AN U

best addition weight fraction of Al is determined by the efficiency coefficient method (ECM). The results show that the Al addition could not only refine grains of the alloy, but also lead to emergence of network Mg–Al compounds hindering the growth of dendrites. The hardness of the alloy increases with increasing Al weight fraction. The efficiency coefficient method reveals that the Mg97Zn1Y2-3wt.%Al alloy exhibits the

TE D

best comprehensive performance.

EP

Keywords Mg–Zn–Y alloys; Mechanical properties; Damping properties

1 Introduction

AC C

Mg alloy has high specific strength, specific rigidity, high specific modulus, high damping, high heat dissipation, electromagnetic shielding, excellent casting and cutting performance, and so on[1], which entails broad potential applications in aerospace, electrical electronics, rails, and so on[2-4]. Although some of Mg alloys have high-strength properties, damping capacity of those Mg alloys is always poor. It is challenging for such high-strength Mg alloys to meet industrial requirements by

∗

E-mail: [email protected];tel: 0791-87046136,fax: 0791-87046122

ACCEPTED MANUSCRIPT improving damping capacity. Therefore, an effective way to enhance high damping capacity of Mg alloys with high mechanical properties is crucial for engineering applications of such alloys. As is well known, Al is the most commonly used element in Mg alloys, showing a great

RI PT

solid solubility in Mg alloy [5-8]. The addition of Al will significantly increase the strength and hardness of Mg alloys. Zhang et al.[9] studied the effect of Al content on the microstructure and mechanical properties of AZ Mg alloys and reported that tensile strength and yield strength increase continuously with the Al content increase. Pan et

SC

al.[10] studied the effect of Al content on properties of Mg–Zn–Y alloys with LPSO phase, finding that the addition of Al can significantly improve their mechanical

Researchers

[11-14]

M AN U

properties.

believe that the pinners on the movement of dislocations will

influence the damping capacity of alloys. In this work, attempts at enhancing the damping capacity of Mg alloys with good mechanical properties were carried out. Different weight fractions (0%, 0.3%, 1.0%, and 3.0%) of Al were added into the

TE D

Mg97Zn1Y2 alloys with LPSO phase. Mechanical properties and damping performance of the designed alloys are studied. The efficiency coefficient method is used to study the comprehensive performance of the alloys.

EP

2 Experimental

Mg97Zn1Y2 alloys were prepared by conventional casting method. High-purity Mg

AC C

and Zn (99.9%, mass fraction), Mg-25wt.%Y (mass fraction) master alloys, and high-purity Al flakes were selected as the raw materials. At first, the surface of the specimen was grinded using different types of sandpaper, then the sample was etched for 3 to 5 seconds using a 4% nitric acid alcohol solution. The microstructure of the specimens were observed by an optical microscope (COOLPIX-4500) and a scanning electron microscope (SEM) with an EDS analyzer (JSM 6701F). The phase analysis was carried out using a Bade D1 kinetic energy diffractometer, and the fractured morphology was observed using a JEM-2010 transmission electron microscope. Moreover, the size of the alloy samples was 50mm×5mm×1mm cut by wire cutting

ACCEPTED MANUSCRIPT machine. The damping performance of each sample was measured by DMAQ800 dynamic thermal analyzer. The HXD-1000TMB/LCD microhardness tester was used to test the hardness with an every 5–10 points method and then take the average. In addition, the comprehensive performance analysis of the Mg97Zn1Y2-xwt.% Al

RI PT

alloys was performed using the efficiency coefficient method (ECM). ECM is based on the principle of multi-objective planning, which determines the satisfaction value and the disallowed value for each evaluation index, as shown by formulas (1-4) and (1-5).

SC

3 Results and discussion 3.1 Microstructure

M AN U

Al is a very important alloy element for Mg because of its high solubility in Mg[15]. Al has a good influence on the properties of Mg alloys, which can increase the strength and plasticity of the alloy and improve the casting ability. Figure 1 shows the microstructure of Mg97Zn1Y2-xwt.%Al alloy. Figure1 (a), (c), (e), and (g) are microstructures under optical microscope, showing that the alloy mainly consists of

TE D

lamellar structure and matrix. Figure1 (b), (d), (f), and (h) are SEM photographs of Mg97Zn1Y2-xwt.%Al alloy. When x=0%, the microstructure exhibits a coarse dendritic structure, and the secondary phase is less generated and unevenly distributed. When Al content is 0.3 wt.%, the morphology of the secondary phase is not changed

EP

significantly. With the increase of Al content, the dendrite growth is hindered, and dendrite size is refined to a certain extent. Figure 2 (a) shows the results of energy

AC C

spectrum analysis. The details are listed in Table 1. The 001 point is located at a-Mg matrix with almost all Mg atoms and only tiny amounts of Zn and Y atoms dissolved in the matrix. The phase located at 002 point with Zn/Y is close to 1:1, which could be LPSO phase. According to the Al content in the phase of 003 points, it is an Al-containing phase. The distribution of the secondary phase between the grain boundaries is becoming even, showing a network distribution, which hinders grain growth during crystallization. This is one reason for grain refinement being caused by addition of Al element. Due to the high solubility of Al in Mg with a maximum solution of 12.5%[16], Al can be dissolved into the matrix, without segregation, agglomeration, and other phenomena in the microstructure from the metallographic

ACCEPTED MANUSCRIPT diagram. According to XRD analysis(Figure 3), it can be seen from the diffraction peak, ɑ-Mg,

Mg12ZnY phase (LPSO),

and

Mg17Al12 phases are detected in

Mg97Zn1Y2-xwt.%Al alloy; thus, the network structure at point 003 is Mg17Al12 phase. As can be seen from the EDS results, it is consistent with the XRD analysis results.

RI PT

3.2 Mechanical properties Figure 4 shows the hardness of Mg97Zn1Y2-xwt.%Al alloy. With the increase of Al content, the hardness value of Mg97Zn1Y2-xwt.%Al alloy increases gradually. When Al content is 3.0 wt.%, the hardness of the alloy is increased by 40% compared with

SC

Mg97Zn1Y2. This is because the addition of Al refines the grain size, leading to a significant improvement of the mechanical properties of the alloy. In addition, the solution strengthening effect of Al in Mg is large. With increasing of Al content, more

M AN U

and more Al elements are dissolved in the matrix, forming a supersaturated solid solution. This solution leads to lattice distortion, which hinders the movement of dislocation at the same time. As a result, the hardness of the alloy is increased. The curve of stresses strain of Mg97Zn1Y2-xwt.%Al alloy are shown in Figure 5. Table 2 shows the hardness, tensile strength and elongation of Mg97Zn1Y2-xwt.% Al

TE D

alloys. It can be seen that the tensile strength and elongation of as-cast Mg97Zn1Y2 alloy are 120 MPa and 8.5%, respectively. According to the curve in the diagram, the addition of Al enhances the tensile strength and elongation of the alloy. The alloys with the addition of 0.3wt.% and 1.0wt.%Al also show good tensile strength and elongation.

EP

Particularly, when x=3.0, the tensile strength and elongation of the alloy are 141MPa and 9.8wt%, respectively, indicating that the Mg97Zn1Y2-3.0wt.%Al alloy has the best

AC C

mechanical properties. Generally, there are three main factors have influence on the mechanical properties of Mg97Zn1Y2-xwt.%Al alloys: grain boundary strengthening, solid solution strengthening and secondary phase strengthening, all of which are commonly used to improve the mechanical properties of Mg97Zn1Y2-xwt.%Al alloys. Analysis of microstructure shows that as-cast Mg97Zn1Y2 has coarse dendritic structure distributed along grain boundary, which easily produces stress concentration and crack, reducing the mechanical properties of the alloy. With the addition of Al, grain size is decreased. Such grain refinement and grain boundary increase will hinder the plastic deformation of the material, so the tensile strength and elongation increase with the increase of Al weight fraction. The addition of Al can not only refine the grain, but also produces Mg17Al12 phase which effectively improves the tensile strength of

ACCEPTED MANUSCRIPT the

alloy.

In

addition,

the

improvement

of

mechanical

properties

of

Mg97Zn1Y2-xwt.%Al alloy is related to solution strengthening. The solution of Al being added into the matrix leads to lattice distortion and hinders the plastic deformation of the material [17]. The tensile fracture morphology of Mg97Zn1Y2-xwt.%Al alloy is shown in Figure 6.

RI PT

The fracture morphology of as cast Mg97Zn1Y2 alloy is typical intergranular fracture and brittle fracture. The tensile fracture of the alloy Mg97Zn1Y2-xwt.%Al forms understanding steps and dimples, and the small secondary cracks reflect the

SC

characteristics of the understanding fracture. The size of the tissue in Figure 6 (d) is small, and a large number of dimples are observed, and the plasticity of the alloy is better than that of other samples. Combined with the fracture morphology of the alloy,

M AN U

it can be clearly seen that the elongation of the alloy is raised after adding Al. 3.3 Damping Properties

Mg alloys have the highest damping capacity among metal structural materials and are typical dislocation damping materials. The movement of dislocations between defects

TE D

is the main cause of dislocation damping [18]. The dislocation damping model proposed by Granato and Lüker[18] uses the motion of dislocations before and after pinning to explain the relationship between dislocation damping and strain amplitude, abbreviated

EP

as G-L dislocation theory. According to this theoretical model, damping of materials can be divided into two stages: Dislocations do a round trips between weak pinning

AC C

points denoted by Q0−1 ; When the strain amplitude is greater than the critical strain amplitude, dislocations move between strong pinning points, denoted by Qh−1 . Therefore, the damping value can be expressed by equation (1-1) [19]:

Q0

−1

and Qh

−1

Q −1 = Q0−1 + Qh−1

(1-1)

are expressed by equations (1-2), (1-3) [20]:

Q0−1 =

ρBL4cω 36Gb 2

(1-2)

ACCEPTED MANUSCRIPT Qh−1 =

 C  exp − 2  ε  ε 

C1

(1-3)

In the above formula: B is a constant, it is a movable dislocation density; b is a Berkeley vector of a dislocation, it is a corner frequency; LC is the interval between

RI PT

adjacent weak pinning points; LN is the distance between adjacent strong pinning points; FB is the point Forces between defects and dislocations; E is the elastic modulus.

Figure 7 shows the damping strain amplitude curve of Mg97Zn1Y2-xwt.%Al alloy.

SC

Clearly, the curve can be divided into two parts for analysis. In the low-strain amplitude region, the damping value changes slightly; when the strain amplitude is greater than

M AN U

the critical strain amplitude, the damping strain amplitude curve begins to rise significantly. It can be seen from the diagram that the Al-added alloy has a larger critical depilation amplitude than that of the Al-free alloy. This is because, with the addition of Al, more solute atoms are solid-solutioned into the Mg matrix, resulting in more weak pinners on the dislocation line. The damping property of the alloy with

TE D

0.3wt.% addition is better than that of the other alloys studied in this work. When Al content is 1.0wt.% and 3.0wt.%, the secondary phase of Mg17Al12 is formed, and the number of strong pinners increases. In this case, the grain boundary increases, which

EP

hinders the movement of dislocation, reducing the damping performance. Therefore, a low weight fraction of Al added in Mg alloys can benefit the damping property at low

AC C

strain amplitude, while too much solute atoms can reduce the damping property of the material.

In order to intuitively show the overall performance of the alloy, the ECM was applied. Using the formula (1-4), (1-5):

xi − xis fi = h xi − xis

(1-4)

ACCEPTED MANUSCRIPT n

F=

∑f i =1

i

(1-5)

n

xih is a satisfactory value; xis is a not-allowed value. Formula (1-4) is the calculate the total efficacy coefficient. According

to

formulae

(1-4)

and

(1-5),

each

RI PT

calculation of the efficacy coefficient of each evaluation index. Formula (1-5) is to

efficiency

coefficient

of

Mg97Zn1Y2-xwt. %Al alloy is calculated. The results are shown in Table 3. As can

SC

be seen from Table 3, the addition of Al makes the overall performance of the Mg97Zn1Y2 alloy significantly improved. Especially the alloys have best

M AN U

performance when the Al addition amount is 3.0wt.%.

In order to deeply analyze the mechanism of the high mechanical properties and high damping properties of the alloy after adding Al element, we have done a lot of analysis, and refer to the outstanding achievements of other reporters. Such as, Shao [21] reported that LPSO structure and magnesium matrix are coherent at their interface. Such a

TE D

structure makes the Mg/LPSO interface has a higher strength, owing to the strong banding force and be able to withstand higher stress than non-coherent interface before cracking. Adding Al element to the alloy produces Mg17Al12 phase, which could

EP

further enhance the mechanical properties of the alloy by solution strengthening and secondary phase (Mg17Al12) strengthening. With respect to the damping capacity of

AC C

the alloy, it will also change, the special structural phases (LPSO phase) appear to create a large number of interfaces. Jiawei Yuan

[22]

reported that, LPSO phases

enhanced the damping capacities within the whole strain range. The internal energy consumption of those interfaces works under certain conditions, such as at high strain amplitude, which could improve the damping capacity of those alloys. Therefore, the increase in damping of the alloy is mainly due to the increase in interface damping.

4 Conclusion (1) The addition of Al elements significantly refines the grain of the alloy. With the

ACCEPTED MANUSCRIPT increase of Al content, the grain size of the alloy becomes smaller and the Mg17Al12 phase appears in the microstructure, which hinders dendrite growth during crystallization. (2) The mechanical properties of the alloy are increased with the Al content increasing.

RI PT

With the addition of Al, grain refinement and grain boundary increase play a role in grain boundary strengthening. Addition of Al solid solution into the matrix causes lattice distortion to solid solution strengthening. A new production of Mg17Al12 phase acts as a secondary phase enhancement.

SC

(3) The ECM was used to calculate the properties of the designed alloys. The results show that the comprehensive performance of Mg97Zn1Y2-3wt.%Al is superior to the alloys.

The

main

reason

is

that

the

mechanical

properties

of

M AN U

other

Mg97Zn1Y2-3wt.%Al are greatly improved; on the other hand, it has good damping capacity at low strain amplitude, which promotes the comprehensive performance of the alloy.

TE D

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (51665012) and the Jiangxi province Science Foundation for Outstanding

References

EP

Scholarship (20171BCB23061,2018ACB21020).

AC C

[1] Mukai T, Yamanoi M, Watanabe H, Scripta Materialia, 2001, 45(1): 89-94. [2] Zheng Ren, Xingguo Zhang, Canfeng Fang, Material guide, 2008, 1: 98-101. [3] Qiuyan Li, Guofeng Jiang, Jie Dong, Jingwen Hou, Guo He, J Alloy Compd, 2016, 680: 522-530.

[4] Jingfeng Wang, ShunLi Zhong, shan Wu, Haibo Wang, Shiqing Gao, Fusheng Pan, J Alloy Compd, 2017,729: 545-555. [5] Mingyang Zhou, Xinxin Su, Lingbao Ren, Rare Metal Mat Eng, 2017, 46(8): 2149-2155. [6] K. Hagiharaa, A. Kinoshitab, Y. Suginob, et al, Acta Materialia, 2010, 58:

ACCEPTED MANUSCRIPT 6282-6293. [7] B.L. Mordike, Mat Sci Eng A, 2002, 324: 103-112. [8] Ming-Hung Tsaia, May-Show Chenc, Ling-Hung Line, et al, J Alloy Compd, 2011, 509 : 813-819.

RI PT

[9] Yaobo Hu, Chao Zhang, Wanqiu Meng, Fusheng Pan, JiPing Zhou, J Alloy Compd, 2017, 727: 491-500.

[10] N.Tahreen, D.F.Zhang, F.S.Pan, X.Q.Jiang, D.Y.Li, J Mater Sci Technol, 2018, 34(7): 1110-1118.

SC

[11] Lifei Wang, Ehsan Mostaed, Xiaoqing Cao,Guangsheng Huang, Mater Design, 2016, 89:1-8.

M AN U

[12] Joong Hwan Jun,Mat Sci Eng A, 2016, 665: 86-89.

[13] L. B. Ren,G. F. Quan,Y. G. Xu, J Alloy Compd, 2017, 699: 976-982. [14] Tong L B, Zheng M Y, Hu X S, Wu K, Xu S, Mater. Sci. Eng. A, 2010, 527 (16): 4250-42-56.

[15] Mingyang Zhou, Xinxin Su, Lingbao Ren, Rare Metal Mat Eng, 2017, 46(8):

TE D

2149-2155.

[16] Liu D, Song J, Jiang B, J Alloy Compd, 2017, 737: 263-270. [17] Caihe Fan, Xihong Chen, Xinpeng Zhou, Ling Ou, Jianjun Yang, T Nonferr

EP

Metal Soc, 2017,27(11): 2363-2370,

[18] Wan D, Wang J, Rare Metal Mat Eng, 2017, 46(10): 2790-2793. [19] Motoyama T, Watanabe H, Ikeo N, Mater Lett, 2017, 201: 144-147.

AC C

[20] Somekawa H, Watanabe H, Basha D A, Scripta Materialia, 2017, 129: 35-38. [21] X.H. Shao, Z.Q. Yang, X.L. Ma, Acta Mater. 2010,58: 4760-4771. [22] Jiawei Yuan et al. J Alloy Compd, 2019,773: 919-926.

ACCEPTED MANUSCRIPT Table 1 Analysis of alloy composition energy spectrum Mg(At%) 98.73 89.12 47.30

Zn(At%) 0.98 5.69 0.58

Y(At%) 0.29 5.19 0.20

Al (At%) 0 0 51.98

AC C

EP

TE D

M AN U

SC

RI PT

spot 001 002 003

ACCEPTED MANUSCRIPT Table 2 The hardness, tensile strength and elongation of Mg97Zn1Y2-xwt.% Al alloys Alloy composition

Tensile strength

Elongation

Mg97Zn1Y2

68HV

120MPa

8.5%

Mg97Zn1Y2-0.3wt.%Al

86Hv

121MPa

9.3%

Mg97Zn1Y2-1.0wt.%Al

91HV

126MPa

8.8%

Mg97Zn1Y2-3.0wt.%Al

95HV

141MPa

AC C

EP

TE D

M AN U

SC

RI PT

Hardness

9.8%

ACCEPTED MANUSCRIPT Table 3 Mg97Zn1Y2-xwt.% Al efficacy coefficient Alloy type Effect coefficient

Mg97Zn1Y2 -0.3wt.%Al

Mg97Zn1Y2-1.0 wt.%Al

Mg97Zn1Y2-3.0 wt.%Al

0.5

0.52

0.67

0.78

AC C

EP

TE D

M AN U

SC

RI PT

F

Mg97Zn1Y2

ACCEPTED MANUSCRIPT

100µm (c)

SC

(d)

RI PT

(b)

(a)

M AN U

LPSO

100µm (e)

TE D

(f)

100µm

(h)

AC C

EP

(g)

LPSO 100µm

Fig.1 Microstructure of as-cast Mg97Zn1Y2-xwt.%Al(a)(b)x=0;(c)(d)x=0.3;(e)(f)x=1.0;(g)(h)x=3.0

ACCEPTED MANUSCRIPT

001

M AN U

003

SC

RI PT

002

AC C

EP

TE D

Fig.2 EDS analysis of Mg97Zn1Y2-3.0wt.%Al alloys

ACCEPTED MANUSCRIPT

•

• α-Mg ♣ Mg12ZnY ♦ Mg17Al12

Mg Zn Y -3.0wt.%Al 97 1 2 ♦

• •

•

♣ ♦

•

♣

•

♦

Mg97Zn1Y2-1.0wt.%Al

♦

♣

•

Mg97Zn1Y2-0.3wt.%Al Mg97Zn1Y2

40

60

2θ/Degree

80

SC

20

RI PT

InIntensity

• ♣

AC C

EP

TE D

M AN U

Fig.3 XRD spectrum of Mg97Zn1Y2-xwt.%Al alloys

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

Fig.4 The hardness of as cast Mg97Zn1Y2-xwt.%Al alloys

ACCEPTED MANUSCRIPT 160

● Mg97Zn1Y2 140

▲Mg97Zn1Y2-0.3wt.%Al ▼Mg97Zn1Y2-1.0wt.%Al

120

■ Mg97Zn1Y2-3.0wt.%Al

Stress(MPa)

100

■

●▲ ▼

80 60 40

0 -20 0

2

4

Strain(%)

6

8

10

RI PT

20

AC C

EP

TE D

M AN U

SC

Fig.5 Tensile strength and elongation of Mg97Zn1Y2-xwt.%Al

ACCEPTED MANUSCRIPT

(d)

M AN U

SC

(c)

RI PT

(b)

(a)

Fig.6 The tensile fracture morphology of Mg97Zn1Y2-xwt.%Al alloys

AC C

EP

TE D

(a)x=0;(b)x=0.3;(c)x=1.0;(d)x=3.0 using SEM technique.

ACCEPTED MANUSCRIPT 0.20

Mg97Zn1Y2 Mg97Zn1Y2-0.3wt%Al Mg97Zn1Y2-1.0wt%Al Mg97Zn1Y2-3.0wt%Al

0.15

Q-1

0.10

0.00

0.05

0.1

0.15

0.2

Strain amplitude X10-2

RI PT

0.05

0.25 0.3 0.35 0.40.45

AC C

EP

TE D

M AN U

SC

Fig.7 Strain amplitude dependent damping of the Mg97Zn1Y2-xwt%Al

ACCEPTED MANUSCRIPT Highlights 1. Al addition improves the damping capacity and mechanical properties of alloys 2. The damping and mechanical strengthening mechanism of alloy was confirmed. 3. Al addition is 3%, the alloy exhibits the best comprehensive performance. 4. LPSO plays an important role in the damping properties of alloys and mechanical

RI PT

properties.

AC C

EP

TE D

M AN U

SC

5. The damping of alloys after adding Al still yield to the G-L theory.