• PDF / 15,257,268 Bytes
• 13 Pages / 593.972 x 792 pts Page_size
• 111 Downloads / 223 Views

DOWNLOAD

REPORT

---

N

AL has a face-centered cubic structure and is slightly anisotropic under plastic deformation, whereas Zn has a hexagonal structure and is strongly anisotropic. This difference in anisotropy involves a variation of interfacial energies, modified microstructural morphologies, and directions of dendritic growth. The difference in the atomic radius of these two elements (0.143 nm for Al and 0.134 nm for Zn) also has a very significant influence on the microstructure of the Al-Zn alloys, which are saturated solid solutions that slowly break apart and reach their state of equilibrium.[1,2] Al-Zn binary systems also have a positive heat of mixing, and

_ EMINE ACER is with the Department of Physics, Institute of _ C¸ADIRLI Science, Erciyes University, 38039 Kayseri, Turkey. EMIN is with the Department of Physics, Faculty of Arts and Sciences, Nig˘de O¨mer Halisdemir University, 51100 Nig˘de, Turkey. HARUN EROL is with the Department of Physics, Faculty of Science, Karatekin University, 18100 C¸ankırı, Turkey. HASAN KAYA is with the Department of Science Education, Education Faculty, Erciyes University, 38039 Kayseri, Turkey. MEHMET GU¨NDU¨Z is with the Department of Physics, Faculty of Science, Erciyes University, 38039 Kayseri, Turkey. Contact e-mail: [email protected] Manuscript submitted December 4, 2016.

METALLURGICAL AND MATERIALS TRANSACTIONS A

the solubility of Zn in Al at room temperature, 298 K (25 C), is less than 2 wt pct.[3] Many researchers[4–9] have studied binary Al-Zn alloys and have demonstrated that the alloys have dendritic and crystallographic morphologies that are dependent on the Zn content. Al-Zn alloys are well known for their excellent tribological and mechanical properties, rendering them suitable for engineering applications, particularly in combustion engine pistons, heat sinks, cylinder liners, as well as machined and pressed items. They are also suitable for many electrical and consumer electronics applications.[10–12] Also, Al-Zn ingot (Al 1.6 wt pct Zn) from recycled aluminum, which is used as a base material in small industries to produce aluminum pans has been used to produce bicycle frames.[13] Al-Zn alloys are particularly interesting as they are the base of the 7xxx industrial aluminum alloys. These excellent properties are strongly dependent on the morphology of the alloy. As shown in Figure 1, the solid solubility limit of Zn in Al is below 2 wt pct Zn. Therefore, Al-Zn alloys with Zn contents higher than 2 wt pct exhibit a microstructure in which Zn particles are spread over a continuous Al-rich matrix. This type of structural morphology leads to good tribological properties because the tough Al-rich matrix is more resistant to high mechanical loads. Furthermore, the addition of Zn

800

700 660.37 L

600 L-α

Temperature oC

500 Compositions of the studied alloys

382 oC

400

82.8

353 oC

Al-α

94.9

α+β

300

99

β+η

o

275 C

31.6

419.58 oC

78

99.4

200 Zn−η

α+η

100

0 0 Al

10

20

30

40

50 60 wt pct Zn

70

80

90

100 Zn

Fig. 1—The binary Al-Zn phase diagram[3].