J. Mater. Sci. Technol. ›› 2010, Vol. 26 ›› Issue (12): 1083-1088.

• Research Articles • 上一篇    下一篇

Hardness-lattice parameter correlation for aged Al-Zn-Mg alloys

Pablo Fernández,Ismeli Alfonso López,Gonzalo Gonzalez   

  1. Instituto de Investigaciones en Materiales. UNAM
  • 收稿日期:2009-08-31 修回日期:2010-05-18 出版日期:2010-12-31 发布日期:2010-12-21
  • 通讯作者: Pablo Fernández

Hardness-Lattice Parameter Correlation for Aged Al-Zn-Mg Alloys

P. Fernandez, G. Gonzalez, I. Alfonso, I.A. Figueroa   

  1. Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Cd. Universitaria, Del. Coyoacan, Mexico, DF. 04510, Mexico
  • Received:2009-08-31 Revised:2010-05-18 Online:2010-12-31 Published:2010-12-21
  • Contact: Pablo Fernández

RichHTML

0

PDF (PC)

1022

摘要： Two ternary Al-2.2Zn-0.95Mg and Al-5.5Zn-2.1Mg (in wt%) alloys, with Zn:Mg ratios close to 2.5 were produced by conventional ingot casting metallurgy. The ingots were solution heat treated at 500 oC for 0.5 h and aged at 180 oC for times between 0.5 and 80 hrs. The structural caracterization was carried out by X-Ray Diffractometry (XRD), Transmission Electron Microscopy (TEM), Selected Area Diffraction (SAD) and Vickers microhardness measurements (Hv). The study was focused on the investigation of the precipitates formation and the relationship between hardness and lattice parameter for a-Al. The results showed that there is an inverse correlation for all the experimental conditions, and that the aged peaks coincide with lattice parameter minima. Significant precipitates formation only occurs for the alloy containing 5.5 %Zn and 2.1 %Mg, provoking an important strengthening and variations in the lattice parameter, however, this was not observed for the alloy containing 2.2 %Zn and 0.95 %Mg. A plausible explanation of the increment of hardness values could be the presence of a well distributed η phase (MgZn2). At initial stages of the precipitation process, η′ was the most abundant precipitate while the phase τ was observed at overaged conditions. These results showed that the aging response of the conventionally cast Al-Zn-Mg alloys can be obtained using the lattice parameter of the a-Al matrix, even for alloy systems with low precipitates formation.

关键词: Aluminum alloy, X-ray diffraction, Precipitation, Lattice parameter, Hardness

Abstract: Two ternary Al-2.2Zn-0.95Mg and Al-5.5Zn-2.1Mg (in wt pct) alloys, with Zn:Mg ratios close to 2.5 were produced by conventional ingot casting metallurgy. The ingots were solution heat treated at 500°C for 0.5 h and aged at 180°C for times between 0.5 and 80 h. The structural characterization was carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and Vickers microhardness measurements (HV). The study was focused on the investigation of the precipitates formation and the relationship between hardness and lattice parameter for α-Al. The results showed that there was an inverse correlation for all the experimental conditions, and the aged peaks coincided with lattice parameter minima. Significant precipitates formation only occurred for the alloy containing 5.5 wt pct Zn and 2.1 wt pct Mg, provoking an important strengthening and variations in the lattice parameter, however, this was not observed for the alloy containing 2.2 wt pct Zn and 0.95 wt pct Mg. A plausible explanation of the increment of hardness values could be the presence of a well distributed μ phase (MgZn2). At initial stages of the precipitation process, μ' was the most abundant precipitate while the phase τ was observed at overaged conditions. These results showed that the aging response of the conventionally cast Al-Zn-Mg alloys could be obtained using the lattice parameter of the α-Al matrix, even for alloy systems with low precipitates formation.

Key words: Aluminum alloy, X-ray diffraction, Precipitation, Lattice parameter, Hardness