Effects of Cu Addition on Age Hardening Behavior and Mechanical Properties of High-Strength Al-1.2Mg-1.2Si Alloy

Abstract

In this study, the effects of Cu addition on artificial age hardening behavior and mechanical properties of Al-1.2Mg-1.2Si-(xCu) alloy was investigated quantitatively and qualitatively by Vickers hardness, tensile test, and transmission electron microscope. The results indicated that Cu addition enhanced the aging response of the alloy at 175 °C. With the increase in Cu content, the time for the alloys to reach peak aging decreased from 12 h to 10 h and 8 h. The tensile strength of the alloy was obviously improved with Cu added in which was 421 MPa of 0Cu alloy, 448 MPa of 0.18Cu alloy, and 459 MPa of 0.37Cu alloy. The results of TEM observation revealed that the addition of 0.37Cu changed the aging precipitation sequence of the alloy, in which the precipitation sequence of 0Cu and 0.18Cu alloy was SSSS→GP zones/pre-β″→β″→β″ + β′, 0.37Cu alloy was SSSS→GP zones/pre-β″→β″ + L→β″ + L + Q′. Moreover, with the addition of Cu, the number density and volume fraction of precipitates of the Al-1.2Mg-1.2Si-(xCu) alloy was evidently increased. The number density was increased from 0.23 × 1023/m3 to 0.73 × 1023/m3 in the initial aging stage and from 1.9 × 1023/m3 to 5.5 × 1023/m3 in the peak aging stage. The volume fraction was increased from 0.27% to 0.59% in the early aging stage and from 4.05% to 5.36% in the peak aging stage. It indicated that Cu addition promoted the precipitation of strengthening precipitates and boosted the mechanical properties of the alloy accordingly.

The Influence of the Proportions of Titanium and Boron in the Al and AlSi7-Based Master Alloy on the Microstructure and Mechanical Properties of Hypoeutectic Silumin, AlSi7Mg

“…The process of the chemical modification of hypoeutectic silumins was described in 1921 [41]. Since then, a lot of works have been written showing the influence of various elements, chemical compounds [42][43][44][45] and the technological processes [46][47][48][49][50][51][52][53][54][55][56][57] on the microstructure and mechanical properties of the tested silumins. Unfortunately, despite such a significant amount of research, it has not been possible to clearly identify the mechanisms causing microstructure refinement and increases in mechanical properties.…”

Effect of Modifier Form on Mechanical Properties of Hypoeutectic Silumin

“…Currently, several ways of increasing their mechanical properties are known. Increasing their mechanical properties can be achieved using various technological factors [11][12][13][14][15][16][17][18]. The mechanical properties of the alloy can be shaped by the use of different cooling rates, pressure casting, thixotropic casting, mechanical vibrations, ultrasonic waves, etc.…”

Effect of Al5TiB Master Alloy with P on Microstructure and Mechanical Properties of AlSi7Mg Alloy

“…• Modification [16][17][18], including, among others, with: calcium [19], sodium [20], sodium chloride [21,22], exothermic mixtures based on natrium [23,24], mischmetal [25], strontium [26,27], lithium [28], scandium and yttrium [29,30], antimony [31], titanium [32][33][34], boron [35], and modification with a homogeneous modifier with a composition similar to a worked alloy (or made from a worked alloy) [36]; • Introduction of alloy additions [37][38][39]; • Directional crystallization process [40][41][42][43];…”