Evolution of Microstructure in Al-Si-Cu System Modified with a Transition Element Addition and its Effect on Hardness

Abstract

The effect of Ni 1-2 wt.% addition on the microstructure and hardness of the aged A319 alloy were studied. Characterization analyses by x-ray diffraction, optical microscopy and scanning electron microscopy suggest clearly that Ni addition forms Al-Ni-Cu-Fe, Al-Cu-Ni and Al-Ni intermetallic compounds that correlates well with equilibria conditions. Analyses by transmission electron microscopy show that aging heat treatment promotes microstructural changes in morphology, size, and spatial distribution of precipitates. Vickers micro-hardness test of Ni 1 and 2 wt.% specimens have a hardness increase from that of A319 alloy of ~6-8% with mean values of 140.98 and 142.93 HV, respectively.

Evolution of Thermo-mechanical Properties of Aluminium-Silicon Alloy (Al-1wt%Si)

“…This decrease in hardness, or softening of the alloy, is reflected through the observed decrease in the hardening parameters σ f , σ y and χ and an increase in ε f given in Figure 1. The thermally induced internal structure of the alloy in the tested temperature range which leads to the observed hardening behavior up to 525 K after which a softening behavior dominates, consists with previous studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14].…”

“…In aluminum alloys, some transition metals like Ni and Fe, and some rare earths like Ce, which the main characteristic is their low solubility in Al e.g. maximum of 0.01% to 0.04%, are employed in Al-Cu and Al-Si alloys to improve strength and hardness at elevated temperature [4][5][6][7]. This is correlated mainly to impact its coefficient of thermal expansion.…”

Experimental Investigation of Ternary Al-Si-Cu Alloy Solidified with Unsteady-State Heat Flow Conditions

“…The solidification thermal parameters have influence on the microstructure and microsegregation andthese, in turn, are key featuresin inducing non-uniformity on the as-cast material mechanical properties. For this reason, the microstructure and microsegregation has been extensively studied both theoretically [1][2][3][4][5][6][7][8][9][10][11] and experimentally [12][13][14][15][16][17][18][19][20][21][22][23][24][25] for the last decades. The Al-1.2wt%Pb and Al-3.2wt%Bi alloys have been chosen by Freitas et al 13 , to study the effect of microstructural parameters on the wear process.…”

“…Several experimental researches have been proposed for binary alloys of metallurgical interest. However, experimental works focused on the multicomponent alloys are still rare in the literature 1,17 . The present experimental paper is based on the research line of previous references, highlighting the correlation between the thermal parameters and tertiary dendrite arm spacing (λ 3 ) and microsegregation during solidification of a ternary Al-9.0wt%Si-4.0wt%Cu alloy under unsteady-state heat flow conditions.…”

Effect of Transition Element Addition on the Microstructure and Microhardness of (Al-Si-Cu) Aged Alloys

“…For example, additions of 1 to 2% Ni to 2xxx and 3xxx series alloys improve hardness and tensile properties at elevated temperatures [2]. Hayajneh et al [3] and others investigations [4] have been reported the effect of Ni additions in the hardness properties in Al-Cu and Al-Si-Cu alloys respectively; they reported that the formation of the Al-Ni, Al-Ni-Cu intermetallic compounds have a direct relationship with mechanical properties and a significant delay in the loss of hardness values during the over-aging stage.…”