Effect of Zr Addition and Aging Treatment on the Tensile Properties of Al-Si-Cu-Mg Cast Alloys

Abstract

The present study focused on the tensile properties at ambient and high temperatures of alloy 354 without and with the addition of zirconium. Tensile tests were performed on alloy samples submitted to various aging treatments, with the aim of understanding the effects of the addition made on the tensile properties of the alloy. Zirconium reacts only with Ti, Si, and Al in the alloys examined to form the phases (Al,Si)2(Zr,Ti) and (Al,Si)3(Zr,Ti). Testing at 25°C reveals that the minimum and maximum quality index values, 259 and 459 MPa, are observed for the as-cast and solution heat-treated conditions, respectively. The yield strength shows a maximum of 345 MPa and a minimum of 80 MPa within the whole range of aging treatments applied. The ultimate tensile and yield strength values obtained at room temperature for T5-treated samples stabilized at 250°C for 200 h are comparable to those of T6-treated samples stabilized under the same conditions, and higher in the case of elevated-temperature (250°C) tensile testing. Coarsening of the strengthening precipitates following such prolonged exposure at 250°C led to noticeable reduction in the strength values, particularly the yield strength, and a remarkable increase in the ductility values.

Effect of Zr and Ti Addition and Aging Treatment on the Microstructure and Tensile Properties of Al-2%Cu-Based Alloys

“…The Al 3 Zr intermetallic structure is dependent on the Zr addition to the alloy and the cooling rate. The L1 2 -Al 3 Zr type can be formed either as a primary phase during solidification with potent nucleating efficiency for α-Al or as a hardening phase decomposed from supersaturated α-Al during solution heat treatment [13].…”

143962

“…This is also the reason why zirconium is sometimes used as a modifier. Zirconium-containing alloys subjected to heat treatment (homogenization annealing, solution annealing or aging) are characterized by higher tensile strength and thermal resistance [13,14]. The purpose of heat treatment is to produce in the alloy an appropriate amount of precipitates of the MgZr2 and Al2Cu intermetallic compounds and triple M and T type compounds, and to ensure that the matrix obtained contains some alloying additives dissolved in it.…”

143961

“…This is also the reason why zirconium is sometimes used as a modifier. Zirconium-containing alloys subjected to heat treatment (homogenization annealing, solution annealing or aging) are characterized by higher tensile strength and thermal resistance [13,14]. The purpose of heat treatment is to produce in the alloy an appropriate amount of precipitates of the MgZr2 and Al2Cu intermetallic compounds and triple M and T type compounds, and to ensure that the matrix obtained contains some alloying additives dissolved in it.…”