The Effects of Defects on Tensile Properties of Cast ADC12 Aluminum Alloy

Abstract

To better understand the effects of cast defects on mechanical properties, cast aluminum alloys with various porosities were used. Porosity in the cast samples was created during the casting process, and to clearly identify the porosity effects on the mechanical properties, artificial defects (porosity-like tiny holes) were created mechanically. The tensile properties for the cast aluminum alloys appear to be attributed to the area fraction of the porosity on the fracture surface (namely, the defect rate, DR), although there were different trends because of the different stress concentrations: the ultimate tensile strength and 0.2 pct proof strength were linearly related to DR, while a non-linear correlation was detected for fracture strain. Even in Al alloys with small amounts of defects, significant reductions in the fracture strain were observed. These results were verified using tensile tests on specimens containing artificial defects. The effects of artificial defects on the tensile properties were further investigated using numerous tiny holes, created in several formations. The artificial defects (several small holes), lined up at perpendicular (90 deg) and 45 deg directions against the loading direction, made significant reductions in the tensile properties, even though only weak defect effects were observed for the 90 deg loading direction. No severe defect effects were obvious for the specimen with a tiny defect of /0.1 mm, because of the lower stress concentration, compared to the microstructural effects in the cast Al alloys: the grain boundaries and the second phases. Such phenomena were clarified using tensile tests on cast samples with differently sized microstructures. There were no clear defect effects on the yield strength as the defect amount was less than 10 pct, and microstructural effects were not detected either in this case. Failure characteristics during tensile loading were revealed directly by in-situ strain observations using high-speed cameras.

Effect of Stirring on the Quality of ADC 12 Cast Aluminium Alloy

“…The event is in agreement with result of RPT, in which three minutes stirring time has less influence on the bifilm index. Mechanical property of the casting is significantly affected with prolonged stirring time, as reported by other works [2], [7]. Tensile strength, impact energy and hardness are decreased as five minutes stirring time was applied to the melt.…”

“…Bifilm and other defects that are formed during melting, normally have adverse effect on the quality of aluminium casting, i.e. mechanical property of castings [2]- [8]. Quality of casting can also be determined using bifilm index, using a procedure called Reduced Pressure Testing (RPT) as proposed by many works [9]- [11].…”

Design of Zirconium Quaternary System Alloys and Their Properties

“…A small peak that originated from an unknown phase was also found at approximately 34°. This unknown phase has been reported by R. Kondo et al in Zr(12,14,16,18)Nb alloys 6) and by X.L. Zhao et al in Zr (13,15,17)Nb alloys.…”

“…It contained multiple dimples, which indicated that the fracture was ductile in nature. Conversely, the fractured surfaces of the Zr14Nb5Ta1Mo and Zr14Nb10Ta1Mo alloys exhibited many casting defects, which decreased the elongation to fracture and caused large variations in tensile strength, 14) as was observed for the alloys listed in Table 1. Therefore, the decrease in UTS with increasing Ta content was not consistent with the trends observed for hardness.…”