Tensile Properties of Aluminium Alloy Casting Melted using a Cold-Crucible Furnace

Abstract

Although many investigations on the mechanical properties of aluminum alloy castings have been performed, there have been few investigations that make positively good use of the effect of impurities reduction. In this study, the influence of impurities on the tensile properties of aluminum alloy casting has been investigated by using aluminum alloy castings of different purity.Al Si Mg alloy castings were melted by cold crucible furnace using the commercial high purity metals. The chemical composition of the melted aluminum alloy casting was same as that of JIS AC4CH. The melted aluminum alloy castings have no strontium modification. Solution treatment and age hardening treatment of the ingot was performed in atmosphere. After the heated treatment, the test pieces for tensile test ware made by machine. Quasi static and impact tensile test were performed in atmosphere at room temperature. The usual AC4CH T6 which has strontium modification was used for comparative material.In both cases of quasi static and impact tensile tests, the tensile strength of Al Si Mg alloy casting melted by cold crucible furnace was lower than that of usual Al Si Mg alloy casting by about some percents and the elongation of Al Si Mg alloy casting melted by cold crucible furnace was bigger than that of usual Al Si Mg alloy casting by more than one and half times. Because there was very little difference in dendrite arm spacing and size, shape, distribution of eutectic silicon between the Al Si Mg alloy castings used in this experiment, it is expected that the impurities reduction is very effective to improve the tensile properties of aluminum alloy casting (AC4CH) from these results.

Influence of Purity on Tensile Property of Al–Si Hypo-Eutectic Alloy Castings

“…These findings reveal that a lot of the large-scale fracture occurred at the interface between -phase and eutectic silicon in L-Alloy, and we surmised that the binding-strength of interface betweenphase and eutectic silicon in L-Alloy might be weaker than that in H-Alloy. In a previous investigation which the present authors have carried out, 7) the improvements of elongation for -phase and binding-strength of interface betweenphase and eutectic silicon in eutectic structure were thought to be the causes of large elongation for AC4CH-T6 by purification. The both alloys of this study extensively reveal the eutectic structure and the eutectic structure exhibits an appreciable difference between them.…”

“…The present authors reported that there was a possibility of improving the elongation by purification without remarkable decreasing of the tensile strength for AC4CH. 7) However, the cause of large elongation has not been clarified yet. Also it was reported that the mechanical properties of Al-Si system alloy are affected by eutectic solidification structure.…”

“…To perform the replacement, it is important to develop the aluminum alloy castings possessing a high quality and a high reliability. To meet these demands, many investigations on the mechanical properties of aluminum alloy castings have been performed, which have examined the effects of casting condition, 1) cooling rate, 2) heat treatment, [3][4][5] modification, 6) impurity elements, 7) structure or cast defect, 8) inclusion, 9) content of hydrogen or oxygen. 10) However, few investigations have been made on the mechanical properties of aluminum alloy castings by making the best use of the reduction of impurities.…”