Grain refinement of Al-Si_9.8-Cu_3.4 alloy by novel Al-3.5FeNb-1.5C master alloy and its effect on mechanical properties

Abstract

Abstract.A novel Al-3.5FeNb-1.5C master alloy with uniform microstructure was prepared using a melt reaction process for this study. In the master alloy, basic intermetallic particles such as NbAl3, NbC act as heterogeneous nucleation substrates during the solidification of aluminium. The grain refining performance of the novel master alloy on Al-Si9.8-Cu3.4 alloy has also been investigated. It is observed that the addition of 0.1 wt.% of Al-3.5FeNb-1.5C master alloy can induce very effective grain refinement of the Al-Si9.8-Cu3.4 alloy. The average grain size of α-Al is reduced to 22.90 µm from about 61.22 µm and most importantly, the inoculation of Al-Si9.8-Cu3.4 alloy with FeNb-C is not characterised by any visible poisoning effect, which is the drawback of using commercial Al-Ti-B master alloys on aluminium cast alloys. Therefore, the mechanical properties of the Al-Si9.8-Cu3.4 alloy have been improved obviously by the addition of the 0.1 wt.% of Al-3.5FeNb-1.5C master alloy, including the yield strength and elongation. IntroductionSome of the most important driving forces for the development of Al-Si cast alloys are the high strength to weight ratio, high fluidity, low shrinkage in casting, superior wear resistance, low coefficient of thermal expansion (CTE), high corrosion resistance and excellent castability which makes them potential materials for a number of applications in automobiles and other engineering sectors [1][2][3]. It is well known that the mechanical properties of aluminium alloys can be improved by means of grain refinement. Actually, this is quite well-established industrial practice for wrought aluminium alloys, where the refinement is done by means of Al-Ti-B master alloys [4][5][6][7]. The Al-Ti-B master alloy offers a remarkable performance in the continuous and semi-continuous casting of wrought alloys but fails to meet the expectations in the case of aluminium cast alloys, especially for the Al-Si alloys with a content of Si larger than 4% [8][9][10]. The reason for this drawback is that the Si in the melt will react with Ti to form titanium silicides which prevent the effective grain refinement of the alloy, a phenomenon known as poisoning [11][12]. By now, various attempts have been done to solve this problem [13][14][15]. One effective method is to reduce the Ti content in the mater alloys. Some new master alloys, such as Al-3Ti-3B, Al-1Ti-3B, Al-3B and Al-3Ti-1B-0.2C have been reported to provide better grain refinement performances than the Al-5Ti-1B master alloy [16][17]. However, these methods have not been adopted and grain refinement problems of Al-Si alloys are still unresolved in Al cast industry. To overcome this poisoning effect, recently Nb-B grain refiner can efficiently refine binary Al-xSi alloys due to the formation of niobium borides which are more stable than titanium

Relationship between Austenite‐Stabilizing Elements and Austenite Fraction in Near‐Rapidly Solidified Fe–Mn–Al–C Lightweight Steel

“…Near-rapid solidification with a cooling rate of 10 0 -10 3 °C s À1 has many advantages such as high solid-solubility, [1] fine structure, [2] less composition segregation, and existing metastable phase formation. [3][4][5][6][7] Liu Y.L.…”