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Creating the Structure and Properties of 7075 Alloy Casts by Thermal and Forming Processes

Majerski Krzysztof, Dziubińska Anna, Winiarski Grzegorz, Szucki Michał, Drozdowski Krzysztof

Advances in Science and Technology. Research Journal

2019

Vol. 13, no 4

15--21

In this paper, the hot formability of 7075 aluminum alloy sand and permanent casting ingots were verified. The experiment was carried out by using casting, heat treatment (homogenization) of ingots and conducting isothermal compression tests at temperatures of 420-500°C. The effect of the forming temperature on the microstructure, the tendency for crack formation and hardness were determined. The results show that ingots in the as-cast state have a dendritic network structure rich in the second phase precipitation on the grain boundaries. After the homogenization process, the microstructure is significantly more balanced. The forming process at 420-480°C of sand casts leads to significant grain elongation and crack formation, mainly at the grain boundaries. Raising the forming temperature to 480-500°C leads to a reduction in the occurrence of cracks. On the other hand, permanent mold castings do not reveal cracks during deformation in the temperature range 420-480°C.

Investigation of the deformability of aluminium-copper casting alloys

Winiarski Grzegorz, Dziubińska Anna, Majerski Krzysztof, Szucki Michał, Drozdowski Krzysztof

Advances in Science and Technology. Research Journal

2018

Vol. 12, no 3

242--249

The paper presents the results of a numerical analysis and experimental tests investigating the deformability of castings made of two aluminium alloys: EN AW-2017A and EN AW-2024. Test specimens were produced by two casting methods: sand casting and permanent mould casting. The castings were first subjected to homogenizing annealing; afterwards, they were shaped into cylindrical specimens for an upsetting test. This test was conducted on a hydraulic press in the temperature range of 420500˚C. Visual inspection of the specimens and examination of their microstructure were performed. Hardness of selected specimens was also measured. The study led to determination of the effect of the mould type on the deformability of the castings and the hardness of forgings obtained from these casting. Obtained results also became a basis for determining the forging temperature ranges for casting preforms made of the investigated aluminium alloys.