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Investigations of the Effect of Heat Treatment and Plastic Deformation Parameters on the Formability and Microstructure of AZ91 Alloy Castings

Majerski Krzysztof, Siemionek Ewa, Szucki Michał, Surdacki Piotr

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no 1

1--9

EN

The article discusses the influence of heat treatment and metal forming parameters on formability and the structure of the AZ91 cast magnesium alloy. The aim of the article is to determine the optimal parameters of homogenization and plastic deformation of sand castings made of the AZ91 alloy in order to improve their properties and structure. In this study, sand castings made from the AZ91 alloy were examined. In the first stage, the castings were homogenized at: 385°C, 400°C, 415°C and 430°C with argon as a shielding gas for 24 hours and then quenched. Subsequently the upsetting tests were conducted at 380 C; 400 C; 420 C; 440 C for two deformation values: ε=0.7 and ε=1.1. After upsetting, the samples were water- and air-cooled. At this stage, a visual assessment was made and samples without cracks were subjected supersaturation at 415 C for 6 h, and artificial aging at 175 C for 24 h. Vickers microhardness tests and microstructure assessment were carried out, at individual stages of testing. Based on the results obtained from the upsetting, structure and hardness tests, the most favorable homogenisation and plastic deformation conditions were determined for AZ91 alloy sand castings. The best results are achieved by homogenizing sand castings at 415 °C for 24 h. Among the tested parameters for conducting metal forming processing in the range of 380-440 °C and deformation values: ε=0.7 and ε=1.1, forging of sand-cast AZ91 magnesium alloy at 420 °C and deformation of ε=0.7 with water cooling seems to be the most favourable. The final heat treatment applied after the deformation process consists of supersaturation at 415 °C for 6 hours water quenching as artificial aging at 175 °C for 24. This combination of heat and plastic treatment parameters of castings allows for improvement of the structure and properties of sand castings made of the AZ91 alloy.

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Effect of Iron Phases Crystallization on the Durability of the Bimetallic Connection Between Ring Inserts and the Piston Casting

Szucki Michał, Piątkowski Jarosław, Czerepak M.

Archives of Foundry Engineering

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2023

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Vol. 23, iss. 2

112--118

EN

The article presents the most important causes of the unstable connection between cast iron ring inserts and the silumin casting of an engine piston. It is shown that manufacturing defects are mainly related to the alfin processing of inserts in Al-Si alloy (the so-called AS9 alloy). Exceeding the permissible iron content in AS9 alloy causes the crystallization of brittle -Al5FeSi phases. Their unfavorable morphology and large size are the main reasons for the weakening of the diffusion connection between the inserts and the piston, causing an unacceptable proportion of defective products. The study presented in this work was conducted under industrial conditions on a population of 10.000 pistons. Quality control data, production parameters, as well as the micro- and macro-structures of the cast iron inserts, and the interface area between the inserts and the silumin piston, were analyzed. Material and technological solutions have been proposed to reduce the occurrence of casting defects at the insert-piston joint. This includes the introduction of so-called "morphological correctors" of the -Al5FeSi phases, reducing the possibility of gaseous impurities in the AS9 alloy and optimizing the temperature of the alfin alloy.

3

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

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2019

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Vol. 13, no 4

15--21

EN

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.

4

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

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2018

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Vol. 12, no 3

242--249

EN

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.