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EN
The paper addresses the microsegregation of Mn, Mo, Cr, W, V, Si, Al, Cu and P in the white cast iron. Eutectic alloy with the content of 4.25% C was studied. The white cast iron was directionally solidified in the vacuum Bridgman-type furnace at a constant pulling rate v=83 μm/s and v=167 μm/s and at a constant temperature gradient G = 33.5 K/mm. The microstructural research was conducted using light and scanning electron microscopy. The microsegregation of elements in ledeburite was evaluated by EDS measurements. Content of elements in ledeburitic cementite and ledeburitic pearlite was determined. The tendency of elements to microsegregation was found dependent on the solidification rate. Microsegregation of elements between pearlite and cementite structural constituents has been specified. The effect of solidification rate on the type and intensity of microsegregation in directionally solidified eutectic white cast iron was observed. A different type of microsegregation was observed in the components of ledeburite in cementite and pearlite.
EN
The current work is dedicated to the mathematical description of a protrusion of the leading phase (cementite) over the wetting phase (austenite) observed during the author’s experiments in previous articles. A cementite protrusion is confirmed in the directionally solidified Fe-4.25% C eutectic alloy. The protrusion is defined due to the mass balance fulfilment. A coordinate system is attached to the solid/liquid interface, which is moving with the constant growth rate v.
EN
The study presents methods to be used for improving the performance parameters of car engine pistons made of EN AC-AlSi12CuNiMg alloy according to the PN-EN 1706: 2011. Pistons of slow sucking and turbocharged engines were researched. A solution heat and ageing treatments were applied according to four variants. Temperatures of the solution heat treatment were: 550 ±5°C; 510°C ±5°C; and alternate: 276 ±5°C/510 ±5°C. The solution time ranged from 6 min to 4 h. Temperatures of the ageing heat treatment were 20°C and 250°C, while the ageing time ranged from 1,5 to 3h. Natural ageing was performed in 5 days. Measurements of hardness HRB and the piston diameters were performed. An improvement in the performance parameters of combustion engines was observed. Three solution heat treatment and ageing variants, allowed to obtain the pistons with hardness equal/higher than pistons of the turbocharged engines. The test results confirmed the possibility of providing a piston with properties exceeding the high load parameters specified by the manufacturer. Further studies will make it possible to improve the effects of the proposed solutions.
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