Wyniki wyszukiwania - BazTech

1

Influence of sand-casting parameters on microstructure and properties of magnesium alloys

Kiełbus A., Stopyra M., Jarosz R.

Archives of Metallurgy and Materials

|

2013

|

Vol. 58, iss. 2

635--640

EN

The paper present the influence of modifying process on chemical composition, microstructure, and selected properties of Mg alloys. Two sand-casting creep-resistant alloys, Elektron 21 and WE43, were analyzed in various forms: without modifiers, with the amount of modifier suggested by the producer, and with this amount increased by 50% and 100%. The volume fraction of eutectic areas, tensile strength, and yield strength were measured and the fluidity and linear contraction were analyzed. The research shows that, in contrast to what is widely assumed to be a positive influence of rare-earth elements on Mg alloys properties, a large increase in the amount of modifiers does not always lead to an improvement in the alloy properties. However, the results are tentative because they may have been influenced by the melting technology used, which can be improved. Rare-earth elements tend to react with fluxes, which could lead to a decrease in mechanical properties and fluidity. More research is planned wherein the alloys are melted under a protective atmosphere.

PL

W artykule zaprezentowano wpływ modyfikacji odlewniczych stopów magnezu na skład chemiczny, mikrostrukturę i wybrane właściwości. Badano 2 stopy odlewane do form piaskowych, przeznaczone do pracy w podwyższonej temperaturze: Elektron 21 i WE43 w czterech wariantach: bez modyfikacji, z ilością modyfikatorów dodaną zgodnie z procedura zalecana przez producenta, powiększona o 50 i 100%. Wykonano ilościową analizę udziału objętościowego eutektyk, zmierzono wytrzymałość na rozciąganie, granice plastyczności, wykonano próbę lejności oraz skurczu liniowego. Wykazano, że mimo powszechnie uznanego za pozytywny wpływu metali ziem rzadkich na właściwosci stopów Mg dodawanie zwiększonych ilości modyfikatorów w stosunku do zaleceń producentów nie zawsze ma dobry wpływ na wyniki. Prawdopodobnie duży wpływ na wyniki badań miała technologia odlewania, wymagająca poprawy - zastosowane topniki mogą reagowac z pierwiastkami stopowymi i powodować obniżenie właściwości mechanicznych i lejności. W przyszłości planowane są podobne badania dla stopów topionych w atmosferze gazowej.

2

Microstructure and mechanical properties of Elektron 21 alloy after heat treatment

Kiełbus A.

Journal of Achievements in Materials and Manufacturing Engineering

|

2007

|

Vol. 20, nr 1-2

127-130

EN

Purpose: Elektron 21 is new magnesium based casting alloy contains neodymium, gadolinium and zinc for used to at 200 degrees centigrade. It is a Mg-RE-Zn-Zr alloy designed for aerospace and specialty application ns. This alloy has high strength, good corrosion resistance and excellent castability. The aim of the research was to determine the effect of heat treatment parameters on the microstructure and mechanical properties of Electron 21 magnesium alloy. Design/methodology/approach: Solution treatment was performed at 520 degrees centigrade/8h with water cooling. Ageing treatments were performed at 200 degrees centigrade/4-96h and then quenched in air. The microstructure was characterized by JEM 2010 ARP microscope. The examination of the mechanical properties was conducted on an MTS-810 servo hydraulic machine at two temperatures: ambient (ca. 20 degrees centigrade) and 200 degrees centigrade. Hardness measurements by Vickers method were performed on a ZWICK/ZHV50 hardness tester. Findings: The microstructure of the cast alloy consists of alpha-Mg phase matrix with precipitates of intermetallic phase Mg12(Ndx, Gd1-x) at grain boundaries. After solution treatment the Mg12(Ndx, Gd1-x) phase dissolves in the matrix. The ageing treatment applied after solution treatment with air-cooling caused precipitation of a beta'', beta' and beta intermetallic phases. The best mechanical properties (Rm=308MPA, R0.2=170MPa, A5-9.5%) has a alloy with beta' intermetallic phase. Research limitations/implications: The future research will contain microstructural investigations of Elektron 21 alloy after creep tests. Practical implications: Elektron 21 magnesium alloy is used in the aircraft industry for engine casings, gear box casings and rotor heads in helicopters. Results of investigation may be useful for preparing heat treatment technology of the Mg-Nd-Gd alloys. Originality/value: The results of the researches make up a basis for the next investigations of magnesium alloys with addition of Gd and Nd designed to exploitation at temperature to 300 degrees centigrade.

3

Corrosion resistance of Electron 21 magnesium alloy

Kiełbus A.

Journal of Achievements in Materials and Manufacturing Engineering

|

2007

|

Vol. 22, nr 1

29-32

EN

Purpose: Elektron 21 magnesium alloy containing neodymium, gadolinium and zinc has high strength, good corrosion resistance and excellent castability. It is designed mainly for aerospace applications. The purpose of the investigation was to study the corrosion resistance of Elektron 21 magnesium alloy in as cast condition and after heat treatment in 3.5% NaCl saturated with Mg(OH)2 solution. Design/methodology/approach: Solution treatment was performed at 525 degrees centigrade/8h/water, while ageing treatments at following conditions 250 degrees centigrade/4-96h/air. Immersion test was performed in 3.5% NaCl saturated with Mg(OH)2 solution at room temperature. Specimens were placed in 3.5% NaCl solution for periods of time between one and 5 days. After immersion test, the microstructure and the appearances of the corroded structure were examind by optical microscopy (Olympus GX-70) and a scanning electron microscopy (Hitachi S3400). Findings: The corrosion rates of Elektron 21 alloy increased with increasing the exposure time and finally (after 5 days) reached maximum value 0.092 mg/cm to the -2 day to the -1. Solution treatment at 520 degrees centigrade for 8 h caused decrease in corrosion rate (0.072 mg cm to the -2 day to the -1) due to dissolving of intermetallic phase precipitates at matrix. Ageing at 200 degrees centigrade for 4 h and 16 h caused next decrease in corrosion rate to value 0.052 and 0.055 mg cm to the -2 day to the -1 respectively, while after ageing for 48h corrosion rate increase to value 0.067 mg cm to the -2 day to the -1 due to increase of volume fraction and size of beta' phase and precipitations of equilibrium beta phase. It was also noticed that the longer time of ageing the higher corrosion rates were observed. Research limitations/implications: Future researches should include investigations of the influence of other environments on the corrosion resistance of Elektron 21 alloy. Practical implications: The improvement of corrosion resistance of Elektron 21 alloy can cause increase in it application in aerospace industry. Originality/value: The relationship between the ageing parameters, microstructure and corrosion resistance in Electron 21 magnesium alloy was specified.