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The influence of heat treatment on the microstructure of GA8 magnesium alloy

Kiełbus A., Adamiec J., Cwajna J., Paśko J.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 20, nr 1-2

131-134

EN

Purpose: GA8 magnesium alloy is a general purpose gravity sand casting alloy containing aluminium, zinc and manganese. Typically, it is used in aerospace or commercial casting applications particularly where there is no high temperature requirement. The aim of this paper is to present the results of investigations on the microstructure of the GA8 magnesium alloy after heat treatment. Design/methodology/approach: The study was conducted on GA8 magnesium alloys in as-cast condition and after heat treatment. The microstructure was characterized by optical microscopy (Olympus GX-70) and a scanning electron microscopy (Hitachi S3400) equipped with an electron dispersive detector EDS (VOYAGER of NORAN INSTRUMENTS). To measure the stereological parameters, an image analysis program "AnalysisPro(R)" was used. Findings: The microstructure of GA8 magnesium alloy has a solid solution structure alpha with alpha+discontinuous beta areas and continuous beta (Mg17Al12) phase at grain boundaries. After solution treatment a reduction of the number of beta precipitations was observed. Application of ageing treatment caused precipitation of discontinuous beta phase. Research limitations/implications: Future researches should involve investigations of the effect of heat treatment parameters on the mechanical properties of GA8 magnesium alloy. Practical implications: The established heat treatment parameters can be useful for preparing heat treatment technology of the GA8 magnesium alloy. Originality/value: The relationship between the initial structure, heat treatment parameters and Mg17Al12 phase morphology in GA8 magnesium alloy was specified.

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The influence of age hardening on the microstructure of GA8 magnesium alloy

Kiełbus A., Adamiec J., Cwajna J., Paśko J.

Archives of Materials Science and Engineering

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2007

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Vol. 28, nr 9

533-540

EN

Purpose: GA8 magnesium alloy is a general purpose gravity sand casting alloy containing aluminum, zinc and manganese. Typically, it is used in aerospace, automotive or commercial casting applications particularly where there is no high temperature requirement. Particularly for elements of the car interior, car body, chassis and driving gears. The aim of this paper is to present the results of investigations on the microstructure of the GA8 magnesium alloy after precipitation hardening. Design/methodology/approach: The study was conducted on GA8 magnesium alloys in as-cast condition and after heat treatment. The microstructure was characterized by optical microscopy (Olympus GX-70) and a scanning electron microscopy (Hitachi S3400) equipped with an electron dispersive detector EDS (VOYAGER of NORAN INSTRUMENTS). To measure the stereological parameters, an image analysis program "AnalysisPro" was used. Findings: A cast of the GA8 magnesium alloy shows the presence of continuous and discontinuous precipitates of ß (Mg17Al12) phase at the solid-solution grain boundaries, Moreover, the occurrence of Mg2Si and Mn5Al8 phases has been provided. After solution treatment at 415°C the area fraction of continuous and discontinuous β phase precipitates decreased. After ageing at 170°C GA8 alloy is characterized by discontinuous β phase along the solid solution grain boundaries. Area fraction of this phase increased compared to supersaturated state. Research limitations/implications: Future researches should involve investigations of the influence of precipitation hardening parameters on the mechanical properties of GA8 magnesium alloy. Practical implications: The established precipitation hardening parameters can be useful for preparing heat treatment technology of the GA8 magnesium alloy. Originality/value: The relationship between the as cast structure, precipitation hardening parameters and Mg17Al12 phase morphology in GA8 magnesium alloy was specified.

3

Procedura ilościowego opisu struktury odlewniczych stopów magnezu

Adamiec J., Kiełbus A., Cwajna J.

Archiwum Odlewnictwa

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2006

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R. 6, nr 18/1

209--214

PL

Celem wykonanych badań było opracowanie kompleksowej procedury ilościowej oceny mikrostruktury odlewniczego stopu magnezu (GA8) w stanie dostawy. Procedura ta obejmuje: dobór parametrów morfologicznych i stereologicznych do ilościowego opisu udziału objętościowego, wielkości i kształtu faz i składników strukturalnych stopu GA8 w stanie lanym, metodykę przygotowania zgładów metalograficznych, metody ujawnienia mikrostruktury, dobór metody akwizycji obrazu, metodykę analizy obrazów, oraz analizę powtarzalności wyników ilościowej oceny mikrostruktury.

EN

The purpose of the investigations executed was to design a complex procedure for quantitative evaluation of the microstructure of magnesium alloy (GA8) in its as-cast state. Te procedure contains: selection of morphological and stereological parameters for quantitative description of volume fraction, size and shape of phases and structural constituents, the suitable method of metallographical sample preparation method, etching methods for selective revealing of method phases, the choice of an image acquisition method, image processing and analysis methods and the analysis of repeatability of the results of quantitative description of primary microstructure of GA8 alloy.

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Mikrostruktura odlewniczego stopu magnezu GA8

Kiełbus A., Adamiec J., Hetmańczyk M.

Archiwum Odlewnictwa

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2006

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R. 6, nr 18/1

203--208

PL

Odlewniczy stop magnezu GA8 należy do grupy najbardziej znanych stopów magnezu z dodatkiem aluminium. Charakteryzuje się wysoką wytrzymałością, dobrą odpornością korozyjną oraz dobrymi właściwościami odlewniczymi. Znajduje zastosowanie w przemyśle lotniczym na elementy pracujące w temperaturze otoczenia. Artykuł zawiera wyniki badań jakościowej i ilościowej oceny mikrostruktury stopu magnezu GA8 w stanie dostawy. Stwierdzono, że mikrostruktura stopu GA8 w stanie dostawy charakteryzuje się obecnością wydzieleń fazy γ-Mg17Al12 w osnowie roztworu stałego α-Mg. Wykazano występowanie dwóch typów wydzieleń fazy γ różniące się morfologią: wydzielenia masywne na granicach ziaren roztworu stałego α oraz wydzielenia płytkowe, tworzące wraz z roztworem stałym α obszary o morfologii przypominającej perlit. Ponadto w mikrostrukturze stopu GA8 obserwowano fazę Laves’a Mg2Si oraz wydzielenia fazy Mn5Al8.

EN

GA8 alloy is one of the most popular Mg-Al magnesium alloy. This alloy has high strength, good corrosion resistance and excellent castability. It is used for casting structural components in civil and military aircraft and automotive industries. The microstructure of GA8 magnesium alloy in the initial state have been investigated. The microstructure of the GA8 alloy consists of α-Mg phase matrix with a continuous and discontinuous γ phase (Mg17Al12) at grain boundaries. Moreover, the occurrence of Laves’ phase in the form of Mg2Si and precipitations of Mn5Al8 phase has been proved.

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Analysis of the possibilities of heat treating the GA8 magnesium alloy

Braszczyńska K. N.

Krzepnięcie Metali i Stopów

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2000

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R. 2, nr 43

57--62

EN

The article presents the results of the preliminary analyses of the effect of T4 and T6 heat treatments on the structural changes in the GA8 magnesium alloy as compared to the as-cast condition, and sets the obtained results against the relevant literature data. Performed microstructural observations and HV microhardness and HB hardness examinations have made it possible to reveal substantial differences in the changes occurring in the material under study. A possibility of applying solution heat treatment in water and a favourable effect of this process on the post-ageing alloy structure have also been found.

PL

W pracy podjęto próbę analizy możliwości stosowania podstawowych zabiegów obróbki cieplnej stopów magnezu na przykladzie odlewniczego stopu magnezu GA8. Skład badanego stopu wynosił: 7,5-9,0% Al, 0,2-0,8% Zn, 0,15-0,5% Mn oraz max. 0.5%.