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Content archived on 2024-04-15

SQUEEZE CASTING OF LIGHT ALLOYS AND METAL MATRIX COMPOSITES MECHANICAL PROPERTY EVALUATION

Objective

1. To determine the optimum squeeze casting conditions for a range of high strength Al and Mg-base alloys in order to maximize metal quality and mechanical properties. 2. To improve mechanical properties even further by producing mmcs using the high strength alloys as the matrix phase for selected particulate and fibre reinforcements.
The objectives of the project are to determine the optimum squeeze casting conditions for a number of high strength aluminium base alloys and magnesium base alloys in order to optimise microstructure and maximise metal quality and mechanical properties and to improve mechanical properties even further by producing metal matrix composites (MMC) using high strength alloys as the matrix phase for selected particulate reinforcements, fibre reinforcements and hybrid reinforcements.

Combinations of squeeze casting parameters such as mould temperatures, melt pouring temperature and applied pressure have been investigated for aluminium casting alloys A357 and 201, for magnesium casting alloy AZ91 and for wrought aluminium alloy 2014 and aluminium alloy 7050. Tensile, fracture toughness and fatigue properties for squeeze cast materials and heat treated materials have been measured and from relationships established between casting parameters, the resulting cast structures and the mechanical properties, an optimum set of casting conditions for each alloy has been established to achieve high integrity castings with a good combination of mechanical properties. With the exception of aluminium alloy 2014, squeeze casting of these materials possessed good mechanical properties with significant potential for applications. MMCs with aluminium alloy A357 matrix and silicon carbide particulate reinforcement and with magnesium alloy. AZ91 matrix and alumina fibre or hybrid reinforcement have been produced by squeeze casting. The squeeze cast MMCs exhibited increased moduli and tensile properties compared to other unreinforced matrices. Fatigue strength of composite materials with A357 matrices and AZ91 matrices have been measured at room temperature and at 150 C. Interactions between pure alumina and 2014 alloy matrices and titanium alloy, silver steel and stainless steel reinforcements after heat treatment sequences have been established on a quantitative basis. The project has bee n completed and all objectives have been achieved.
THE CURRENT PROJECT HAS BEEN DEVELOPED BETWEEN SIX COLLABORATORS IN FIVE DIFFERENT COUNTRIES WITH THE SPECIFIC OBJECTIVE OF OBTAINING MECHANICAL PROPERTY DATA FROM A RANGE OF LIGHT SQUEEZE CASTINGS AND COMPOSITES. THE RESEARCH PROGRAMME WILL BE STRUCTURED ACCORDING TO THE FOLLOWING SCHEME, WITH HI-TEC R&D METAL LTD HAVING OVERALL MANAGEMENT RESPONSIBILITY FOR CO-ORDINATING THE WHOLE PROJECT.

1. THE CENTRAL SQUEEZE CASTING ACTIVITY WILL TAKE PLACE AT HI-TEC METALS R&D LTD WHERE 750 TON AND 250 TON PRESSES WILL BE AVAILABLE FOR THIS WORK. SEVERAL TYPICAL GEOMETRICAL SHAPES AND TEST COUPONS WILL BE PREPARED UNDER DIFFERENT CASTING CONDITIONS TO OPTIMISE GRAIN SIZE AND CHEMICAL HOMOGENEITY WITHIN THE CASTINGS. THROUGHOUT THIS PHASE OF THE WORK MICROSTRUCTURAL ANALYSIS, UNIAXIAL TENSILE TESTING AND FRACTURE TOUGHNESS TESTING WILL NEED TO BE PERFORMED IN PARALLEL WITH THE CASTING WORK IN ORDER TO CREATE THE NECESSARY FEEDBACK AND GENERATE THE REQUIRED DATA ON STRUCTURE/PROPERTY RELATIONSHIPS.

2. FATIGUE TESTING OF THE MONOLITHIC CASTINGS AND THE TEST PIECES WILL BE CARRIED OUT AT THE NATIONAL AEROSPACE LABORATORY. THIS STAGE OF THE PROJECT WILL COMMENCE EARLY IN 1988 AFTER CASTINGS OF SUITABLE AEROSPACE ALUMINIUM ALLOYS HAVE BEEN MADE: IN THIS REGARD, THE LITAL AND 7000 SERIES HIGH STRENGHT WROUGHT ALUMINIUM ALLOYS WILL BE TARGETED FOR INVESTIGATION IN THE CAST AND FULLY HEAT TREATED CONDITION.

3. FATIGUE AND CREEP TESTING OF THE MMCS WILL BE UNDERTAKEN AT AGUSTA. SQUEEZE CASTINGS GIVES BETTER MATRIX-FIBRE INTERFACIAL CONTACT THAN THE LOW PRESSURE LIQUID METAL INFILTRATION TECHNIQUES, WHICH HAVE A TENDENCY TO LEAVE MICROSPOROSITY BETWEEN FIBRES; HENCE THE FATIGUE AND CREEP PROPERTIES OF THE SQUEEZE CAST COMPOSITES SHOULD BE EXTREMELY GOOD AND MUCH BETTER THAN THE PROPERTIES OF THE COMPOSITES PRODUCED BY LOW PRESSURE LIQUID INFILTRATION.

4. A PARALLEL RESEARCH PROGRAMME WILL BE UNDERTAKEN AT THE UNIVERSITY OF SOUTHAMPTON ON FUDAMENTAL ASPECTS OF METAL MATRIX COMPOSITS WHICH REQUIRE DETAILED INVESTIGATION.

ALTOGETHER, THIS COMBINED PROJECT WILL PROVIDE AN IN-DEPTH EVALUATION OF THE MECHANICAL PROPERTIES OF INDUSTRIALLY IMPORTANT SQUEEZE CAST LIGHT ALLOYS AND SELECTED METAL MATRIX COMPOSITES IN ORDER THAT DESIGNING WITH SQUEEZE CAST COMPONENTS CAN PROCEED UNIMPEDED IN EUROPE.

Topic(s)

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Call for proposal

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Coordinator

Hi Tec Metals Ltd
EU contribution
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Address
Unit B4, Millbrook Close Chandlers Ford
SO5 3BZ Eastleigh
United Kingdom

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Participants (5)