The influence of chopped carbon fibre on mechanical properties of AlSi10Mg alloy matrix composites
Małgorzata Łągiewka, Zbigniew Konopka, Andrzej Zyska, Maciej Nadolski
Quarterly No. 4, 2009 pages 317-321
DOI:
keywords: aluminium alloys, metal composites, carbon fibre, mechanical properties
abstract The work presents a comparison of results concerning mechanical properties of AlSi10Mg alloy matrix composites rein-forced with chopped carbon fibre of 4 mm length and 7 μm diameter, added in amount of 5 or 10 volume percent. First series of samples have been produced by gravity casting of composite suspension, the second one by squeezing in semi-solid state. Bar-shaped specimens of 15 mm diameter have been gravity cast into a metal mould, while 15 mm thick plates have been squeezed by means of hydraulic press under the pressure equal to 100 MPa. Specimens cut out of the achieved castings have been tested for tensile strength, yield point, Young’s modulus and elongation. Metallographic microsections of the broken samples have been prepared after performing mechanical tests in order to examine microstructures of the tested materials. It has been found that more uniform arrangement of carbon fibre has been achieved in gravity castings as compared with squeezed samples, whereas the matrix structure has been better refined in casting squeezed in mushy (semi-solid) state than in gravity cast composite samples. Mechanical examinations have revealed an increase in strength properties and a drop in elongation for composite castings, produced by both gravity and squeeze casting technologies, as compared with pure matrix alloy castings. Comparing in turn the two types of produced composites it can be noticed that the achieved changes of examined properties have been more beneficial for composites squeezed in semi-solid state than for gravity cast composites. It has been also been found that an addition of carbon fibre in amount of 5 volume percent has resulted in the greatest improvement of mechanical properties of the examined materials. An addition of 10% of carbon fibre has also caused an improvement in mechanical properties as compared with the pure matrix alloy, but not so significant as in the case of 5% addition of chopped carbon fibre.