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The effect of extrusion ratios and solution heat treatment on microstructure and tensile properties of extruded Al-15%Mg2Si-1.0%Gd composite was investigated. The as-cast composite was hot extruded using three different dies and solution heat treated. After conducting heat treatment on extruded samples, microstructure alteration was examined using scanning electron microscope (SEM). Furthermore, mechanical properties of the composites were studied with tensile test. The results demonstrated that extruded and heat treated composite possesses higher strength and ductility compared to as-extruded composites. It was also found that the extrusion and heat treatment processes altered the morphology of primary Mg2Si particles as well as reduction in their size especially when the extrusion ratio increases. Fracture surface examination revealed a transition from ductile fracture in as-extruded samples to more ductile fracture in extruded and heat treated ones. This can be attributed to the change in size and morphology of primary Mg2Si particles as well as fragmentation of Gd intermetallic compounds.

Advantage of Al-Mg2Si metal matrix composite (MMC) is due to the particulate reinforced Mg2Si in the Al matrix that has improved mechanical properties of the in situ composite. In particular, the composite has been chosen as the structural material for automotive and aerospace components. The hypereutectic Al-Mg2Si composite should be comprised of two morphologies, namely primary Mg2Si and pseudo-eutectic Al-Mg2Si phase. However, as-received commercial Al-20Mg2Si-2Cu in situ composite contained a wide range of elements that affect the resultant microstructure of the in situ composite. In fact, four different morphologies have been identified in the in situ composites. The first phase is dark facet primary Mg2Si particles, surrounded by pseudo-eutectic Al-Mg2Si phase in lamellar structure. Along the eutectic boundary is the formation of needle-like Al5FeSi intermetallic and the phase is surrounded by Al5Mg8Si6Cu2+Al2Cu as last phase nucleated. Optical micrograph, SEM imaging, EDX analysis and elemental mapping have revealed these phases correspond to shape of morphologies and respective molecular compound.

The effect of the formation of CuO flowers and SnO2 on tin whiskers formation and growth in 30°C/60%RH environmental condition for tin surface finish had been studied. Immersion plating method was used to coat a layer of tin onto a copper, Cu substrates. The coated surface was subjected to external stress by micro hardness indenter with 2N load in order to simulate an external stress in coating layer and to promote the formation of tin whiskers. FESEM and EDX was used to study the type and chemical composition of whiskers and oxides formed. Image analyser was used to measure the whiskers length using JEDEC Standard No 22-A121A. After 1 week of the exposure under 30°C/60%RH environmental condition, kinked-type whiskers were formed and the whiskers growth were discontinued at week 4 due to the distruction at the end-tip of kinked-type tin whisker to grow further when it touched the coating surface. An obervation until 52 weeks of exposure time found that the formation and growth of CuO flowers and the oxidation of non-kinked-type of tin whiskers to form SnO2 promoted by external stress also contributed to the discontinuity of whiskers growth.

Al-Mg2Si in-situ composite have received wider attention due to their improved properties which mark them as attractive candidate to manufacture most of automotive and aerospace components. Result show that the melt treatment of the in-situ composite by addition of antimony caused to refining the morphology of primary Mg2Si reinforcement which would expect to improve the mechanical properties. Effect of Sb on the characteristics parameters of Mg2Si particles have been investigated by thermal and microstructural analysis. The result has revealed that addition of 0.8 wt.% Sb produced optimum refinement effect on the morphology as coarse structure has been changed to polygon one. The result also showed depression with nucleation temperature, TN and growth temperature, TG which also correspond to the refinement effect.