Although glass wool and polyurethane foam are the most widely used sound-absorber and
insulating materials, there are some critical problems related to the environmental issues. In this
reason, there is a lot of attention on the aluminum foam as a sound absorption material, therefore, in
this research, sound absorption and transmission loss properties were studied. The results showed that
low density aluminum foam performed better in both sound absorption and transmission loss and the
properties were improved as increased air cavity and space.
The as-cast microstructure of Mg-5Al-3Ca-xY alloy consists of dendritic -Mg matrix, (Mg, Al) 2 Ca eutectic phase and Al 2 Y intermetallic compounds. These two kind of (Mg, Al) 2 Ca compounds were observed: coarse irregular-shape structure at grain boundary and fine needle-shape structure in the -Mg matrix grain. This (Mg, Al) 2 Ca phase of the extruded alloys was elongated to extrusion direction and size of this phase was refined comparing with that of as-cast alloys because of severe deformation during hot extrusion. Maximum yield and ultimate strength value of extruded alloys was 326 and 331 MPa at Mg-5Al-3Ca-3Y alloy, respectively. From these results, it is conclusively demonstrated that Y additions on Mg-5Al-3Ca alloy have more effect to improve mechanical properties.
The as-cast microstructure of Mg-5Al-3Ca-xNd alloys consists of equiaxed -Mg matrix, (Mg, Al) 2 Ca eutectic phase and Al-Nd rich intermetallic compounds. With the increase of Nd addition, -Mg matrix morphology was changed from dendritic to equiaxed grains due to suppression of grain growth by formation of homogeneous intermetallic compounds containing Nd dispersed at grain boundary and -Mg matrix. And the grain size of as-cast alloys was decreased as addition of Nd was increased. This eutectic phase of the extruded alloys was elongated to extrusion direction and size of this phase was redined comparing to that of as-cast alloys because of severe deformation during hot extrusion. Maximum yield and ultimate tensile strength value of the as-extruded alloys was 322 and 335 MPa at Mg-5Al-3Ca-2Nd alloy, respectively.
The aims of this research are to investigate the effect of Sm addition in Mg-Al-Ca alloys on microstructure and mechanical properties. Sm addition to Mg-5Al-3Ca based alloys results in the change from dendritic to equiaxed grain morphorlogy and formation of Al-Sm rich itermetallic compounds at grain boundary and α-Mg matrix. And these Al-Sm rich intermetallic compounds were dispersed homogeously and stabilized at high temperature. And maximum yield and ultimate strength value was obtained at Mg-5Al-3Ca-2Sm alloys at elevated temperature because of homogeneous dispersion of stable Al-Sm rich intermetallic compound at high temperature.
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