Search

This study investigated the improvement in the electrical conductivity and mechanical properties obtained by adjusting the amount of the Sr addition to the Al-Zn-Mg-Mn alloy. The addition of Sr formed an intermetallic compounds, and the volume fraction of the intermetallic compounds increased with increasing Sr content. As the amount of Sr added increased from 0 to 1.0 wt%, the electrical conductivity of the extruded alloy decreased to 48.9, 45.2 and 42.5% IACS. As the addition amount of Sr increased, the average grain size of the rolled alloy decreased to 55.5, 53.1 and 42.3 μm. And, the ultimate tensile strength increased to 195, 212 and 216 MPa.

In this study, the effects of heat-treatment conditions of Fe powder compacts on densification, microstructure, strength and magnetic properties were investigated. The prepared Fe powder was compressed in a mold of diameter 20 mm at a pressure of 800 MPa for 30 sec. This Fe powder compact was heat-treated under different atmospheres (air and 90% Ar + 10% H2 and heat-treatment temperatures (300 and 700℃). The Fe powder compacts heat-treated in an Ar+H2 mixed gas atmosphere showed a denser microstructure and higher density than the Fe powder compacts heat-treated in an air atmosphere. Oxygen content in the heat-treatment conditions played a significant role in the improvement of the densification and magnetic properties.

This research describes effects of Si addition on microstructure and mechanical properties of the Al-Cr based alloys prepared manufactured using gas atomization and SPS (Spark Plasma Sintering) processes. The Al-Cr-Si bulks with high Cr and Si content were produced successfully using SPS sintering process without crack and obtained fully dense specimens close to nearly 100% T. D. (Theoretical Density). Microstructure of the as-atomized Al-Cr-Si alloys with high contents of Cr and Si was composed multi-phases with hard and thermally stable such as Al13Cr4Si4, AlCrSi, Al8Cr5 and Cr3Si intermetallic compounds. The average hardness values were 703 Hv for S5, 698 Hv for S10 and 824 Hv for S20 alloy. Enhancement of hardness value was resulted from the formation of the multi-intermetallic compound with hard and thermally stable and fine microstructure by the addition of high Cr and Si using rapid solidification and SPS process.

In this study, we investigated the effect of Fe addition (0, 0.25, 0.50 and 0.75 wt.%) on the microstructure, mechanical properties and electrical conductivity of as-cast and as-extruded Al-RE alloys. As the Fe element increased by 0 and 0.75wt.%, the phase fraction increased to 5.05, 5.76, 7.14 and 7.38 %. The increased intermetallic compound increased the driving force for recrystallization and grain refinement. The electrical conductivity of Al-1.0 wt.%RE alloy with Fe addition decreased to 60.29, 60.15, 59.58 and 59.13 %IACS. With an increase in the Fe content from 0 to 0.75 wt.% the ultimate tensile strength (UTS) of the alloy increased from 74.3 to 77.5 MPa. As the mechanical properties increase compared to the reduction of the electrical conductivity due to Fe element addition, it is considered to be suitable for fields requiring high electrical conductivity and strength.

In this study, the extrusion characteristics of Al-2Zn-1Cu-0.5Mg-0.5RE alloys at 450, 500, and 550? were investigated for the high formability of aluminum alloys. The melt was maintained at 720°c for 20 minutes, then poured into the mold at 200? and hot-extruded with a 12 mm thickness bar at a ratio of 38:1. The average grain size was 175.5, 650.1, and 325.9 μm as the extrusion temperature increased to 450, 500 and 550°C, although the change of the phase fraction was not significant as the extrusion temperature increased. Cube texture increased with the increase of extrusion temperature to 450, 500 and 550?. As the extrusion temperature increased, the electrical conductivity increased by 47.546, 47.592 and 47.725%IACS, and the tensile strength decreased to 92.6, 87.5, 81.4 MPa. Therefore, the extrusion temperature of Al extrusion specimen was investigated to study microstructure and mechanical properties. [ABSTRACT FROM AUTHOR]