MICROSTRUCTURE AND MECHANICAL PROPERTIES OF THE AS-CAST AND EXTRUDED AL-SI-FE-CU-MN BASED ALLOYS FABRICATED BY ADDING GRAIN REFINER

摘要

Effects of AlTiB addition on microstructure and mechanical properties of as-cast and as-extruded Al-0.15Si-0.2Fe-0.3Cu-0.9Mn alloys were investigated. After the as-cast billets were kept at 400 ?C for 1 h, hot extrusion was carried out with a reduction ratio of 38:1. AlTiB addition to Al- 0.15Si-0.2Fe-0.3Cu-0.9Mnbased alloys resulted in the formation of the globular dendritic morphology grains and grain refinement. In this microstructure of as-cast alloys, these two kind of Mn containing phases were observed: Al_6(Fe,Mn) intermetallic compound with lamellar morphology and Al15(Fe,Mn)3Si2 intermetallic compound with polygon shape. In room temperature tensile test, In the stress-strain curves at room temperature, with increasing AlTiB addition, yield strength and ultimate tensile strength was increased slightly. And elongation was improved from 49 to 52% as AlTiB content was increased from 0.1 to 1.0wt%. In the stressstrain curves at 420 ?C, ultimate tensile strength of the all alloys was similar. On the other hand, elongation was improved from 77 to 92% as AlTiB contents was increased from 0.1 to 1.0 wt%. AlTiB addition plays an important role for the enhancement of elongation at elevated temperature of 420 ?C.