Paper Title
Microstructure Evolution and Mechanical Properties of Al-1.94mn-0.5cu Alloy Produced by Directional Solidification

In this investigation, Al-1.94Mn-0.5Cu (wt.%) alloy was directionally solidified at different solidification rates varying from 8.3 to 978 􀀀m/s at a constant temperature gradient (7.1 K/mm). The microstructure was analyzed by optical microscopy and scanning electronic microscopy. Especially, cell-dendritic transition was detected for low solidification rate (8.3 􀀀m/s). Then with increasing solidification rate, the microstructure is completely converted to a dendritic form. The microhardness increased from 470 to 520 MPa and the tensile strength increased from 109 to 145 MPa with increasing the solidification rate from 8.3 to 978 􀀀m/s. Exponent values of the V for the microhardness and tensile strength were calculated as 0.04 and 0.06, respectively. Fracture surface images of the studied alloys were analyzed depending on solidification rate. These fracture surfaces exhibited a lot of small dimples, a characteristic of ductile fracture. Many micro-cracks start from these voids and dimples. The mode of fracture significantly changed from ductile to less ductile with the increase of the solidification rate. Index Terms- Directionally solidification, microstructure, microhardness, tensile strength, fracture