Microstructures of Cast Fe-Mn-Si-Cr-Ni Shape Memory Alloys Characterized by Metallography

Abstract In the present paper, we selected or designed several etchants to characterize the solidification modes, the distribution of micro-segregation and the grain morphology of cast Fe-Mn-Si-Cr-Ni SMAs solidifying as A, AF, FA and F modes based on the principle of metallography. The results showed that a tint etchant based on 0.5 g K 2 S 2 O 5 , 20 g NH 4 HF 2 and 100 ml H 2 O can only characterize the grain morphology of cast Fe-Mn-Si-Cr-Ni SMAs solidifying as F and FA modes and can reveal the typical microstructures of FA, AF and A modes. An ordinary etchant (1 ml HF, 15 ml H 2 O 2 , 1 g C 2 H 2 O4 and 15 ml H 2 O) can only reveal the typical microstructures of F mode. As a result, the solidification modes of cast Fe-Mn-Si-Cr-Ni SMAs are determined by using both tint etchants together. Another tint etchant (20 g K 2 S 2 O 5 , 1 g NH 4 HF 2 and 100 ml H 2 O) can qualitatively characterize the distribution of micro-segregation in cast Fe-Mn-Si-Cr-Ni SMAs with four solidification modes.