A new high-strength spinodal alloy

Abstract

Preliminary investigations of a new high-strength alloy of composition Fe 30 Ni 20 Mn 25 Al 25 (at.%) are described in this paper. The as-cast alloy consisted of a periodic two-phase microstructure of interconnected, ∼50-nm-wide rods with fully coherent {100} interfaces, strongly suggestive of formation by a B2 to [(B2 + body-centered cubic (bcc)] spinodal decomposition. The (Ni,Al)-rich B2 and (Fe,Mn)-rich bcc phases differed in lattice parameter by <0.5%. Hardness and yield strength of the as-cast alloy were found to be approximately 500 VPN and 1500 MPa, respectively, and increased by more than 50% after annealing at 550°C for several days. (Fe,Mn)-rich precipitates with a ␤-Mn structure were observed in the annealed material.

The Al Effects of Co-Free and V-Containing High-Entropy Alloys

“…These were found to be similar to the inter-dendritic and inter-plate region structures in the selected AlxCoCrFeNi alloys [13], which were believed to have been formed by a spinodal decomposition mechanism [14]. Similar structures were also reported in the AlxCoCrCuFeNi [15] and AlFeMnNi HEAs [16]. In order to further confirm the microstructures of both the HEAs, TEM and STEM analyses were performed in this research study.…”

Deviation from high-entropy configurations in the atomic distributions of a multi-principal-element alloy

“…However, multiphase microstructures should not be dismissed, not only because they provide valuable test cases for understanding phase separation in high-entropy alloys, but also because many are technologically significant in their own right. For example, high-strength spinodal alloys have recently been developed using four principal elements (Al, Fe, Mn and Ni) 36,51 , which potentially enhances their DS conf mix . The success of using multiple principal elements in the development of these spinodal alloys is relevant to These results indicate that Cu diffuses faster than the other elements, which is consistent with the observed precipitation of Cu-rich phases (Fig.…”

“…The I ratio trend indicates a gradual strengthening of the B2 order, and decrease in the DS conf mix , as the spinodal microstructure is heated. This entropy decrease is thermodynamically favourable only if it produces an offsetting benefit, such as lattice-strain minimization, as may be expected in multi-element spinodal alloys 36 . The overlapping B2 and BCC peaks in the present diffraction data indicate that close lattice-parameter matching is indeed maintained in the spinodal microstructure, even as the lattice parameters change with temperature (Fig.…”

Dislocation identification and in situ straining in the spinodal Fe30Ni20Mn25Al25 alloy

“…A number of BCC-based spinodal alloys have recently been discovered in the Fe-Ni-Mn-Al system near the equiatomic composition (Baker et al, 2005a,b;Hanna et al, 2005;Saxey et al, 2005;Wittmann et al, 2005). These alloys typically have modulated structures consisting of coherent, alternating rods or platelets of BCC and B2 phases aligned along h100i directions, characteristic of a spinodal decomposition.…”

“…Depending on the preparation method, Fe 30 Ni 20 Mn 25 Al 25 has displayed as-cast Vickers hardness values ranging from 445 to 504 VPN and yield strengths from 1,300 to 1,570 MPa (Baker et al, 2005a;Hanna et al, 2005). Despite significant work on characterizing the microstructure and selected mechanical properties for this composition (Baker et al, 2005a,b;Hanna et al, 2005;Saxey et al, 2005), a study of dislocation structures and behavior in this alloy has not been previously performed. The purpose of this article is to determine the active slip system(s) in order to understand this alloy better and to contribute to what little literature exists on deformation in BCC spinodals.…”