Influences of Growth Velocity and Fe Content on Microstructure, Microhardness and Tensile Properties of Directionally Solidified Al-1.9Mn-xFe Ternary Alloys

Abstract

In this study, influences of growth velocity and composition (Fe content) on the microstructure (rod spacing) and mechanical properties (microhardness, ultimate tensile strength and fracture surface) of Al-Mn-Fe ternary alloys have been investigated. Al-1.9 Mn-xFe (x=0.5, 1.5 and 5 wt. %) were prepared using metals of 99.99% high purity in the vacuum atmosphere. At a constant temperature gradient (6.7 K/mm), these alloys were directionally solidified upwards under various growth velocities (8.3-978 μm/s) using a Bridgman-type directional solidification furnace. The results show that two kinds of Al-rich α-Al phase and Fe-rich intermetallic (Al 6 FeMn) phase may be present in the final microstructures of the alloys when the Fe content increases from 0.5 wt.% to 5 wt.%. Al 6 FeMn intermetallic rod spacing, microhardness and ultimate tensile strength were measured and expressed as functions of growth velocity and Fe content by using a linear regression analysis method. According to experimental results, the microhardness and ultimate tensile strength of the solidified samples increase with increase in the growth velocity and Fe content and decrease in rod spacing. The elongations of the alloys decrease gradually with increasing growth velocity and Fe content.

Relationship Between Aluminum-Rich/Intermetallic Phases and Microhardness of a Horizontally Solidified AlSiMgFe Alloy

“…This hardening occurs through the formation of barriers that hinder the movement of dislocations. It is highlighted that the Al-(5 to 12)wt%Si casting alloys with addition of magnesium ranging from 0.2 to 0.5 wt% allows the hardening of the matrix by precipitation of second phases, with emphasis to the Mg 2 Si phase, after solution and artificial aging heat treatments [29][30][31][32] .…”

“…Although the literature has presented in the last decades a large number of studies on the structural evolution of casting alloys, due to the number of operational and thermal parameters involved during the solidification, several aspects of physical nature related to the formation of the macrostructure and microstructure of products obtained by casting still need to be effectively understood, especially with respect to the solidification growth direction and, consequently, the effect of the gravity that acts during the process. It is evidenced from the literature that most studies on directional solidification consider the upward direction, where the direction of the gravity is parallel to that of heat extraction, but contrary to the advance of solidification, promoting better thermal stability to the process 2,5,6,8,9,17,18,23,[25][26][27]31,36 . On the other hand, in horizontal solidification, the gravity is perpendicular to the heat flow and solidification advance direction and, in this case, thermal instabilities are always present due to the effects of thermal and solutal convections 3,4,21,25,28,37 .…”

Synthesis and mechanical testing of grain boundaries at the micro and sub-micro scale

“…However, the technique is limited to a specific materials, which tend to form an eutectic and the specific shape of fibers (e.g. Mn-Sb pillars in Sb matrix [67,68] or Al-Fe-Mn pillars in Al matrix [69]. So far, no reports on bi-crystalline micropillars produced via this route are published.…”

Influence of solidification rate and alloying elements on structure, mechanical and electrical properties of Al-Cu-X alloys

“…Thus, the microstructures play a crucial role in the physical properties (mechanical and electrical) of metallic alloys. The effects of applied solidification parameters on physical properties have been studied intensively [8,10,12,15,[26][27][28][29][30][31][32][33][34][35][36]. Experimental researches show that the solidification condition and AE strengthen the alloy through refined grains and improve the mechanical properties.…”