One-Step Annealing Cu-Al-Mn-Fe Cast Alloys to Induce Abnormal Grain Growth and Produce Single Crystals with New Mechanism of Continue Misorientation Gradient

Abstract

In this paper, the microstructure of Cu-Al-Mn-Fe cast alloys, phase transformation, microstructural evolution and abnormal grain growth when one-step annealing their cast alloys were investigated. A new mechanism of a continue misorientation gradient to induce abnormal grain growth and produce single crystals only through one-step annealing cast alloys was reported. Only taking such simple process once, the grain can abnormally grow to 56 mm in length. This continue misorientation gradient results from the dissolution of bcc β(FeAl) nanoparticles with preferable volume fraction of 5% ~ 6% that come from bcc two-phase separation. The present results confirm that the energy (57 × 10^-2 J*mol^-1) depending on the continue misorientation gradient and average misorientation angle (1.53°) is the most important role in the grain boundary migration and the driving force for abnormal grain growth. The estimated velocity of abnormal grain growth is about 1.1 × 10^-4 m*s^-1, being close to experimental value of 9.3 × 10^-5 m*s^-1. Since the phase separation is a common phenomenon in many alloys, we also expect that our proposed design idea of a continue misorientation gradient can be applied to the preparation of single crystals for more metallic materials.

Keywords: Cu-based alloys, Bcc phase separation, Abnormal grain growth, Dissolution, Continue misorientation gradient