The Microstructure in an Al–Ti Alloy Melt: The Wulff Cluster Model from a Partial Structure Factor

Xiaohang Lin,Lin Song,Minghao Hua,Xuelei Tian,Hui Li,Anchen Shao

doi:10.3390/met11111799

Abstract

In the present work, the Wulff cluster model—which has been proven to successfully describe pure metals, homogeneous alloys, and eutectic alloys—has been extended to complex binary Al80Ti20 alloys, containing intermetallic compounds. In our model, the most probable structure in metallic melts should have the shape determined by Wulff construction within the crystal structure inside, and the cluster’s size could be measured by pair distribution function. For Al80Ti20 binary alloy, three different types of clusters (Al cluster, Al3Ti cluster, and Ti cluster) were proposed. Their contributions in XRD results are investigated by a comparison with the partial XRD pattern. Ti–Ti and Al–Ti partial structural factors are completely contributed by a pure Ti cluster and an Al3Ti cluster, respectively. Al–Al partial structural factor is contributed not only by a pure Al cluster but is also related to part of the Al3Ti cluster. The simulated XRD curve shows a good agreement with the experimental partial I(θ), including the peak position, width, and relative intensity.

Highlights

Titanium (Ti)-based alloys are widely applied as a high-performance, lightweight material for marine light engineering equipment due to their low density, high specific strength, non-magnetism, and strong seawater corrosion resistance [1,2,3,4]
The Wulff cluster model could successfully describe the melts structure of pure metals and binary homogeneous and eutectic alloys [25,26,27], one should be very careful to extend it to general binary alloys containing intermetallic compounds
The melt structures cannot be fully reflected by the solid structures after solidification

Summary

Introduction

Titanium (Ti)-based alloys are widely applied as a high-performance, lightweight material for marine light engineering equipment due to their low density, high specific strength, non-magnetism, and strong seawater corrosion resistance [1,2,3,4]. Considering the different application scenarios of Al–Ti alloys in a variety of complex areas, it is necessary to design its structure, composition, and physical and chemical properties to achieve more extensive applications. Due to the special, high temperature, liquid environment of alloy melt, these direct characterization methods can not reflect the real microscopic physical image of the melt In this case, it is reasonable to use a model description method [13,14,15,16], such as the crystal defect model, the quasi-crystalline mode, or the cluster model, etc. A thermodynamic model based on the Wulff theory was proposed, the so-called Wulff cluster model, which was successfully applied to describe the melt structures of pure metals and binary homogeneous and eutectic alloys [25,26,27]. The partial structure factors from experiments are analyzed in order to investigate the internal details of the melt structure with multiple mixed phases

Theoretical Methods

Experimental Methods

Results and Discussion