I. Introduction
Metals are valuable resources the Earth provides to human beings and take an irreplaceable place in the development of human civilization. As nonrenewable resources, the classification and recycling of metals are attracting more and more concern [1], [2]. Alloys are widely used in the automotive, construction, and other industries in real life, and the classification of alloys is an important part of metal classification and recycling [3], [4], [5].