High-strength AZ91HP magnesium-alloy and its production

Abstract

A high-strength AZ91HP magnesium-alloy and its production are disclosed. The magnesia-alumina alloy consists of Mg-9% Al-1% Zn; primary crystal alpha-Mg grain size is 10-20mum; the second-phase beta-Mg17A112 particle is uniform and dispersant; grain size is 3-5mum; space of secondary branch crystal is 6-10mum. It adopts copper-mould pouring method. The alloy crystal grain size is refined after cooling. It has better compression strength and plasticity.

Description

technical field [0001] The invention relates to a magnesium alloy preparation technology, in particular to a high-strength AZ91HP magnesium alloy and a preparation method thereof. Background technique [0002] Environmental protection and energy saving are major strategic requirements for the sustainable development of human society in the 21st century. Magnesium has a series of advantages such as abundant reserves, light weight, high specific strength, and good shock absorption. It is an ideal environmental protection and energy-saving material that meets the requirements of sustainable development. In recent years, it has been widely concerned by people, and its application fields have been continuously expanded. Magnesium alloys produced by traditional methods often have low strength and poor corrosion resistance. Therefore, how to improve the mechanical properties of magnesium alloys has become a frontier and hot spot in the field of magnesium alloy materials research. ...

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Problems solved by technology

The main problems that limit the wide application of magnesium alloys are: due to the extremely active magnesium element, magnesium alloys are extremely easy to oxidize and burn during smelting and processing. Therefore, the production of magnesium alloys is very difficult; the production technology of magnesium alloys is not yet mature and perfect. In particular, the forming technology of magnesium alloys needs to be further developed; the corrosion resistance of magnesium alloys is poor; the high temperature strength and creep properties of existing industrial magnesium alloys are low, which limits the application of magnesium alloys in high temperature (150-350°C) occasions; The normal temperature mechanical properties of magnesium alloys, especially the strength and ductility, need to be further improved

At present, the smelting process of AZ91HP magnesium alloy is flux method and flux-free smelting method. The disadvantages are: salt and fluoride salt are easy to volatilize at high temperature and produce some toxic gases, and the volatilized gas such as HCl may penetrate into the alloy liquid and become The source of corrosion during the use of materials, accelerates the corrosion of materials, and reduces the service life of materials

The casting process of AZ91HP magnesium alloy is die-casting technology and semi-solid forming technology. The disadvantage is that when magnesium alloy is die-casting, due to the high injection speed, when the magnesium liquid is filled into the mold cavity, there will inevitably be turbulent flow of the molten metal. And air entrainment occurs, resulting in hole defects inside and on the surface of the workpiece. Therefore, how to improve the yield of castings with high requirements is one of the main problems faced by magnesium alloy die-casting.

The semi-solid forming technology of magnesium alloys includes thixotropic casting. The preparation of prefabricated blanks requires huge investment, and the key technology is monopolized by a few foreign companies, resulting in high costs. It is only suitable for the manufacture of key parts that require high strength.

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