Study On The Preparation Of Arsenic-iron Alloy By Mechanical Alloying And Its Optimization And Modification By Sintering

Arsenic pollution is a chronic disease that restricts the green development of non-ferrous smelting industry in our country.With the consumption of high-quality resources,the content of arsenic in smelting raw materials is increasing year by year;due to the toxicity of arsenic,the market for traditional arsenic products has shrunk sharply,and arsenic is eventually stored in various hazardous wastes,with high pollution risks,and non-ferrous smelting enterprises are facing enormous pressure.How to expand the ways to absorb arsenic resources is imminent.Because of its special magnetic and mechanical properties,arsenic-iron alloy has potential application value in the fields of non-magnetic counterweights such as high-end equipment and magnetic refrigeration compression motor balance blocks.However,the research on the preparation and optimization of arsenic-iron alloys with low magnetic properties and high density is extremely lacking,which hinders the application and development of arsenic-iron alloys.In this study,based on the systematic analysis of the occurrence state and physical and chemical properties of typical arsenic-iron alloy products,the research on the efficient preparation of arsenic-iron alloy by mechanical alloying and the characteristics of the reaction process were carried out,and the optimization and modification process of arsenic-iron alloy bulk sintering was studied.The main conclusions are as follows:（1）The typical arsenic-iron alloy occurrence phase and its physicochemical properties were systematically studied.The properties of arsenic-iron alloy product"arsenic ice iron"in smelting enterprises were analyzed.The results showed that the density of arsenic ice iron was low（4.7 g/cm³）,the leaching toxicity of arsenic was high（12.43 mg/L）,and it mainly contained Fe₂As and other phases.In order to study the effect of arsenic-iron relative to alloy properties,a new method for preparing arsenic-iron compounds by"vacuum roasting-pickling and impurity removal"was invented,and the physical and chemical properties of various pure arsenic-iron compounds（Fe As,Fe As₂,Fe₂As）were analyzed.The results show that the formation and transformation of arsenic-iron alloy phase have a significant effect on arsenic toxicity and alloy properties.Compared with Fe As₂ and Fe₂As,Fe As has higher density,better environmental stability,and relatively lower magnetic properties.Therefore,the efficient synthesis of Fe As phase is the key to optimizing the properties of arsenic-iron alloys.However,Fe As is a metastable state,which is formed by the decomposition of Fe As₂ and dearsenic at a temperature of 807°C,and the most stable Fe₂As phase is formed after dearsenic at a high temperature（997°C）.The above research provides a research basis for the efficient preparation of arsenic-iron alloys.（2）In order to improve the degree of arsenic-iron alloying,the high-efficiency preparation method and reaction process characteristics of arsenic-iron alloy by mechanical alloying were studied.The optimal process parameters of mechanical alloying were determined:the ratio of balls to material was 20:1,the ratio of balls to diameter was 1:1,the speed of ball milling was 320 r/min,the milling time was 40 h,and the particle size of Fe powder was 200 mesh.Under these conditions,the alloying rate of arsenic reached 88.5%,the leaching toxicity of arsenic was 1.2mg/L,and the density of alloy powder was 6.65 g/cm³.The characteristics of the arsenic alloying process are revealed:the arsenic-iron alloy powder undergoes an activation reaction under the action of high-strength mechanical force,and the particle size decreases,the grain refinement and the specific surface area increase;After activation,part of the iron and arsenic form an arsenic-rich phase（Fe As₂）,and part of the iron is converted into active nano-iron（Fe⁰）.Mechanically alloyed arsenic-iron alloy powder has the characteristics of high magnetic properties and low toxicity,but in order to meet the requirements of low magnetism and high strength for the balance weight of the magnetic refrigeration compression motor,it is also necessary to optimize the physical phase and microstructure properties.（3）In order to control the phase composition of arsenic-iron and optimize the properties of the alloy,the hot-pressing sintering modification process of arsenic-iron alloy was studied.The research shows that under the condition of hot pressing at 800℃and 50 Mpa,the alloy block with high strength and low magnetic properties can be obtained,and the main phase is Fe As phase.And the alloy has the best comprehensive mechanical properties（107.7 Mpa compressive strength,13.7 fracture strain and 673 HV microhardness）,its density is 7.68 g/cm³,and the maximum magnetization is 1.0 emu/g.The mechanism of hot-pressing modification of arsenic-iron alloy was investigated,and the results showed that the size and number of voids in the alloy block and microstructure properties such as iron arsenide grains caused by the difference of sintering process would significantly affect its properties.The study also found that in the process of sintering solid-phase reaction,the arsenic-rich phase（Fe As₂）first decomposed to produce Fe As phase and arsenic element,and the arsenic element would continue to combine with the active iron produced by ball milling to form Fe As.The results of microstructure analysis show that the Fe As phase distribution in the alloy is dense and uniform,and only a small amount of iron-rich phase（Fe₂As）appears at the Fe As grain boundaries.This paper contains:37 figures,8 tables,147 references...