Study On Preparation And Refining Ability Of Al-V-B Master Alloy

Cast aluminum-silicon alloy has the advantages of low thermal cracking tendency,good air tightness,low shrinkage and good fluidity,and is widely used in many important fields such as automobile,aerospace and national defense,etc.However,the strength of aluminum-silicon alloy is medium and can only withstand ordinary load,which is difficult to meet the demand for the development of high strength and toughness aluminum alloy,and grain refinement is one of the most effective means to improve the strength and toughness of the alloy.The most widely used Al-Ti-B series intermediate alloys cause Si poisoning in Al-Si alloys and reduce the refining efficiency,so it is crucial to develop refining agents that resist Si poisoning.In this paper,we used Al-V-B intermediate alloy to refine Al-Si alloy,and explored the effects of composition design and ultrasonic treatment process parameter design on the organization and morphology of the intermediate alloy and its refining ability during the preparation of Al-V-B intermediate alloy by using OM,XRD,SEM,tensile test and other characterization means,and obtained the optimal composition design and optimal ultrasonic treatment process of Al-V-B intermediate alloy,which can provide theoretical support for the development of Al-V-B intermediate alloys,and provide theoretical support for the development of Al-V-B intermediate alloys.The main conclusions obtained in this paper are as follows:（1）The V/B of the Al-V-B intermediate alloy has a significant effect on its refining ability.when the V/B is less than 10,the organization in the intermediate alloy is mainly（Al,V,B）,Al B₁₂and（Al,Fe,Si）;when the V/B is greater than 20,the main organizations in the refiner are Al₁₀V,Al B₁₂,（Al,V,B）,（Al,Fe,Si）,Al₄₅V₇and Al₃V.With the increase of V/B,the ability of Al-V-B intermediate alloy to refine A356 aluminum alloy is weaker,and the comprehensive mechanical properties of A356 aluminum alloy show a trend of improving first and then decreasing.The average grain size was reduced from1000.3μm to 62.77μm,and the grain size was reduced by 93.72%,while the comprehensive mechanical properties reached the peak.The tensile strength of A356aluminum alloy increased by 4.4%and the elongation increased by 146.47%after Al-V-B refinement.（2）The V and B contents of the Al-V-B intermediate alloy have an effect on its refinement ability.With the increase of V and B content in the intermediate alloy,the（Al,V,B）ring diameter and thickness increased,the ring diameter expanded from 42μm to 86μm,the ring thickness increased from 3μm to18μm,and the second phase organization gradually coarsened.With the increase of V and B content in the intermediate alloy,the comprehensive mechanical properties of A356 aluminum alloy showed a trend of increasing and then decreasing,1.5 wt.%of V content showed the best comprehensive mechanical properties,the tensile strength of A356 aluminum alloy was 195MPa and elongation was 6.63%.（3）The ultrasonic treatment time has a certain influence on the refinement ability of Al-1.5V-0.3B intermediate alloy.Within 6 min,the size of agglomerated Al B₁₂and VB₂showed a trend of constant,then decreasing and then increasing as the ultrasonic treatment time increased,and the size was 100-200μm without ultrasonic treatment,and after 4 min of ultrasonic treatment,its size was the smallest and decreased to less than 50μm,and The distribution was the most uniform.With the increase of ultrasonic treatment time,the refinement ability of Al-1.5V-0.3B intermediate alloy showed a tendency of increasing and then decreasing,and the refinement effect was the best after 4 min of ultrasonic treatment,and the comprehensive mechanical properties of A356 aluminum alloy were the strongest.The ultrasonic introduction temperature has an effect on the refinement ability of Al-1.5V-0.3B intermediate alloy.At 660-800°C,the Al B₁₂and VB₂sizes increased from 70μm to 70-100μm with the increase of ultrasonic treatment temperature.with the increase of ultrasonic introduction temperature,the refinement ability of Al-1.5V-0.3B intermediate alloy showed a trend of enhancing first and then weakening,and the refinement effect was the best at 750°C,while the comprehensive mechanical properties were the best.Therefore,the ultrasonic treatment process is best for 4 min at 750°C.The average grain size of A356 aluminum alloy is 56.5μm,the tensile strength is 200MPa,and the elongation is 8.08%,which are 2.56%and21.87%higher than those without ultrasonic treatment.