Effect Of Modification Of W On The Morphology Of Iron-rich Phase Of A356 Aluminum Alloy

Compared with the production of primary aluminum,the vigorous development of recycled aluminum can significantly reduce resource and energy consumption,reduce pollutant emissions and has good social,environmental and economic benefits.Aluminum alloys are inevitably enriched with Fe in the recycling process and Fe is often present in the form of needle-like iron-rich phases in aluminum alloys,which harms the mechanical properties of the alloy.Therefore,in order to reduce the harm of needle-like iron-rich phase,it is particularly important to modify the iron-rich phase.This article uses Optical Microscope?OM?,Scanning Electron Microscope?SEM?,Transmission Electron Microscope?TEM?,Diffractometer of X-ray?XRD?,quantitative metallographic analysis and mechanical properties Tests.The influence of W on the iron-rich phase morphology and the mechanical properties of A356 aluminum alloy were studied.The research results are as follows:The effect of W modification on the morphology of iron-rich phase in Al-Fe binary alloy was studied.The result shows:In the Al-Fe binary alloy without W modification,The iron-rich phase is a long rod-shaped Al₆Fe phase.After W modification treatment,the iron-rich phase in the Al-Fe binary alloy changed from the original long rod-shape to the fine rod-shape,small block-shape and granular phase,and existed on the grain boundary in the network eutectic structure.The effect of W addition on the iron-rich phase morphology of A356 aluminum alloy with different Fe contents was studied.The result shows:When the amount of W added in the A356-1%Fe aluminum alloy is less than 0.5%,the iron-rich phase still has needle-like morphology.When the amount of W added is 0.5%,the needle-like iron-rich phase transforms into fishbone-like,Chinese-like shape,but there are still some needle-like iron-rich phases in the alloy structure,that is,the iron-rich phase is not completely modified.Further increase the amount of W added to 1%,the iron-rich phase is still co-existing with fish-bone shape,Chinese character shape and partial needle-shape.But when the amount of W added increases to 5%,in addition to the fishbone-like,Chinese-shaped and needle-like morphology,the iron-rich phases with larger sized lath,block and core-shell morphologies have been added to the alloy structure.In addition,at a certain W content,the larger the Fe content in the alloy,the more favorable the formation of block iron-rich phase.The surface scan results of the microstructure show that,The modified iron-rich phase Fe element has a good correspondence with W element,and through phase analysis and energy spectrum analysis,The iron-rich phase of the needle-like morphology is?-Fe phase,the fishbone-like,Chinese-shaped,block iron-rich phase and core-shell iron-rich is?-Fe iron-rich phase,the lath iron-rich phase is Al₃FeSi.The effect of ultrasonic-assisted W modification on the microstructure and mechanical properties of iron-containing A356 aluminum alloy was studied.The result shows:For the A356 aluminum alloy without ultrasonic treatment,the primary?-Al phase is dendritic and the iron-rich phase is distributed in the eutectic region in a typical needle-like shape.Under the ultrasonic power of 1.2KW,with the extension of ultrasonic time,the roundness of?-Al phase increases,the?-Al phase changes from dendrite to equiaxed crystal,but the iron-rich phase still maintains the needle-like morphology,but Compared with the unsonicated iron-rich phase,its size is significantly reduced and the iron-rich phase is refined.And after adding W element,When ultrasound is conducted at a relatively high temperature?700-670??,the?-Al phase in the structure of A356 aluminum alloy exhibits a good roundness shape,and the iron-rich phase mainly exists in the form of Chinese characters and grains.When the ultrasonic temperature drops to 670-640?and 640-610?,the microstructure of A356 aluminum alloy is mainly equiaxed.When ultrasonic treatment is carried out at 670-640?,part of the iron-rich phase is spherical and dendritic,and the other part is polygonal.Compared with the morphology of 700-670?,the number of spherical and dendritic iron-rich phase decrease;After ultrasonication at 640-610?,almost all the iron-rich phases are polygonal.That is,as the ultrasonic temperature decreases,the iron-rich phase gradually changes from spherical and dendritic to polygonal.Moreover,under the optimal melt treatment temperature,the tensile strength and elongation of A356 with ultrasonic assisted W modification were 268.453MPa and 9.8%,respectively.Compared with the unmodified treatment,the tensile strength and elongation increased by 36.16%And 206.25%.The long-term effectiveness of the W modification treatment was studied.The result shows:When the melt holding time is at least 30min,the iron-rich phase can achieve good metamorphism,In addition,during the holding time of up to 300min,the modification effect of the iron-rich phase was not found to be invalid or further increased with the extension of the melt holding time.