Research On Cold Heading Forming And Heat Treatment Microstructure Of A286 High Temperature Alloy

Super alloy A286 is an austenitic iron based high-temperature alloy with good performance near 650 ℃,suitable for aerospace fastener products.Usually,A286high-temperature alloy fasteners are processed and formed at temperatures above950 ℃,which is difficult to manufacture and costly.However,there is a lack of systematic research on its low-temperature formability,cold heading structure,and heat treatment process.In response to the above issues,this article uses the cold heading method to trial produce an aviation bolt,and studies its cold heading structure and subsequent heat treatment structure.The specific research content is as follows:1.Finite element simulation of A286 high-temperature alloy bolt forming.Firstly,Gleeble room temperature compression experiment was conducted on A286 alloy specimens with a deformation of 20%～70%,and the true stress-strain curve at a strain rate of 0.1～10 s-1 was obtained.A finite element model was established based on the bolt size;Secondly,design a multi-station forming cold heading process plan and study the deformation law of A286 high-temperature alloy bolts.2.Research on the microstructure of A286 high-temperature alloy during cold heading.According to the simulated cold heading forming process,compression tests were conducted,and the microstructure after cold heading was observed through characterization methods such as XRD,OM,SEM,TEM,etc.The Vickers hardness after cold heading was measured.The results show that after cold heading forming of A286 high-temperature alloy,the grains and carbides undergo a certain degree of fragmentation,and the deformation mode is a combination of twin deformation and slip deformation.The precipitates are mainly titanium carbide and chromium carbide,and manganese element is enriched.3.Research on the heat treatment microstructure of A286 high-temperature alloy.Perform aging heat treatment on the A286 high-temperature alloy sample after cold heading,observe the grain structure and precipitate morphology,and test its Vickers hardness.The results indicate that: There are two forms of γ’ phases in the grain,namely square and spherical;The η phase is distributed in a strip shape near the grain boundary;The granular precipitates of titanium carbide and chromium carbide are distributed within the grains.The hardness of A286 alloy mainly depends on quantity of η phase precipitation,with the lowest hardness value on the outermost layer of the sample.