Study on In-Situ Deformation and Fracture of SLM+HIP Beryllium-Aluminum Alloy AITranslate

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Chinese Library Classification Number:TG146.2[金属学及工艺—金属材料]

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Beryllium-aluminum alloy was fabricated using selective laser melting(SLM)technology,and then the alloy was subjected to hot isostatic pressing(HIP)at 700℃or HIP at 700℃followed by annealing at 500℃for 12 h.The microstructure of SLM beryllium-aluminum alloy in both deposited and heattreated states was analyzed using FESEM,EDS,and EBSD methods,and their hardness was also tested.The deformation and fracture behaviors of HIP-treated SLM beryllium-aluminum alloy were studied using FESEM and in-situ tensile stage.Microstructural analysis reveals that the as-deposited microstructure of SLM beryllium-aluminum alloy consists of a small amount of stable beryllium/aluminum crystalline structure,microcrystalline structure,and a large amount of metastable structure.Severe lattice distortion and metastable structure collectively result in large residual internal stress in the material.After HIP treatment of SLM beryllium-aluminum alloy,the beryllium and aluminum phases in the as-deposited microstructure are fully diffused,and the metastable structure is transformed into a stable structure.EBSD orientation analysis shows that the grain orientation distribution of beryllium and aluminum phases in the alloy after HIP treatment is random,and the material properties tend to be isotropic.After the SLM beryllium-aluminum alloy is subjected to HIP treatment,subsequent annealing treatment has no significant improvement effect on the alloy microstructure.The hardness of both heat-treated alloys decreases from 258 HV(asdeposited state)to about 200 HV.In-situ tensile test results indicate that the SLM beryllium-aluminum alloy after HIP treatment has high strength but poor plasticity.The generation and propagation time of the main crack during tensile is very short.Before fracture,the aluminum phase activates slip deformation along a specific slip system with coarse aluminum phases showing relatively noticeable deformation,while the beryllium phase barely parti-cipates in the deformation.In the late stage of deformation,the main crack likely first initiates at the phase boundary and then propagates through the interior of the beryllium phase to grow.The crack expands ra-pidly and leads to instantaneous unstable fracture.The fracture mode is a mixed fracture of interphase fracture and transgranular fracture,with transgranular fracture in the beryllium phase being the dominant mechanism.