【摘要】：采用激光熔化沉積技術(shù)制備了4045鋁合金薄壁試樣,研究了沉積試樣熱處理前后的顯微組織演化,并測試其顯微硬度。結(jié)果表明,沉積試樣顯微組織具有定向快速凝固特征,由Al枝晶和Al-Si共晶組成,其一次枝晶間距約22.3μm,二次枝晶間距約7.5μm,體積分?jǐn)?shù)約42.7%,沉積試樣頂部出現(xiàn)柱狀樹枝晶向等軸樹枝晶轉(zhuǎn)變。當(dāng)前沉積層從底部到頂部冷卻速度的降低導(dǎo)致Si相從珊瑚形貌向片狀形貌轉(zhuǎn)變,足夠高的重熔率能保證后續(xù)沉積層重熔掉當(dāng)前沉積層頂部片狀Si相,以獲得變質(zhì)效果良好的珊瑚形貌Si相,熱影響作用使緊鄰熔合線過熱區(qū)的珊瑚形貌Si相發(fā)生粗大等軸粒狀化,導(dǎo)致其顯微硬度低于層內(nèi)區(qū)。珊瑚形貌Si相在540℃等溫?zé)崽幚肀?0 min即可完成粒狀化,并且隨著保溫時間延長,Si相發(fā)生粗化長大,顯微硬度下降。
[Abstract]:4045 aluminum alloy thin wall specimens were prepared by laser melting deposition technique. The microstructure evolution and microhardness of 4045 aluminum alloy samples before and after heat treatment were studied. The results show that the microstructure of the deposited samples has the characteristics of directional rapid solidification and consists of Al dendrite and Al-Si eutectic. The primary dendritic spacing is about 22.3 渭 m, the secondary dendritic spacing is about 7.5 渭 m, the volume fraction is about 42.7, and the columnar dendritic to equiaxed dendritic transition appears at the top of the deposited sample. The decrease of cooling rate from the bottom to the top of the current sedimentary layer leads to the transition of the Si phase from the morphology of the coral to the morphology of the sheet. The high remelting rate can ensure that the subsequent deposit layer remelts the Si phase at the top of the current deposit. In order to obtain the Si phase with good metamorphic effect, the Si phase near the superheated zone of the fusion line is coarse and equiaxed, resulting in the microhardness of which is lower than that of the inner layer. The morphology of coral Si phase can be grained after isothermal heat treatment at 540 鈩，

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