發(fā)布時間：2018-04-27 23:16

  本文選題：激光技術(shù) + 激光沉積修復(fù)��； 參考：《沈陽航空航天大學(xué)》2017年碩士論文

【摘要】：Al-Si7-Mg(ZL114A)鋁合金屬于高強(qiáng)度鑄造Al-Si系亞共晶合金,具有優(yōu)良的鑄造性能和綜合力學(xué)性能,廣泛應(yīng)用于汽車、航空航天等高性能、承受高載荷結(jié)構(gòu)件中。本文針對ZL114A合金鑄造缺陷的快速修復(fù)需求,開展了對表面損傷、溝槽類大面積損傷的激光沉積修復(fù)工藝研究。研究了激光沉積修復(fù)ZL114A合金激光沉積修復(fù)沉積態(tài)、熱處理態(tài)修復(fù)試樣的顯微組織、硬度、拉伸性能、熱輸入量影響等情況。主要研究內(nèi)容如下:采用多參數(shù)組合激光沉積工藝實(shí)驗(yàn)制備了單道單層試樣,在分析了其表面形貌、氣孔等缺陷產(chǎn)生的原因的基礎(chǔ)上,得到了一組相對優(yōu)化的工藝參數(shù),制備了無缺陷的塊狀修復(fù)試樣,并對試樣進(jìn)行了組織分析及力學(xué)性能檢測。鋁合金修復(fù)試樣修復(fù)區(qū)與基材形成良好的冶金結(jié)合,沉積區(qū)底部為近似平行于熔合線法線外延生長的柱狀樹枝晶,一次枝晶間距約15.7μm,二次枝晶間距約5.2μm,共晶組織呈分叉棒狀或塊狀連續(xù)分布于枝晶間隙,在沉積層頂層頂部出現(xiàn)α-Al柱狀枝晶轉(zhuǎn)變?yōu)榈容S枝晶現(xiàn)象。熱處理后修復(fù)區(qū)柱狀枝晶的二次枝晶臂因高溫原子擴(kuò)散作用,形態(tài)發(fā)生變化,且共晶Si相粒狀化明顯,粒徑約4.93μm,部分顆粒均勻分散分布于一次枝晶臂的兩側(cè)。對試樣的顯微硬度和室溫拉伸性能進(jìn)行了測試。由于晶粒細(xì)化和固溶強(qiáng)化作用,沉積態(tài)修復(fù)區(qū)顯微硬度較基材提高25.8%。熱處理后修復(fù)區(qū)硬度較基材平均提高55.5%,且修復(fù)試樣的室溫拉伸力學(xué)性能優(yōu)于鑄造基材。對不同激光沉積修復(fù)占比試件拉伸性能進(jìn)行檢測。修復(fù)占比為10%和20%室溫拉伸的抗拉強(qiáng)度達(dá)到鑄件標(biāo)準(zhǔn)的90.4%和87.56%,斷后伸長率均優(yōu)于鑄件標(biāo)準(zhǔn)。斷口分析表明基材區(qū)斷裂機(jī)制為脆性斷裂,修復(fù)區(qū)為韌性斷裂。激光沉積修復(fù)ZL114A試件拉伸過程中,基材區(qū)微裂紋萌生于共晶硅顆粒密集處,沿著共晶硅顆粒擴(kuò)展,其斷裂方式為穿晶斷裂。修復(fù)區(qū)裂紋繞過細(xì)小共晶硅顆粒,沿著Al-Si共晶組織與晶胞結(jié)合處進(jìn)行擴(kuò)展,斷裂方式為沿晶斷裂。對于較大損傷零件(修復(fù)占比大于等于30%)的修復(fù),采用修復(fù)后整體熱處理工藝,修復(fù)后整體熱處理試件強(qiáng)度優(yōu)于鑄造件基材強(qiáng)度。示溫漆測試熱輸入量分析表明,激光沉積修復(fù)最高溫度不超過250℃,熱影響范圍符合生產(chǎn)要求。沉積修復(fù)試件變形測試表明,變形量符合生產(chǎn)要求。
[Abstract]:Al-Si7-MgZL114A) aluminum alloy is a kind of high strength cast hypoeutectic alloy of Al-Si system. It has excellent casting properties and comprehensive mechanical properties. It is widely used in automobile, aerospace and other high performance parts with high load. Aiming at the requirement of rapid repair of ZL114A alloy casting defects, the laser deposition repair technology for surface damage and large area damage of grooves has been studied in this paper. The effect of laser deposition on the microstructure, hardness, tensile properties and heat input of ZL114A alloy was studied. The main research contents are as follows: single channel monolayer samples were prepared by multiparameter combined laser deposition process. On the basis of analyzing the causes of the defects such as surface morphology and porosity, a group of relatively optimized process parameters were obtained. The defect-free bulk repair specimens were prepared, and the microstructure and mechanical properties of the samples were analyzed. The repair zone of aluminum alloy repair specimen formed a good metallurgical bond with the substrate, and the bottom of the deposition zone was a columnar dendrite grown approximately parallel to the fusion line normal line epitaxial growth. The primary dendritic spacing is about 15.7 渭 m, and the secondary dendritic spacing is about 5.2 渭 m. The eutectic structure is distributed continuously in the dendritic gap in the form of branched bars or blocks, and the 偽 -Al columnar dendrites change to equiaxed dendrites at the top of the deposition layer. After heat treatment, the secondary dendritic arms of columnar dendrites in the repair zone changed due to the effect of high temperature atomic diffusion, and the eutectic Si phase granulated obviously, with a particle size of about 4.93 渭 m. Some of the particles were distributed uniformly on both sides of the primary dendritic arm. The microhardness and tensile properties at room temperature were tested. Due to the effect of grain refinement and solution strengthening, the microhardness of the depositional repair zone is 25.8% higher than that of the base material. After heat treatment, the hardness of the repair zone is 55.5 higher than that of the base material, and the tensile mechanical properties of the repaired sample at room temperature are better than that of the foundry substrate. The tensile properties of different laser deposition repair specimens were tested. The tensile strength of 10% and 20% room temperature tensile strength reached 90.4% and 87.56% of the casting standard, and the elongation after break was better than that of the casting standard. Fracture analysis shows that the fracture mechanism of the base material is brittle and the repair zone is ductile. During the tensile process of the ZL114A specimen repaired by laser deposition, the microcracks in the substrate region originated from the dense eutectic silicon particles and propagated along the eutectic silicon particles, and the fracture mode was transgranular fracture. The crack in the repair zone bypasses the fine eutectic silicon particles and propagates along the Al-Si eutectic structure where the crystal cell binds. The fracture mode is intergranular fracture. For the large damaged parts (the repair ratio is more than 30%), the strength of the whole heat treatment specimen after repair is better than that of the foundry material. The analysis of the heat input of the temperature indicating paint test shows that the maximum temperature of laser deposition repair is not more than 250 鈩，

本文編號：1812770