激光沉积修复ZL114A工艺及性能研究

发布时间：2018-04-27 23:16

  本文选题：激光技术 + 激光沉积修复　； 参考：《沈阳航空航天大学》2017年硕士论文

【摘要】：Al-Si7-Mg(ZL114A)铝合金属于高强度铸造Al-Si系亚共晶合金,具有优良的铸造性能和综合力学性能,广泛应用于汽车、航空航天等高性能、承受高载荷结构件中。本文针对ZL114A合金铸造缺陷的快速修复需求,开展了对表面损伤、沟槽类大面积损伤的激光沉积修复工艺研究。研究了激光沉积修复ZL114A合金激光沉积修复沉积态、热处理态修复试样的显微组织、硬度、拉伸性能、热输入量影响等情况。主要研究内容如下:采用多参数组合激光沉积工艺实验制备了单道单层试样,在分析了其表面形貌、气孔等缺陷产生的原因的基础上,得到了一组相对优化的工艺参数,制备了无缺陷的块状修复试样,并对试样进行了组织分析及力学性能检测。铝合金修复试样修复区与基材形成良好的冶金结合,沉积区底部为近似平行于熔合线法线外延生长的柱状树枝晶,一次枝晶间距约15.7μm,二次枝晶间距约5.2μm,共晶组织呈分叉棒状或块状连续分布于枝晶间隙,在沉积层顶层顶部出现α-Al柱状枝晶转变为等轴枝晶现象。热处理后修复区柱状枝晶的二次枝晶臂因高温原子扩散作用,形态发生变化,且共晶Si相粒状化明显,粒径约4.93μm,部分颗粒均匀分散分布于一次枝晶臂的两侧。对试样的显微硬度和室温拉伸性能进行了测试。由于晶粒细化和固溶强化作用,沉积态修复区显微硬度较基材提高25.8%。热处理后修复区硬度较基材平均提高55.5%,且修复试样的室温拉伸力学性能优于铸造基材。对不同激光沉积修复占比试件拉伸性能进行检测。修复占比为10%和20%室温拉伸的抗拉强度达到铸件标准的90.4%和87.56%,断后伸长率均优于铸件标准。断口分析表明基材区断裂机制为脆性断裂,修复区为韧性断裂。激光沉积修复ZL114A试件拉伸过程中,基材区微裂纹萌生于共晶硅颗粒密集处,沿着共晶硅颗粒扩展,其断裂方式为穿晶断裂。修复区裂纹绕过细小共晶硅颗粒,沿着Al-Si共晶组织与晶胞结合处进行扩展,断裂方式为沿晶断裂。对于较大损伤零件(修复占比大于等于30%)的修复,采用修复后整体热处理工艺,修复后整体热处理试件强度优于铸造件基材强度。示温漆测试热输入量分析表明,激光沉积修复最高温度不超过250℃,热影响范围符合生产要求。沉积修复试件变形测试表明,变形量符合生产要求。
[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 伪 -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，

本文编号：1812770