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摘要: 本文利用ANSYS有限元分析软件对AlSi10Mg的选区激光熔化成形过程进行热–力耦合分析并进行实验验证。针对目前铝合金选区激光熔化数值模拟不够精确，残余应力预测效率低的问题，利用JMatPro软件计算出AlSi10Mg在不同温度下的非线性热物性参数，并通过ANSYS的UDMAT子程序实现材料状态的转换，以此提高数值模拟的准确度。通过建立的热力耦合数值模型，研究不同的激光工艺参数对温度场和应力场的影响，最后进行相应的AlSi10Mg样件打印实验，并通过X射线应力分析仪测量样件残余应力。结果表明：每一层的扫描过程中，曲线均有明显的波峰，轨道间和层间可实现较好的重熔搭接；随着扫描速率的减小或激光功率的增加，最高温度和熔池尺寸随之增加；在成形过程中，沿着扫描方向的应力最大，垂直于扫描方向的应力最小。通过热力耦合模型所得到的残余应力与实验值误差小于8%，可以通过该热力耦合模型对选区激光熔化制件的残余应力进行预测。Abstract: In this paper, the thermal and mechanical coupling analysis of AlSi10Mg SLM forming process is carried out by using ANSYS finite element analysis software and experimental verification is carried out. Aiming at the problem that SLM numerical simulation of aluminum alloy is not accurate enough and the residual stress prediction efficiency is low, JMatPro software is used to calculate the nonlinear thermal physical property parameters of AlSi10Mg at different temperatures, and the material state transformation is realized by UDMAT subroutine of ANSYS, so as to improve the accuracy of numerical simulation. The influence of different laser process parameters on temperature field and stress field was studied through the thermodynamic coupling numerical model established. Finally, the corresponding AlSi10Mg sample printing experiment was carried out, and the residual stress of the sample was measured by X-ray stress analyzer. The results show that there are obvious peaks in the curves during the scanning of each layer, and good remelting lap between tracks and layers can be achieved. With the decrease of scanning rate or the increase of laser power, the maximum temperature and molten pool size increase. In the forming process, the stress along the scanning direction is the largest, and the stress perpendicular to the scanning direction is the smallest. The error between the residual stress and the experimental value obtained by the thermodynamic coupling model is less than 8%. The residual stress of SLM can be predicted by the thermodynamic coupling model.
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图 2 （a）选区激光熔化过程有限元模型；（b）激光扫描策略
Figure 2. (a) SLM process finite element model; (b) laser scanning strategy
图 4 不同激光功率下粉末床点1处的温度变化曲线
Figure 4. Temperature curve of point 1 in powder bed with different laser power
图 5 不同扫描速度下粉末床点1处的温度变化曲线
Figure 5. Temperature curve of point 1 in powder bed with different scanning speeds
图 6 不同工艺参数条件下粉末床第二层中心点点2的熔池温度分布：（a）300 W，1200 mm·s−1；（b）350 W，1200 mm·s−1；（c）400 W，1200 mm·s−1；（d）350 W，600 mm·s−1；（e）350 W，1200 mm·s−1；（f）350 W，1800 mm·s−1
Figure 6. Temperature distribution of molten pool at point 2 with different process parameters: (a) 300 W, 1200 mm·s−1; (b) 350 W, 1200 mm·s−1; (c) 400 W, 1200 mm·s−1; (d) 350 W, 600 mm·s−1; (e) 350 W, 1200 mm·s−1; (f) 350 W, 1800 mm·s−1
图 7 不同工艺参数条件下粉末床第二层中心点点2的熔池尺寸：（a）1200 mm·s−1；（b）350 W
Figure 7. Molten pool size of molten pool at point 2 with different process parameters: (a) 1200 mm·s−1; (b) 350 W
图 8 1.5 ms时的应力场云图：（a）Von Mises等效应力；（b）σx；（c）σy
Figure 8. Cloud map of stress field at 1.5 ms: (a) Von Mises equivalent stress; (b) σx; (c) σy
图 9 3 ms时的应力场云图：（a）Von Mises等效应力；（b）σx；（c）σy
Figure 9. Cloud map of stress field at 3 ms: (a) Von Mises equivalent stress; (b) σx; (c) σy
图 10 4.5 ms时的应力场云图：（a）Von Mises等效应力；（b）σx；（c）σy
Figure 10. Cloud map of stress field at 4.5 ms: (a) Von Mises equivalent stress; (b) σx; (c) σy
图 11 AlSi10Mg粉末（a）扫描电子显微形貌和（b）粒径分布
Figure 11. SEM morphology (a) and particle size distribution (b) of AlSi10Mg powder
图 13 不同工艺参数条件下测量点2的实验与模拟残余应力对比图：（a）1200 mm·s−1；（b）350 W
Figure 13. Comparison diagram of experimental and simulated residual stress at measuring point 2: (a) 1200 mm·s−1; (b) 350 W
表 1 选区激光熔化仿真工艺参数
Table 1. Process parameters of SLM simulation
吸收率 光斑半径 /
μm扫描轨道
间距 / μm激光功率 /
W扫描速度 /
(mm·s−1)0.1 40 100 300、350、
400600、1200、
1800
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表 2 AlSi10Mg粉床的热物性参数
Table 2. Thermal property parameters of AlSi10Mg powder bed
温度 / ℃ 密度 / (g ·cm−3) 比热容 / (J·g−1·℃−1) 导热率 / (W·m−1·℃−1) 热膨胀系数 / (×10−6 ℃−1) 杨氏模量 / GPa 泊松比 25 2.65753 0.87997 217.89012 — 75.72943 0.32542 100 2.64506 0.92513 211.40824 20.95286 73.15603 0.32818 200 2.62733 0.97655 201.02603 21.89192 69.30448 0.33252 300 2.60851 1.03507 189.49059 22.77649 64.88316 0.33772 400 2.58942 1.13316 176.7597 23.38009 59.7545 0.34362 500 2.57085 1.22454 162.71879 23.65836 53.60389 0.35054 600 2.4474 1.12218 80.06206 49.77232 0 0.50000 700 2.41423 1.15151 83.28231 49.76534 0 0.50000 800 2.38002 1.15297 86.50256 50.15062 0 0.50000
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表 3 AlSi10Mg粉末的化学成分（质量分数）
Table 3. Chemical composition of AlSi10Mg powder
% Si Mg Fe Mn N O Ti Al 9～11 0.25～0.45 ≤0.25 ≤0.10 ≤0.20 ≤0.20 ≤0.15 余量
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表 4 实验与数值模拟残余应力对比
Table 4. Comparison of residual stress between experimental and numerical simulation MPa
测量点 300 W，1200 mm·s−1 350 W，1200 mm·s−1 400 W，1200 mm·s−1 350 W，600 mm·s−1 350 W，1800 mm·s−1 模拟值 实验值 偏差 / % 模拟值 实验值 偏差 / % 模拟值 实验值 偏差 / % 模拟值 实验值 偏差 / % 模拟值 实验值 偏差 / % 1 228.74 251.61 10.0 255.82 272.51 6.5 289.57 312.15 7.8 276.28 296.53 7.0 224.17 250.94 11.9 2 246.22 255.84 3.9 261.16 273.64 4.8 292.59 303.47 3.8 280.21 295.56 5.5 236.60 247.47 4.6 3 234.55 260.21 10.9 262.52 280.88 7.0 277.49 305.39 10.1 282.38 304.73 7.9 229.54 251.81 9.7
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