Invar alloy has an important application in the manufacture of composite forming mould. The laser melting deposition (LMD) technology was utilized to fabricate multi-layer multi-pass deposited samples in this study. The effect of heat accumulation on the microstructure of deposition layer (DL) was investigated through experimental and simulation method. A finite element (FE) model was established to study the temperature field distribution in LMD process. Microstructure of DL was investigated by optical microscope (OM), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). The thermal cycle curves were extracted for analysis. The accumulation of heat during the deposition process would make the higher location DL reach a higher peak temperature. It could be seen from the observation of the transverse section of the deposited samples that the microstructure consisted of elongated cellular crystals and regular cellular crystals. At the bottom of the DL were columnar crystals grown epitaxially along the maximum temperature gradient and gradually transitioned to equiaxed crystals at the top of the DL. EDS detection results showed that there was no element aggregation phenomenon in the DL. The grains in the remelted zone were coarsened due to suffering a state of overheating.

因瓦合金在复合成型模具的制造中有着重要的应用。在本研究中，利用激光熔化沉积 (LMD) 技术制造多层多道沉积样品。通过实验和模拟方法研究了热量积累对沉积层（DL）微观结构的影响。建立有限元（FE）模型来研究LMD过程中的温度场分布。通过光学显微镜 (OM)、扫描电子显微镜 (SEM) 和能谱仪 (EDS) 研究了 DL 的微观结构。提取热循环曲线进行分析。沉积过程中热量的积累会使较高的位置 DL 达到较高的峰值温度。从沉积样品的横截面观察可以看出，微观结构由细长的蜂窝状晶体和规则的蜂窝状晶体组成。在DL底部是沿着最大温度梯度外延生长的柱状晶体，并在DL顶部逐渐转变为等轴晶体。EDS检测结果表明DL中没有元素聚集现象。重熔区的晶粒因过热状态而变粗。EDS检测结果表明DL中没有元素聚集现象。重熔区的晶粒因过热状态而变粗。EDS检测结果表明DL中没有元素聚集现象。重熔区的晶粒因过热状态而变粗。