激光熔敷铜合金的组织特征及结晶过程分析

Microstructure Characterization and Crystallizing Procedure of Cu Based Alloy Fabricated By Laser Cladding Process

在ZL1 0 4铝合金表面激光熔敷铜基混合粉末体系 (质量分数ω(% ) :1 6 2Ni,8.0Co,6 .0Fe,6 .0Mo ,3.5Si,1 .5Cr ,余为Cu)制得了高硬度铜基涂层。激光熔敷快速凝固过程中 ,合金中富Mo、Fe、Co等元素的高熔点相通过偏晶或胞晶反应首先析出 ,使得铜基合金背散射电子像明显地分为白色区和灰色区。部分残余合金元素在随后的快速凝固过程中析出 ,形成大量弥散分布的细小颗粒。铜基合金涂层的组织具有快速凝固组织特征 ,由涂层界面处逆热流方向生长的粗大枝晶逐步过渡为涂层中上部无明显方向性的细小枝晶和胞晶。铜基合金涂层的显微硬度达 35 0～ 40 0HV ,较基材的表面硬度 (90～ 1 1 0HV)有显著提高。

WT5”BZ][ST5”BZ]In this paper,a high hardness Cu based alloy was fabricated from a mixed powder system (content at wt%:16.2Ni,8.0Co,6.0Fe,6.0Mo,3.5Si,1.5Cr,Cu as the base) on surface of Al alloy ZL104 via laser cladding process.During rapid solidification of the alloy,phases rich of Mo,Fe,Co and other alloyed elements firstly separated out from the liquid in monotectic or peritectic reaction,because they had higher crystallizing points.This caused the fact that SEM BSE photograph of the Cu alloy apparently took on gray areas and light areas.Meanwhile,part of the residual alloyed elements precipitated as fine particles dispersing in the alloy.Optical microscope observation demonstrated that microstructure of the Cu alloy clad gradually transferred from orientated coarse dentritic reversing the heat transferring direction at the interface to nearly uniform fine dentritic and cellular in the upper area.The Cu based alloy had high microhardness of 350～400HV,which greatly improved the surface hardness of the Al alloy(90～110HV). [HT5”H]