Cao Xia, Tian Songya, Xu Fan, Zhang Genyuan
Changzhou Institute of Technology, 213032, Changzhou, Jiangsu, PR China.
Hohai University, 213002, Changzhou, Jiangsu, PR China.
Heliyon. 2024 Aug 17;10(16):e36492. doi: 10.1016/j.heliyon.2024.e36492. eCollection 2024 Aug 30.
To study the thermal cracking susceptibility of laser-welded CoCrFeMnNi high-entropy alloys, stainless steel and aluminum alloy plates were each used as backing for welding. The microstructure of the weld and morphology of the fracture were examined. In addition, the chemical compositions of the fractures, the interfacial tension between the CoCrFeMnNi high-entropy alloy and liquid aluminum alloy, and the linear expansion coefficient of the CoCrFeMnNi high-entropy alloy were determined. The results show that when stainless steel is used as the base plate, no cracking is apparent in the weld, and the microstructure is made up of dendrites and equiaxed crystals. Conversely, when an aluminum alloy plate is adopted, solidification cracks are seen at the center of the weld, and the microstructure consists of bright polygonal dendrites scattered in a dark gray matrix. In the later stage of solidification, the contact angle between the Al-dominated low-melt liquid metal and the CoCrFeMnNi high-entropy alloy is about 14.6°, which is distributed in the form of a liquid film between the dendrite of the CoCrFeMnNi high-entropy alloy weld, and the linear expansion coefficient of the high-entropy alloy is 23 × 10-25 × 10 K in the temperature range of 900-1100 K, which is higher than the thermal expansion coefficient of austenitic stainless steel in this range, and the solidification temperature range is 1000-1400K. Therefore, thermal cracks tend to occur during the solidification process.
为研究激光焊接CoCrFeMnNi高熵合金的热裂纹敏感性，分别采用不锈钢板和铝合金板作为焊接垫板。对焊缝的微观组织和断口形貌进行了观察。此外，还测定了断口的化学成分、CoCrFeMnNi高熵合金与液态铝合金之间的界面张力以及CoCrFeMnNi高熵合金的线性膨胀系数。结果表明，以不锈钢为垫板时，焊缝未见明显裂纹，微观组织由树枝晶和等轴晶组成；相反，采用铝合金板时，焊缝中心出现凝固裂纹，微观组织由亮多边形树枝晶分散在深灰色基体中组成。在凝固后期，以Al为主的低熔点液态金属与CoCrFeMnNi高熵合金之间的接触角约为14.6°，以液膜形式分布在CoCrFeMnNi高熵合金焊缝树枝晶之间，且高熵合金在900 - 1100K温度范围内的线性膨胀系数为23×10 - 25×10 K，高于该温度范围内奥氏体不锈钢的热膨胀系数，凝固温度范围为1000 - 1400K。因此，在凝固过程中容易产生热裂纹。
