La含量对GH5188合金凝固过程及铸态组织的影响

Effect of La content on solidification process and as-cast microstructure of GH5188 alloy

利用高温共聚焦激光扫描显微镜对不同La含量的GH5188合金在冷速为10℃/min条件下的凝固过程进行动态原位观察,并研究了La含量对GH5188合金凝固过程、铸态组织及析出相的影响。结果表明,当La含量为0.03%、0.07%、0.10%和0.40%时,随着La含量的增加,GH5188合金的初凝温度越高,固-液两相区区间越大;凝固过程为缓慢凝固-快速凝固-缓慢凝固过程,La含量越高,峰值凝固速度越小;La含量的增加使合金铸态组织由树枝晶转变为等轴晶,析出相尺寸增大,当La含量达到0.40%时,析出相由M_(6)C+M_(23)C_(6)转变为(Ni,Co)_(x)La+M_(23)C_(6),且形成的含La金属间化合物在凝固过程中容易开裂。

The solidification process of GH5188 alloy with different La contents(0.03%,0.07%,0.10%and 0.40%)at the cooling rate of 10℃/min was dynamic in-situ observed by using confocal laser scanning microscope(CLSM),and the effects of La content on the solidification process,as-cast microstructure and precipitated phases of the GH5188 alloy were studied.The results show that with the increase of La content,the initial solidification temperature and the solid-liquid two-phase region of the GH5188 alloy become higher and larger.The solidification process is slow-rapid-slow solidification,and the higher the La content,the smaller the peak solidification rate.With the increase of La content,the as-cast microstructure of the alloy changes from dendrite to equiaxed crystal,and the size of the precipitated phases increases.When the La content reaches 0.40%,the precipitated phases change from M_(6)C+M_(23)C_(6)to(Ni,Co)_(x)La+M_(23)C_(6),and the formed La-containing intermetallic compound is easy to crack during solidification.