材料期刊网

采用原位热压烧结工艺,以Cr_3C_2、Cr和Al粉为原料制备Cr_2AlC块体材料.采用X射线和扫描电镜(SEM)对制备的样品进行表征.利用差热法对反应过程进行了研究,以失重法研究Cr_2AlC在酸和碱溶液中的腐蚀性能.结果表明,以n(Cr_3C_2):n(Cr):n(Al)=0.5:0.5:1.2配比,1350℃,30MPa压力热压2h得到高纯Cr_2AlC块体,其合成过程首先为Al的溶化,在700℃时Cr与Al生成Cr_5Al_8,最后Cr_5Al_8与Cr_3C_2反应生成Cr_2AlC.样品断面的扫描照片显示,烧结试样呈板状和片状结晶形貌特征,平均粒径为6.4μm.除在浓H_2SO_4和浓HCl中失重较大外,Cr_2AlC在其它溶液中均表现较低的失重.样品浸泡在浓和稀的NaOH溶液150d几乎没有质量损失,腐蚀率仅为0.4和0.7μm/a.

Cr_2AlC bulk material was prepared in-situ by hot pressing sintering using Cr_3C_2, Cr and Al as the starting materials. The samples were characterized using X-ray diffraction (XRD) and scanning electron mi-croscope (SEM). The reaction process was investigated by means of differential scanning calorimetry (DSC). The corrosion properties of Cr_2AlC in the acid and alkali solutions were obtained by weight loss method. The XRD result shows that high purity Cr_2AlC bulk material can be synthesized by hot pressing with n(Cr_3C_2): n (Cr): n (Al) = 0.5: 0.5: 1.2 at 1350℃ for 2h under 30 Mpa. The XRD patterns in different temperatures suggest that the reaction process of starting materials is that Al melts at first, then Cr_5Al_8gener-ates at 700℃, Cr_2AlC is produced with the temperature elevation by the reaction of Cr_5Al_8 and Cr_3C_2 at last.SEM images of fracture faces of the sintered sample show the laminated and well plate-shaped grains with a mean particale size of 6.4μm. Cr_2AlC exhibits low weight loss except immersion in the concentrated H_2SO_4and HCl solutions. The weight loss is negligible after immersing samples in the concentrated and dilute NaOH solutions for 150d and the corrosion rates are only 0.4 and 0.7μm/a, respectively.