WC-40%Al_2O_3复合粉末二步热压烧结

Two-step hot-pressing sintering of composite WC-40%Al_2O_3 compacts

以高能球磨机械合金化制得的WC-40%Al2O3复合粉末为原料,采用二步热压烧结法制备复合块体。首先将粉末坯体在压力条件下加热到较高的温度T1,获得相对致密的坯体结构,此时存在临界的可收缩气孔,然后将其保温在一个相对较低的温度T2,通过低温保温实现致密化。由于烧结过程温度相对较低,晶粒长大被有效抑制。采用XRD、SEM、扫描探针(SPM)对复合材料的物相、微观结构进行表征,并进行正交实验分析第二步烧结温度以及保温时间对复合块体微观组织和力学性能影响。结果表明:当T1=1600℃、T2=1450℃保温6h时,WC-40%Al2O3复合材料成形致密度达到99.03%,维氏硬度和断裂韧性分别为18.36 GPa和10.4MPa·m1/2,抗弯强度为1162.1MPa.

The WC-40%Al2O3 composite powder synthesized by high-energy ball milling was used as raw material followed by two-step hot-pressing sintering （TSS）.The first step sintering at a constant heating rate with a higher temperature T1 to obtain an initial high density and guarantees the disappearance of supercritical pores, while the other pores become unstable. The second step was held at lower temperature T2 by isothermal for a period of hours to increase bulk density with a limited grain size. The phase and microstructure of the composite were characterized by XRD, SEM and SPM technology. The present work dealt with the influence of deliberate temperature and holding time at second step, which had been well documented by orthogonal analysis, on microstructure and mechanical properties of WC-40%Al2O3 nanocomposite. The results show that when the sample sintered at 1600 ℃（T1） and holding 6 h at 1450 ℃（T2） obtains a relative density of 99.03%, Vickers hardness of 18.36 GPa, a fracture toughness of 10.4 MPa·m1/2 and a bending strength of 1162.1 MPa.