(中南大学 粉末冶金国家重点实验室,长沙 410083)
摘 要: 以喷雾干燥−H2还原法制备的纳米级90W-7Ni-3Fe复合粉末为原料,研究稀土La-Y含量对试样烧结特性的影响,采用高倍SEM和金相仪器分别对断口进行形貌观察和W晶粒测试;对烧结样的相对密度、抗拉强度、延伸率等性能进行测定与分析。结果表明:不添加稀土La-Y时,试样在液相烧结时容易出现孔洞和气泡,导致力学性能偏低;添加0.4%稀土La-Y(质量分数)时,合金的相对密度、抗拉强度和延伸率分别为99.4%、983.5MPa和15.2%; 添加0.4% La-Y后,在相界或晶界上形成了W13.61Ni2.61Fe1.07Y20.52La25.27On的中间相,阻止了W原子在粘结相中的扩散,阻碍了W晶粒长大,W晶粒由原来的20~25 μm减少到12~15 μm。
关键字: 90W-Ni-Fe合金;纳米粉末;稀土La-Y;微观结构;力学性能
mechanical properties of nano-powder 90W-Ni-Fe alloy
(State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China)
Abstract:Using nano-sized 90W-7Ni-3Fe composite powder synthesized by spray drying-H2 reduction method as raw material, the effects of La-Y content on sintering characteristic for specimens were studied. Fracture morphology and W crystal sizes were measured by SEM and optical metallography, respectively. And the relative density, tensile strength and elongation of sintering specimens were also measured and analyzed. The results show that the emergence of cavities and bubbles in sintering specimens leads to lower mechanical properties after liquid phase sintering when no La-Y is added. When 0.4% La-Y is added, the relative density, tensile strength and elongation of the alloy are 99.4%, 983.5MPa and 15.2%, respectively. When the La-Y content is 0.4%, the middle phase W13.61Ni2.61Fe1.07Y20.52La25.27On (molar ratio) forms at interface, which restrains the diffusion of W atom in matrix phase and prevents W crystal from growing up, and the average W crystal size decreases from 20−25 μm to 12−15 μm.
Key words: 90W-Ni-Fe alloy; nanosized powder; rare earth La-Y; microstructure; mechanical properties