稀土元素Ce及热处理工艺对27wt%Co--Fe合金冲击韧性的影响

Effect of Rare Earth Element Ce and Heat Treatment on Impact Toughness of 27wt%Co-Fe Alloy

要本文通过夏比冲击试验机、金相显微镜、扫描电镜(SEM)和X射线残余应力检测仪对27wt%Co-Fe在不同热处理工艺下的冲击韧性、断口、显微组织和残余应力进行了系统研究。在27wt%Co-Fe合金中添加0.03wt%的Ce元素后,锻造合金的冲击功由1.2J提高到50J以上,冲击断口由脆性断裂转变为韧性断裂,微裂纹和微空洞减少。Ce的添加使27wt%Co-Fe合金晶粒细化、均匀化,Ce含量为0.03wt%时,晶粒尺寸由20.2um细化至12.9um,随Ce含量的进一步增加,晶粒细化趋势减小。淬火温度为700℃~750℃时,C27(27wt%Co-Fe)、C27R1(27wt%Co-Fe-0.03wt%Ce)和C27R2(27wt%Co-Fe-0.06wt%Ce)的冲击功分别提高至50J以上。将C27R2在800℃下保温2h水淬后,在300℃下分别回火2h、4h和8h,随回火时间由2h延长至8h,C27R2的残余应力由547MPa降低至281MPa,冲击功由2.5J增加至78J。

A systematic study of impact toughness,fracture section,microstructure and residual stress of 27wt%Co-Fe was carried out using charpy impact tester,metalloscope,scanning electron microscope(SEM)and X-ray residual stress detector.After adding 0.03wt%Ce,the impact energy of 27wt%Co-Fe increases from 1.2J to more than 50J and the impact fracture changes from brittle fracture to ductile fracture with dimples.Microcracks and microvoids are reduced.Ce refines and homogenizes the grain of 27wt%Co-Fe.It's obvious when Ce content is 0.03wt%,the grain size decreases from 20.2μm to 12.9μm,but the tendency of refinement decreases with the further increase of concent.After quenching and tempering,C27,C27R1 and C27R2 are basically increased to more than 50J when quenching temperature is 700℃-750℃.C27R2 was held at 800℃for 2h,quenched with water and tempered at 300℃for 2h,4h and 8h respectively,to test impact energy and residual stress.The residual stress of C27R2 decreases from 547MPa to 281MPa when the tempering time is 8h,and the impact energy increases from 2.5J to 78J.