摘要
The effects of Mn addition (1 wt.%, 2 wt.% and 4 wt.%) and friction stir processing (FSP) on the microstructure and mechanical properties of Al-4Ni alloy were studied. The results showed that Mn promoted the formation of Al6Mn and Al60Mn11Ni4 intermetallics. These Mn-rich compounds increased the strength and hardness, but decreased the ductility and fracture toughness of the alloy. To improve the ductility and toughness, the as-cast alloys were then subjected to FSP (rotation speed of 1600 r/min and traverse speed of 12 mm/min). According to the results, FSP greatly improved the mechanical properties. The tensile strength, yield strength, fracture strain, microhardness, and fracture toughness of FSPed Al-4Ni-2Mn increased by 67%, 30%, 230%, 20%, and 1185%, respectively. The fine redistribution of Mn-rich compounds, formation of ultrafine grains, microstructural densification, and the elimination of casting defects such as micropores and oxide bifilms were found to be the most important factors responsible for improving the mechanical properties. The fractographic investigations also revealed that the fracture of as-cast Mn-rich alloys changed from the brittle mode containing micro-facets to a more ductile fracture mode containing fine and equiaxed dimples in FSPed alloys.
研究锰加入量(1 wt.%、2 wt.%、4 wt.%)和搅拌摩擦加工(FSP)对Al-4Ni合金显微组织和力学性能的影响。结果表明,锰促进了Al6Mn和Al60Mn11Ni4金属间化合物的形成。这些富锰化合物提高了合金的强度和硬度,但降低了其延性和断裂韧性。为了提高延性和韧性,对铸态合金进行搅拌摩擦加工(转速为1600 r/min、横移速度为12 mm/min)。结果表明,FSP大大改善了材料的力学性能,合金的抗拉强度、屈服强度、断裂应变、显微硬度和断裂韧性分别提高了67%、30%、230%、20%和1185%。研究发现,富锰化合物的细化再分布、超细晶粒的形成、显微结构致密化以及铸件微孔和氧化双膜等缺陷的消除是提高合金力学性能重要的因素。断口形貌研究表明,铸态富锰合金为脆性断裂模式,其断口含微解理面,而搅拌摩擦加工后的合金为韧性断裂,其断口含细小的等轴韧窝。
