ABSTRACT

Post-sintering cyclic heat treatment of W–Ni–Co alloys results in the formation of an intermetallic phase which subsequently dissociates into fine tungsten precipitates in the matrix. The volume fraction of such precipitates in the matrix phase increases with the number of heat treatment cycles. In an effort to understand the influence of increasing fraction of precipitates on the mechanical properties of 92W–5Ni–3Co alloy, this study has been carried out with an increasing number (2, 4, 6 and 8) of heat treatment cycles. In addition, to understand and avoid the re-formation of the brittle intermetallic phase upon cooling, the cooling rate has also been varied by incorporating oil and water quenching in the processing. This study assumes significant importance considering the fact that W–Ni–Co alloys with fine precipitates in the matrix phase reportedly exhibit an excellent combination of tensile and impact properties in undeformed condition. With scope for further improvement in the properties by means of thermomechanical treatments, any refinement in the heat treatment parameters of these alloys will enhance the potential of this alloy system that is already being widely used in critical applications such as kinetic energy penetrators.

摘要

W-Ni-Co 合金的烧结后循环热处理导致形成金属间相，随后在基体中分解成细小的钨沉淀物。基体相中此类析出物的体积分数随着热处理循环次数的增加而增加。为了了解析出物比例增加对 92W-5Ni-3Co 合金机械性能的影响，本研究通过增加（2、4、6 和 8 个）热处理循环次数进行。此外，为了了解和避免冷却时脆性金属间相的重新形成，还通过在加工中加入油淬和水淬来改变冷却速度。考虑到在基体相中有细小析出物的 W-Ni-Co 合金据报道在未变形条件下表现出优异的拉伸和冲击性能组合，该研究具有重要意义。随着通过热机械处理进一步改善性能的余地，这些合金热处理参数的任何改进都将增强这种合金系统的潜力，该系统已经广泛用于关键应用，例如动能穿透器。