Abstract

Residual stresses were studied in tungsten heavy alloy bars produced by powder metallurgy and deformed by rotary swaging at room temperature (RT) and at 900 °C. Neutron diffraction technique was used to scan the residual stresses across the bars. Both tungsten particles and NiCo2W solid solution matrix were analysed. Maximum axial stresses of ~ 300 MPa and ~ 200 MPa were observed for the tungsten phase at the centre in the RT and in the high-temperature deformed samples, respectively. Compressive residual axial stresses were found close to the sample surface, showing that rotary swaging is a suitable deformation method for tungsten heavy alloys to provide an appropriate surface modification for its use in metallic parts undergoing, e.g., fatigue. Residual stresses developed in the NiCo2W-phase are larger than those found in the tungsten particles although with a secondary role in the overall equilibrium conditions due to its lower strength and smaller volume fraction. Total stresses for each phase were separated into macro- and microstresses. Macrostresses can be mainly influenced by the incompatibility of the elliptical cross-section of the sintered sample with the head of the rotary machine while microstresses are mainly developed by the elastic mismatch between the constituent phases.

Graphic Abstract

中文翻译：

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W-Ni-Co重合金在室温和高温下旋转锻造后残余应力的中子衍射研究

摘要

研究了粉末冶金生产的钨重合金棒中的残余应力，并在室温（RT）和900°C下通过旋转型锻将其变形。使用中子衍射技术扫描横杆上的残余应力。分析了钨颗粒和NiCo2W固溶体基体。在RT中心和高温变形样品中，钨相的最大轴向应力分别为〜300 MPa和〜200 MPa。在靠近样品表面的地方发现了压缩残余轴向应力，这表明旋转型锻是钨重合金的一种合适的变形方法，可为遭受疲劳的金属零件提供合适的表面改性。NiCo2W相中产生的残余应力大于钨颗粒中的残余应力，尽管由于其较低的强度和较小的体积分数而在整体平衡条件中起着次要作用。每个阶段的总应力分为宏观应力和微观应力。宏观应力主要受烧结样品的椭圆形横截面与旋转机械头部不兼容的影响，而微观应力主要受组成相之间的弹性失配的影响。

图形摘要