Effect of Strain Rate on the Plastic Deformation and Fracture of 90W-7Ni-3Fe Alloy Prepared by Liquid-Phase Sintering
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Effect of Strain Rate on the Plastic Deformation and Fracture of 90W-7Ni-3Fe Alloy Prepared by Liquid-Phase Sintering Yang Yu, Ming Zu, Chaoyuan Ren, and Wencong Zhang (Submitted December 9, 2017; in revised form July 11, 2018; published online November 26, 2018) In this study, the effect of the strain rates on the plastic deformation behavior and fracture mechanism of 90W-7Ni-3Fe heavy alloy prepared by liquid-phase sintering was investigated. Stress–strain tests were carried out in tensile and compression under quasi-static condition with the strain rate ranging from 1023 to 1 s21. Dynamic test was examined using a compression split Hopkinson bar at strain rates ranging from 1000 to 1700 s21 in order to evaluate the effects of high strain rate on dynamic plastic deformation behavior. Quasi-static tests results show that the strength and hardness of this alloy increase with increasing strain rate. Results indicate that the as-sintered 90W-7Ni-3Fe heavy alloy has obvious strain-hardening characteristic under tensile or compression deformation under quasi-static condition. At this time, strain hardening is the main factor. Nevertheless, strain-hardening and strain-softening behaviors of the specimens occur simultaneously under dynamic compression condition. The effect of compressive stress on the work hardening is more obvious. A strong relevance of work-hardening effect on strain rate is also found. And the fracture mode of quasi-static and dynamic compression samples is also different. Keywords
dynamic compression, fracture, microstructural evolution, strain rate, tungsten heavy alloy, work-hardening rate
1. Introduction Tungsten heavy alloy (WHAs) and depleted uranium (DU) are mainly used as a penetrator material against an armor plate (Ref 1). Under the same launch conditions, the DU alloy has a higher armor piercing power than tungsten heavy alloy. However, the use of DU alloy brings serious environmental pollution and health problems due to radioactivity. Compared with DU alloy, WHAs have the advantages of no toxicity and no radiation pollution (Ref 2, 3). Nevertheless, WHAs are easy to form mushroom-like head when they are armor piercing, thus reducing the power of armor piercing. The conventional fabrication process of WHAs is powder metallurgy technology including cold pressing, liquid-phase sintering and heat treatment (Ref 4). Generally, tungsten heavy alloy has best penetration performance because it has high density, strength, hardness, toughness, ductility and so on. Consequently, WHAs with a tungsten content of more than 90 (wt.%) are used to make a projectile piercing core material by powder metallurgy and hot working technologies in order to acquire optimal properties. Previous works showed that the liquid-phase-sintered 90W-7Ni-3Fe alloy had higher strength and ductility (Ref 5, 6). Yang Yu, Ming Zu, Chaoyuan Ren, and Wencong Zhang, School of Materials Science and Engineering, Harbin Institute of TechnologyWeihai, No. 2, West Wenhua Road, Weihai 264209 Shandong,
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