Effects of warm die on high velocity compaction behaviour and mechanical properties of iron based PM alloy

Abstract

An iron based alloy powder (Fe-2.0Ni-1.0Cu-0.8Cr-0.5C) was used as raw material to prepare high density iron based alloy by warm die high velocity compaction (WHVC). The effects of warm die on high velocity compaction (HVC) densification behaviour, variations of stress waves and the resulting mechanical properties of iron based alloy were studied. The results show that, under the warm die condition at 1008C, the HVC behaviour of powder changes and the green density improves. Compared with the compacts prepared by HVC, the green density of compacts prepared by WHVC is 0.09-0.27 g cm 23 higher at the impact velocity range of 6.2-8.7 m s 21 . The green density of compacts prepared by WHVC reaches 7.62 g cm 23 at 7.9 m s 21 . The compacts were sintered at 11508C in H 2 atmosphere. The tensile strength, yield strength and hardness of the heat treated samples reach 1571 MPa, 1360 MPa and 51.2 HRC respectively.

Archives of Metallurgy and Materials

“…Where, V is the impact velocity of the hammer, m/s; m is the mass of impact hammer, kg; S is the whole powder particles moving distance during HVC process, m. The apparent density of the tested Fe-based alloy powder is about 3.05 g/cm 3 , the thickness of HVC green compact with the die wall lubrication under the impact velocity of 5 m/s is 4.85 mm, the whole powder particles moving distance S is calculated to be 6.94 mm, the impact force F is 90.06 kN from the equation (1). It is noticed that the calculated impact force is smaller than the measured one of 124 kN, the reason is that the whole powder particles moving distance S is used to calculate the maximum impact force in the equation (1), the maximum impact force is the first peak of stress wave [9], and the actual powder particles moving distance where the maximum impact force reaches is much smaller than the whole powder particles moving distance S in the HVC process, which lead to the greater value of measured impact force. In fact, the above calculated value of the impact force can be accepted as the average impact force during the HVC process.…”

“…Unlike the conventional compaction process, the transfer of impact energy during the HVC process is in the form of s tress wave, which will dissipate rapidly after transmitting several cycles in the compact. The stress wave rises from zero to several tens MPa in tens of microseconds and drops to zero again as it transmits through the Fe-based alloy particles to the bottom punch and then reflects back to upper punch through the compact, and the first peak of stress wave is considered as the main impact force [5,9]. As the impact energy acting on powder body increases with the increase of the impact velocity, so the compacting force also increases.…”

Comparative Study on Cold Compaction Behavior of TiH2 Powder and HDH‐Ti Powder

“…For this reason, the cold compaction ability of titanium powders and the relationships between characteristics of green titanium compacts and their densification behavior have become the important subject of numerous studies. Many research articles have reported on the compressibility and the theoretical analysis of the cold compaction behavior of titanium powders using existing or developed compaction equations [17][18][19][20][21]. However, most of the research on the cold compaction was focused on the ductile titanium powder which is similar to that for other ductile metal particles, with relatively high contribution of plastic deformation mechanism to the green density.…”

Numerical investigation into the densification of ferrous powder in high velocity compaction

“…High velocity compaction (HVC) is a forming method of powder metallurgy and can rapidly achieve densification through one or more high-energy impact [1,2]. HVC and conventional compaction (CC) employ almost the same steps as uniaxial compression, but the type of loading method mainly differs among them.…”