Effect of strain rate on the flow stress of three liquid phase sintered tungsten alloys

Kang

et al. 1999

Metall Mater Trans A

This study is concerned with the effects of microstructural parameters on the cracking phenomenon occurring during cold forging of two AISI 1010 steels that were fabricated by converter steel making and electric furnace steel making, respectively. This allowed a comparison between microstructures that contained a small or large amount of nitrogen. Detailed microstructural analyses of the cracked region showed that a number of adiabatic shear bands, along which cracks initiated and propagated, were formed in the top interior part of the cold-forged pulley. Dynamic torsional tests were conducted using a torsional Kolsky bar in order to investigate the dynamic deformation behavior during cold forging, and then the test data were compared via microstructures, mechanical properties, adiabatic shear banding, and fracture mode. From the dynamic shear stress-strain curves, the steel containing a considerable amount of nitrogen showed a smaller shear strain of 0.2 at the maximum shear stress point, after which the shear stress decreased rapidly prior to fracture, whereas the other steel containing a smaller amount of nitrogen showed relatively homogeneous shear deformation. This dynamic torsional behavior correlated well with the cracking and adiabatic shear banding behavior, together with the yield-point phenomenon occurring in the steel containing more nitrogen. Because the cracking occurring during cold forging was associated with the adiabatic shear banding and the yield-point phenomenon, the minimization of nitrogen and the fast cooling rate after hot rolling were suggested to prevent the cracking.

Section: Discussionmentioning

confidence: 99%

Analysis and prevention of cracking phenomenon occurring during cold forging of two AISI 1010 steel pulleys

Kang

et al. 1999

Metall Mater Trans A

“…To improve the penetration performance of tungsten heavy alloy penetratots, recent studies focus on the process and microstructural factors to promote the adiabatic shear banding to the level in DU alloys [4][5][6][7][8][9][10]. However, the formation of adiabatic shear bands in tungsten heavy alloys is not as active as in other metals.…”

Section: Introductionmentioning

confidence: 99%

Effect of size and shape of tungsten particles on penetration performance in tungsten heavy alloys

Song

1999

Metals and Materials

The effects of the size and shape of tungsten particles on dynamic torsional properties in tungsten heavy alloys were investigated. Dynamic torsional tests were conducted on seven tungsten alloy specimens, four of which were fabricated by repeated sintering, using a torsional Kolsky bar, and then the test results were compared via microstructure, mechanical properties, adiabatic shear banding, and deformation and fracture mode. The size of tungsten particles and their hardness were increased with the increasing of the sintering temperature and time, thereby deteriorating the fracture toughness. The dynamic torsional test results indicated that a cleavage fracture occurred predominantly with little shear deformation in the specimens whose tungsten particles were coarse and irregularly shaped whereas shear deformation was concentrated into the center of the gage section in the conventionally fabricated specimens. The deformation and fracture behavior of the specimens having coarse tungsten particles correlated well with the observation of the in situ fracture test results, i.e., cleavage crack initiation and propagation. These findings suggested that there would be an appropriate tungsten particle size condition in the penetration performance since the cleavage fracture mode would be beneficial for the self-sharpening of tungsten heavy alloys.

“…[4][5][6][7][8][9][10][11][12][13] made on the effect of microstructural modification in the size The formation of an adiabatic shear band is postulated as and shape of tungsten particles on the dynamic properties in follows. [14] When plastic deformation occurs in a material, order to provide the optimum microstructural condition.…”

Section: Introductionmentioning

confidence: 99%

Effect of size and shape of tungsten particles on dynamic torsional properties in tungsten heavy alloys

Song

1999

Metall Mater Trans A

The effect of the size and shape of tungsten particles on dynamic torsional properties in tungsten heavy alloys was investigated. Dynamic torsional tests were conducted on seven tungsten alloy specimens, four of which were fabricated by repeated sintering, using a torsional Kolsky bar, and then the test results were compared via microstructure, mechanical properties, adiabatic shear banding, and deformation and fracture mode. The size of tungsten particles and their hardness were increased as sintering temperature and time were increased, thereby deteriorating fracture toughness. The dynamic torsional test results indicated that in the specimens whose tungsten particles were coarse and irregularly shaped, cleavage fracture occurred predominantly with little shear deformation, whereas shear deformation was concentrated into the center of the gage section in the conventionally fabricated specimens. The deformation and fracture behavior of the specimens having coarse tungsten particles correlated well with the observation of the in situ fracture test results, i.e., cleavage crack initiation and propagation. These findings suggested that there would be an appropriate tungsten particle size because the cleavage fracture mode would be beneficial for the "self-sharpening" of the tungsten heavy alloys.