The role of pore evolution during supersolidus liquid phase sintering of prealloyed brass powder

Abstract

The aim of this research is to study the pore structure as well as to assess the liquid phase sintering behaviour of Cu-28Zn powder specimens at different green density levels and temperatures. For this purpose, samples were compacted to obtain six different green densities and then sintered at 870°C, 890°C and in part at 930°C for 30 min. The results revealed that the spherical pores which are formed inside the grains can be swept by grain boundaries due to grain growth and join to primary pores so that secondary intragranular pores are eliminated and intergranular pores enlarged at higher temperatures. Also, the pores move upwards to the top of sample due to buoyancy forces. The role of pore structure in distortion is more tangible at higher temperatures (930°C) so that O-shape and X-shape distortions were observed at high and low green density samples, respectively.

High Densification Level and Hardness Values of Additively Manufactured 316L Stainless Steel Fabricated by Fused Filament Fabrication

“…Secondly, the dimensional integrity was not maintained after sintering for all samples, in which all of them suffered from bulging at the centre to lower-half portion of the cubes by about 10%. The sintered part at Tn=200°C and 210°C exhibit 'stairshaped' bulging, while those at Tn=215°C and 220°C display 'A-shaped' bulging, which are known distortion modes that are also observed in other sintered metals and alloys [20,21]. Such distortions are typically attributed to the sintering environment, e.g.…”

Supersolidus liquid phase sintering of water-atomized low-alloy steel in binder jetting additive manufacturing

“…Meanwhile, as a result of the high heating rate, reaction vapor products such as CO, H 2 O, and CO 2 that are nearly insoluble in iron-FCC can remain entrapped within pores and lead to pore enlargement through Ostwald ripening as a result of grain growth [ 41 ] or particle rearrangement [ 24 ]. Based on the finding of Ghasemi and Azadbeh et al [ 42 ], large pores migrated to the top of samples due to buoyancy force, while the liquid settled to the bottom area due to gravity. The resultant heterogeneous distribution of pore and liquid phase can cause geometric distortion of the part upon densification.…”

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“…Sintering is a crucial stage in the development of raw materials based on powder metallurgy, used in numerous applications . One of key elements in determining the powder metallurgy’s mechanical properties is the sintered density. − The bonding between particles is mainly connected by diffusion. Usually, porosity strongly affects the mechanical properties of the material presents in PM products. , The literature has shown that the tensile strength decreases by increasing the porosity .…”

“… 5 One of key elements in determining the powder metallurgy’s mechanical properties is the sintered density. 6 − 8 The bonding between particles is mainly connected by diffusion. Usually, porosity strongly affects the mechanical properties of the material presents in PM products.…”