Effect of cyclic annealing heat treatment on tungsten particles and matrix interface in heavy tungsten alloy

Document Type : Original Article

Authors

Ali Harimi ¹

gholamreza ebrahimi ²

A Rezaie bazaz ¹

Hasan Najafi ¹

kazem Zuichi Turk ²

¹ Department of material science and engineering, Faculty of Engineering, Ferdowsi university of Mashhad, Mashhad, Iran.

² Department of material science and engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Iran.

10.22067/jmme.2024.88925.1151

Abstract

Heavy tungsten alloys are made by liquid phase sintering for application in protective weights, radiation shields, and anti-missiles. The change in each of the production parameters of these alloys affects the mechanical behavior of these alloys. The aim of this research is to assess the effect of annealing heat treatment cyclic on the bonding strength of tungsten particles with the matrix. Tungsten alloy with a chemical composition of 93.5W-5.4Ni-1.95Fe (in wt.%) is first compressed in a plastic mold (cold isostatic) following by liquid phase sintering at 1480 °C and two cycles of annealing heat treatment. In order to study the mechanical properties, tensile and hardness tests are used. Also, the microstructures and fracture surfaces (after tensile test) of the samples are examined using optical and scanning electron microscopes. The obtained results show that due to the thermal stresses during cooling and heating through the cyclic annealing heat treatment, the matrix phase is penetrated into the interface of tungsten particles which causes a decrease in the contiguity (from 0.44 to 0.31). Also, the cyclic annealing heat treatment reduces the impurities in the interface between tungsten particles and the matrix, resulting in an increase in strength (from 842 MPa to 960 MPa). Comparison of fracture surfaces of samples with annealing cyclic shows the change of brittle fracture mechanism to soft fracture. Keywords: Heavy tungsten alloys; Sintering; Heat treatment; Particles/matrix interface; Contiguity.

Keywords

Heavy tungsten alloys

particles/matrix interface

cyclic heat treatment

sintering

contiguity

Subjects

• Mechanical Metallurgy

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