Papers by Keyword: Multi Directional Forging

Abstract: In this study, Al-7Si-4Zn-3Cu alloy was processed by multi-directional forging (MDF) at 3, 6 and pass corresponding one, two and three cycle, respectively. The structural and mechanical properties of the alloys were investigated at as-cast, homogenised and MDF states. The MDF resulted in a severely deformed and refined microstructure with eliminated casting defects like micro-porosity and formation of nearly homogeneous distributed finer silicon particles. The tensile (UTS) and yield (YS) of the alloy increased up to two cycle, above which they showed a decrease, while the percent elongation increased continuously as the cycle number increased. The comprehensive strength and micro and macro hardness of the alloy decreased with increasing MDF cycles. The results were evaluated according to microstructural changes depending on MDF cycles.

Abstract: The static recrystallization (SRX) behavior of nano grained (NGed) Cu-30mass%Zn alloy processed by Multi-directional forging (MDF) was investigated. The NGed Cu-Zn alloy showed characteristic annealing behavior. The SRX nucleation and its grain growth occurred more readily in the samples deformed to higher cumulative strain at lower temperature. The frequency of new grain formation in the samples MDFed at 77 K was much higher than that at 300 K. The new grains were composed of fine annealing twins with thickness from 10 to 200 nm. The average grain size fully recrystallized was less than 300 nm.

Abstract: A Ni-30 mass% Fe alloy with dispersed coarse oxide particles, ranging from 1 to 3 μm in diameter, was multi-directionally forged (MDF) at temperatures between 773 K and 873 K at a true strain rate of 1 x 10-3 s-1 in vacuum. For comparison, a particle-free Ni-Fe alloy was also prepared and MDFed. At 873 K, an obvious flow softening occurred during MDF especially in the alloy with dispersed particles, while work hardening followed by steady-state flow appeared at 773 K in both alloys. With increasing cumulative strain, the average grain size became gradually finer. However, the evolved microstructure was quite different depending on temperature and dispersion of particles. At 873 K, in the alloy with particles, equi-axed fine grains of about 1.3 μm in average was uniformly evolved at a cumulative strain of Σε = 2.4, while at 773 K the microstructure was still inhomogeneous. The above experimental results suggest important role of coarse particles to stimulate grain refinement.