New concept in analysis of supersolidus liquid phase sintering of alpha brass

Abstract

The present study focuses on modelling, optimisation and experimental investigation into properties and microstructure of supersolidus liquid phase sintered Cu-28Zn brass from prealloyed powder. The experiments are designed using response surface methodology based on central composite rotatable design to evaluate the effect of process variables on liquid phase sintering of prealloyed brass powder. Three variables namely temperature, time and atmosphere were changed during sintering. The mathematical equations were derived to predict densification and impact energy using second order regression analysis. The optimum condition was predicted when the sintering variables were set at about 876uC, 43 min and N 2 atmosphere. Selecting optimum sintering parameters is an important factor for achieving improved properties and relatively homogeneous microstructure. Gravitational force has a detrimental influence on homogeneity which is reflected by a graded structure that is formed especially at higher sintering temperature and extended time. Also structural coarsening occurs at higher sintering temperatures and longer times. It is concluded that both gravitational effect and structural coarsening should be considered in manufacturing of Cu-28Zn alloy parts. Furthermore, a combination of modelling and experimental investigation provide a new concept for better understanding and analysing the sintering process of brass and related structures.

Microscopic Illustration of Zinc evaporation and ZnO nanowire production during brass alloy sintering

“…Regarding previous research, the materials used were chosen as brass alloyed powder with Cu-28%Zn composition [13,14]. Prepared by water atomization method, the powder was stirred at 65 RPM with 75 wt% lithium stearate for 20 minutes.…”

“…The pressed samples were sintered in a three-zone tube furnace under Ar and N 2 atmosphere with 2 liter.min -1 flow rate. Although the optimum sintering condition is reported to be 1146 K and 45 minutes [14], higher temperatures were also investigated to explore ZnO formation.In order to recover zinc evaporates from the sintering step, the copper catalyst was subjected to outgoing gas at temperatures lower than that of sintering (573-973 K) and zinc is precipitated as ZnO on the catalyst. To prevent catalyst and samples' surfaces from being oxidized, a graphite boat was placed on the gas entrance of the furnace and 15-20 centimeters before brass samples.…”

Understanding Fiber-Matrix Integrity in Fiber-Reinforced Polymer Composites from Strain Rate Sensitivity Concept

“…This is measured by a parameter, m, called strain rate sensitivity index, given in eq. (4), at constant strain, ϵ, and temperature, T (Hart, 1967;Gobble and Wolff, 1993;Mohammadzadeh et al, 2014):…”

Supersolidus Sintering of Cr Prealloyed Steels by Inductive Heating

“…Therefore, the application of SSLPS so far has been limited to a few materials, mainly high speed steels [11,12], although studies have been done also with other materials such as e.g. brass [13]. The aim of the present investigation is to show that the SSPLS process can also be adopted to Cr prealloyed low alloy steel grades.…”