Synthesizing and characterization of Cu-WC-Si composite prepared by using planetary ball milling
Cu-WC-Si composites were synthesized by using a planetary ball milling. Different composition of elemental Cu, WC and Ti powders were mixed and milled for 5 and 10 hours in an open air. The powder characterized before and after milling to expose the effect of milling variables on particle size, homogenization and contamination. Analyzing carried out by using X-ray and scanning electron microscope (SEM). The as milled particle size and homogenization generally influenced by milling time and tungsten Carbide (WC) content. With longer milling time and higher tungsten carbide content, particle size becomes smaller and smaller. The average particle sizes of the as milled powder are in ranged from 5µm to 30 µm and strongly depend on the copper content.
Phase formation during mechanical alloying in the Ti–Si system
Abstract Mechanical alloying of Ti–Si powder mixture or TiH 1.924 –Si powder mixture was performed by high-energy ball milling, in which the Ti to Si mole ratio was 1:2. The phase formations in both mixtures during milling were investigated by X-ray diffraction. Mechanical alloying a mixture of elemental powders led to the formation of TiSi 2 equilibrium compound, while when starting from Si + TiH 1.924 , a metastable phase was formed. The metastable phase completely transforms to TiSi 2 when the mechanically alloyed powder is annealed at temperatures above 800 °C. Two different pathways of phase transitions during mechanical alloying are attributed to the existence of hydrogen atoms, i.e., when starting from Si + TiH 1.924 compared to Si + Ti, the kinetics for the formation of the TiSi 2 intermetallic compound slows down. The kinetics related to the different phase transitions depending on the starting powder mixture are discussed.
Densification of porous alloy steel preforms at high temperature
Abstract Thermoplastic response and densification behavior of porous alloy steel preforms under P M forging are studied at various initial relative densities, strain rates and temperatures. Experimental data for porous alloy steel preforms are also compared with several yield functions from the literature. To provide a better theoretical prediction with experimental data, a new yield function is proposed based on the yield functions of Kim and Shima and Oyane. Finally, plastic response and densification behavior of porous alloy steel preforms during P M forging have been investigated by both experiments and finite element calculations.