| Transient liquid phase sintering has a possible role in forming high performance powder metallurgy alloys. The process uses a liquid phase to advantage while minimizing the microstructural damage associated with a persistent liquid. This study has demonstrated the metallurgical concepts necessary for implementation of transient liquid phase sintering using commercial iron and Fe(,2)Ti powders. The experimental plan included examination of several processing variables to investigate the mechanism of transient liquid phase sintering based on the Fe-Ti system. The effects of variables were investigated on the basis of examination of microstructures, densification, mechanical properties, and resistance measurements. All these experiments were well in agreement with each other. Densification critically depends on the amount of liquid formed at the eutectic temperature and its duration as determined by the several processing factors. The amount of liquid and its duration are controlled by the sintering temperature, particle size, heating rate, and amount of additive. Therefore, best overall processing requires manipulation of the variables to control the amount of liquid formed during heating. During the study, mathematical models for interrelation between heating rate and amount of titanium are introduced to show how the processing variables effect the amount of liquid formed and the resulting microstructure. Best overall sintering occurs with 3% Ti giving a strength of 375 MPa and an elongation of 25.5%. These mechanical properties are achieved from -325 mesh iron and Fe(,2)Ti powders when the sintering cycle was a hold at 1400(DEGREES)C for one hour at the 200(DEGREES)C/min heating rate. Besides investigation of the mechanism of transient liquid phase sintering, several additional experiments were undertaken for possible technological applications. |
