Effect of ultrasonic on hot compaction of AA1100 and Ti-6Al-4V powders

Hot pressing of metal powders is used in production of parts for similar properties to wrought materials. Since residual porosity, inhomogeneous properties, dimensional and geometrical instability and therefore reduction in mechanical strength are the main problems in powder metallurgy components which are due to friction between powder particle interfaces and powder compact and die walls. Because of this, access to parts with high density and homogeneous structure is the great object in powder metallurgy. One of the remedies can be employment of ultrasonic vibrations which is thought to result in increased rates of densification and therefore higher efficiency of the process in increase of part density and strength. To evaluate this solution, this paper deals with the effects of high power longitudinal ultrasonic vibrations on the densification of AA1100 aluminum and Ti-6Al-4V titanium alloy powder under constant applied stress and different temperatures. The effects of powder type and process temperature on the densification behavior and ultrasonic efficiency are discussed. For experimental tests, setup of ultrasonic assisted hot pressing of powders were designed and fabricated. The results show that applying ultrasonic vibrations leads to obtaining higher relative density. In addition, it is found that the effect of ultrasonic vibrations is greater for Ti-6Al-4V powders. However, the temperature has different effects on the ultrasonic vibrations efficiency in two types of powders.