Effect Of Si In AL Alloy On Intermetallic Compounds Growth Behavior During Reaction Between Solid Ti And Liquid AL

One of the problems related with the joining processes for dissimilar metals such as Ti and Al is the formation of hard and brittle intermetallic compounds (IMCs) at the bonding interfaces. The objective of the paper is to study the reactions between Ti-6Al-4V titanium alloy and Al alloy (pure Al, Al-5Si alloy and Al-12Si alloy) and to investigate the effects of Si on the morphology and types of intermetallic compounds. On this basis, this paper study on the reaction mechanism between different intermetallic compounds and Zn-Al-Si alloy and analysis of the effect of the ultrasonic field on the interfacial reaction.Research results show that the Ti/pure Al solid-liquid interface generate a single TiAl₃ with ultrasound or not, and intermetallic layer become loose structure with holding time prolonged. Ti/Al-5Si solid-liquid interface reaction layer is composed of non-continuous of thin layer and massive reaction layer which are Ti₇Al₅Si₁2 and TiAl₃ compound, respectively. Due to the growth of Ti₇Al₅Si₁2 consumes a lot of Si, and the growth rate of TiAl₃ is faster than that of Ti₇Al₅Si₁2. With the holding prolonged, intermetallic compounds TiAl₃ become thick and Ti₇Al₅Si₁2 no longer continue to grow. The intermetallic layer of TiAl-5Si solid-liquid interface is composed of Ti₇Al₅Si₁2 and TiAl₃ after the adding of ultrasonic field. The effect of temperature on the Ti/Al-12Si interface reaction is great. The reactant Ti₇Al₅Si₁2 is arranged granular at 700℃, while the intermetallic compounds of solid-liquid interface are divided into three layers including continuous Ti₇Al₅Si₁2 phase near the Ti matrix, lamellar-like Ti₇Al₅Si₁2 and the massive TiAl₃ at 800℃. When ultrasonic wave was added into the Al-12Si alloy for 1min, it inhibited the generation of slice layer of Ti₇Al₅Si₁2 and promoted the growth of massive TiAl₃. under the effect of ultrasonic waveResearch results show that the reactions between TiAl₃ at the Ti/Al interface and Si to form uniform Ti₇Al₅Si₁2 at 420℃, and reaction between Ti₇Al₅Si₁2 and Zn-Al-0.8Si alloy did not be found. It is thought that the reaction mechanism of the process is Si element concentration on the surface of Ti alloy at first, and then solution in TiAl₃. The reaction between Si and TiAl₃ may form lamellar-like Ti₇Al₅Si₁2 after Si reached the saturated solubility. The process of Si moves to the surface of Ti alloy and Si element solution in TiAl₃ will be significantly accelerated under the effect of ultrasonic wave. TiAl₃ at the Ti/Al interface and Zn-Al-0.8Si alloy will react, but only generates massive Ti₇Al₅Si₁2 at 700℃.Nano-Hardness of TiAl₃ at the Ti/Al interface is 9.3-10.6 GPa. When Si content is 10 at.% in TiAl₃, nano-Hardness of TiAl₃ is 11.1 GPa, and nano-Hardness for granular Ti₇Al₅Si₁2 is 12.5 GPa. We can see that hardness of intermetallic compounds will increase with the growing of Si content.