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Physical Vapor Deposition
Published in Robert Doering, Yoshio Nishi, Handbook of Semiconductor Manufacturing Technology, 2017
The composition and purity of the target are obviously quite important to the deposition application. In the semiconductor industry, target composition is almost always described in the form of weight percent, which can differ significantly from atomic percent, which is used in traditional chemical analysis or chemical formulas. For example, Ti0.8 W0.2 is a compound composed of 80% Ti atoms and 20% W atoms. However, since the atomic weight of W is 3.8 × that of Ti, the weight percent of this compound is Ti(50)W(50), where the general nomenclature is that weight percents are written with parenthesis. To further complicate the description, if one component in an alloy or compound is allowed with a trace amount of another material, the dominant percentage is often dropped. An example of this is AlCu(0.5), which has 0.5% by weight of Cu and 99.5% by weight of Al.
Development of Al/Cu/SiC bimetallic nano-composite by friction stir spot welding
Published in Materials and Manufacturing Processes, 2023
Amin Abdollahzadeh, Behrouz Bagheri, Ali Shamsipur
The fabrication of hard and brittle intermetallic compounds phases during the joining process of dissimilar Al alloy and Cu alloys, namely AlCu, Al2Cu, and Al4Cu9, has been determined to be the most vital factor influencing the mechanical behavior of weld samples.[24] The generation of the IMCs layer with large thickness has been considered with detrimental consequences on the mechanical characteristics of the bond specimens.[24] That is, the mechanical effect of the rotating tool shoulder in axial and tangential directions at the lap interface decreases as the thickness of the layer in the interface is large. During the FSSW process, different factors have affected the thickness of the IMCs layer such as heat input, second phase size, stir action, the mutual reaction between materials, etc.[25] To study the interfacial reaction of aluminum and copper, a comparison of IMCs formation at the interface of the dissimilar welding by a line scanning of SEM has been used during the conventional FSSW and FSSW with SiC reinforcing particle (Fig. 6). Table 2 summarized the corresponding EDS results marked in Fig. 6. It is evident that the thickness of the IMCs layer during the joining process decreases as SiC particle is added because of high interaction and intermixing between aluminum and copper materials. Worth noticing is that an adequate IMCs thickness is associated with enhanced Al-Cu reaction, material flow, stir action, and higher temperature values. Consequently, this occurrence intensifies the diffusion of aluminum and copper atoms at the bond interfaces to fabricate strong aluminum-copper metallurgical joints. According to Zuo et al.[26] report regarding the influence of IMCs fabrication on mechanical characteristics of joint samples during the dissimilar aluminum-copper welding, three certain reaction layers namely AlCu, AlCu2, and Al2Cu/α-Al eutectic layer are generated at the aluminum-copper interface. Furthermore, unlike the thickness of the Al2Cu phase, the thickness of the Al2Cu/α-Al eutectic phase improves as ultrasonic vibration is used during the welding process.