Friction Stir Welding(FSW) experiments are conducted using 6061-T6 aluminum as specimens. The temperatures at different distances from the center of the joint are measured. Curve fitting analyses are used to predict the temperature distribution and calculate the central temperature of the joint, proceeding by measuring temperature. A second order curve is found to better fit the experiment values by the least square method.

In this research, one solid state processing technique, friction stir processing, is applied to modify the AZ61 magnesium alloy billet and to incorporate 5-10 vol% nano-sized ceramic particles SiO2 into the AZ61 magnesium alloy matrix to form bulk composites, using the characteristic rotating downward and circular material flow around the stir pin. The microstructure and mechanical properties of the modified alloy and composite samples are examined and compared. The FSP modified AZ61 alloy could be refined to 3-8um via the dynamic recrystallization during processing. However, the one-pass FSP modified alloy appeared the inhomogeneous grain structures to influence the tensile ductility along the welding direction at elevated temperatures due to the onion splitting. In contrast, the multi-pass FSP could improve the inhomogeneous grain structures to reduce the influence of the onion-splitting to the deformation at elevated temperatures. The FSP modified alloys show the lower yielding stress due to the unique texture of (0002) basal planes, with roughly surround the pin column surface of the pin tool in the stirred zone. In addition, it is suggested that the second processing of the subsequent compression along the normal direction might be necessary to alter the texture and to improve the lower yielding stress after modifying the grain size by FSP. Friction stir processing could successfully fabricate bulk AZ61 Mg based composites with 5 to 10 vol% of nano-sized SiO2 particles. The nano-sized SiO2 particles added into magnesium matrix could be uniformly dispersed after four FSP passes. The average grain sizes of the composites varied within 0.5-2um, and the composites nearly double the hardness as compared with the as-received AZ61 cast billet. This composite exhibited high strain rate superplasticity, with a maximum ductility of 470% at 1x10-2 s-1 and 300oC or 454% at 3x10-1 s-1 and 400oC while maintaining fine grains less than 2um in size.

Friction stir process (FSP) was employed to investigate the grain evolution of AA1050 aluminum alloy in this study. The rotation speeds for the tool were set from 500 to 2000 rpm with a constant traverse speed of 0.5mm/s. The temperature under pin was measured by K-type thermocouple imbedded under the pin. Grain sizes were determined by scanning electron microscopy. The maximum temperature at the bottom of pin increased with the increasing of rotation speed but not exceeding 0.8Tm. Grain size at center and bottom of stirred zone was in linear increase at low rotation speed, but increased a little at high rotation speed (>1000rpm). The grain size grew rapidly into a stable size in a 2mm distance measured from the passing of pin. When rotation speed is above 1000rpm, average grain growth rate is 1£gm/s. When rotation speed is lower than 700rpm, average grain growth rate is slower than 0.2£gm/s. BEI/ECCI observations revealed that grains in SZ became equaxied.

This study aimed at dissimilar metal butt friction stir welding in various types of processing conditions on the welding product hardness, tensile strength, etc. At first, using the AA-5052 as the similar material in FSW(friction stir welding) process. Compare the affected in different working parameter such like tool rotation speed, tool feed rate, etc. During FSW process, using the K-type thermal couple to monitoring the temperature history at different position in the specimen. According the result and finding the best working parameter. As the result shown, the high speed rotating rate or the low feeding rate will cause more heat energy in the specimen. In completed FSW condition, the range of rotating rate is 600-900rpm, the feeding rate is 40-80mm/min, the preheating temperature is suitable in 350¢J. For the aluminum alloy and copper alloy of the dissimilar metal friction stir welding, specimen¡¦s surface has holes and large chip by lacking heat during using the tool diameter of 12mm to weld, use the tool diameter of 15mm to weld can enhance the heat during the welding process and improve the production of surface.

Friction stir processing (FSP) has recently become an effective microstructural modifications technique. Reported results showed that for different alloys, FSP produces very fine equiaxed and homogeneous grain structure. FSP is considered to be a new processing technique and more experimental and analytical investigations are needed to advance the industrial utilization of FSP. Most of the work that has been done in the friction stir processing field is experimental and limited modeling activities have been conducted. Attempts to develop a predictive model to correlate the resulting microstructure with process parameters are scarce. In this work, commercial 5052 Aluminum alloy sheets are friction stir processed at different rotational and translational speeds. The effects of process parameters on the resulting microstructure and mechanical properties are investigated. The results show that FSP produces very fine and homogenous grain structure, and it is observed that smaller grain size structure is obtained at lower rotational speeds. It is also observed that the hardness of the processed sheet depends strongly on the rotational and translational speeds and varies widely within the processed region. The results suggest that the temperature achieved during processing plays an important role in determining the microstructure and properties of the processed sheet. In addition, a new modeling approach based on experiments and theory is proposed to predict the grain size of the friction stir processed material as a function of process parameters. The proposed approach involves determination of the strain rate distribution in the processed (deformation) zone based on the velocity fields of the material and correlating the strain rate distribution with the average grain size of the resulting microstructure using Zener-Holloman parameter.

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains xi, 73 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 63-66).

Thesis (M. S. in Mechanical Engineering)--Vanderbilt University, May 2009. / Title from title screen. Includes bibliographical references.

Thesis (M. S. in Mechanical Engineering)--Vanderbilt University, May 2009. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--Ohio State University, 2009. / Title from first page of PDF file. Includes vita. Includes bibliographical references (p. 108-109).

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (p. 95-96).