A new Track of Fatigue crack growth in Aluminum Alloy (2219) under Cyclic Stresses

A study of new Track of Fatigue crack growth in aluminum alloy (2219) under cyclic stresses has been made. It was found out that this crack grow and propagate in three phases, the first phase though the grain size (micro-structure short cracks(MSC)), second phase cross the boundary of the grain size to about 1mm in length (physically short cracks (PSC)) and the third phase up to the final fracture (Length cracks(LC)). In addition, two programs were designed on MATLAB to perform the compute calculations to collect the results. The first program to calculate the practical constants and the second to make the calculations required to complete the work schedules. The stress and the parameters effecting the growth of these cracks in each phase were studied. A model consisting of three formulas was established from the experimental results. Each formula describes the behavior of the cracks in the particular phase. The comparison showed that the proposed model is safer than the experimental results for the designed parts of aircraft.

Characterization of Microstructure and Mechanical Properties of AA2219-O and T6 Friction Stir Welds

In the present study, aluminum alloy 2219 of two different heat treatment states were selected and welded using the friction stir welding process to evaluate the effect substrate on the joint properties. The microstructural observations have exhibited the difference in their characteristics between two heat treatment conditions of 2219-O and T6 conditions. The tensile strength of the AA2219-T6 joints much higher than the AA2219-O joints. Consequently, the microhardness distribution across the different zones varying with two different heat treated conditions. The failure locations and fracture surface features are revealed the significant differences among these two heat treated conditions with the change in their failure location and the fracture morphologies. The optimal welding conditions were analyzed to determine the high strength of the welds with excellent metallurgical properties of the welds.

Tensile Deformation Behaviors of Aluminum Alloy 2219 at High Temperatures from 415°C to 515°C

This study is carried out to provide detailed hot deformation information on aluminum alloy AA2219-O. The uniaxial tensile tests are carried out to study the hot deformation behaviors. The test temperature ranges from 415°C to 515°C, and the strain rates are 0.001s-1 and 0.01s-1. Additionally, the analysis of the strain rate sensitivity coefficient indicates that the AA2219-O exhibits the trend of superplasticity at temperatures above 475°C.

An Experimental Study of Process Parameters on Friction Stir Welded Aluminum Alloy 2219 Joint Properties

Aluminum alloy 2219 is widely used in aerospace applications since it has a unique combination of good weldability and high specific strength. Furthermore, it can provide a high strength after heat treatment with superior properties in cryogenic environment so they have been widely used for cryogenic fuel tank of space launch vehicles. It is known that solid state welding like friction stir welding can improve the joint properties of this alloy. Friction stir welding is a solid state welding technology which two materials are welded together by the frictional heat due to the rotation of the tool. In this study, friction stir welding was performed on aluminum alloy 2219 sheets. The range of welding parameter is four rotation speeds from 350 to 800 rpm and six travel speeds from 120 to 420 mm/min. The results include the microstructural change after friction stir welding. The microstructure was characterized and material in the stirred zone experience sufficient deformation and heat input which cause the complete dynamic recrystallization. The present work represents the strength at each process condition and the optimum friction stir welding process parameters. The optimum weld efficiency obtained in this study was 76.5 %.