Mechanical Properties Of Heat-treated Alloys Research Articles

Investigation on microstructure evolution and mechanical properties of Mg–Li–Al–Ca alloy after a series of heat treatments

Four heat treatment process routes were designed to study the microstructure evolution and mechanical properties of Mg–Li–Al–Ca alloy in relation to the heat treatment process. After heat treatment (Mg,Al)2Ca phase decomposed, and Li element volatilized. A large number of fine α-Mg precipitated phases appeared in β-Li matrix. The optimum mechanical properties of heat-treated alloy were obtained at 350 °C for 120 min, which are 190 MPa and 12% for tensile properties and 507 MPa and 51.9% for compression properties. Segregation of Al and Ca element was observed at grain boundaries. The phase boundaries between newly precipitated α-Mg phase and β-Li matrix impeded the slip of dislocations. It is believed that both the precipitation strengthening due to the formation of α-phase and the solid solution strengthening enhanced by the decomposition of (Mg,Al)2Ca phase play crucial roles in the improvement of mechanical properties.

Process parameter optimization in underwater Friction Stir welding of dissimilar aluminium alloy butt joints by design of experiment

Friction Stir Welding (FSW) is a nontraditional joining method that is used for the attachment of similar and divergent substances, which are comparatively difficult to be welded by fusion techniques. They are extensively used for joining metals in different applications. Also, this welding is more energy-competent and eco-responsive when contrasted with traditional fusion methods. The FSW has various degrees of prevalence when compared with conventional fusion. Generally, the mechanical properties of heat-treatable alloys are reduced due to thermal cycles and the roughening of the reinforcing expeditions in the FSW, resulting in joint softening. The Underwater Friction Stir Welding (UWFSW) is a preferred methodology to prevail over these problems. This procedure is appropriate for the heat treatable materials which are responsive to thermal activities throughout the fusion cycle. In this work, the UWFSW was carried for welding dissimilar alloys AA7075 and AA6082 with dimensions of 150 × 100 × 6 mm. The Hot work steel H13 was used as a tool material. Also, the influence of the fusion characteristics, including tool rotational speed, tool traverse speed, and tool tilt angle on the micro-arrangement and tensile characteristics of the UWFSW joints of AA7075 and AA6082 alloy, were investigated using Taguchi’s method. The S/N fraction scrutiny revealed that the optimum mechanical rigidity was attained at a tool rotational speed of 1200 rpm, tool fusion speed of 40 mm/min, and tool tilt angle of 1°. In accordance with the ANOVA method, the maximum input of parameters were analyzed for the objective functions, including the UTS (MPa), % of elongation, and micro hardness in the different zones (NZ, TMAZ, HAZ).

Mo Addition to the A354 (Al–Si–Cu–Mg) Casting Alloy: Effects on Microstructure and Mechanical Properties at Room and High Temperature

Cast aluminum alloys are widely used in the automotive field for the production of complex engine parts. However, the mechanical properties of heat-treatable alloys (e.g., Al–Si–Mg or Al–Si–Cu–Mg) are negatively affected by prolonged exposure to temperatures higher than about 200 °C. To date, several researchers have proposed the addition of alloying elements, such as Sc or Hf, for enhancing the high temperature behavior of cast Al alloys, while Mo has not been widely investigated. The present study aimed to assess the effects of Mo addition on microstructure, mechanical properties, and thermal stability of the A354 alloy. Samples of A354 alloy with different amount of Mo (in the range 0.1 to 0.8 wt %) were produced. The casting conditions and heat treatment parameters were optimized by means of optical and scanning electron microscopy, thermal analysis and hardness tests. Tensile tests highlighted that Mo induces a moderate increase of yield strength at room temperature (about 10%), but no appreciable improvement in the performance of the alloy at 250 °C was observed.

Research on Sheet Metal of a New Ni-Based Superalloy Prepared by EB-PVD

The sheet metal of a new Ni-based superalloy has been prepared by Electron Beam Physical Vapor Deposition (EB-PVD) technology. The phases, the microstructures and mechanical properties of this alloy before and after heat treatment have been analyzed by X-ray diffractometer, transmission electron microscope, optical microscope, scanning electrical microscope and tensile equipment. Results showed that the size of γ' particles increases gradually and the morphologies of γ' particles changed from spherical shape into cubical shape when temperature increased from low to high. Compared with as-deposited alloy, mechanical properties of heat-treated alloy were improved obviously. It is feasible that superalloy of better properties can be prepared by EB-PVD technology.