Shi Taihe

Effect of Different Heat Treatments on Microstructure and Mechanical Properties of Ti6Al4V Titanium Alloy

Abstract This paper analyzed the microstructure of Ti6Al4V titanium alloy after different heat treatments. The tensile experiment and instrumented impact test were performed. The relationship among the microstructure, impact fracture characteristic and mechanical properties was analyzed by metallurgical microscope and environment scanning electron microscope (ESEM). Results show that the microstructure, mechanical properties and impact toughness of Ti6Al4V titanium alloy are affected by the solution and aging treatment. The yield strength and ultimate tensile strength are improved remarkably. The ductility increases firstly, and then decrease. The good comprehensive properties can be obtained when the Ti6Al4V titanium alloy is treated under the condition of 960 °C/1 h + WQ and 500 °C/4 h + AC. σ0.2 is 1050 MPa, σb is 1120 MPa and Ak is 46.22 J·cm−2. The microstructure of the titanium alloy after solution and aging treatment consists of the β matrix and the precipitation of the α-phase. The lamellar β-phase and the α-phase structure of the small needle plexiform can enhance comprehensive properties.

Theoretical and Experimental Study of Bimetal-Pipe Hydroforming

The corrosion of oil country tubular goods (OCTG) gets more and more serious especially in the acidic environment. So, it is very important to develop a perfect anticorrosion technology for exploring sour oil and gas fields economically and safely. Analysis indicates that the bimetal-pipe (BP) which consists of the base layer of low carbon steel and a corrosion resistant alloy (CRA) cladding layer is an economic and reliable anticorrosion technology and has broad application prospects in the transportation of acid medium. However, theoretical study of hydraulic expansion mechanism for BP is not enough. In this paper, the deformation compatibility condition of BP was obtained by studying the deformation rule of the (CRA) liner and the outer pipe of carbon steel in the forming process; the mechanical model which can compute the hydroforming pressure of BP has been established based on the nonlinear kinematic hardening characteristics of material; furthermore, based on the stress strain curve of inner pipe simultaneously, the calculation method of the plastic hardening stress has been proposed. Thus, the accurate method for computing the forming pressure was obtained. The experimental data show that results are consistent with results of the proposed model. It indicates that the model can be used to provide theoretical guidance for the design and production as well as use of BP.

Research into sulfide resistant polymer latex cement for sour well applications

Purpose – The long-term durability of cement becomes an important challenge in oil and gas wells due to the aggressive acid gas. H2S has been found in more and more wells. The purpose of this research was to add polymer latex to the Class G cement in order to promote the H2S corrosion resistance of oilwell cement. Design/methodology/approach – The water loss and thickening time of cement slurry and compressive strength and gas permeability of bond cement were investigated to determine the cement formulation. The corrosion resistance of the polymer cement was compared to base Class G cement in solution with 1.8 MPa H2S at 120°C. Findings – The optimum concentration of polystyrene latex was determined as 5 percent. The permeability change, compressive strength loss and corrosion ratio of latex cement were all lower than for the base Class G cement. The electrochemical impedance spectroscopy results and microstructure details confirmed that the latex cement had stronger resistance to the aggressive medium. T...