Mechanical Properties And Microstructure Analysis Of Some Nuclear Materials

For its corrosion resistance and good overall performance, austenitic stainless steels obtaina comprehensive range of applications. 304 is one of the widely used brands. In nuclear power plant, the 304stainless steel is widely used in the reactor core components, circuit pipes and a variety of equipments. Study the mechanical properties of the 304 stainless steel, not only measure its performance at high temperature, but also provide data for subsequent research of localization of main pipe material. Meanwhile, this paper also studies pure tungsten material and tungsten alloy. Pure tungsten material is a high hardness, high melting point but a relatively brittle material. So by adding oxides, carbides in pure tungsten material and through heat treatment process (forging, rolling, etc), scientists are trying to find a way to improve the toughness of the tungsten alloy material. We study several tungsten alloy materials developed for fusion reactor, in the microscopic point to determine whether it can improve the toughness of tungsten alloys.This paper mainly investigates the following sections:(1) Tensile tests of the 304 stainless steel specimens were carried out at the temperatures of 450～800℃at different strain rates ranging from 2×10-4 to 1×10-2s-1, the equipment is the universal testing machine type Shimadzu AG-100KNA.The results indicated that the dynamic strain aging phenomenon accompanied by a negative strain rate sensitivity appears in the temperatures ranging from 500 to 700℃. The critical strain increases with larger strain rate and decreases with increasing temperature The serration types, A, A+B and E, were observed. The effective activation energy for serrated flow occurrence has been calculated to be about 212.8 kJ/mol. The dynamic strain aging caused by the interactions between substitutional solutes, Cr and Mn, and moving dislocations, unrelated to the carbon atoms.(2) Using Optical Microscopy (OM), Scanning Electron Microscopy and (SEM), we study the microstructure of four samples about tungsten and tungsten alloy, including surface morphology, microstructure and elementary compositons.Experiments show that the average grain size of pure W is about 50⁸0μm, have more pores and low relative density. Rolling sample of pure W changes its grain shape but have more pores. W-1%La₂O₃ rolling and forging samples improve its microstructure to some degree, La₂O₃ particles have uniform size and distribute along the grain boundaries and in the grain. La₂O₃ and W formed a new W-La-O compounds. The particle's size of La₂O₃ in the forging sample is smaller than the particle's size of La₂O₃ in the rolling sample.