The experimental data are employed to develop constitutive equations on the basis of the Arrhenius-type equation by introducing the strain with nonlinear fitting. The flow stress increases with decreasing temperature and increasing strain rate. It is found that dynamic recovery only occurs as strain rate is 10 s −1 at 900 ☌, and the dynamic recrystallization is the main softening mechanism. The true stress-true strain curves at different temperatures and strain rates of P/F steel were obtained. 5C-2Cu steel, the hot compression tests were conducted at temperatures ranging from 900 to 1000 ☌ and strain rates from 0.1 to 10 s −1 using Gleeble-1500 thermal simulator. To investigate the hot deformation behavior of powder-forged (P/F) Fc-0. In the case of 6Y3A2S addition, high fracture strength of 960 MPa and fracture toughness of 6.5 MPa m 1/2 were obtained. Densification near theoretical density was attained by using sintering additives, such as 6 wt.% Y 2O 3+3 wt.% Al 2O 3+2 wt.% SiO 2 (6Y3A2S) and 9 wt.% Y 2O 3+1.5 wt.% Al 2O 3+3 wt.% SiO 2 (9Y1.5A3S). The effects of sintering additives on the densification behavior of RBSN prepared by using coarse powders were also investigated. Higher values of fracture strength were obtained for the specimens made by using fine powders, however, higher values of fracture toughness were obtained when large elongated grains were developed in a fine grained matrix. As a result, the content and distribution of the liquid phase became suitable for complete densification, which resulted in density increase. The specimens made with fine powders shows high density because of the melting of the secondary oxynitride phase. The specimens prepared by using coarse powders did not show high density at high-temperature gas-pressure sintering, because of the abnormal growth of elongated β-Si 3N 4 grains owing to the insufficiency and the inhomogeneous distribution of the liquid phase. Different secondary phases were formed in each specimen reaction-sintered with different particle sizes due to the content difference in native oxide on the surface layer of particles. The effect of raw-Si particle size on the properties of sintered reaction-bonded silicon nitride (sintered RBSN) was investigated by the use of Si powders with different particle sizes containing various native SiO 2 oxide contents. This was explained by the exothermic nature of the reaction between Si and N 2 and the fact that small samples with a large surface-to-volume ratio attain thermal equilibrium with their environment better than large samples which may be subject to local overheating. Within the investigated range of sample dimensions (0.2–4.0 g) the unexpected observation was made, that with decreasing sample weight the nitridation rate also decreased. By varying the added amounts of the sintering aids, it was found that increasing the Y 2O 3 and MgO contents both improved the nitridation rate, whereas an increase of Al 2O 3 content resulted in reduced nitridation rates. For the processing of micro-components it was of special interest to study, how a decreasing sample size and wall thickness would influence the rate of Si 3N 4 formation. One question to be answered was how the sintering aids affect the nitridation behaviour of a silicon green body. It does not store any personal data.In order to establish a process for the manufacturing of injection moulded micro-components of sintered reaction-bonded silicon nitride (SRBSN) several process parameters were investigated with regard to their influence on the reaction-bonding step. The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. The cookie is used to store the user consent for the cookies in the category "Performance". This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Other. The cookies is used to store the user consent for the cookies in the category "Necessary". The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". The cookie is used to store the user consent for the cookies in the category "Analytics". These cookies ensure basic functionalities and security features of the website, anonymously. Necessary cookies are absolutely essential for the website to function properly.
0 Comments
Leave a Reply. |