Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract： High speed steels with high V content (HVHSS, 10 mass % of V) were fabricated by a process of pressing plus super solid-liquid phase sintering (SLPS) with atomized alloy powder as raw material. The effect of sintering parameters such as sintering temperature and holding time on densification, microstructure evolution as well as mechanical properties were systematically investigated, and the composition, morphology and distribution of the phases existed in the alloy were carefully analyzed. The results show that sintering temperature is the most important parameter affecting the performance of the sintered alloys, however holding time shows the main effect on the precipitation and evolution of carbides. The matrix of the as prepared HVHSS consists of acicular martensite and retained austensite, and there are three types of carbides, i.e. VC, complex molybdenum carbide and complex chromium carbide. Small spherical VC particles mainly distribute in the grains and along their boundaries. As sintering temperature and holding time increased, not only grains and carbides gradually coarsened but also more and more carbides precipitated. However, the precipitation of complex carbides deteriorates the alloy’s strength and toughness due to their poor morphology which cause serious stress concentration or forming carbide network along grain boundaries. The HVHSS possess high performance, such as hardness HRC 65-68, impact toughness and bending strength over 6 J/cm2 and 1800 MPa respectively.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： The 6鬃� series aluminum alloys Al-Mg-Si-Cu are widely used in the transportation and building industries due to their comprehensive mechanical properties, adequate formability, high corrosion resistance and good weldability. For decades, ultrafine grain structure (UFG) produced by severe plastic deformation (SPD) has been proved to be a promising way in strengthening Al alloy materials. Although this method can guarantee a great improvement in strength, the obtained ductility is always disappointing. Besides, this method has a limitation to fabricate products suitable for practical use. Recently, combining deformation and aging has been proposed to produce high-strength Al alloys. This strategy is very effective in achieving Al alloys with strength-ductility synergy even through conventional producing process, for example, rolling and aging. The strain ratio of deformation is critical in tuning the mechanical properties which could be acquired by the above method. The effect of deformation strain ratio on the age-hardening behaviors and microstructure in Al-Mg-Si-Cu alloy produced by combining coldrolling and aging are investigated using hardness test, tensile test, EBSD and TEM in this work. The results show that the as-rolled hardness increases gradually with deformation strain ratio. The age-hardening potential declines with the increase of strain ratio, though post-aging could further strengthen the as-rolled alloys. The grains elongate along the rolling direction during deformation and finally have a lamellar structure. Fragmentation and extensive defects like sub-grain boundaries occurs inside the grains. The dislocations become denser inside the alloy with the increase of the deformation ratio. When the deformation ratio is large (above 60%), formation of dislocation tangling and sub-grains are observed. Deformation-induced change of the dislocation configuration affects the precipitation significantly. Due to the interaction between solutes precipitation and defects annihilation, the distribution of precipitates undergoes a change from being isolated to a continuous manner.
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-15 Cooperative journals: 《金属学报》
Abstract：采用XRD、SEM、TEM、硬度测试和拉伸实验研究了冷轧Mn12Ni2MoTi(Al)钢经不同工艺退火后的显微组织及力学性能。结果表明，马氏体Mn12Ni2MoTi(Al)钢经65%冷轧及710~745 ℃退火处理后转变成主要由奥氏体晶粒和铁素体晶粒组成的亚微米级超细晶粒双相组织，并且弥散分布着第二相析出物颗粒；在退火中形成的富Ti、Mo及Si的第二相颗粒阻碍了超细再结晶晶粒的粗化，从而提高了钢的屈服强度和热稳定性；经710 ℃, 24 h长时间退火后，超细晶粒双相钢的平均晶粒尺寸仍然小于500 nm；超细晶粒双相钢延伸率随室温奥氏体体积分数增加而增加，室温奥氏体体积分数随退火温度升高或退火时间延长先增加后降低，且在745 ℃, 0.5 h退火时达到最大值。超细晶粒钢的屈服强度和总延伸率可达到900 MPa和23%以上，比同种材料淬火马氏体钢提高了约一倍。
Hits
Hits
Downloads
Comment