The mechanical properties of many materials prepared by additive manufacturing technology have been greatly improved.High strength is attributed to grain refinement,formation of high density dislocation and existence ...The mechanical properties of many materials prepared by additive manufacturing technology have been greatly improved.High strength is attributed to grain refinement,formation of high density dislocation and existence of cellular structures with nanoscale during manufacturing.In addition,the super-saturated solid solution of elements in the matrix and the solid solution segregation along the wall of the cellular structures also promote the improvement of strength by enhancing dislocation pinning.Hence,the existence of cellular structure in grains leads to differences in the prediction of material strength by Hall-Petch relationship,and there is no unified calculation method to determine the d value as grain size or cell size.In this work,representative materials including austenite 316L SS were printed by selective laser melting(SLM),and the strength was predicted.The values of cell size and grain size were substituted into Hall-Petch formula,and the results showed that the calculation error for 316L is increased from 4.1%to 11.9%.Therefore,it is concluded that the strength predicted by grain size is more accurate than that predicted by cell size in additive manufacturing materials.When calculating the yield strength of laser additive manufacturing metal materials through the Hall-Petch formula,the grain size should be used as the basis for calculation.展开更多
通过OM、SEM、EBSD等手段,对20Cr Mn Ti H实验钢在不同淬火温度后的组织和力学性能进行分析。结果表明:随淬火温度升高,实验钢原奥氏体晶粒、马氏体块和马氏体束均增大,强度有所下降但拉伸塑性基本不变。按照hall-petch准则,各个组织参...通过OM、SEM、EBSD等手段,对20Cr Mn Ti H实验钢在不同淬火温度后的组织和力学性能进行分析。结果表明:随淬火温度升高,实验钢原奥氏体晶粒、马氏体块和马氏体束均增大,强度有所下降但拉伸塑性基本不变。按照hall-petch准则,各个组织参数均对拉伸强度有控制作用,其中晶粒贡献最大。拉伸断裂方式为韧性断裂,断口均由韧窝组成,并伴随有二次裂纹的产生。展开更多
For developing new binder phase with high performance, Co-Ni-Fe alloy was used as binder in cemented carbides. The mechanical properties of WC-CoNiFe and WC-Co cemented carbides with different grain sizes were studied...For developing new binder phase with high performance, Co-Ni-Fe alloy was used as binder in cemented carbides. The mechanical properties of WC-CoNiFe and WC-Co cemented carbides with different grain sizes were studied. The results show that the reprecipitation of WC-CoNiFe is inhibited compared with that of WC-Co during sintering process, and the grains in WC-CoNiFe cemented carbides are more of smooth shape, resulting in a slightly lower hardness and higher transverse rupture strength. With the increase of the grain size, the hardness of the two cemented carbides decreases, and the transverse rupture strength increases. However, the slope values of K in Hall-Petch relationship are higher in WC-CoNiFe than those in WC-Co, indicating the high toughness of medium entropy alloy Co-Ni-Fe.展开更多
基金Projects(51505166,51871249)supported by the National Natural Science Foundation of ChinaProject(Guike AB19050002)supported by the Guangxi Key Research and Development Program,China+1 种基金Project(2020JJ2046)supported by the Hunan Science Fund for Distinguished Young Scholars,ChinaProject(2020WK2027)supported by the Hunan Key R&D Plan,China。
文摘The mechanical properties of many materials prepared by additive manufacturing technology have been greatly improved.High strength is attributed to grain refinement,formation of high density dislocation and existence of cellular structures with nanoscale during manufacturing.In addition,the super-saturated solid solution of elements in the matrix and the solid solution segregation along the wall of the cellular structures also promote the improvement of strength by enhancing dislocation pinning.Hence,the existence of cellular structure in grains leads to differences in the prediction of material strength by Hall-Petch relationship,and there is no unified calculation method to determine the d value as grain size or cell size.In this work,representative materials including austenite 316L SS were printed by selective laser melting(SLM),and the strength was predicted.The values of cell size and grain size were substituted into Hall-Petch formula,and the results showed that the calculation error for 316L is increased from 4.1%to 11.9%.Therefore,it is concluded that the strength predicted by grain size is more accurate than that predicted by cell size in additive manufacturing materials.When calculating the yield strength of laser additive manufacturing metal materials through the Hall-Petch formula,the grain size should be used as the basis for calculation.
文摘通过OM、SEM、EBSD等手段,对20Cr Mn Ti H实验钢在不同淬火温度后的组织和力学性能进行分析。结果表明:随淬火温度升高,实验钢原奥氏体晶粒、马氏体块和马氏体束均增大,强度有所下降但拉伸塑性基本不变。按照hall-petch准则,各个组织参数均对拉伸强度有控制作用,其中晶粒贡献最大。拉伸断裂方式为韧性断裂,断口均由韧窝组成,并伴随有二次裂纹的产生。
基金Project(51671217)supported by the National Natural Science Foundation of ChinaProject(2016YFB0700302)supported by the National Key Research and Development Plan of China。
文摘For developing new binder phase with high performance, Co-Ni-Fe alloy was used as binder in cemented carbides. The mechanical properties of WC-CoNiFe and WC-Co cemented carbides with different grain sizes were studied. The results show that the reprecipitation of WC-CoNiFe is inhibited compared with that of WC-Co during sintering process, and the grains in WC-CoNiFe cemented carbides are more of smooth shape, resulting in a slightly lower hardness and higher transverse rupture strength. With the increase of the grain size, the hardness of the two cemented carbides decreases, and the transverse rupture strength increases. However, the slope values of K in Hall-Petch relationship are higher in WC-CoNiFe than those in WC-Co, indicating the high toughness of medium entropy alloy Co-Ni-Fe.
