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In this paper, fabrication and characterisation of Mg–SiC nanocomposite are investigated. Micrometre-sized Mg powder with the different volume fraction of SiC nano particles were dynamically compacted using a modified Split Hopkinson Pressure Bar. Moreover, the compaction process was simulated using AUTODYN commercial software to demonstrate that the stress in the powder sample was sufficient for consolidation. To achieve the best quality samples, the effects of lubrication and compaction velocity on dynamic compaction process were initially studied by experiment. It was observed that the temperature of 450°C and the compaction velocity of 15.5?m/s led to the best samples with relative density more than 99%. The effects of reinforcing phase content on the relative density, micro-hardness, and compressive behaviour of the compacted samples along with their microstructures were investigated. The results showed that the micro-hardness and the compressive strength of the samples fabricated at 450°C increased about 70% and 50%, respectively.  相似文献
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利用分离式霍普金森压杆装置(SHPB)对低间隙Ti-6Al-4V(TC4 ELI)合金的等轴组织、双态组织和魏氏组织试样进行了动态压缩试验。应变率分别为ε=2000,3000,4000 s-1,得到了动态压缩真应力-应变(σ-ε)曲线,并对试验后发生剪切失效破坏的试样沿纵剖面切开,利用金相显微镜(OM)进行显微组织观察。结果表明:动态压缩条件下TC4 ELI合金3种组织试样的真应力-应变曲线大致分为弹性阶段和塑性阶段,没有明显的屈服平台,3种组织状态下的试样在高应变率下应变强化效应不明显,表现出一定的应变率强化效应;在4000 s-1应变率加载条件下,平均动态流变应力(σ)、均匀动态塑性应变(ε)以及冲击吸收功(E)按等轴组织、双态组织和魏氏组织顺序依次减小,等轴组织试样的σ,ε和E分别达到了1400 MPa,0.34%和470 kJ.m-3,具有较好的动态力学性能;在4000 s-1应变率加载条件下3种组织状态的试样均发生了剪切失效破坏,并在其纵剖面上都观察到了一条白亮的绝热剪切带(ASB),裂纹沿着绝热剪切带由圆柱试样的圆柱面向中心扩展,与ASB形成和扩展的方向一致,剪切带与导致断裂的裂纹密切相关。  相似文献
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During high speed machining in the field of manufacture,chip formation is a severe plastic deformation process including large strain,high strain rate and high temperature.And the strain rate in high speed cutting process can be achieved to 105 s 1.30CrMnSiNi2A steel is a kind of important high-strength low-alloy structural steel with wide application range.Obtaining the dynamic mechanical properties of 30CrMnSiNi2A under the conditions of high strain rate and high temperature is necessary to construct the constitutive relation model for high speed machining.The dynamic compressive mechanical properties of 30CrMnSiNi2A steel were studied using split Hopkinson pressure bar (SHPB) tests at 30-700 ℃ and 3000 10000 s-1.The stress-strain curves of 30CrMnSiNi2A steel at different temperatures and strain rates were investigated,and the strain hardening effect and temperature effect were discussed.Experimental results show that 30CrMnSiNi2A has obvious temperature sensitivity at 300 ℃.Moreover,the flowstress decreased significantly with the increase of temperature,The strain hardening effect of the material at high strain rate is not significant with the increase of strain.The strain rate hardening effect is obvious with increasing the temperature.According to the experimental results,the established Johnson-Cook (J-C) constitutive model of 30CrMnSiNi2A steel could be used at high strain rate and high temperature.  相似文献
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