Microstructure,interfacial reaction behavior,and mechanical properties of Ti_3AlC_(2)reinforced Al6061 composites

The interfacial reaction behavior of Al and Ti_3AlC_(2)at different pouring temperatures and its effect on the microstructure and mechanical properties of the composites were investigated.The results show that the addition of3.0 wt.%Ti_3AlC_(2)refines the average grain size ofα(Al)in the composite by 50.1%compared to Al6061 alloy.Morphological analyses indicate that an in-situ Al_(3Ti)transition layer of-180 nm in thickness is generated around the edge of Ti_3AlC_(2)at 720℃,forming a well-bonded Al-Al_(3Ti)interface.At this processing temperature,the ultimate tensile strength of A16061-3.0 wt.%Ti_3AlC_(2)composite is 199.2 MPa,an improvement of 41.5%over the Al6061 matrix.Mechanism analyses further elucidate that 720℃is favourable for forming the nano-sized transition layer at the Ti_3AlC_(2)edges.And,the thermal mismatch strengthening plays a dominant role in this state,with a strengthening contribution of about 74.8%.

Experimental and numerical investigations on the tensile mechanical behavior of marbles containing dynamic damage

To investigate the degradation mechanism of static tensile mechanical behaviors of marble containing dynamic damage,multiple impact loading tests were performed on the disc marble samples,and then static Brazilian tests were conducted for the damaged samples.Besides,coupling modeling technology of finite difference method(FDM)—discrete element method(DEM)was used to carry out the numerical investigation.The results show that after multiple impacts,more white patches appear on the surface,and some microcracks,macro-fractures as well as pulverized grains are found by optical microscopic.The static tensile strength decreases with the increase of the dynamic damage variable characterized by the ultrasonic wave velocity of sample.The interaction between grains in the damaged sample becomes intense in the subsequent static loading process,causing a relatively large strain.The volume of the fragments falling off around the loading points becomes larger as impact number increases.As the dynamic damage increases,the absorbed energy of sample during the static loading first decreases and then tends to be stable.Both the stress concentration and the breakage of the force chains are the root causes of the degradation of the static tensile strength.

Tensile behaviors of fatigued AZ31 magnesium alloy

The relationship between microstructure and tensile behaviors of fatigued AZ31 magnesium alloy was investigated. Axial fatigue tests were performed on PLG-100 fatigue machine at stresses of 50 and 90 MPa. Tensile samples were cut from the fatigued samples, named as L-sample and H-sample respectively, and the O-sample was cut from original rolled AZ31 alloy. The EBSD and TEM were used to characterize the microstructure. It is found that the twinning-detwinning was the main deformation mechanism in high stress fatigue test, while dislocation slipping was dominant in low stress fatigue test. After fatigue tests, the average grain size of the L-sample and H-sample decreased to 4.71 and 5.33 μm, and the tensile and yield strength of the L-sample and H-sample increased slightly. By analyzing SEM images, the ultimate fracture region of the L-sample consisted of dimples, while there were many microvoids in the ultimate fracture region of the H-sample. Consequently, the tensile behaviors of fatigued magnesium have a close relationship with microstructure.

Effects of Steaming on the Tensile Mechanical Properties of Cashmere Fiber

The cashmere yarns were set in steam of 120℃ for 5 minutes after they had been extended to about 3% and wrapped onto the glass mandrels, which was relevant to the industrial setting processes. The effects of the steaming on the tensile mechanical properties of cashmere fiber are investigated. The extension in ' yield region' and the extension at rupture of the set cashmere fiber are obviously decreased.

Transplantation of human amniotic epithelial cells repairs brachial plexus injury:pathological and biomechanical analyses

A brachial plexus injury model was established in rabbits by stretching the C6 nerve root. Imme- diately after the stretching, a suspension of human amniotic epithelial cells was injected into the injured brachial plexus. The results of tensile mechanical testing of the brachial plexus showed that the tensile elastic limit strain, elastic limit stress, maximum stress, and maximum strain of the injured brachial plexuses were significantly increased at 24 weeks after the injection. The treatment clearly improved the pathological morphology of the injured brachial plexus nerve, as seen by hematoxylin eosin staining, and the functions of the rabbit forepaw were restored. These data indicate that the injection of human amniotic epithelial cells contributed to the repair of brachial plexus injury, and that this technique may transform into current clinical treatment strategies.

Effects of SiC Nanoparticle Content on the Microstructure and Tensile Mechanical Properties of Ultrafine Grained AA6063-SiC_(np) Nanocomposites Fabricated by Powder Metallurgy

Ultrafine grained AA6063-SiCnpnanocomposites with 1, 5 and 10 vol.% SiCnphave been fabricated by a novel powder metallurgy process. This process combines high energy ball milling of a mixture of 6063 alloy granules made from machining chips and Si C nanoparticles and thermomechanical powder consolidation by spark plasma sintering and hot extrusion. The microstructure and tensile mechanical properties of the samples were investigated in detail. Increasing the Si C nanoparticle content from 1 to 10 vol.%,the yield strength and ultimate tensile strength increased from 296 and 343 MPa to 545 and 603 MPa respectively, and the elongation to fracture decreased from 10.0%, to 2.3%. As expected, a higher Si C nanoparticle content generates a stronger inhibiting effect to grain growth during the thermomechanical powder consolidation process. Analysis of the contributions of various strengthening mechanisms shows that a higher Si C nanoparticle content leads to a higher contribution from nanoparticle strengthening, but grain boundary strengthening still makes the largest contribution to the strength of the nanocomposite.When the Si C nanoparticle content increased to 10 vol.%, the failure of the nanocomposite was initiated at weakly-bonded interparticle boundaries(IPBs), indicating that with a high flow stress during tensile deformation, the failure of the material is more sensitive to the presence of weakly-bonded IPBs.

A potential candidate structural material for molten salt reactor:ODS nickel-based alloy

The commercialisation of molten salts reactors(MSRs)is hindered by the lack of structural materials capable of withstanding the corrosive environment therein.To address this problem,we herein prepared1 wt%Y_(2)O_(3)mdispersion-strengthened Ni Mo-based alloys using powder metallurgy and evaluated their potential as structural materials for MSRs based on their mechanical properties,He swelling behaviour,and molten salt corrosion resistance.In view of the strengthening provided by homogenously dispersed Y_(2)O_(3)particles,all NiMo-Y_(2)O_(3)samples exhibited ultimate tensile strengths and yield strengths exceeding those of the Hastelloy N alloy,a state-of-the-art structural material for MSRs.Moreover,the volume fraction of He bubbles in the NiMo-Y_(2)O_(3)samples(~0.3%)was lower than that in the Hastelloy N alloy(0.58%),which showed that the introduction of Y_(2)O_(3)nanoparticles effectively inhibited He swelling.All NiMo-Y_(2)O_(3)samples showed excellent resistance to molten salt corrosion(as reflected by the absence of obvious holes therein),thus holding great promise for the development of irradiation-and molten salt corrosion-resistant structural materials for high-temperature MSRs.