In-situ white beam microdiffraction study of the deformation behavior in polycrystalline magnesium alloy during uniaxial loading

Scanning white beam X-ray microdiffraction has been used to study the heterogeneous grain deformation in a polycrystalline Mg alloy (MgAZ31). The high spatial resolution achieved on beamline 7.3.3 at the Advanced Light Source provides a unique method to measure the elastic strain and orientation of single grains as a function of applied load. To carry out in-situ measurements a light weight (~0.5kg) tensile stage, capable of providing uniaxial loads of up to 600kg, was designed to collect diffraction data on the loading and unloading cycle. In-situ observation of the deformation process provides insight about the crystallographic deformation mode via twinning and dislocation slip.

In-situ studies of X-ray diffraction line profiles from strained copper foils

The development of an in-situ tensometer is described along with preliminary results of x-ray line profiles from copper foils under tensile stress. The tensometer was designed and constructed on the high resolution diffraction instrument, Station 2.3 at the synchrotron radiation source (SRS) Daresbury Laboratory, and is capable of collecting data in either symmetric or asymmetric geometry including transmission and reflection modes. Experiments were carried out using 18 J..Lm thick copper foil up to strain levels of 5 % using both symmetric reflection and symmetric transmission diffraction. All profiles displayed diffraction broadening and asymmetry which increased with strain. In addition, the asymmetry observed in symmetric transmission was associated with extended tails on the low angle side of the profiles, but in symmetric reflection data the opposite asymmetry was observed. In the analysis, the measured profiles were fitted using the software TOPAS, a fundamental parameters approach to profile fitting. The instrumental profile function was characterised and modelled using annealed LaB6 powder. The diffraction broadening was then determined by refining the convolution of a Voigt function, an asymmetric exponential function and a fixed instrument function to reproduce the observed broadened profiles. The integral breadth and asymmetry results display a strong order dependence and increase almost linearly with strain. The results were interpreted by assuming crystallite size broadening in combination with dislocation broadening arising from fcc a/2( 110) {Ill } dislocations.

Facile fabrication of polyolefin/carbon nanotube composites via in situ friedel-crafts polyalkylation : structure and properties

Despite major advances in addressing the dispersion of carbon nanotubes (CNTs) in polymers and their interfacial interactions, exploring a facile approach for massively creating them is still fascinating. We interestingly find that the CNT dispersion is considerably improved in polypropylene (PP), and ?19.1 wt % of PP chains were in situ chemically grafted onto CNT surfaces only using a trace of AlCl3 via a one-step melt-blending. Compared with the PP/CNT composite, adding 0.2 wt % of AlCl3 enables an increase in tensile strength and Young's modulus of 30% and 25%, respectively. Moreover, the elongation at break is almost maintained, while adding CNTs alone causes significant decreases. Additionally, 0.2 wt % AlCl3 makes the thermal degradation temperature further improved. These remarkable improvements in properties are mainly attributed to better dispersion of CNTs and enhanced interfacial compatibility. This work opens up an innovative approach for scalable preparation of polyolefin/CNT composites applying to industrial production.