Thermal analysis of the chip formation in austenitic stainless steel

The most important property of austenitic stainless steels is corrosion resistance. In these steels, the transition between paramagnetic and ferromagnetic conditions occurs at low temperatures. Therefore, the use of austenitic stainless steels in conditions in which ferromagnetism absence is important can be considered. On the other hand, the formation of strain-induced martensite is detected when austenitic stainless steels are deformed as well as machined. The strain-induced martensite formed especially in the machining process is not uniform through the chip and its formation can also be related to the Md temperature. Therefore, both the temperature distribution and the gradient during the cutting and chip formation are important to identify regions in which martensite formation is propitiated. The main objective here is evaluate the strain-induced martensite formation throughout machining by observing microstructural features and comparing these to thermal results obtained through finite element method analysis. Results show that thermal analysis can give support to the martensite identified in the microstructural analysis.

Enhancement of laser induced Au nanoparticle formation by femtosecond pulse shaping

We report the control of Au nanoparticle (NP) formation by using shaped 30 fs pulses, in a solution containing HAuCl4 and chitosan. By using a sinusoidal spectral phase, a periodic train of pulses is generated. When the period of the pulse train matches certain Raman resonances of chitosan, the reducing agent of the process, an enhancement of the Au NP formation is observed. Theoretical quantum chemical calculations indicate that the outer groups of the chitosan are mostly influenced by low Raman frequencies, which is in reasonably agreement with the experimental data and indicates an enhancement in the Au NP formation as the pulse train period increases (low frequency).