Effect of Heat Treatment of 316L Stainless Steel Produced by Selective Laser Melting (SLM)

Selective Laser Melting (SLM) shows a big potential within additive manufacturing of metals. The competitive mechanical properties compared to conventional processes as well as the geometry freedom are the main advantages of SLM. 316L stainless steel has been investigated in previous works regarding microstructure and mechanical properties. However, the influence of heat treatments has not been fully reported yet. This work studies the influence of different heat treatments applied to 316L stainless steel produced by SLM. The microstructure evolution was investigated for different conditions. Tensile, Charpy and hardness tests were performed on the as built and heat treated samples.Mechanical Engineerin

Staircase-like metamagnetic transitions in phase-separated manganites: influence of thermal and mechanical treatments

Substitutions in the Mn-sublattice of antiferromagnetic, charge and orbitally ordered manganites was recently found to produce intriguing metamagnetic transitions, consisting of a succession of sharp magnetization steps separated by plateaus. The compounds exhibiting such features can be divided in two categories, depending on whether they are sensitive to thermal cycling effects or not. One compound of each category has been considered in the present study. The paper reports on the influence of two treatments: high-temperature annealing and grinding. It is shown that both of these treatments can drastically affect the phenomenon of magnetization steps. These results provide us with new information about the origin of these jumps in magnetization.Comment: accepted for publication in J.Appl.Phy

AMBRA1 is able to induce mitophagy via LC3 binding, regardless of PARKIN and p62/SQSTM1

Damaged mitochondria are eliminated by mitophagy, a selective form of autophagy whose dysfunction associates with neurodegenerative diseases. PINK1, PARKIN and p62/SQTMS1 have been shown to regulate mitophagy, leaving hitherto ill-defined the contribution by key players in 'general' autophagy. In basal conditions, a pool of AMBRA1 - an upstream autophagy regulator and a PARKIN interactor - is present at the mitochondria, where its pro-autophagic activity is inhibited by Bcl-2. Here we show that, upon mitophagy induction, AMBRA1 binds the autophagosome adapter LC3 through a LIR (LC3 interacting region) motif, this interaction being crucial for regulating both canonical PARKIN-dependent and -independent mitochondrial clearance. Moreover, forcing AMBRA1 localization to the outer mitochondrial membrane unleashes a massive PARKIN- and p62-independent but LC3-dependent mitophagy. These results highlight a novel role for AMBRA1 as a powerful mitophagy regulator, through both canonical or noncanonical pathways

Irreversibility in two-stage martensitic transformations of Cu-Al-Ni and Cu-Zn-Al-Mn alloys

The thermoelastic martensitic transformation undergone in shape-memory alloys is considered to be thermodynamically reversible. However, the existence of irreversible heat dissipated is made evident in the special case of several Cu-based alloys which display a complex transformation from b.c.c. to a mixture of 18R and 2H martensites. The simultaneous growth of both the martensites is suggested as the main responsibility for the irreversible behaviour. In this sense, as a first approach, the entropy production associated to the irreversible heat is related to the degree of coexistence, and shows a maximum for a structure consisting of 50% 18R and 50% 2H.status: publishe

Phenomenological approach to the coexistence of 2 types of martensites in cu-zn-al-mn alloys

Certain compositions of polycrystalline Cu-Zn-Al-Mn alloys have been found to transform, on stress-free cooling, to a mixture of two types of martensites, 18R (beta') and 2H (gamma'). Due to the different thermal hysteresis shown by the beta reversible beta' and beta reversible gamma' transformations, the corresponding reverse transformations take place separately. The coexistence of two types of martensites has been investigated by means of non-conventional differential scanning calorimetry. The relative amount of each phase existing in the martensite product depends on composition and thermal treatment, ageing promoting the beta' martensite at the expense of the gamma'. To get a better understanding of this phenomena, a phenomenological model, based on the Gibbs free energy balance currently accepted for thermoelastic transformations, has been applied. The model gives an insight on the influence of different physical effects, either chemical (changes in the relative stability of the related phases) and non-chemical (frictional and elastic energy contributions), on the final relative fraction of each martensite and on the transformation temperatures.status: publishe

Stabilisation of Martensite During Training of Cu-Al-Ni Single Crystals

Cu-Al-Ni single crystals with composition 82.6Cu-13.4Al-4Ni (wt%) were heat treated at 800°C for 30 min and subsequently water quenched to room temperature. The samples with 3 mm diameter and length between 100 and 200 mm had a longitudinal orientation close to the [001] direction of the β-phase at high temperature. The martensite start temperature after the initial heat treatment was Ms=93°C. Training was performed by loading the sample above Af, followed by cooling under constant load. After removal of the load the sample was heated to recover its original shape. Repeating this cycle several times introduces the two-way memory effect. Several strains involved in the process were measured. It was found that a large residual deformation (RD) persisted after cycling between the training temperatures. Most of this residual deformation was recovered by overheating the sample. The non recoverable residual strain was observed to increase with increasing load. From the overheating experiments and differential scanning calorimetry measurements, it becomes evident that the total residual deformation is due to two contributions : the stabilisation of martensite and a plastic deformation