Microstructure and mechanical properties of a new type of austempered boron alloyed high silicon cast steel

In the present paper, a new type of austempered boron alloyed high silicon cast steel has been developed, and its microstructures and mechanical properties at different temperatures were investigated. The experimental results indicate that the boron alloyed high silicon cast steel comprises a dendritic matrix and interdendritic eutectic borides in as-cast condition. The dendritic matrix is made up of pearlite, ferrite, and the interdendritic eutectic boride is with a chemical formula of M2B （M represents Fe, Cr, Mn or Mo） which is much like that of carbide in high chromium white cast iron. Pure ausferrite structure that consists of bainitic ferrite and retained austenite can be obtained in the matrix by austempering treatment to the cast steel. No carbides precipitate in the ausferrite structure and the morphology of borides remains almost unchanged after austempering treatments. Secondary boride particles precipitate during the course of austenitizing. The hardness and tensile strength of the austempered cast steel decrease with the increase of the austempering temperature, from 250℃ to 400 ℃. The impact toughness is 4-11 J.cm^-2 at room temperature and the impact fracture fractogragh indicates that the fracture is caused by the brittle fracture of the borides.

Refining Effect of Boron on Hypoeutectic Al-Si Alloys

Several concepts of the grain refinement mechanism of B on hypoeutectic Al-Si alloys have been adopted: the refining effect of B on the a-AI and eutectic Si with the different additions of Al-B master alloys made at 850℃ was investigated; and the Al-B master alloys formed under different temperature conditions have been studied to explore the morphologies of AIB2 particles; slowly cooled sample with addition of Al-B was made to explore the refinement mechanism. AI-B master alloy can refine not only a-AI, but eutectic Si. Theoretical analysis indicates that, although AIB2 does not take part directly in the nucleation process in pure Al in the presence of Si, it provides a substrate for precipitation of a small content of Si from which a-At will grow without any undercooling. When the temperature decreases to eutectic line, AIB2 subsequently nucleates eutectic Si; AIB2 particles appear in two different morphologies, namely, hexagonal platelet and tetradehedron morphology which depend on the processing temperature conditions.

Study on Electrochemical Formation of Neodymium-Iron Alloy

The cyclic voltammetry was used to investigate the electrode processes of Nd(III) reduced on iron electrode and Nd(III),Fe(II) reduced on molybdenum electrode in molten chlorides. The Nd-Fe and Nd-rich RE-Fe alloys contained rare earth up to 90wt% were prepared by consumable cathode and electrolytic codeposition. The mechanism of electrochemical formation of Nd-Fe alloy had been discussed.

Effect of Heat Treatment on Structure and Wear Resistance of High Chromium Cast Steel Containing Boron

The microstructure, mechanical properties and wear resistance of high chromium cast steel containing boron after different heat treatments were studied by means of the optical microscopy （OM）, the scanning electron microscopy （SEM）, X-ray diffraction （XRD）, hardness, impact toughness, tensile and pin-on-disc abrasion tests. The results show that as cast microstructures of boron-free high chromium steel consist of martensite and a few （Cr, Fe）_7C_3 carbide, and the macro-hardness of boron-free high chromium steel is 55-57 HRC. After 0.5 mass% B was added into high chromium cast steel, as-cast structure transforms into eutectic （Fe, Cr）2B, （Cr, Fe）7 （C, B）a and martensite, and the macro-hardness reaches 58-60 HRC. High temperature quenching leads to the disconnection and isolated distribution of boride, and there are many （Cr,Fe）_23 （C,B）_6 precipitated phases in the quenching structure. Quenching from 1050 ℃, high chromium steel obtained the highest hardness, and the hardness of high chromium cast steel containing boron is higher than that of boron-free high chromium steel. The change of quenching temperature has no obvious effect on impact toughness of high chromium steel, and the increase of quenching temperature leads to tensile strength having an increasing tendency. At the same quenching temperature, the wear resistance of high chromium cast steel containing boron is more excellent than that of boron-free high chromium steel. High chromium cast steel guide containing boron has good performance while using in steel bar mill.

Impact of B alloying on ductility and phase transition in the Ni–Mn-based magnetic shape memory alloys:Insights from first-principles calculation

Brittleness is a bottleneck hindering the applications of fruitful functional properties of Ni–Mn-based multiferroic alloys.Recently,experimental studies on B alloying shed new light on this issue.However,the knowledge related to B alloying is limited until now.More importantly,the mechanism of the improved ductility,which is intrinsically related to the chemical bond that is difficult to reveal by routine experiments,is still unclear.In this context,by first-principles calculations,the impact and the correlated mechanism of B alloying were systemically studied by investigating four alloying systems,i.e.,(Ni_(2-x)B_(x))MnGa,Ni_(2)(Mn_(1-x)B_(x))Ga,Ni_(2)Mn(Ga_(1-x)B_(x))and(Ni_(2)MnGa)_(1-x)B_(x).Results show that B prefers the direct occupation manner when it replaces Ni,Mn and Ga.For interstitial doping,B tends to locate at octahedral rather than tetrahedral interstice.Calculations show that the replacement of B for Ga can effectively improve(reduce)the inherent ductility(inherent strength)due to the weaker covalent strength of Ni(Mn)–B compared with Ni(Mn)–Ga.In contrast,B staying at octahedral interstice will lead to the formation of new chemical bonds between Ni(Mn)and B,bringing about a significantly improved strength and a greatly reduced ductility.Upon the substitutions for Ni and Mn,they affect both the inherent ductility and strength insignificantly.For phase transition,the replacement of B for Ga tends to destabilize the austenite,which can be understood in the picture of the band Jahn–Teller effect.Besides,the substitution for Ga would not lead to an obvious reduction of magnetization.