World-class Xincheng gold deposit： An example from the giant Jiaodong gold province

The Jiaodong gold deposits are currently the most important gold resources（with Au reserves of〉4000 t） in China,and the leading gold-producing country globally（with Au production of ～428 t in2013）.Jiaodong is also considered as perhaps the only world-class to giant gold accumulation on the planet where relatively young gold ores（ca.130-120 Ma） were deposited in rocks that are 2 Ga older.The Xincheng world-class high-grade gold deposit,with a proven reserve of 〉200 t gold,is one of the largest deposits in the giant gold province of the Jiaodong Peninsula.It is located in the northwestern part of the jiaobei Uplift,and hosted by ca.132-123 Ma Xincheng quartz monzonites and monzogranites.Ore zones are structurally controlled by the NE-trending and NW-dipping Jiaojia Fault and subsidiary faults,and are mainly restricted to the footwall of the fault.The dominant disseminated- and stockworkstyle ores are associated with strong sericitization,silicification,sulfidation and K-feldspathization,and minor carbonate wallrock alteration halos.The four mineralization stages are pyrite-quartz-sericite（stage 1）,quartz-pyrite（stage 2）,quartz-polysulfide（stage 3） and quartz-carbonate（stage 4）.Gold occurs dominantly as electrum,with lesser amounts of sulfide-hosted native gold and rare native silver and argentite,normally associated with pyrite,chalcopyrite,galena and sphalerite：the latter with proven resources of about 105 t Ag,713 t Cu,and 5100 t S.There are three types of ore-related fluid inclusions：type 1 aqueous-carbonate（H2O-CO2）,type 2aqueous（liquid H2O＋vapor H2O）,and type 3 CO2（liquid CO2 and vapor CO2） inclusions.Homogenization temperatures range from 221 to 304℃ for type 1 inclusions,with salinities of 2.4-13.3 wt.%NaCl eq.,and bulk densities of 0.858-1.022 g/cm～3.The δ～（34）S（CDT） values of hydrothermal sulfides are 4.3-10.6‰and δ～（18）O values of hydrothermal quartz have a median value of 13.0‰.δD values of fluid inclusions in hydrothermal quartz have a median value of-75‰.Calculated δ～（18）Owater has a median value of 5.2‰.The timing of gold mineralization at the Xincheng gold deposit is younger than 123±1 Ma,and likely between 120.9 and 119.9 Ma.A minerals system genetic model for the probable epizonal orogenic Xincheng deposit suggests an initial medium temperature,CO2-rich,and low salinity H2O-CO2 deeply sourced metamorphic ore fluid associated with dehydration and decarbonization of subducting Paleo-Pacific lithosphere.The Jiaojia Fault constrained the migration of ore-forming fluids and metals at the brittle-ductile transition.Fluid immiscibility,caused by episodic pressure drops,led to significant high-grade gold deposition in the giant Xincheng gold deposit.

Effect of Hot Isostatic Pressing Conditions and Cooling Rate on Microstructure and Properties of Ti-6Al-4V Alloy from Atomized Powder

The effects of temperature and pressure on density, microstructure and mechanical properties of powder compacts during hot isostatic pressing（HIPping） were investigated. Optimized HIPping parameters of temperature range from 900 to 940℃, pressure over 100 MPa and holding time of 3 h, were obtained. Tensile properties after different heat treatments show that both the geometry of samples and cooling rate have a significant influence on mechanical properties. Finite element method was used to predict the temperature field distribution during HIPped sample cooling, and the experimental results are in agreement with simulation prediction. The interaction of HIPping parameters was analyzed based on the response surface methodology（RSM） in this study.

Effect of Hot Isostatic Pressing Loading Route on Microstructure and Mechanical Properties of Powder Metallurgy Ti_2AlNb Alloys

In this work, hot isostatic pressing （HIPing） technique was used to densify the Ti2AINb pre-alloyed powder. The influence of HIPing loading route parameters （temperature and rates of heating and pressurizing） on microstructure and properties of PM Ti2AINb alloys was studied. The results showed that HIPing loading route parameters affected the densification process and mechanical properties （especially high temper- ature rupture lifetime） of PM Ti2AINb alloys in the present work. A finite element method （FEM） model for predicting the final densification was developed and was used to optimize the HIPing procedure.

Directed graph-based distribution network reconfiguration for operation mode adjustment and service restoration considering distributed generation

We present a directed graph-based method for distribution network reconfiguration considering distributed generation. Two reconfiguration situations are considered: operation mode adjustment with the objective of minimizing active power loss(situation Ⅰ) and service restoration with the objective of maximizing loads restored(situation Ⅱ). These two situations are modeled as a mixed integer quadratic programming problem and a mixed integer linear programming problem, respectively. The properties of the distribution network with distributed generation considered are reflected as the structure model and the constraints described by directed graph. More specifically, the concepts of "in-degree" and "out-degree"are presented to ensure the radial structure of the distribution network, and the concepts of "virtual node" and"virtual demand" are developed to ensure the connectivity of charged nodes in every independent power supply area.The validity and effectiveness of the proposed method are verified by test results of an IEEE 33-bus system and a 5-feeder system.

Effect of thermal induced porosity on high-cycle fatigue and very high-cycle fatigue behaviors of hot-isostatic-pressed Ti-6Al-4V powder components

The present work reports the effect of thermal induced porosity(TIP)on the high-cycle fatigue(HCF)and very high-cycle fatigue(VHCF)behaviors of hot-isostatic-pressed(HIPed)Ti-6Al-4V alloy from gasatomized powder.The results show that the residual pores in the as-HIPed powder compacts present no obvious effect on the HCF life.The regrowth of the residual pores can be observed after solution heat treatment.The pore location ranks the most harmful for the fatigue life compared with the other initiating defects.The maximum stress intensity factors were calculated.The plastic zone size of fine granular area(FGA)is much less than the characteristic size of the microstructure,and the crucial size of the internal pores in this study is about 40μm.The failure types of fatigue specimens in the VHCF regime were classified,and the competition of different failure types was described based on the modified Poisson distribution.

Probing into the Yield Plateau Phenomenon in Commercially Pure Titanium During Tensile Tests

To explain the intrinsic mechanism of the yield plateau phenomenon in commercially pure titanium,the tensile behaviors of commercially pure titanium specimens after 91.6%cryorolling and subsequent annealing at 280℃,335℃,450℃and 600℃have been studied.The results show that the yield plateau phenomenon is a result of dislocation behaviors controlled by grain size and thus only exists within a given range of mean grain size.αgrain boundaries are the main dislocation multiplication sources of commercially pure titanium.Fine-grained microstructure could offer numerous dislocation multiplication locations during deformation.Once the applied stress is above the yielding strength,dislocations multiply rapidly and the mobile dislocation density is high.To retrieve the imposed strain rate,the mean dislocation velocity is bound to be low.Therefore,it takes time for them to interact with each other.As a result,the movement of dislocations is hardly blocked and the deformation could continue at a nearly constant applied stress.Consequently,the so-called yield plateau behavior presents in the tensile curves.The disappearance of yield plateau phenomenon in coarse-grained and ultrafi ne-grained microstructures is attributed to the quick realization of the mutual interactions among dislocations at the initial stage of tensile test.