Effect of thermal residual stresses on yielding behavior under tensile or compressive loading of short fiber reinforced metal matrix composite

1　ＩＮＴＲＯＤＵＣＴＩＯＮＤｕｅｔｏｓｐｅｃｉａｌｍａｔｅｒｉａｌｓｔｒｕｃｔｕｒｅｏｆｓｈｏｒｔｆｉｂｅｒｒｅｉｎｆｏｒｃｅｄｍｅｔａｌｍａｔｒｉｘｃｏｍｐｏｓｉｔｅ (ＳＦＲＭＭＣ) ,ｔｈｅｍａｔｒｉｘａｎｄｔｈｅｆｉｂｒｅｄｅｆｏｒｍｅｖｉｄｅｎｔｌｙｎｏｎ ｕｎｉｆｏｒｍｌｙ .Ｔｈｉｓｎｏｎ ｕｎｉｆｏｒｍｄｅｆｏｒｍａｔｉｏｎｃａｎｂｅｆｕｒｔｈｅｒｅｎ ｈａｎｃｅｄｄｕｅｔｏｔｈｅｐｒｅｓｅｎｃｅｏｆｔｈｅｒｍａｌｒｅｓｉｄｕａｌｓｔｒｅｓｓｅｓ(ＴＲＳ)ｄｅｖｅｌｏｐｅｄｄｕｒｉｎｇｃｏ…     

两种纳米晶铜的拉伸性能比较

分别采用直流和脉冲电沉积工艺制各了两种纳米晶铜DC-Cu和PE-Cu,平均晶粒尺寸分别为65nm和33nm.室温单向拉伸试验表明,DC-Cu和PE-Cu的屈服强度分别为332 MPa和545 MPa,基本符合Hall-Petch经验公式;其断裂应变分别为18.2%和3.4%,与粗晶铜相比韧性大幅下降.随着应变速率的升高,两种纳米晶铜均表现出强度增大、韧性降低的规律.DC-Cu和PE-Cu的应变速率敏感系数分别为0.020和0.029,激活体积分别为90b3和36b3.分析认为,两种纳米晶铜的变形机制仍以位错模式为主.     

Synthesis and characteristics of large-scale ZnO rods by wet chemical method

The large-scale ZnO rods of submicrometer were prepared on the bare glass using a wet chemical method under different experimental parameters, such as the reactant concentration and the growth time. The microstructure of the ZnO rods was characterized by X-ray diffractometry（XRD） and field emission scanning electron microscopy （FESEM） with the energy dispersive X-ray spectroscopy（EDX）, and the optical property was investigated by the room-temperature photoluminescence （PL） spectra. XRD and FESEM results show that the wurtzite structure and rod-like ZnO is obtained. The length （3-8 μm） and the diameter （400 nm- 3 μm） vary with the experimental parameters. A strong UV emission at 384 nm and a weak visible yellow-green emission around 570 nm are observed in the PL spectrum. After annealing at 600 ℃ in air, the UV peak intensity increases obviously and the yellow-green peak intensity decreases greatly. The near-band-edge UV emission is attributed to the exciton recombination; the yellow-green emission can be associated with the defect recombination; and some defect complexes may be responsible for the latter emission.     

LY12CZ 铝合金超塑性孔洞长大及其对断裂的影响~*

供应状态 LY12CZ 铝合金具有超塑性,平均晶粒尺寸为15.3μm,在490℃,(?)_0=1.67×10~(-4)s~(-1)时,延伸率为346%,m 值为0.52—0.6。该材料为孔洞敏感材料,孔洞长大规律可用本文提出的二阶段孔洞模型描述。同时考虑材料的应变速率敏感性(m)和孔洞长大效应,可从理论上预测该材料的延伸率。     

锌铝涂层的研究开发与应用

锌铝涂层(也叫达克罗涂层)是一种新兴的金属防腐涂覆技术。它具有高耐蚀、无污染、无氢脆等优点。对锌铝涂层的配方、工艺及其应用进行了研究。通过对分散剂、流平剂等的优选,获得了多层片状叠加的致密涂层。通过盐雾试验和酸碱浸泡腐蚀试验比较了锌铝涂层、磷化膜和电镀锌层的性能,表明锌铝涂层是一种优良的耐腐蚀涂层。