Powder metallurgy (PM) of titanium is a potentially cost-effective alternative to conventional wrought titanium. This article examines both traditional and emerging technologies, including the production of powder, and the sintering, microstructure, and mechanical properties of PM Ti. The production methods of powder are classified into two categories: (1) powder that is produced as the product of extractive metallurgy processes, and (2) powder that is made from Ti sponge, ingot, mill products, or scrap. A new hydrogen-assisted magnesium reduction (HAMR) process is also discussed. The mechanical properties of Ti-6Al-4V produced using various PM processes are analyzed based on their dependence on unique microstructural features, oxygen content, porosity, and grain size. In particular, the fatigue properties of PM Ti-6Al-4V are examined as functions of microstructure. A hydrogen-enabled approach for microstructural engineering that can be used to produce PM Ti with wroughtlike microstructure and properties is also presented.

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The efficacy of Cognitive Behaviour Therapy (CBT) in the treatment of depression is now established. However, explanations for the efficacy of CBT are mixed. The evidence needed to support the explanation advanced by cognitive theory is lacking. This paper critically reviews the available empirical evidence. Forty‐four outcome or process studies of therapy with depression are reviewed and 21 of these are subjected to a meta‐analysis to investigate the relationship between change in cognitions and change in level of depression during different kinds of therapy. Our analysis shows that: (1) change in cognitive style occurs in all four categories of treatment: CBT, Drug Therapy, Other‐Psychological Therapy, and Waiting List; (2) there was a significant difference between Waiting List and all the active treatments in change in cognitions, but not between active treatments; (3) the degree of change in cognitive style is significantly related to change in depression as measured by the Beck Depression Inventory (BDI), but not the Hamilton Rating Scale for Depression (HRS‐D); and (4) the relationship between cognitive change and depression is not unique to CBT. Our findings show that CBT does provide some support for the cognitive models of depression but the relationship between cognitive change and recovery from depression is not unique to CBT.